U.S. patent application number 12/021068 was filed with the patent office on 2008-06-26 for curved lamp manufacturing method, curved lamp, and backlight unit.
Invention is credited to Hayato Kameyama, Akio Kikuchi, Yoshimitsu Mino, Hironobu Ueno, Takaharu Yanata.
Application Number | 20080148778 12/021068 |
Document ID | / |
Family ID | 35046639 |
Filed Date | 2008-06-26 |
United States Patent
Application |
20080148778 |
Kind Code |
A1 |
Ueno; Hironobu ; et
al. |
June 26, 2008 |
CURVED LAMP MANUFACTURING METHOD, CURVED LAMP, AND BACKLIGHT
UNIT
Abstract
A curved lamp manufacturing method including a curving process
in which a straight glass tube sealed with reduced pressure inside
is heated and curved. The curving process includes: a first step of
holding a predetermined portion of the glass tube using a first
chuck, and holding one end portion of the glass tube using a second
chuck such that the second chuck can slide in a longitudinal
direction of the glass tube; and a second step of, while heating a
planned curved portion of the glass tube positioned between the
predetermined portion and the end portion by a heater, curving the
planned curved portion by moving the second chuck relative to the
glass tube. The end portion is moved in the second step so that a
weight of the end portion is applied to the planned curved portion
that has been softened by the heater.
Inventors: |
Ueno; Hironobu;
(Takaishi-shi, JP) ; Yanata; Takaharu;
(Ibaraki-shi, JP) ; Kameyama; Hayato;
(Takatsuki-shi, JP) ; Mino; Yoshimitsu;
(Souraku-gun, JP) ; Kikuchi; Akio; (Hirakata-shi,
JP) |
Correspondence
Address: |
SNELL & WILMER L.L.P. (Matsushita)
600 ANTON BOULEVARD, SUITE 1400
COSTA MESA
CA
92626
US
|
Family ID: |
35046639 |
Appl. No.: |
12/021068 |
Filed: |
January 28, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11084674 |
Mar 18, 2005 |
|
|
|
12021068 |
|
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Current U.S.
Class: |
65/108 |
Current CPC
Class: |
H01J 9/247 20130101;
C03B 23/065 20130101; C03B 23/045 20130101; C03B 23/043 20130101;
H01J 61/325 20130101 |
Class at
Publication: |
65/108 |
International
Class: |
C03B 23/06 20060101
C03B023/06; C03B 23/043 20060101 C03B023/043 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 2004 |
JP |
2004-083635 |
Mar 29, 2004 |
JP |
2004-096767 |
Mar 30, 2004 |
JP |
2004-100958 |
Claims
1. A curved lamp manufacturing method including a curving process
in which a straight glass tube, which was sealed with inside
thereof being under reduced pressure, is heated and curved, the
curving process comprising: a first step of holding a predetermined
portion of the straight glass tube using a first chuck, and holding
one end portion of the straight glass tube using a second chuck in
a manner that the second chuck can slide in a longitudinal
direction of the straight glass tube; and a second step of, while
heating by a heater a planned curved portion of the straight glass
tube, which is positioned between the predetermined portion and the
end portion, curving the planned curved portion by moving the
second chuck relative to the straight glass tube, wherein the end
portion is moved in the second step so that a weight of the end
portion is applied to the planned curved portion that has been
softened by heat of the heater.
2. The curved lamp manufacturing method of claim 1, wherein in the
second step, the second chuck is rotated by a predetermined amount
of angle around a center of curvature of a curved portion of a
glass tube generated by curving the straight glass tube, a
trajectory thereof drawing an arc.
3. The curved lamp manufacturing method of claim 2, wherein in the
first step, the straight glass tube is held so as to extend in a
substantially horizontal direction, and in the second step, the
second chuck is rotated upward by substantially 90 degrees along a
vertical plane that includes a tube axis of the glass tube.
4. The curved lamp manufacturing method of claim 1, wherein in the
second step, the heater and the second chuck are simultaneously
moved so that a heating position of the glass tube heated by the
heater moves in a same direction as the second chuck.
5. The curved lamp manufacturing method of claim 3, wherein in the
first step, another end portion of the straight glass tube, which
is across the predetermined portion from the end portion, is
further held using a third chuck in a manner that the third chuck
can slide in the longitudinal direction of the straight glass tube,
and in the second step, another planned curved portion of the
straight glass tube, which is positioned between the predetermined
portion and the other end portion, is further heated by another
heater, the other planned curved portion is curved by moving the
third chuck relative to the straight glass tube, and a weight of
the other end portion is applied to the other planned curved
portion that has been softened by heat of the heater, wherein the
second and third chucks are rotated so that trajectories thereof
substantially produce a plane symmetry on either side of a plane
that is perpendicular to the tube axis of the straight glass tube
at a center of the predetermined portion.
6. The curved lamp manufacturing method of claim 5, wherein in the
second step, the heater and the second chuck are simultaneously
rotated so that a heating position of the glass tube heated by the
heater moves in a same direction as the second chuck, and the other
heater and the third chuck are simultaneously rotated so that a
heating position of the glass tube heated by the other heater moves
in a same direction as the third chuck.
7. The curved lamp manufacturing method of claim 1, wherein a
sheath heater is used as the heater, the sheath heater is disposed
at the planned curved portion, and the planned curved portion is
locally heated by the sheath heater.
8. The curved lamp manufacturing method of claim 7, wherein the
sheath heater is in a shape of a coil that is formed by winding a
heater wire, and the curving process further comprises a step of
letting the straight glass tube pass through the coil of the sheath
heater so that the planned curved portion is positioned at the coil
of the sheath heater.
9. The curved lamp manufacturing method of claim 8, wherein
adjacent turns of the heater wire in the coil are in contact with
each other.
10. The curved lamp manufacturing method of claim 8, wherein the
coil has three turns of the heater wire.
11. The curved lamp manufacturing method of claim 7, wherein the
sheath heater has been formed by bending the heater wire into a
shape of a cylinder whose side has an opening, and the curving
process comprises a step of inserting the planned curved portion of
the straight glass tube through the opening into the sheath
heater.
12. The curved lamp manufacturing method of claim 11, wherein the
sheath heater in the shape of a cylinder whose side has an opening,
when viewed from top of the cylinder, is in a shape of character C
or U or a concave.
13. The curved lamp manufacturing method of claim 1 further
including: a removing chuck arrangement process of arranging a
removing chuck so that straight tube portions of a glass tube,
which was generated by curving the straight glass tube in the
curving process, is placed between a first member and a second
member of the removing chuck, wherein in the removing chuck, the
first member is attached to a first base, the second member is
attached to a second base to face the first member, and at least
one of the first member and the second member can be inclined
against a plane perpendicular to a direction in which the first
base and the second base move relatively to each other; and a glass
tube removing process of bringing the first base and the second
base relatively close to each other, causing the first member and
the second member to sandwich and hold the straight tube portions
of the glass tube, and moving the removing chuck in a predetermined
direction while the first member and the second member hold the
straight tube portions.
14. The curved lamp manufacturing method of claim 13, wherein the
at least one of the first member and the second member can be
inclined to be in contact with the straight tube portions of the
glass tube.
15.-18. (canceled)
Description
[0001] This application is based on applications No. 2004-083635,
No. 2004-096767 and No. 2004-100958 filed in Japan, the contents of
which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] (1) Field of the Invention
[0003] The present invention relates to a curved lamp manufacturing
method for manufacturing a curved lamp by curving a straight glass
tube, a curved lamp, and a backlight unit.
[0004] (2) Description of the Related Art
[0005] Cold-cathode fluorescent lamps (hereinafter referred to as
fluorescent lamps) used in backlight units for liquid crystal
display screens are one example of conventional curved lamps. The
fluorescent lamps are in the shape of character "U" or "L". When
they are used in a direct-below-type backlight unit, a plurality of
fluorescent lamps in the shape of character "U" are arranged at the
back of the screen. When they are used in an edge-light-type
backlight unit, the fluorescent lamps in the shape of character "L"
are attached to the rim of a rectangular optical waveguide.
[0006] In the fluorescent lamps, it is required that the bending
radius (curvature radius) of the curved portion is as small as
possible (as close to the right angle as possible). The following
is the reason for it. In the case of the direct-below type
backlight unit, the larger the curvature radius of the curved
portion is, the less the number of fluorescent lamps to be arranged
is. If a small number of fluorescent lamps are used, only low
brightness is provided by the backlight unit. In the case of the
edge-light type, the larger the curvature radius at the curved
portion is, the greater the distance between the fluorescent lamps
and the optical waveguide is. If there is a great distance between
the fluorescent lamps and the optical waveguide, only a small
amount of light enters the optical waveguide, the light
distribution characteristics is deteriorated, and the backlight
unit becomes large in size.
[0007] In the direct-below type, to average the light distributed
to the screen, for example, the curved portion in the shape of
character "U" is arranged at a position outside the screen display
area. The larger the curvature radius of the curved portion is, the
greater the length of the curved portion is. As a result, if the
curvature radius of the curved portion is increased, the curved
portion outside the screen display area is extended as much, and a
large amount of light, among the light emitted from the lamp, is
wasted (not illuminating the screen). Also, this makes the outer
frame of the screen larger in width, making the monitor apparatus
itself larger in size.
[0008] In manufacturing such a fluorescent lamp, first a straight
lamp (hereinafter referred to as a straight-tube lamp) is
manufactured by applying a fluorescent substance onto the inner
surface of a straight glass tube, attaching electrodes to both ends
of the straight glass tube, and filling the glass tube with
mercury, a rare gas or the like. The manufactured straight-tube
lamp is then curved into the shape of character "U" or "L". It
should be noted here that the pressure inside the glass tube is
kept to be lower than the atmospheric pressure.
[0009] The curving of the straight-tube lamp into the shape of
character "U" or "L" is performed after the planned curved portion
of the straight-tube lamp is heated and softened. As one example of
the method for heating and softening the straight-tube lamp,
Japanese Laid-Open Patent Application No. 6-243782 discloses use of
a coil that is formed by winding a heating lead wire made of a
nichrome wire or a Kanthal wire (hereinafter, the coil of the
heating lead wire is referred to as a coil heater).
[0010] More specifically, while being held to extend in a
horizontal direction, the straight-tube lamp is passed through the
coil heater. One end of the straight-tube lamp is then fixed by a
fixed chuck and the other end is held by a roller guide chuck in a
manner that the roller guide chuck can move in the longitudinal
direction of the straight-tube lamp. When the straight-tube lamp is
in the above-mentioned state, the coil heater is electrified to
heat and soften the planned curved portion, while rotating the
fixed chuck along a horizontal plane around a predetermined
axis.
[0011] Meanwhile, in recent years, as display panels of the liquid
crystal display apparatuses have become thinner, glass tubes used
in such displays have become narrower. Accordingly, glass tubes as
narrow as 1-8 mm in the outer diameter have been used.
[0012] However, the above-described conventional method has a
problem in manufacturing such narrow lamps. That is to say, the
conventional method cannot be used to curve such narrow glass
tubes, or such narrow lamps are manufactured at extremely low
manufacturing efficiency. This is because the curving process makes
the outer side of the curved portion thinner and weaker. As a
result, when such a narrow glass tube is partially curved, the
curved portion becomes weak, and by the negative pressure inside
the glass tube and the atmospheric pressure, the weak portion is
collapsed. In the conventional method, to prevent such collapses, a
predetermined level of the curvature radius is required. This
prevents the backlight unit from being made compact, and also
prevents the improvement in the brightness and light
distribution.
SUMMARY OF THE INVENTION
[0013] The object of the present invention is therefore to provide
a curved lamp manufacturing method for manufacturing a curved lamp
by locally heating a glass tube, the method being efficient even if
the glass tube to be curved is narrow in diameter and has been
sealed with inside thereof being under reduced pressure; a curved
lamp that contributes to downsizing of the backlight unit, enables
the light emitted therefrom to be used effectively, and has
improved brightness and light distribution; and a backlight unit
using the curved lamp.
[0014] The above object is fulfilled by a curved lamp manufacturing
method including a curving process in which a straight glass tube,
which was sealed with inside thereof being under reduced pressure,
is heated and curved, the curving process comprising: a first step
of holding a predetermined portion of the straight glass tube using
a first chuck, and holding one end portion of the straight glass
tube using a second chuck in a manner that the second chuck can
slide in a longitudinal direction of the straight glass tube; and a
second step of, while heating by a heater a planned curved portion
of the straight glass tube, which is positioned between the
predetermined portion and the end portion, curving the planned
curved portion by moving the second chuck relative to the straight
glass tube, wherein the end portion is moved in the second step so
that a weight of the end portion is applied to the planned curved
portion that has been softened by heat of the heater. It should be
noted here that the above-stated "curved lamp" may be a
cold-cathode fluorescent lamp, hot-cathode fluorescent lamp, a
low-pressure discharge lamp of a dielectrics barrier discharge type
or the like, and each of these discharge lamps is divided into (a)
a type in which a fluorescent substance has been applied to the
lamp and (b) a type in which no fluorescent substance has been
applied to the lamp.
[0015] The above-stated construction provides an advantageous
effect that the method is efficient even if the glass tube to be
curved by local heating is narrow in diameter and has been sealed
with inside thereof being under reduced pressure. This is because
with above-stated construction, the planned curved portion is
curved while it is softened by heat and compressed by the weight of
the moved portion of the glass tube. This enables the amount of
extension of the curved portions to be suppressed, and makes the
outer sides of the curved portions thicker than the conventional
method in which the glass tube is curved along a horizontal plane.
The glass tube curved by this method has higher strength than the
glass tube curved by the conventional method. This enables even a
glass tube, which has a small diameter and was sealed with its
inside being under reduced pressure, to be partially curved by
heat. This method therefore provides an advantageous effect of
manufacturing the curved lamps with high efficiency.
[0016] The above object is also fulfilled by a curved lamp having
at least one curved portion, the curved lamp being generated by
heating and curving a straight glass tube that was sealed with
inside thereof being under reduced pressure, wherein outer diameter
of the straight glass tube ranges from 1.8 mm to 6.5 mm inclusive,
thickness of the straight glass tube ranges from 0.2 mm to 0.6 mm
inclusive, and curvature radius of an inner side of the curved
portion is equal to or larger than 0.5 mm and smaller than 4.0
mm.
[0017] With the above-stated construction in which the curvature
radius of an inner side of the curved portion is equal to or larger
than 0.5 mm and smaller than 4.0 mm, it is possible to downsize the
backlight unit without decreasing the strength of the outer sides
of the curved portions, and to use the light emitted from the lamp
effectively. Also, with the outer diameter of the straight glass
tube being set to 1.8 mm or more in the above-stated construction,
the electrodes, which, for example, to be attached to the glass
tube at the ends thereof, can be manufactured more easily. This is
another advantageous effect provided by the present invention.
Also, with the outer diameter of the straight glass tube being set
to 6.5 mm or less in the above-stated construction, it is possible
to decrease the backlight unit in thickness, namely, in length
perpendicular to screen, enabling the backlight unit to be made
thinner. The distance between the inner surface of the glass tube
and the discharge path is shortened by this. As a result, for
example, in the case where a fluorescent substance is applied to
the inner surface of the glass tube, the light emitted from the
fluorescent substance is increased in brightness and the
light-emitting efficiency is improved. Also, with the thickness of
the straight glass tube being set to a range from 0.2 mm to 0.6 mm
inclusive, it is possible to prevent the curved portion from being
deformed during the curving process, reduce the time required for
the curving process, and reduce the manufacturing cost.
[0018] The above object is also fulfilled by a backlight unit
having the curved lamp defined above, that is to say, the curved
lamp having at least one curved portion, the curved lamp being
generated by heating and curving a straight glass tube that was
sealed with inside thereof being under reduced pressure, wherein
outer diameter of the straight glass tube ranges from 1.8 mm to 6.5
mm inclusive, thickness of the straight glass tube ranges from 0.2
mm to 0.6 mm inclusive, and curvature radius of an inner side of
the curved portion is equal to or larger than 0.5 mm and smaller
than 4.0 mm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] These and the other objects, advantages and features of the
invention will be come apparent from the following description
thereof taken in conjunction with the accompanying drawings which
illustrate a specific embodiment of the invention.
In the drawings:
[0020] FIG. 1 is a perspective view of a backlight unit 1;
[0021] FIG. 2 shows a curved lamp;
[0022] FIGS. 3A and 3B show the construction of a curving apparatus
used for manufacturing the curved lamp in the curving process;
[0023] FIGS. 4A and 4B are cross-sectional views of the heater wire
of the heater, FIG. 4A being a longitudinal sectional view, and
FIG. 4B being a transverse sectional view;
[0024] FIG. 5 is a front view showing how the driven chucks move
upward as the holding units rotate;
[0025] FIG. 6 shows the shrinkage ratio calculated from the
measurement results of an experiment conducted to observe the
shrinkage after curving the glass tube using the conventional
method and the method of the present embodiment;
[0026] FIG. 7 shows the shrinkage ratio calculated from the
measurement results of an experiment conducted to observe the
shrinkage after curving the glass tube using the method of the
present embodiment;
[0027] FIG. 8 shows the shrinkage ratio calculated from the
measurement results of an experiment conducted to observe the
shrinkage after curving the glass tube using the conventional
method;
[0028] FIG. 9 shows the shrinkage ratio calculated from the
measurement results of an experiment conducted to observe the
shrinkage after curving the glass tube by the conventional method
using a gas burner for heating;
[0029] FIG. 10 shows the manufacturing process after the lamp is
curved;
[0030] FIG. 11 is a perspective view showing an outline of the
removing apparatus;
[0031] FIG. 12 is a perspective view showing an outline of the
chuck mechanism;
[0032] FIG. 13 is a view of the chuck mechanism viewed in the X
direction indicated in FIG. 12;
[0033] FIG. 14 is a view of the chuck mechanism viewed in the Y
direction indicated in FIG. 12;
[0034] FIGS. 15A, 15B, and 15C illustrate the removing process;
[0035] FIG. 16 shows the chuck mechanism viewed in the Z direction
in FIG. 12;
[0036] FIG. 17 is a plan view of another chuck mechanism;
[0037] FIG. 18 shows a modification of the heater;
[0038] FIG. 19 shows another modification of the heater;
[0039] FIG. 20 is a perspective view of a chuck mechanism in a
modification; and
[0040] FIG. 21 is a plan view of a chuck mechanism in a
modification.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0041] The following describes a cold-cathode fluorescent lamp, a
curved lamp in the shape of character "U", to which the present
invention has been applied, with reference to the attached
drawings.
1. Outline of Backlight Unit
[0042] FIG. 1 is a perspective view of a direct-below-type
backlight unit, of which a part of the front surface is partially
cut away to show the construction inside. Here, the "front" surface
of the backlight unit is closer to the screen than the opposite
surface after the backlight unit is attached to the display.
[0043] As shown in FIG. 1, a backlight unit 1 includes: curved
lamps 100, 101, 102, 103, and 104 in the shape of character "U"
arranged in rows at regular intervals in a predetermined direction
(in the example shown in FIG. 1, the direction is the vertical
direction); a rectangular housing 10 for housing the curved lamps;
and a front panel 20 covering the front side (opening) of the
rectangular housing 10.
[0044] A bottom plate 11 of the rectangular housing 10 is a
reflection plate that reflects the light emitted backward from the
curved lamps 100-104 toward the front side. The bottom plate 11 is
made of, for example, polyethylene terephthalate (PET). Side plates
12 of the rectangular housing 10 are made of the same resin as the
bottom plate 11.
[0045] The front panel 20 is used to extract parallel light beams
(in parallel with the normal direction of the front panel 20) by
diffusing the light from the curved lamps 100-104. The front panel
20 includes, for example, a diffusion plate 21, a diffusion sheet
22, and a lens sheet 23. It should be noted here that the diffusion
plate 21 contains acrylic.
2. Construction of Curved Lamp
[0046] FIG. 2 shows a curved lamp, of which one end is cut away to
show the electrode construction inside.
[0047] As shown in FIG. 2, a curved lamp 100 includes: a glass tube
110; and electrodes 125 that are respectively attached to ends 111
and 112 of the glass tube 110. The curved lamp 100 is in the shape
of character "U" whose curved portions are identified as 113 and
114, respectively.
[0048] The electrodes 125 are each in the shape of a cylinder with
a bottom. The ends 111 and 112 of the glass tube 110 are sealed
with electrode bars 121 and 126 attached to the bottoms of the
electrodes 125, respectively. It should be noted here that although
it is not shown in FIG. 2, the electrode 125 at the end 111 of the
glass tube 110 has the same construction as the electrode 125 at
the end 112.
[0049] The glass tube 110 is made of, for example, borosilicate
glass. A fluorescent substance (of, for example, three-wavelength
type) 115 is applied to the inner surface of the glass tube 110.
The glass tube 110 is filled with mercury, a rare gas or the like.
The inner pressure of the glass tube 110 is negative in relation to
the atmospheric pressure. The curved lamps 101-104 have basically
the same construction as the above-described curved lamp 100, and
the description thereof is omitted here.
3. Method of Manufacturing Curved Lamp
[0050] Next, the method of manufacturing the curved lamp 100 will
be described by dividing it into the straight lamp manufacturing
process, curving process, and extraction process.
(3-1) Straight Lamp Manufacturing Process
[0051] In the straight lamp manufacturing process, a straight lamp
is manufactured by applying a fluorescent substance to the inner
surface of the straight glass tube, attaching the electrodes to
seal the glass tube and the like.
[0052] These procedures will be described more specifically.
Firstly, a straight glass tube with a desired measurement is
prepared, and a fluorescent substance is applied to the inner
surface thereof. The application of the fluorescent substance is
performed by, for example, introducing a suspension containing the
fluorescent substance into the inside of the glass tube from one
end thereof, then draining out the suspension, and drying the
suspension that remained in the glass tube by a heating furnace
using electricity, gas or the like.
[0053] Next, a pair of electrodes are respectively attached to the
ends of the glass tube. This is performed by, for example,
attaching one of the pair of electrodes to one end of the glass
tube, temporarily attaching the other of the pair of electrodes to
the other end of the glass tube, and in this state, exhausting
gases from the inside of the glass tube to outside through the
other end of the glass tube, filling the glass tube with mercury
and a rare gas, and then sealing the other end of the glass tube
completely. In this way, a straight lamp with a desired length is
manufactured. This process can be performed by a conventional
method. In the following description, to differentiate between the
straight lamp and the curved lamp, the straight lamp is identified
as 100a, and the glass tube in the straight lamp is identified as
110a. It is supposed here that the straight lamp 100a used in this
example has 600 (mm) of overall length L, approximately 3 (mm) of
outer diameter D1, and approximately 2 (mm) of inner diameter D2,
that the curved lamp 100 manufactured in this example has 0.5 (mm)
of curvature radius r at the inside of the curved portion of the
glass tube, and that the distance W between the two straight tube
portions of the curbed lamp is approximately 20 (mm).
[0054] It should be noted here that the curvature radius r can be
indicated by the curvature radius of curves 1131 and 1141 which are
respectively inner outline curves of curved portions 113 and 114,
the inner outline curves being observed in a top plan view of the
curved lamp 100 as in FIG. 2. It should also be noted here that
when a curved portion partially includes a straight line, convex,
or concave in shape, the curvature radius r is defined as the
curvature radius of the entire curve that is obtained by extending
a curving part that actually exists in the curve.
[0055] It should be noted here that the measurement values of the
curved lamp at various portions (glass tube outer diameter,
curvature radius, and so on) provided in the present document in
relation to FIG. 2 are different from the actually measured values.
This arrangement is made for the sake of convenience. This also
applies to the other drawings.
(3-2) Curving Process
[0056] The curving process is a process in which the planned curved
portions (which correspond to the curved portions 113 and 114 and
are hereinafter identified as 113a and 114a, respectively) of the
glass tube 110a of the straight lamp 100a are heated and curved by
90 degrees. Now, the curving process will be described in detail
with reference to FIGS. 3-6.
[0057] FIGS. 3A and 3B show the construction of a curving apparatus
50 used for manufacturing the curved lamp in the curving process.
FIG. 3A is a top plan view of the curving apparatus 50. FIG. 3B is
a front view of the curving apparatus 50 viewed in the direction
indicated by the arrows of FIG. 3A and is a cross-sectional view
substantially taken along the line A-A of FIG. 3A.
[0058] As shown in FIGS. 3A and 3B, the curving apparatus 50
includes holding units 60 and 70, a fixing unit 80, and a
positioning unit 90. These units are supported by a base (not
illustrated). The holding unit 60 includes plate-like members 61
and 62, a driven chuck 63, and a heater 64.
[0059] The plate-like members 61 and 62 are linked with each other
by a linking member (not illustrated) so that the main surfaces are
substantially in parallel with a vertical plane with a
predetermined distance between them. The plate-like members 61 and
62 have a rotational axis 67 that is in parallel with the Y
direction. The plate-like members 61 and 62 are held in a manner
that they can rotate, as one unit, around the rotational axis 67
along the vertical plane. Although the rotary drive apparatus for
rotating the plate-like members 61 and 62 are not shown in the
figures, it can be achieved by a known technology as, for example,
an apparatus that uses a feed screw system in which the plate-like
members 61 and 62 are engaged with feed screws, and the plate-like
members 61 and 62 are driven by rotating the feed screws by a
motor. Also, the rotary drive apparatus may be any apparatus that
has the above-described function, such as the one that has a gear
fixed to the rotational axis 67, and drives the gear to rotate
using a mechanism for transferring a motion to the gear.
[0060] The driven chuck 63 holds the glass tube 110a in a manner
that it can slide (move) along the tube axis of the glass tube 110a
(a direction in parallel with the X direction), namely in the
longitudinal direction of the glass tube 110a. The driven chuck 63
includes: plate-like holding members 631, 632, 633, and 634 (hidden
under the member 633 in FIG. 3A); metal rollers 635 and 636 each
having a V-shaped groove; and cylindrical metal rollers 637 and
638.
[0061] The holding members 631 and 632 hold the rollers 635 and 636
in a manner that the rollers 635 and 636 can rotate around the axes
respectively in the directions indicated by the arrows in FIG. 3A.
The holding members 631 and 632 are bonded with the inner surface
of the plate-like member 61.
[0062] The holding members 633 and 634 hold the rollers 637 and 638
in a manner that the rollers 637 and 638 can rotate around the axes
respectively in the directions indicated by the arrows in FIG. 3A.
The holding members 633 and 634 are bonded with the inner surface
of the plate-like member 62.
[0063] The rollers 635-638 hold the glass tube 110a by what is
called a three-point support in which the rollers 635 and 636
respectively have contact with the outer surface of the glass tube
110a at two points, and the rollers 637 and 638 respectively have
contact with the outer surface of the glass tube 110a at one point,
in a manner that the driven chuck 63 can slide along the tube axis
of the glass tube 110a, the rollers 635 and 637 making a pair in
sandwiching the glass tube, and the rollers 636 and 638 making a
pair in sandwiching the glass tube. It should be noted here that
the driven chuck is not limited to the above-described one, but may
be any member that can hold the glass tube 110a in a manner that
that the driven chuck 63 can slide along the tube axis of the glass
tube 110a. For example, the glass tube 110a may be inserted into a
tube-like member with a room between them, and the tube-like member
may be lifted up for curving the glass tube. The rollers may be
replaced with belts. Also, the material of the members is not
limited to metal, but may be resin, for example.
[0064] The heater 64 is a coil heater that has a coil of three
turns, and is formed by winding one heater wire so as to have the
same coil diameter (in this example, so as to have the coil
diameter of 8 mm).
[0065] Leads 65 and 66 of the heater 64 are held by the plate-like
member 62 via a heater holding member (not illustrated) so that the
axis of the coil matches the tube axis of the glass tube 110a, in a
manner that the heater 64 can move in the X direction between the
positions indicated by the dotted line and the solid line. In the
curving process, the heater 64 is moved by a moving apparatus (not
illustrated) in the X direction between the positions indicated by
the dotted line and the solid line. As is the case with the rotary
drive apparatus, the moving apparatus may be achieved as an
apparatus that uses a feed screw system in which the heater holding
member is engaged with a feed screw, and the heater 64 is moved by
rotating the feed screw by a motor.
[0066] The tips of the leads 65 and 66 further extend to connect to
a power apparatus 68 for the lamp heating. The power apparatus 68
supplies power to the heater 64.
[0067] FIGS. 4A and 4B are cross-sectional views of the heater wire
of the heater 64. FIG. 4A is a longitudinal sectional view. FIG. 4B
is a transverse sectional view.
[0068] As shown in FIGS. 4A and 4B, the heater wire is composed of
three layers. More specifically, the heater wire includes a heat
wire 641 made of a Kanthal wire or a nichrome wire, which is
covered with an insulator 642 made of magnesium oxide, which is
covered with a metal pipe (sheath) 643 made of inconel. For this
reason, the heater 64 is also referred to as a sheath heater. In
this example, the heat wire 641 is approximately 0.3 (mm) in
diameter, the sheath 643 is approximately 1.6 (mm) in outer
diameter and approximately 1.0 (mm) in inner diameter, and the
insulator 642 is approximately 0.35 (mm) in thickness.
[0069] The reason why the heater wire is constructed as described
above is as follows. If a heater coil made of a nichrome wire or a
Kanthal wire is kept to be red-hot to soften the glass tube, the
heater coil tends to be deformed over time due to the residual
stress of the coil. More specifically, if the heater coil is heated
for a long time, the coil diameter may be decreased at the center
turn and increased at the two end turns due to a difference in
temperature between the center turn and the two end turns. When
this happens, the ring-like shape of the coil may be deformed, and
the pitch may become uneven, and a local heating point, at which
the straight-tube lamp is heated by the coil, may be shifted. This
means that the manufactured fluorescent lamps vary in terms of the
position of the curved portion since the portion is curved as the
coil heats the planned portion. Products having a large amount of
variation are regarded as defective products. Increase of the
defective products decreases the yielding ratio. In actuality, if a
heater coil is heated for approximately 150 hours, the amount of
variation reaches such an extent that the heater coil needs
replacing with a new one. The time and effort, management, cost and
the like required for the replacement are burdensome.
[0070] With use of the sheath heater, it is possible to make the
turns of the coil close to each other since in the sheath heater,
the heat wire 641 is isolated from the sheath 643 surrounding the
heat wire 641. This makes it possible to decrease the coil in
length in the direction of the coil axis (The length is also
referred to as a coil width, and the coil used in this example is
approximately 6 mm in coil width.) to such an extent that it can be
used to locally heat the glass tube 110a. The sheath heater also
provides an advantage effect that if the heat wire 641 suffers
stress by heat over time due to the residual stress or the like
when the sheath heater is kept to be at a temperature as high as
possible to soften the glass tube, the sheath coil is hardly
deformed since the adjacent turns of the coil, which are close to
each other, suppress the strength of the deformation.
[0071] Also, since the sheath 643 itself is not a heating element,
the sheath 643 may be made of a material that is higher in rigidity
than the Kanthal or nichrome wire. Further, if the heat wire 641 is
deformed by heat, the insulator 642 prevents the sheath 643 and the
coil from being deformed by playing a role of a buffer that absorbs
the strength of deformation. Actually, when a coil of the sheath
heater was heated for approximately 700 hours in an experiment,
hardly a deformation was observed in the coil. This proves that the
sheath heater is far superior than a heater that is a coil of a
bare wire of Kanthal or nichrome, which can be used only for
approximately 150 hours. The use of the sheath heater therefore
prevents the above-described problems: the time and effort and the
like required for replacing the heater; and the variation in the
position of the curved portion of the glass tube due to shifting of
the heating position caused by the deformation of the coil over
time.
[0072] It should be noted here that the heater is not limited to
the sheath heater, but a Kanthal wire or the like may be used.
Also, a gas burner may used as the heater.
[0073] Back to FIG. 3, the holding unit 70 includes plate-like
members 71 and 72, a driven chuck 73, and a heater 74, which
basically have the same construction as the plate-like members 61
and 62, driven chuck 63, and heater 64. These elements of the
holding units 60 and 70 are arranged symmetrically on either side
of the fixing unit 80. The plate-like members 71 and 72 are held in
a manner that they can rotate, as one unit, around a rotational
axis 77 along a vertical plane. A rotary drive apparatus (not
illustrated), which has the same mechanism as the rotary drive
apparatus for the holding unit 60, is disposed for rotating the
holding unit 70. The heater 74 receives power from the power
apparatus 68 that also supplies power to the heater 64. The power
apparatus 68 supplies the same amount of power to the heaters 64
and 74.
[0074] The fixing unit 80, which includes a known metal fixed
chuck, is used to fix a predetermined portion of the glass tube
110a. The fixed chuck used in this example divides into two pieces
in the Y direction. The fixed chuck is opened to let the glass tube
110a pass through, and is closed to fix the glass tube 110a. The
fixed chuck is not limited to the above-described one, but may have
any shape and material in so far as it can hold the glass tube
110a. For example, the fixed chuck may be made of resin. The
predetermined portion to be fixed may be approximately the center
of the length of the glass tube 110a. However, not limited to this,
the predetermined portion may be determined based on the planned
positions of the curved portions 113 and 114.
[0075] The positioning unit 90 is used to position the straight
lamp 100a in the direction of the tube axis when the straight lamp
100a is set in the curving apparatus 50. The positioning unit 90
includes a contact plate 91 used to determine a standard position
in the direction of the tube axis.
[0076] The curving process is performed as follows.
(1) Setting Step
[0077] In the setting step, the straight lamp 100a, which has been
manufactured in the straight lamp manufacturing process, is set in
the curving apparatus 50. More specifically, as shown in FIGS. 3A
and 3B, the driven chuck 63, heater 64, fixing unit 80, heater 74,
and driven chuck 73 are arranged in series in the X direction. The
glass tube 110a is then passed through, in order from the left-hand
side to the right-hand side of FIGS. 3A and 3B, the space between
each pair of rollers of the driven chuck 63, inside the coil of the
heater 64, the fixing unit 80 (in the open state), inside the coil
of the heater 74, and the space between each pair of rollers of the
driven chuck 73 until one end of the glass tube 110a is brought
into contact with the contact plate 91. In this state, the fixed
chuck of the fixing unit 80 is closed to fix the glass tube
110a.
[0078] Currently, the glass tube 110a is substantially in the
horizontal direction and is fixed at its center by the fixed chuck
in a manner that the driven chuck 63 can slide along one half of
the tube axis of the glass tube 110a and the driven chuck 73 can
slide along the other half of the tube axis of the glass tube 110a.
In this state, the heaters 64 and 74 are respectively at the
positions indicated by the dotted lines in FIG. 3A.
(2) Power Supply Step
[0079] In the power supply step, the power apparatus 68 and the
moving apparatus are activated, the power apparatus 68 supplies
power to the heaters 64 and 74, and the heaters 64 and 74 are moved
to and stopped at the positions, which are, as indicated by the
solid lines in FIG. 3A, under the rotational axes 67 and 77,
respectively. In this step, while the heaters 64 and 74 move from
the positions indicated by the dotted lines to the positions
indicated by the solid lines, the heaters 64 and 74 are supplied
with power and heated. The amount of power supplied to the heaters
64 and 74 is controlled in accordance with the moving speed so that
when the heaters 64 and 74 stop, they are at a predetermined
temperature that is higher than the softening temperature of the
glass tube. The portions of the glass tube 110a, which are each a
portion between the dotted-line position and the solid-line
position and are each the planned curved portion, are heated as the
heaters 64 and 74 move and become easy to curve. This makes the
planned curved portions easier to curve in the curving operation.
Also the portions may be preparatively heated. This increases the
speed at which the portions are curved.
[0080] When the heaters 64 and 74 move and stop at the positions
indicated by the solid lines, the glass tube 110a starts to soften.
The amount of power supplied to the heaters 64 and 74 is determined
beforehand as the amount of power that causes the heaters to soften
the glass tube enough to be curved. In this example, a glass tube
having the softening temperature of approximately 760.degree. C. is
used, and the amount of power supplied to the heaters 64 and 74 is
set to a value that causes the glass tube temperature to be in a
range from 750.degree. C. to 760.degree. C., a range that is equal
to or lower than the softening temperature.
(3) Drive Step
[0081] In the drive step, the rotary drive apparatus is activated,
the holding units 60 and 70 are each rotated upward around the
rotational axes 67 and 77 at a predetermined speed by a
predetermined angle (in this example, 90 degrees), along the
vertical plane that includes the tube axis of the glass tube
110a.
[0082] FIG. 5 is a front view showing how the driven chucks 63 and
73 move upward as the holding units 60 and 70 rotate. In FIG. 5,
the plate-like member 61 and the like are omitted to show the
trails in the movement of the driven chucks and heaters. In FIG. 5,
the centers of the rotational axes 67 and 77 are indicated by G and
G'.
[0083] As shown in FIG. 5, the driven chucks 63 and 73 rotate
around G and G' drawing arcs. In other words, the driven chucks 63
and 73 rotate so that the trajectories of the driven chucks 63 and
73 produce a plane symmetry on either side of a plane that is
perpendicular to the tube axis of the glass tube 110a at the
position fixed by the fixing unit 80. With this operation, the two
end portions of the glass tube 110a except for the central portion
fixed by the fixing unit 80 are respectively curved by 90 degrees,
and the glass tube 110a is shaped into the character "U". In this
sense, G and G', which represent the centers of the rotational axes
67 and 77, also represent the centers of the curvatures of the
curved portions 113 and 114, respectively.
[0084] In the above operation, the heaters 64 and 74 also move by
rotating around G and G' at the same time as the driven chucks 63
and 73 move in a similar manner. This means that heating points of
planned curved portions 113a and 114a move upward as the two end
portions of the glass tube 110a are curved. This prevents the glass
tube from breaking in the middle of the curving, and enables each
end portion of the glass tube 110a to be curved with a
predetermined curvature radius.
[0085] Also, as stated earlier, the driven chucks 63 and 73 hold
the glass tube 110a in a manner that they can slide along the tube
axis of the glass tube 110a. This means that they move relatively
to the glass tube 110a during the curving. Accordingly, a
tube-axis-direction component of the weight received by the lifted
portions of the glass tube 110a is applied to the portions softened
by the heat of the heaters. In other words, when the glass tube
110a is curved, the weight of the two end portions of the glass
tube 110a is applied to the softened portions, and the softened
portions are compressed by the weight.
[0086] In case the glass tube is curved by a conventional method,
in which the glass tube is curved along a horizontal plane, outer
sides 131 and 131' of the curved portions of the glass tube become
very thin because the driven chucks pull the softened portions with
tension without no forth for compression, and the softened portions
extend in the direction of length. In contrast, according to the
method of the present embodiment, the softened portions are
compressed by a forth, which reduces the amount of extension of the
curved portions per unit volume and makes the outer sides 131 and
131' thicker than the conventional method.
[0087] FIG. 6 shows the shrinkage ratio calculated from the
measurement results of an experiment conducted to observe the
shrinkage after curving the glass tube using the conventional
method and the method of the present embodiment.
[0088] More specifically, in this experiment, the straight-tube
lamp was marked at regular intervals of 1 mm, the straight-tube
lamp was curved by the different methods, and the marking interval
P (mm) of the inner side of the curved portions were measured. The
shrinkage ratio was then calculated from the measurement results.
The shrinkage ratio here is represented by (1-P).times.100(%). The
greater the shrinkage ratio is, the narrower the marking interval P
is, and the thicker the inner side of the curved portion is.
[0089] As shown in FIG. 6, the average values of five samples for
each of the conventional method and the method of the present
embodiment indicate that the present embodiment has greater
shrinkage ratio than the conventional method. Accordingly, the
inner sides (represented by 132 and 132' in FIG. 5) of the curved
portions are thicker in the glass tube curved by the method of the
present embodiment than in the glass tube curved by the
conventional method.
[0090] This also applies to the outer sides of the curved portions.
That is to say, a ratio of marking interval between the inner and
outer sides of the curved portions is substantially equal to a
ratio of curvature radius between the inner and outer sides of the
curved portions. Accordingly, if the marking interval of the inner
sides of the curved portions is narrower than those of the
conventional method, the marking interval of the outer sides of the
curved portions is also narrower than those of the conventional
method. This means that the outer sides of the curved portions
curved by the method of the present embodiment are smaller in the
amount of extension, greater in the shrinkage ratio, and thicker
than the outer sides of the curved portions curved by the
conventional method. It is understood from this that the present
embodiment makes the curved portions thicker than the conventional
method. It was also confirmed by the experiment that the circular
shape of cross section of the glass tube was substantially
maintained in the curved portions after they were curved.
[0091] As described above, the present embodiment makes the curved
portions thicker than the conventional method. Also, in relation to
this, the present embodiment makes the curvature radius r smaller
than the conventional method. If the curvature radius r is
excessively small, the outer sides of the curved portions become
weak. Conversely, if the curvature radius r is large, the backlight
unit becomes large in size, and a large amount of light, among the
light emitted from the lamp, is wasted. Also, if a glass tube 110a
with a small outer diameter is intended for use, the inner diameter
thereof, which becomes small as much, should also be taken into
account since the electrodes to be inserted into the glass tube
need to be small as much. It is difficult to manufacture extremely
small electrodes. Also, if the inner diameter is small, the
distance between the inner surface of the glass tube 110a and the
discharge path becomes short, which makes the discharge space
narrow, reduces the brightness of the light emitted from the
fluorescent substance, and decreases the light-emitting efficiency.
Conversely, if the outer diameter is large, the backlight unit
becomes thick, going against the demand for thin backlight units,
and since the inner diameter becomes large, the distance between
the inner surface of the glass tube 110a and the discharge path
becomes large, which, as is the case with the short distance,
reduces the brightness of the light emitted from the fluorescent
substance, and decreases the light-emitting efficiency. If the
glass tube 110a is excessively thin, the planned curved portions
apt to be deformed and squashed when they are heated and curved,
and if the glass tube 110a is excessively thick, the amount of heat
increases and a more amount of time is taken for the curving, which
increase the manufacturing cost.
[0092] Taking the above-described problems into consideration, the
inventors of the present invention confirmed through experiments
that glass tubes with the outer diameter ranging from 1.8 mm to 6.5
mm inclusive, and thickness ranging from 0.2 mm to 0.6 mm inclusive
are suitable for manufacturing the curved lamps by the curving
method of the present invention, and the suitable curvature radius
r is equal to or larger than 0.5 mm and smaller than 4.0 mm, for
achieving the improved strength of the curved portions, downsizing
of the backlight unit, effective use of light emitted from the
lamp, improvement of the light-emitting efficiency, simplified
manufacturing of the electrodes, and reduced manufacturing cost for
the curving process.
[0093] FIGS. 7-9 show the shrinkage ratio calculated from the
measurement results of an experiment using the glass tube with the
outer diameter 3.0 mm and the thickness of 0.5 mm, with the
curvature radius r being 3.9 mm, as one example meeting the
suitable ranges. FIG. 7 shows the obtained values with the method
of the present invention. FIG. 8 shows the obtained values with the
conventional method. FIG. 9 shows the obtained values with the
conventional method using a gas burner for heating.
[0094] In FIGS. 7-9, the values "A" and "B" indicate the outer
diameters measured at a straight tube portion of the curved lamp in
two different directions perpendicular to the tube axis.
[0095] The values "C" and "D" indicate the largest and smallest
outer diameters of the glass tube obtained by cutting it at the
center of the length of the curved portion in a direction
perpendicular to the tube axis.
[0096] The value "G" indicates the glass tube thickness (minimum)
at the outer side of the curved portion (corresponding to 131 and
131' of FIG. 5). The value "H" indicates the glass tube thickness
(minimum) at the inner side of the curved portion (corresponding to
132 and 132' of FIG. 5).
[0097] The value "E" indicates the glass tube thickness at the
outer side of the planned curved portion before it is curved. The
value "F" indicates the glass tube thickness at the inner side of
the planned curved portion before it is curved.
[0098] From the average values of the inner and outer shrinkage
(H/F and G/E), which are provided in the "AVE" row in each of FIGS.
7-9, it is understood that the curved lamp manufactured by the
method of the present invention has larger values of the inner and
outer shrinkage than the curved lamp manufactured by the
conventional method. That is to say, the curved lamp manufactured
by the method of the present invention is thicker at the curved
portions than the curved lamp manufactured by the conventional
method. The curved lamp manufactured by the method of the present
invention, whose data is shown in FIG. 7, is thicker and as much
stronger than the curved lamp manufactured by the conventional
method of FIGS. 8 and 9. The method of the present invention
therefore has high manufacturing efficiency. As shown in FIG. 8,
the samples of the conventional method include many lamps that may
be deformed or broken easily due to insufficient strength.
Accordingly, the conventional method has low manufacturing
efficiency. Also, in terms the flatness (D/C), there is hardly a
difference between data of FIGS. 7 and 8. However, it is understood
by comparing the values of flatness (D/C) of FIGS. 7 and 8 with
those of FIG. 9 that heating a glass tube by a gas burner
deteriorates the glass tube in flatness.
[0099] It is preferable to use glass tubes with the outer diameter
ranging from 2.4 mm to 5.0 mm inclusive, and thickness ranging from
0.3 mm to 0.5 mm inclusive, for achieving the improved strength of
the curved portions, improvement of the light-emitting efficiency
and the like.
[0100] Back to FIG. 5 in regards with the operation in the drive
step, after the holding units 60 and 70 are each rotated by 90
degrees, the rotation is stopped, and the supply of power to the
heaters 64 and 74 is stopped.
[0101] In this way, the planned curved portions 113a and 114a of
the glass tube 110a on the sides of the fixing unit 80 are curved
by rotating around the rotational axes 67 and 77 by 90 degrees with
a predetermined bending radius, and the curved lamp 100 is
manufactured. It should be noted here that in this example, a
stepping motor is used as the motor of the rotary drive apparatus,
and that the number of rotations (the number of steps) required for
curving the glass tube 110a by 90 degrees is determined beforehand
based on the experiment results or the like, and the operation of
the rotary drive apparatus is set to stop when the motor has
rotated as many times as the predetermined number of steps.
[0102] As described above, according to the manufacturing method of
the present embodiment, the glass tube 110a of the straight lamp
100a being in the horizontal direction is fixed at its substantial
center by the fixed chuck (the first chuck), one end portion of the
glass tube on one side of the first chuck is held by the driven
chuck 63 (the second chuck) in a manner that the driven chuck 63
can slide along the tube axis (length) of the glass tube 110a, the
other end portion of the glass tube on the other side of the first
chuck is held by the driven chuck 73 (the third chuck) in a manner
that the driven chuck 73 can slide along the tube axis, the driven
chucks 63 and 73 are moved upward relative to the glass tube along
the vertical plane including the tube axis, and the planned curved
portions 113a and 114a are curved while they are softened by heat
and compressed by the weight of the two end portions of the glass
tube 110a positioned above. This enables the amount of extension of
the curved portions to be suppressed, and makes the outer sides of
the curved portions thicker than the conventional method in which
the glass tube is curved along a horizontal plane. The glass tube
curved by the method of the present embodiment has higher strength
than the glass tube curved by the conventional method. This enables
even a glass tube, which has a small diameter and was sealed with
its inside being under reduced pressure, to be partially curved by
heat. The method of the present embodiment therefore provides an
advantageous effect of manufacturing the curved lamps with high
efficiency.
[0103] Also, by adopting a rotation mechanism that enables the
driven chucks 63 and 73 to simultaneously rotate around
predetermined positions, the method of the present embodiment can,
in the curving process, speedily curve the glass tube 110a into the
character of "U" with a predetermined curvature radius and by a
predetermined angle and without varying.
[0104] Furthermore, the curving apparatus 50 provides the following
advantageous effect. As shown in FIG. 3, the driven chucks 63 and
73 of the curving apparatus 50 have rollers that make pairs (a pair
of 635 and 637, a pair of 636 and 638 and the like) sandwiching the
glass tube 110a, and they move upward (in the Z direction) as they
are in this state. Accordingly, as shown in FIG. 5, even after two
straight tube portions 1021 and 1031 stand erect by the curving,
the rollers in each pair are arranged along the Y direction (a
direction perpendicular to a plane of FIG. 5, namely, a direction
being substantially in parallel with a plane perpendicular to the
tube axis of a portion of the glass tube 110a held by the fixed
chuck, the direction) sandwiching the glass tube 110a and facing
each other. This arrangement prevents a conventional problem that
if, for example, the rollers in each pair are arranged along the Z
direction sandwiching the glass tube 110a and facing each other
(that is to say, in the state after the driven chucks 63 and 73 are
rotated around the tube axis by 90 degrees in FIG. 5), one of the
rollers may be inserted between the two straight tube portions 1021
and 1031 after the curving, and distance W between the two straight
tube portions 1021 and 1031 cannot be reduced due to the presence
of the roller. In contrast, according to the method of the present
embodiment, it is possible to manufacture a curved lamp in the
shape of character "U" with reduced distance W, which is also an
advantageous effect of the present invention.
[0105] In the present embodiment, a sheath heater is used to heat
the glass tube 110a. This provides advantageous effects that the
variation of the position of the curved portion generated over time
is reduced compared with the case where the Kanthal or nichrome
wire is used, and that the cost for the replacement of the heaters
to prevent the variation is suppressed. Also, since the turns of
the coil using the sheath wire can be made to be in close contact
with each other, it is possible to shorten the coil width, which
makes it possible to heat a local portion of the glass tube 110a
with a reduced length, at the same time achieving a reduced bending
radius. Furthermore, the shortened coil width makes it possible to
reduce the length of a linkage portion 1041 located at the center
of the lamp curved into the character U, fixed by the fixed chuck,
and sandwiched by the two heaters (see FIG. 5). This indicates that
a distance W between the two straight tube portions of the curved
lamp can be reduced, which makes it possible, for example in the
case of a direct-below-type backlight unit, to increase the number
of lamps arranged per unit area.
(3-3) Removing Process
[0106] In the removing process, the curved lamp 100 is removed from
the curving apparatus 50 as will be described later, and hung on a
horizontal pole 109 as shown in FIG. 10. This process is performed
using a removing apparatus that will be described later. The
removing process includes: (a) removing chuck arrangement step of
arranging a chuck mechanism of the removing apparatus; (b)
sandwich-holding step of sandwiching and holding end portions 105
and 106 that are on the side of the linkage portion 1041 among
portions of the straight tube portions 1021 and 1031, using the
chuck mechanism, and moving the chuck mechanism downward; (c)
inverting step of rotating the chuck mechanism by 180 degrees to
invert the curved lamp 100 upside down at the lowered position; and
(d) hanging step of hanging the curved lamp 100 on the horizontal
pole 109.
[0107] The following describes the removing apparatus first, and
then the removing process.
(3-3-1) Removing Apparatus
[0108] FIG. 11 is a perspective view showing an outline of the
removing apparatus.
[0109] As shown in FIG. 11, the removing apparatus includes: a
chuck mechanism (corresponding to the removing chuck) 300 for
sandwiching and holding the curved lamp 100; a rotating/holding
mechanism 400 for holding the chuck mechanism 300 and rotating
while holding it; and a moving/holding mechanism 500 for holding
the rotating/holding mechanism 400 and moving in a vertical
direction while holding it.
[0110] In FIG. 11, the curved lamp 100 is sandwiched and held by
the chuck mechanism 300, the chuck mechanism 300 is rotated by the
rotating/holding mechanism 400 to invert the curved lamp 100 upside
down, and the chuck mechanism 300 is moved downward by the
moving/holding mechanism 500 to move the curved lamp 100
downward.
[0111] FIG. 12 is a perspective view showing an outline of the
chuck mechanism. FIG. 13 is a view of the chuck mechanism viewed in
the X direction indicated in FIG. 12. FIG. 14 is a view of the
chuck mechanism viewed in the Y direction indicated in FIG. 12.
[0112] The chuck mechanism 300 is achieved by, for example, an air
chuck. Jaws 330 and 340 (corresponding to the first base and the
second base) are attached to the air chuck, and plate members 310
and 320 (corresponding to the first member and the second member)
are attached to the jaws 330 and 340, respectively.
[0113] The jaws 330 and 340 are arranged to face each other, and
can move away from and near to each other. When they come closer to
each other, they sandwich the curved lamp 100 by the plate members
310 and 320 attached thereto.
[0114] The air chuck includes a guide member 350 and a drive unit
360. The guide member 350 guide the jaws 330 and 340 so as to move
away from and near to each other in a direction (which is the C
direction in FIGS. 12 and 14. The direction is referred to as "far
near direction" or "sandwiching direction"). The drive unit 360
causes the jaws 330 and 340 to move away from and near to each
other in the far near direction along the guide member 350. The
drive unit 360 includes an air cylinder that uses a compressed air
to cause the jaws 330 and 340 to move away from and near to each
other in the far near direction.
[0115] It should be noted here that in this example, the chuck
mechanism 300 is achieved by an air chuck that uses a compressed
air. However, not limited to this, the chuck mechanism 300 may use
a magnet chuck. That is to say, any drive mechanism or method may
be used in so far it can move a pair of jaws away from and near to
each other.
[0116] The plate members 310 and 320 are each in the shape of, for
example, character U when viewed from the far near direction, as
shown in FIG. 13, so that they can simultaneously hold both of the
end portions 105 and 106 (also referred to as "sandwiched
portions") that are on the side of the linkage portion 1041 among
portions of the straight tube portions 1021 and 1031.
[0117] The upper-end portions of the plate members 310 and 320
(that is to say, two pairs of upper-end portions of two character
Us facing each other) extend toward each other. The extended
upper-end portions substantially simultaneously come into contact
with the end portions 105 and 106 of the curved lamp 100.
[0118] The extended upper-end portions of the plate member 310 are
identified as contact portions 311 and 312, and the surfaces of the
contact portions 311 and 312 are respectively identified as contact
surfaces 311a and 312a. Similarly, the extended upper-end portions
of the plate member 320 are identified as contact portions 321 and
322, and the surfaces of the contact portions 321 and 322 are
respectively identified as contact surfaces 321a and 322a.
[0119] The contact portions 311, 312, 321, and 322 are extended as
described above so that when the plate members 310 and 320 sandwich
the end portions 105 and 106 of the curved lamp 100, the contact
surfaces 311a, 312a, 321a, and 322a do not come in contact with the
curved portions 113 and 114 of the curved lamp 100, as shown in
FIGS. 13 and 14. This is because the manufactured curved lamps 100
may be varied in terms of outer diameter since they are
manufactured by curving the straight lamps 100a. That is to say,
the plate members 310 and 320 have recesses under the contact
portions 311, 312, 321, and 322 so that when the contact portions
are in contact with the curved lamp 100, the plate members 310 and
320 are not in contact with the curved portions 113 and 114 of the
curved lamp 100.
[0120] Of the plate members 310 and 320 making a pair, the plate
member 320 is made able to incline so that its main surface can
change the direction. More specifically, the plate member 320 is
held by a pin 345 provided in the jaw 340 so that the plate member
320 can rotate around an axis of the pin 345. On the other hand,
the plate member 310 is fixed to the jaw 330 by screws 331 and 332
(see FIG. 16).
[0121] This arrangement of making the plate member 320 able to
incline makes it possible to hold the curved lamp in a stable
manner. For example, in the case of a chuck 900 shown in FIG. 17,
plate members 910 and 920 come close to each other in the G
direction and sandwich a straight tube portion of a curved lamp
that extends in a right angle to the plane of FIG. 17. With such a
construction, there is no problem when the two straight tube
portions of the curved lamp have the same outer diameter. However,
in the actual manufacturing process, there may be a case where the
two straight tube portions have different outer diameters, as in
straight tube portions 951 and 952 whose outer diameters are
indicated by dotted lines in FIG. 17. In such a case, a gap with a
distance S between the plate member 920 and the straight tube
portion 952 is created. When this happens, the curved lamp is held
by the chuck in an unstable manner. Therefore, when it is removed
from the curving apparatus, the curved lamp may collide with the
curving apparatus and may be broken. The above-described
arrangement of the present embodiment, in which the plate member
320 can be inclined, prevents the curved lamp from being held
unstably and broken.
[0122] Back to FIGS. 12-14, the pin 345 is provided substantially
in parallel with the straight tube portions 1021 and 1031. The pin
345 is positioned in the middle of the contact portions 321 and
322, and is closer to the outside of the chuck mechanism 300 than
the contact surfaces 321a and 322a of the plate member 320 in the X
direction. With such a construction, the pin 345 does not come into
contact with the curved lamp 100 when the lamp is sandwiched by the
plate members.
[0123] It should be noted here that not limited to the
above-mentioned position, the pin 345 may be provided at another
position in so far as an extension of the pin passes through a
space between the contact portions 321 and 322 of the plate member
320 when the curved lamp 100 in the sandwiched state is viewed from
the plate member 320. This is because with such an arrangement, the
plate member 320 can be inclined in accordance with a difference in
outer diameter between the straight tube portions 1021 and
1031.
[0124] In this example of the present embodiment, a length H (also
referred to as a height H) of the contact portions 311, 312, 321,
and 322, which extends in a direction in which the straight tube
portions 1021 and 1031 of the curved lamp 100 extend (namely the
height H is also a height of the contact surfaces), is set to
approximately five times the outer diameter D1 of the straight tube
portions 1021 and 1031 (see FIG. 14). More specifically, the outer
diameter D1 of the straight tube portions 1021 and 1031 is
approximately 3 mm, and the height H of the contact surfaces is
approximately 15 mm. It should be noted here that if the height H
is at least approximately three times outer diameter D1 of the
straight tube portions 1021 and 1031, the curved lamp 100 is held
stably.
[0125] The guide member 350 has, as shown in FIGS. 12 and 13, a
groove extending in the far near direction. The jaws 330 and 340
are fixed to an inner fitting member 355 by screws 333 and 334,
respectively.
[0126] As shown in FIG. 11, the rotating/holding mechanism 400 is
provided with a rotation drive apparatus (motor) 420 for rotating
the chuck mechanism 300. The chuck mechanism 300 is attached to a
rotational axis 421 of the rotation drive apparatus 420 via an
L-shaped member 430 which is in the shape of character "L". The
L-shaped member 430 is attached, at one side 431 thereof, to the
chuck mechanism 300, and at the other side 432, to the rotational
axis 421. With this construction, the chuck mechanism 300 can
rotate in the B direction.
[0127] The rotation drive apparatus 420 is attached to, for
example, one side 411 of an L-shaped member 410. The other side 412
of the L-shaped member 410 is attached to the moving/holding
mechanism 500.
[0128] As shown in FIG. 11, the moving/holding mechanism 500
includes: a guide member 510 that extends in a vertical direction;
a movable member 530 that is provided inside the guide member 510
and can move in the vertical direction (the A direction in FIG.
11); a threaded axis 520 that is an axis with threads for
supporting and moving the movable member 530; and a drive unit (not
illustrated) for rotating the threaded axis 520.
[0129] The guide member 510 is rectangular in a transverse
sectional view. The guide member 510 has a rectangular opening 512
extending in the vertical direction, in one side thereof. The
movable member 530 is fixed to the side 412 of the L-shaped member
410 via the opening 512.
(3-3-2) Removing Process
[0130] FIGS. 15A, 15B, and 15C illustrate the removing process.
[0131] Now, the removing process will be briefly explained with
reference to FIGS. 15A-15C.
[0132] After the curved portions 113 and 114 of the curved lamp
100, which has been curved as shown in FIG. 5, are cooled, the end
portions of the curved lamp 100 are held by a chuck (not
illustrated) that is different from the above-described one, and
are removed from the fixed chuck of the fixing unit 80. The chuck
is then moved downward vertically by a predetermined distance. This
causes the curved lamp 100 to move downward by the same distance.
The chuck mechanism 300 is then moved so that the end portion 105
of the curved lamp 100 is inserted into a space between the contact
surfaces 311a and 321a of the plate members 310 and 320, and the
end portion 106 of the curved lamp 100 is inserted into a space
between the contact surfaces 312a and 322a of the plate members 310
and 320 (the removing chuck arrangement step).
[0133] The curved lamp 100 is then sandwiched and held by the chuck
mechanism 300 of the removing apparatus 200. While they are in this
state, the chuck mechanism 300 is moved to a predetermined position
in a predetermined direction, downward in this example (the
sandwich-holding step). It should be noted here that the
predetermined position mentioned above is a position where the
curved lamp 100 does not come into contact with the curving
apparatus when the chuck mechanism is rotated together with the
curved lamp 100.
[0134] FIG. 16 shows the chuck mechanism viewed in the Z direction
indicated in FIG. 12.
[0135] As shown in FIG. 16, the plate member 320 can rotate in the
D direction around the axis of the pin 345, which is substantially
in parallel with a direction in which the straight tube portions
1021 and 1031 of the curved lamp 100 extend (the phantom lines in
FIG. 16 indicate positions of the plate member 320 after
rotations).
[0136] With such an arrangement, even if the straight tube portions
1021 and 1031 (the end portions 105 and 106) of the curved lamp 100
to be held by the chuck mechanism 300 are different from each other
in outer diameter, the plate member 320 is inclined until it firmly
comes into contact with the straight tube portions 1021 and 1031.
This enables the contact surfaces 321a and 322a of the plate member
320 to firmly come into contact with the end portions 105 and 106
of the curved lamp 100, thus causing the curved lamp 100 to be held
stably.
[0137] The above-described construction prevents the curved lamp
100 from being inclined when it is removed from the curving
apparatus 50, preventing the curved lamp 100 from being damaged by,
for example, coming into contact with the heater 64 or 74 or the
like.
[0138] The chuck mechanism is then rotated by the rotating/holding
mechanism 400 by 180 degrees to invert the curved lamp 100 upside
down (the inverting step). The state after this rotation is shown
in FIG. 15B. When it is inverted upside down like this, the curved
lamp 100 does not fall off the chuck mechanism 300 since it is held
by the chuck mechanism 300 firmly.
[0139] The chuck mechanism 300 is moved downward by the
moving/holding mechanism 500 so that the curved lamp 100 is moved
down to a predetermined position. The state after this descent is
shown in FIG. 15C. The curved lamp 100 is then removed from the
chuck mechanism 300 and is hung on the horizontal pole 109 (the
hanging step). It should be noted here that when such a glass tube
110a that has substantially the same outer diameter at any position
thereof can be used, the chuck mechanism shown in FIG. 17, for
example, may be used.
4. Modifications
[0140] Up to now, the present invention has been described based an
embodiment thereof. However, not limited to this, the present
invention may be modified in various ways, for example, as
follows.
(4-1) Curving Process
[0141] (4-1-1) In the curving apparatus 50 of the above-described
embodiment, for example, the driven chuck 63 and the heater 64 are
held by the plate-like member 61 and are rotated together around
the rotational axis 67, and the driven chuck 73 and the heater 74
are held by the plate-like member 71 and are rotated together
around the rotational axis 77. However, not limited to this
construction, any construction may be adopted in so far as the
heating point of the glass tube changes according to the operation
of curving the glass tube. For example, the driven chucks and the
heaters may move separately. (4-1-2) In the above-described
embodiment, rollers are used as the driven chucks 63 and 73. Not
limited to this, any holding members may be used in so far as they
hold the glass tube 110a in a manner that they can move in the tube
axis direction, that is to say, in a manner that they can slide
relative to the glass tube 110a in the tube axis direction. For
example, the rollers may be replaced with tube-like members that
can hold the glass tube 110a in a manner that they can slide
relative to the glass tube 110a with the glass tube 110a passed
through them. Also, the rollers may be replaced with a holding
member that, having a groove shaped into character U or V in the
cross sectional view, supports from underneath the glass tube 110a
fitted in the groove.
[0142] Also, in the above-described embodiment, a fixed chuck is
used to hold the glass tube 110a substantially at its center.
However, any member may used in stead in so far as it can hold a
predetermined portion of a glass tube.
(4-1-3) In the above-described embodiment, heaters in the shape of
coils are used. However, not limited to this, a heater 150 shown in
FIG. 18, for example, may be used. The heater 150 is formed by
bending a heater wire into a shape of a cylinder whose side has an
opening 151, through which the planned curved portion of the glass
tube is inserted into the heater 150, where the heater 150 is in
the shape of character C when viewed from top of the cylinder. With
this construction, it is possible to insert the planned curved
portion directly into the heater through the opening 151, without
letting the long straight glass tube pass through the heater until
the planned curved portion is positioned at the heater. For
example, if the holding member introduced in (4-1-2) above that has
a groove in the shape of character U in the cross sectional view is
used as the driven chuck, the glass tube can be set in both the
driven chuck and the heater in the setting step only by moving the
glass tube downward. This makes the glass tube setting operation
easier.
[0143] Also, a heater 160 shown in FIG. 19 may be used. The heater
160 is formed by wrapping the heater 150 with a member 161 made of
a heat-resistant material such as ceramics. With this arrangement,
even if the heater 150 is deformed by heat, the deformation is
suppressed by the member 161, thus preventing the variation in the
position of the curved portion of the glass tube due to shifting of
the heating position caused by the deformation of the heater over
time. The shape of the heater of this modification is not limited
to the cylinder which is in the shape of character C when viewed
from top of the cylinder, but may be any shape in so far as the
heater has an opening. For example, the heater may be in the shape
of cylinder which is in the shape of character U or a concave when
viewed from top of the cylinder.
(4-1-4) In the above-described embodiment, the straight tube lamp
is formed into the shape of character U: that is to say, the two
curved portions are formed simultaneously. However, not limited to
this, the manufacturing method of the present invention can be
applied to the case where one curved portion is formed or to the
case where three curved portions are formed. A curved lamp with
only one curved portion, namely, an L-shaped curved lamp can be
manufactured by using either of the holding members 60 and 70.
(4-1-5) In the above-described embodiment, a straight tube lamp
that is approximately 3 mm in outer diameter is curved. However,
values of the measurement such as the outer diameter, inner
diameter, length, bending radius r, or distance W of the glass tube
are not limited to the above-described ones. The present invention
is effective in curving such narrow glass tubes that are difficult
for conventional technologies to curve. (4-1-6) In the
above-described embodiment, a straight tube lamp is curved by 90
degrees. However, the curvature angle is not limited to 90 degrees.
It is possible to curve a straight tube lamp by predetermined
degrees of angle such as 30 degrees or 150 degrees that conform to
the format of the backlight unit in which the manufactured lamp is
used, by adjusting the rotation angle of the holding members 60 and
70. It is preferable however to set the curvature angle to 30
degrees or more so as to enable a partial weight of the glass tube
to be applied to the softened portions to compress them.
[0144] Also, in the above-described embodiment, to curve the
straight tube lamp by 90 degrees, it is arranged that the driven
chucks 63 and 73 rotate around the rotational axes 67 and 77,
respectively. However, if the curvature angle is as small as 30
degrees, and if a holding member that is in the shape of character
U in the cross sectional view is used instead of the driven chucks
63 and 73, the glass tube may be curved by moving the holding
member itself upward linearly to a position corresponding the
curvature angle of 30 degrees.
(4-1-7) In the above-described embodiment, the curved lamp 100 is
manufactured by setting the straight-tube lamp 100a in the curving
apparatus 50 to extend in a horizontal direction, and rotating the
driven chucks 63 and 73 upward around the rotational axes 67 and 77
by 90 degrees along the vertical plane. However, based on the
technological concept of the present invention of moving part of
the glass tube 110a upward to enable the weight of the lifted part
to be applied to the softened portions so that the softened
portions are compressed and become thicker, the construction for
achieving the technological concept is not limited to the
above-described construction. For example, after the glass tube is
set in the setting step, the end portions of the glass tube may be
moved upward.
[0145] It should be noted here that the present invention may be
any glass tube curving method that moves part of the glass tube and
enables the weight of the moved part to be applied to the softened
portions to compress them. In this sense, the glass tube curving
method is not limited to the above-described method of setting the
glass tube 110a to extend in a horizontal direction, and moving the
driven chucks 63 and 73 upward.
[0146] For example, a straight glass tube may be curved into the
shape of character L by the following method. While it is made to
stand substantially vertically, the glass tube is held by a fixed
chuck at a predetermined position, and held by a driven chuck at a
position higher than the predetermined position. In this state, a
planned curved portion, which is positioned between the fixed chuck
and the driven chuck, is heated and at the same time the driven
chuck is rotated downward around a predetermined rotational axis
drawing an arc by 90 degrees along a vertical plane including the
tube axis. In this method, as is the case with the method of the
above-described embodiment, the driven chuck moves relative to the
glass tube, and in the process between the start and end of the
curving, the weight of the moving part of the glass tube is applied
to compress the softened portion.
(4-1-8) In the above-described embodiment, a cold-cathode
fluorescent lamp for a direct-below-type backlight unit is
described as one example. However, the present invention can be
applied to curved lamps in the shape of character L for an
edge-light-type backlight unit or the like. Also, not limited to
for use in backlight units or cold-cathode fluorescent lamps, the
present invention can be applied generally to discharge lamps such
as those having been curved spirally or into the shape of character
U, in so far as they are manufactured by curving straight tube
lamps that have been sealed with inside thereof being under reduced
pressure. The present invention can also be applied to a
low-pressure discharge lamp of a dielectrics barrier discharge type
in which the first and second external electrodes are arranged at
the rims of the ends of a glass bulb.
[0147] It should be noted here that optimum values for the heating
temperature of the heaters, the moving speed of the holding members
60 and 70 and the like can be predetermined from results of
experiments or the like in accordance with the diameter, material,
or inner pressure of the glass tube, the bending radius of the
curved portions or the like so that, for example, the curved
portions do not get crushed, and are not limited to the specific
values or value ranges provided in the above-described
embodiment.
(4-1-9) In the curving apparatus 50 of the above-described
embodiment, the driven chuck 63 and the heater 64 are held by the
plate-like member 61, and they rotate together around the
rotational axis 67. However, not limited to this, any mechanism may
be adopted in so far as it enables a planned curved portion of a
straight tube lamp to be curved with a predetermined bending
radius. For example, a straight tube lamp can be curved by a
general mechanism in which a predetermined portion of the glass
tube 110a is held by a first chuck in a manner that the first chuck
can move (or cannot move) in the tube axis direction (longitudinal
direction) of the glass tube, one end portion of the glass tube is
held by a second chuck in a manner that the second chuck cannot
move (or can move) in the longitudinal direction, and the second
chuck is moved in a predetermined direction or rotated around a
rotational axis so that the trajectory draws an arc. (4-1-10) In
the above-described embodiment, the coil of the heater has three
turns. However, it may have, for example, two turns in so far as it
can keep the heating temperature. To locally heat the glass tube,
it is preferable that the number of turns is small as possible.
However, depending on the value of the bending radius, the coil
having four turns may be used since according to the present
embodiment, the coil width is as much shorter as turns of the coil
can be made closer to each other than in the case where Kanthal
wire is used.
[0148] The sheath heater may be constructed in any manner in so far
as a heating wire, which generates heat when it receives electrical
current, is covered with a metal pipe via an insulating layer
(insulator). Optimum materials or values for the materials such as
the heating wire constituting the sheath heater, thickness of the
heating wire, number of heating wires, outer diameter of the pipe,
coil width, coil diameter, number of turns or the like can be
predetermined from results of experiments or the like in accordance
with the heater use time, temperature at which the glass tube is
heated, bending curvature or the like, and are not limited to the
materials or values provided in the above-described embodiment.
[0149] Also, from the viewpoint of preventing the variation in the
position of the curved portion of the glass tube due to shifting of
the heating position caused by the deformation of the coil over
time, the heater disclosed in the present embodiment is not limited
to such lamps that were sealed with the inside thereof being under
reduced pressure, but may be used to curve straight glass tubes
that have not been sealed.
(4-2) Removing Process
[0150] FIGS. 20 and 21 show modifications of the chuck mechanism of
the present embodiment.
(4-2-1) Object of Chuck Mechanism
[0151] In the above-described embodiment, the object sandwiched by
the chuck mechanism is a curved lamp in the shape of character U.
However, the shape of the object is not limited to character U.
[0152] For example, as shown in FIG. 20, the object (a lamp 396)
may be in the shape of character V. That is to say, the object may
be in any shape in so far as it includes a pair of bar-like
portions, which may extend in any directions. When the pair of
bar-like portions extend in parallel with each other, the object is
in the shape of character U. When the distance between the bar-like
portions in a pair is wider at the ends of the curved glass tube
than at the linkage portion, the object is in the shape of
character V. Also, the object in the shape of character U or V may
be inverted before it is sandwiched.
(4-2-2) Members
[0153] In the above-described embodiment, the plate members are in
the shape of character U when they are viewed from the X direction
indicated in FIG. 12. However, the shape of the plate members is
not limited to this. For example, the plate members may be in the
shape of a home plate as shown in FIG. 20, inverted triangle, or
rectangle. In this case, not like the contact surfaces 311a, 312a,
321a, and 322a that make two pairs corresponding to the U-shaped
plate members 310 and 320 (see FIG. 12), plate members 392 and 394
respectively have contact surfaces 393 and 395 having only one
continuous plane for coming into contact with the object. With such
a construction, if the position at which the object is held shifts
in the F direction (a direction including a line connecting the
bar-like portions sandwiched by the plate members), which is
observed when viewed from the X direction indicated in FIG. 20, the
object can be held firmly.
[0154] A pair of plate members in the shape of character U as in
the present embodiment, or character V may be used in the curved
lamp forming process so that the curved lamp is directly sandwiched
and held by the pair of plate members in the state where the
linkage portion of the curved lamp is fixed by a fixed chuck of the
curving apparatus.
[0155] In this case, however, the fixed chuck of the curving
apparatus needs to be inserted between the straight portions of the
plate members in the shape of character U or V.
[0156] Also, in the above-described embodiment, plate-like members
are used. However, not limited to this, the members may be, for
example, bar-like, or block-like (in the shape of rectangular
solid).
[0157] (4-2-3) Mechanism for Inclination
[0158] In the above-described embodiment, the plate member 320 is
held by the pin 345 provided in the jaw 340 so that the plate
member 320 can rotate around the axis of the pin 345. However, the
mechanism for inclining the plate member is not limited to the
above-stated one that causes the plate member rotate around the
axis of a pin.
[0159] FIG. 21 is a plan view of a chuck mechanism that inclines
the plate member differently from the one described in the present
embodiment.
[0160] As shown in FIG. 21, chuck mechanism 700 includes plate
members 710 and 720 facing each other, as is the case with the
present embodiment. Of the two plate members, the plate member 710
is fixed to a jaw 730 by screws, and the other plate member 720 is
attached to a jaw 735 via an attachment plate 722 such that the
plate member 720 can be inclined. The jaws 730 and 735, as is the
case with the present embodiment, can be moved away from and near
to each other in a direction by a drive unit having an air
cylinder.
[0161] The plate member 720 is attached to the attachment plate 722
by screws 723 and 724 (in the actuality three or more screws may be
used) such that the plate member 720 can move in the thickness
direction. The ends of the screws 723 and 724 pass through
through-holes 722a and 722b and are fixed by nuts 725 and 726 to
the attachment plate 722, respectively. This enables the tips of
the screws 723 and 724 to protrude from the attachment plate 722
when the plate member 720 is pushed in the E direction indicated in
FIG. 21.
[0162] Between the plate member 720 and the attachment plate 722,
provided is a biasing means that biases the plate member 720 toward
the plate member 710. More specifically, the biasing means is
composed of springs 727 and 728 that are attached to the screws 723
and 724 to surround them. With such an arrangement, even if the
straight tube portions 1021 and 1031 (the end portions 105 and 106)
of the curved lamp 100 are different from each other in outer
diameter, the plate member 720 is inclined until it firmly comes
into contact with the straight tube portions 1021 and 1031. This
enables the pair of plate members 710 and 720 to firmly hold the
curved lamp 100.
[0163] A buffer 721, which is made of, for example, silicon rubber,
is attached on the contact surface of the plate member 720. The
material of the buffer 721 is lower in elasticity than the material
of the plate member 720, and preferably is lower in elasticity than
a material (in this example, glass) of the object to be sandwiched
by the chuck mechanism. With this arrangement, it is possible to
soften a shock caused to the object by the plate member 720 when
the object is sandwiched. And therefore, when an object such as a
glass tube is sandwiched, the object is protected from damages.
[0164] It should be noted here that in the above-described
embodiment, a buffer made of silicon rubber or the like is not
attached on the contact surface of the plate member since the
curved lamp is sandwiched while it is still at a high temperature
after it has been heated and curved. However, a buffer made of a
material that resists heat at a temperature of, for example,
approximately the softening point of the glass tube may be attached
on the contact surface of the plate member in the above-described
embodiment.
[0165] It should be noted here that the heads of the screws 723 and
724 are embedded in the plate member 720 so that the heads do not
protrude from a surface on the other side of the plate member 720
facing the plate member 710. Also, in this example of the
modification, the plate member 710 is in the shape of character U,
as is the case with the above-described embodiment, and the plate
member 720 is in the shape of a rectangle that extends in a
direction including a line connecting the screws 723 and 724 (in
the horizontal direction in FIG. 21).
[0166] In this example of the modification, the plate member 720 is
held by the attachment plate 722 via the screws 723 and 724 such
that the plate member 720 can be inclined toward the plate member
710. However, instead of this, the plate member 720 may be held by
the attachment plate 722 via four screws such that the plate member
720 can be inclined toward the plate member 710. The plate member
720 of this case can be inclined with a more amount of direction
than the plate members 320 and 720 of the above-described
embodiment and the present modification.
[0167] When the plate member 710 is viewed from above, as shown in
FIG. 21, it is found that two pairs of protrusion 713 and
protrusion 714 are provided respectively at edges of the surfaces
of the two straight upper end portions of the plate member 710
facing the plate member 720. The protrusions 713 and 714 have a
function of preventing the sandwiched curved lamp 100 from shifting
in the horizontal direction in FIG. 21 (namely, in the F direction
in FIG. 20, or in a direction including a line connecting the
straight tube portions). A distance L2 between the two protrusions
714 of the plate member 710 and a distance L1 between the
protrusions 713 and 714 making a pair are determined according to a
distance between the two bar-like portions of the object to be
sandwiched.
[0168] A shock absorber 750 is provided between the jaws 730 and
735 to prevent excessive load from being applied to the two
straight tube portions 1021 and 1031 when the curved lamp 100 is
sandwiched. This prevents the curved lamp 100 from being broken
even if there is a fear that the straight tube portions 1021 and
1031 may be broken due to its thinness. The shock absorber may be
replaced with another mechanism such as a cylinder with a toggle
mechanism.
(4-2-4) Bases (the Jaws in the Embodiment)
[0169] In the above-described embodiment, the jaws making a pair
can move in the far near direction. However, not limited to this,
another construction may be adopted. For example, one of the jaws
making a pair may be fixed, and the other jaw may be made able to
move away from and near to the jaw. That is to say, any
construction may be adopted in so far as a pair of jaws move
relatively to each other, moving away from and near to each
other.
[0170] Also, in the above-described embodiment, the jaws (bases)
making a pair can move linearly away from and near to each other.
However, not limited to this, bases making a pair may move away
from and near to each other on a circle so that the first and
second members can sandwich the object.
[0171] Also, in the above-described embodiment, one member that
cannot be inclined, among the two members making a pair, is fixed
to a base by screws. However, the two members may be formed as one
unit. That is to say, the chuck may be constructed in any manner in
so far as at least one of the two members making a pair is made
able to be inclined. Also, in the above-described embodiment, only
one among the two members making a pair is made able to be
inclined. However, an advantageous effect can be obtained if both
members are attached to bases in a manner that they both can be
inclined.
[0172] Although the present invention has been fully described by
way of examples with reference to the accompanying drawings, it is
to be noted that various changes and modifications will be apparent
to those skilled in the art. Therefore, unless such changes and
modifications depart from the scope of the present invention, they
should be construed as being included therein.
* * * * *