CA1312906C - Liquid cooled cathode ray tube apparatus for video projection system - Google Patents
Liquid cooled cathode ray tube apparatus for video projection systemInfo
- Publication number
- CA1312906C CA1312906C CA000599942A CA599942A CA1312906C CA 1312906 C CA1312906 C CA 1312906C CA 000599942 A CA000599942 A CA 000599942A CA 599942 A CA599942 A CA 599942A CA 1312906 C CA1312906 C CA 1312906C
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- Prior art keywords
- ray tube
- cathode ray
- projection lens
- radiator
- video
- Prior art date
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- Common Detailed Techniques For Electron Tubes Or Discharge Tubes (AREA)
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Abstract
ABSTRACT
A liquid cooled cathode ray tube apparatus for a video projection system comprises a cathode ray tube for making a video image; a plastic projection lens disposed in front of the cathode ray tube for projecting the video image to a predetermined position; a radiator disposed between the cathode ray tube and the projection lens; and a transparent refrigerant fluid consisting essentially of a mixture of ethylene glycol, diethylene glycol and glycerine and contained in a liquid-tight space defined by the cathode ray tube, the projection lens and the radiator. Focussing and resolution performance of the projection lens are maintained without being affected by temperature change or temperature drift.
A liquid cooled cathode ray tube apparatus for a video projection system comprises a cathode ray tube for making a video image; a plastic projection lens disposed in front of the cathode ray tube for projecting the video image to a predetermined position; a radiator disposed between the cathode ray tube and the projection lens; and a transparent refrigerant fluid consisting essentially of a mixture of ethylene glycol, diethylene glycol and glycerine and contained in a liquid-tight space defined by the cathode ray tube, the projection lens and the radiator. Focussing and resolution performance of the projection lens are maintained without being affected by temperature change or temperature drift.
Description
~ 1312906 The present invention relates to a cooling system for a video projector.
In the accompanying drawings:
Fig. 1 is an exploded view of a typical video projector havin~ a cooling system.
Fig. 2 is a sectional assembled view of the video projector shown in ~ig. 1.
Fig. 3 is a graphical representation of vapor pressure versus temperature characteristics of various refrigerant fluids.
Fig. 4 is a graphical representation of displacement between a projection lens and a cathode ray tube versus pressure characteristics of the refrigerant in the space enclosed by the cathode ray tube, the projection lens and the radiator in the projector of Figs. 1 and 2.
Fig. S is a graphical representation of loss versus tir.le characteristics of the refrigerant at 80C.
Fig. 6 is an exploded view of a preferred embodiment of a video projector in accordance with the present invention.
Fig. 7 is a sectional assembled view of the video projector shown in Fig. 6.
A conventional video projector cooling system is first described with reference to Figs. 1, 2,~3, 4 and 5.
A typical video projecting apparatus having a cooling system is shown in Figs. 1 and 2. Fig. 1 is an exploded view showing the construction of a monochrome video projecting apparatus for projecting a video image of red, blue or green color images. Fig. 2 is a sectional assembled drawing of the monochrome video pro;ecting~apparatus.
As shown in Figs. 1 and 2, the mono~chrome video projecting apparatus comprises a cathode ray tube 1 (hereinafter abbreviated to CRT), a spacer 2, a radiator 10 made of metal for radiating heat from the CRT 1 and a projection lens 11 for projecting video images from a front;phosphor screen la of the CRT 1. The lens 11 is watertightly fixed to a front face lOa of the radiator 10 by silicone adhesive 8. Inner periphery lOb of the radiator 10 is watertightly bonded around outer periphery lb of the CRT l by the silicone adhesive 8. The spacer 2 is ~sandwiched between the CRT 1 and the radiator 10 for positioning the radiator 10 in a desired~position against the front :: :
'' `' , ' ' ,' ' ' , ~ :
~ 1 3 1 2qO6 phosphor screen la of the cRT 1. The CRT 1, the radiator 10 and the projection lens 11 define a watertight space 9. The watertight space 9 is filled with refrigerant 12 from a tapped hole 15 which is formed on a side wall of the radiator 10. The tapped hole 15 is sealed by an 0-ring 13 and a screw 14 is screwed therein for sealing the refrigerant 12 in the waterti~ht spsce 9 and preventing leakage of same through the tapped hole 15.
When working potentials and a video signal are applied to the CRT 1, a video image is formed on the front phosphor screen la of the CRT 1. Heat is generated on the front phosphor screen la of the CRT 1 by the impinging of electron beams thereon.
If the video projection apparatus is not cooled, the temperature at the front phosphor screen la of the CRT 1 rises to about 120--150C, and heat from the screen transfers to the projection ~ens 11. As a result, the temperature of the projection lens 11 is raised to about 100~-140C.
The refrigerant 12, however, is contained in the watertight space 9 enclosed by the CRT 1, the radiator 10 and the projection lens 11. Most of the heat from the front phosphor screen la of the CRT 1 is absorbed by the refrigerant 12. Heated refrigerant 12 convects to the top part of the watertight space 3 and radiates heat from the upper radiating fins lOc of the radiator 10, and the refrigerant 12 is cooled. The cooled refrigerant 12 convects to the bottom part of the watertight space 9, and accordingly, the overall temperature of the refrigerant 12 is kept in a range of 70--80C by convection.
As the refrigerant 12, a mixed fluid of ethylene glycol and water, for example, as shown in Japanese Published Unexamined Patent Application Sho 62-35428, is used. The mixing ratio of ethylene glycol and water is e.g.
100:20 by wt.
The above-mentioned conventional video projector cooling system, however, has a number of disadvantages.
Firstly, the~vapor pressure of ethylene glycol is relatively low but that of water is high, as shown in Fig. 3- Therefore, when the temperature in the watertight space 9 is about 80C, the vapor pressure of the mixed fluid of ethylene glycol and water refrigerant 12 becomes very high. Because o~` such vapor pressure, the adhesive 8, which is used for bonding the CRT l to the radiator lO and the radiator lO to the projection lens 11, expands.
PAT 13315~
In the accompanying drawings:
Fig. 1 is an exploded view of a typical video projector havin~ a cooling system.
Fig. 2 is a sectional assembled view of the video projector shown in ~ig. 1.
Fig. 3 is a graphical representation of vapor pressure versus temperature characteristics of various refrigerant fluids.
Fig. 4 is a graphical representation of displacement between a projection lens and a cathode ray tube versus pressure characteristics of the refrigerant in the space enclosed by the cathode ray tube, the projection lens and the radiator in the projector of Figs. 1 and 2.
Fig. S is a graphical representation of loss versus tir.le characteristics of the refrigerant at 80C.
Fig. 6 is an exploded view of a preferred embodiment of a video projector in accordance with the present invention.
Fig. 7 is a sectional assembled view of the video projector shown in Fig. 6.
A conventional video projector cooling system is first described with reference to Figs. 1, 2,~3, 4 and 5.
A typical video projecting apparatus having a cooling system is shown in Figs. 1 and 2. Fig. 1 is an exploded view showing the construction of a monochrome video projecting apparatus for projecting a video image of red, blue or green color images. Fig. 2 is a sectional assembled drawing of the monochrome video pro;ecting~apparatus.
As shown in Figs. 1 and 2, the mono~chrome video projecting apparatus comprises a cathode ray tube 1 (hereinafter abbreviated to CRT), a spacer 2, a radiator 10 made of metal for radiating heat from the CRT 1 and a projection lens 11 for projecting video images from a front;phosphor screen la of the CRT 1. The lens 11 is watertightly fixed to a front face lOa of the radiator 10 by silicone adhesive 8. Inner periphery lOb of the radiator 10 is watertightly bonded around outer periphery lb of the CRT l by the silicone adhesive 8. The spacer 2 is ~sandwiched between the CRT 1 and the radiator 10 for positioning the radiator 10 in a desired~position against the front :: :
'' `' , ' ' ,' ' ' , ~ :
~ 1 3 1 2qO6 phosphor screen la of the cRT 1. The CRT 1, the radiator 10 and the projection lens 11 define a watertight space 9. The watertight space 9 is filled with refrigerant 12 from a tapped hole 15 which is formed on a side wall of the radiator 10. The tapped hole 15 is sealed by an 0-ring 13 and a screw 14 is screwed therein for sealing the refrigerant 12 in the waterti~ht spsce 9 and preventing leakage of same through the tapped hole 15.
When working potentials and a video signal are applied to the CRT 1, a video image is formed on the front phosphor screen la of the CRT 1. Heat is generated on the front phosphor screen la of the CRT 1 by the impinging of electron beams thereon.
If the video projection apparatus is not cooled, the temperature at the front phosphor screen la of the CRT 1 rises to about 120--150C, and heat from the screen transfers to the projection ~ens 11. As a result, the temperature of the projection lens 11 is raised to about 100~-140C.
The refrigerant 12, however, is contained in the watertight space 9 enclosed by the CRT 1, the radiator 10 and the projection lens 11. Most of the heat from the front phosphor screen la of the CRT 1 is absorbed by the refrigerant 12. Heated refrigerant 12 convects to the top part of the watertight space 3 and radiates heat from the upper radiating fins lOc of the radiator 10, and the refrigerant 12 is cooled. The cooled refrigerant 12 convects to the bottom part of the watertight space 9, and accordingly, the overall temperature of the refrigerant 12 is kept in a range of 70--80C by convection.
As the refrigerant 12, a mixed fluid of ethylene glycol and water, for example, as shown in Japanese Published Unexamined Patent Application Sho 62-35428, is used. The mixing ratio of ethylene glycol and water is e.g.
100:20 by wt.
The above-mentioned conventional video projector cooling system, however, has a number of disadvantages.
Firstly, the~vapor pressure of ethylene glycol is relatively low but that of water is high, as shown in Fig. 3- Therefore, when the temperature in the watertight space 9 is about 80C, the vapor pressure of the mixed fluid of ethylene glycol and water refrigerant 12 becomes very high. Because o~` such vapor pressure, the adhesive 8, which is used for bonding the CRT l to the radiator lO and the radiator lO to the projection lens 11, expands.
PAT 13315~
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13~2906 Accordingly, the distance between the front phosphor screen la of the CRT 1 and the projection lens 11 significantly changes in accordance with the temperature changes or temperature drift, as shown in Fig. 4 and, thereby, the projection performance of the lens 11 (e.g. focussing or resolution) is 5 adversely affected.
Secondly, if a plastic lens is used as the projection lens 11, water contained in the refrigerant 13 at about 20 wt % is partly absorbed in the plastic lens, and water vapor permeates and evaporates through the projection lens 11. Therefore, the amount of the refrigerant 12 gradually decreases, as 10 shown in Fig. 5. When the level of the refrigerant 12 drops below a predetermined level, rays from the CRT 1 are eclipsed, and the projection performance of the lens 11 (e.g. focussing or resolution) is again adversely affected.
The object of the present invention is to provide an improved cathode 15 ray tube apparatus for a video projection system wherein focussing and resolution performance of the projector lens are maintained without being affected by temperature change or temperature drift.
A liquid cooled cathode ray tube apparatus for a video projection system, in accordance with the present invention, comprises:
a cathode ray tube for making a video image;
a plastic projection lens disposed in front of the cathode ray tube for projecting the video image to a predetermined position;
a radiator disposed between the cathode ray tube and the projection lens; and a transparent refrigerant fluid consisting essentially of a mixture of ethylene glycol, diethylene glycol and glycerine and watertightly filled in a space defined by the cathode ray tube, the projection lens and the radiator.
As mentioned above, the refrigerant does not contain water at all.
Therefore, the vapor pressure of the refrigerant in the space enclosed by the 30 cathode ray tube, the projection lens and the radiator is relatively low evenwhen the temperature of the refrigerant is about 80C as shown in Fig. 3.
Furthermore, as the refrigerant does not contain water, the refrigerant is hardly absorbed by the material (e.g. plastic) of the projection lens and loss of the refrigerant due to permeation of vapor is very little. As a result, 35 the projection performance (e.g. focussing and/or resolution) is maintained ~, ."
,.
, ' : . ' . ' : , regardless of temperature dependency or secular change.
The invention w~ll now be described further by way of example only and with reference to Figs. 6 and 7 of the accompanying drawings.
Fig. 6 is an exploded view of a video projector according to one 5 embodiment of the invention and Fig. 7 is a sectional view of the assembled video pro;ector shown in Fig. 6. The video projector shown in Figs. 6 and 7 is in this case a monochrome video projector for projecting a video image in either blue, green or red. For a color video projector, three monochrome video projectors as shown in Figs. 6 and 7, respectively projecting a video 10 image of blue) green or red, are used. Hereinafter, one monochrome video projector is described.
In Figs. 6 and 7, the monochrome video pro~ector comprises a CRT 1 for forming video images on a front phosphor screen la which is a single color selected from red, green and blue; a radiator 20 made of metal and having 15 radiating fins ZOa, filling port 16 and diaphragm 5 inserted therein; a spacer 2 disposed between the CRT 1 and the radiator 20 for maintaining the front face of the CRT 1 and the rear face of the radiator 20 a predetermined distance apart; and a proJection lens 4 disposed on the front face of the radiator 20. A rubber gasket 7 has a diameter of about 0.1--0.2 mm, which is 20 wider than the gap A between the outer periphery lb of the CRT 1 and the inner periphery 20b of the radiator 20 as shown in Fig. 7. The rubber gasket 7 is compressed in the gap A and is watertightly bonded by filling the gap with an adhesive 8, such as silicone. At this time, the centers of the CRT 1 and the radiator 20 are aligned. The rear face of outer periphery B of the projection 25 lens 4 is watertightly bonded to front mounting face C of the radiator 20 by the adhesive 8. Thereby, a watertight space 9 is formed by the CRT 1, the radiator 20 and the projection lens 4.
After that, refrigerant 21 is introduced into the watertight space 9 through the injection port 16 until the level of t~e refrigerant reaches a 30 predetermined upper limit. When the required~refrigerant level is reached, the diaphragm 5 (made of fluoro rubber) is inserted into the f~illing port 16, and then the port 16 is covered by a filler cap 6 which is secured to the radiator 20 by screws 17.
When video signals are applied to the CRT 1, the front phosphor 35 screen 12 on the CRT 1 is heated by impingement thereon of electrons. Heat ~ ~ - 4 -.
: ' ; . . :
- from the CRT 1 is conducted to the refrigerant 21 and the refrigerant 21 expands. To accommodate the expanded volume of the refrigerant 21, the diaphragm 5 expands. Thereby, any pressure caused by the expansion of the refrigerant 21 does not adversely act on the CRT 1 and the projection lens 4.
Furthermore, the refrigerant 21 convects in the watertight space 9 and the heat of the refrigerant 21 is radiated and the refrigerant is cooled by the radiating fins 20a of the radiator 20. Therefore, the temperature of the refrigerant 20 is kept below a predetermined level and does not rise above that level.
Furthermore, even when the project~on lens 4 is heated and expanded by the temperature rise of the refrigerant 21, stress is not applied to the projection lens 4 because the adhesive 8 for bonding the radiator 20 and the projection lens 4 i9 an elastic material such as silicone. Accordingly, deformation or breakage of the pro~ection lens 4 is completely avolded.
In the above-men~ioned embodiment, a mixed fluid of ethylene glycol diethylene glycol and glycerine is used as the refrigerant 21. Preferably, the mixture contains 80--50 wt % of ethylene glycol, 40--10 wt % of diethylene glycol and 5--40 wt % of glycerine. The vapor pressure of the mixed fluid of ethylene glycol, diethylene glycol and glycerlne is lower than that of the 20 conventional mi~ed fluid of ethylene glycol and water, because the vapor pressure of diethylene glycol is lower than that of water at a temperature of about 80;C.
A comparison between the mixed fluid consisting of ethylene glycol, diethylene glycol and glycerine of the above-mentioned embodiment and the 25 conventional mixed fluid consisting of ethylene glycol and water, both under conditions that the refrigerant 21 is fully filled in the watertight space 9 and is heated to 80;C, is described below. In the case of the conventional mixed fluid having 80 wt % of ethylene glycol and 20 wt % of water, the vapor pressure of the mixture is very high at about 450 mmHg at 80-C. At that time, 30 the internal pressure of the watertight space 9, which is filled with the mixture was 0.2 Kg/cm2. Such an internal pressure causes expansion of the adhesive 8 for bonding the CRT 1 and the radiator 10 (in Fig. 2) or 20 (in Fig. 7) and for bonding the radiator 10 (in Fig. 2) or 20 (in Fig. 7) and the projection lens 4. ~The distance between the CRT 1 and the projection lens 4 35 is significantly changed as shown in Fig. 4, so that the projection ;
~, ~ ' , , ' .: '' :, ' - ., - ' performance (e.g. focussing and resolution) of the projectiorl lens 4 is adversely affected in the prior art.
On the other hand, in a ~luid mixture having 60 wt % of ethylene glycol, 30 wt % of diethylene glycol and 10 wt % of glycerine, in accordance 5 with the present invention, the vapor pressure of the fluid mixture becomes relatively low at about 50 mmHg. Therefore, the internal pressure of the watertight space 9, which is filled with the mixture of ethylene glycol, diethylene glycol and glycerine, was only 0.02 Kg/cm2. As a result of such low pressure, expansion of the adhesive 8 for bonding the CRT 1 and the 10 radiator 10 or 20 and for bonding the radiator 10 or 20 and the projection lens 4 is very small. The distance between the front face of the CRT 1 and the pro~ections lens 4 ~s changed very little - the displacement being about 0.03 mm as shown in Fig. 4. Accordingly, the projection performance of the pro~ection lens 4 is hardly affected by temperature dependency or temperature 15 drift.
Furthermore, loss of the refrigerant 21 in the watertight space 9 is measured at 80;C because the plastic of the pro~ection lens 4 and the silicone for the adhesive 8 are permeable and vapor from the refrigerant 21 permeates to the pro~ection lens 4 and the adhesive 8. The amount of conventional mixed 20 fluid of ethylene glycol and water which is as much as 9.8 g per 100 g after 4000 Hr as shown by the characteristic curve of loss versus time given in Fig. 5. On the contraryj loss of the fluid mixture consisting of ethylene glycol, diethylene glycol and glycerine in accordance with the present invention is as little as only about 1.2 g per lOO g after 4000 Hr.
As mentioned above, the present invention uses a fluid mixture of 80--50 wt % of ethylene glycol, 10--40 wt % of diethylene glycol and 5--20 wt % of glycerine as refrigerant. The vapor pressure of the mixed fluid is relatively low and the loss due to the permeation through the plastic lens 4 or silicone adhesive 8 is low. Therefore, the mixed fluid directly 30 comes into contact with the projection lens 4. As a result, the video pro~ector can be made compact and inexpensive without adverse influence on its optical performance by temperature dependency or temperature drift.
The 1uid mixture of the present invention further has the advantage that a desired index of refraction thereof can easily be reali~ed by us~ing the 35 feature that the indices of refraction of ethylene glycol (1.4316), diethylene ~ - 6 -. : : ., . :
, . : ,: ~ ~
: ~. . : - :
,, ~ .
: :, 1312~06 glycol (1.4472) and glycerine (1.4746) are different from each other.
When the mixed fluid is, for example, made of only ethylene glycol and glycerine, the inde~ of refraction thereof is in a range of 1.4395 to 1.4477. However, when the mixed fluid is made of ethylene glycoll diethylene 5 glycol and glycerine in accordance with the present invention, the index of refraction thereof is in a range of 1~4361 to 1.4517 as shown in following table 1.
10No. Fluid Mixture Mixing Ratio Index o Refraction 1 ethylene glycol 80 wt % 1.4395 glycerine 20 wt %
152 ethylene glycol 60 wt % 1.4497 glycerine 40 wt %
ethylene glycol 80 wt %
3 diethylene glycol 10 wt % 1.4361 glycerine 10 wt %
ethyIene glycol 50 wt %
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.
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13~2906 Accordingly, the distance between the front phosphor screen la of the CRT 1 and the projection lens 11 significantly changes in accordance with the temperature changes or temperature drift, as shown in Fig. 4 and, thereby, the projection performance of the lens 11 (e.g. focussing or resolution) is 5 adversely affected.
Secondly, if a plastic lens is used as the projection lens 11, water contained in the refrigerant 13 at about 20 wt % is partly absorbed in the plastic lens, and water vapor permeates and evaporates through the projection lens 11. Therefore, the amount of the refrigerant 12 gradually decreases, as 10 shown in Fig. 5. When the level of the refrigerant 12 drops below a predetermined level, rays from the CRT 1 are eclipsed, and the projection performance of the lens 11 (e.g. focussing or resolution) is again adversely affected.
The object of the present invention is to provide an improved cathode 15 ray tube apparatus for a video projection system wherein focussing and resolution performance of the projector lens are maintained without being affected by temperature change or temperature drift.
A liquid cooled cathode ray tube apparatus for a video projection system, in accordance with the present invention, comprises:
a cathode ray tube for making a video image;
a plastic projection lens disposed in front of the cathode ray tube for projecting the video image to a predetermined position;
a radiator disposed between the cathode ray tube and the projection lens; and a transparent refrigerant fluid consisting essentially of a mixture of ethylene glycol, diethylene glycol and glycerine and watertightly filled in a space defined by the cathode ray tube, the projection lens and the radiator.
As mentioned above, the refrigerant does not contain water at all.
Therefore, the vapor pressure of the refrigerant in the space enclosed by the 30 cathode ray tube, the projection lens and the radiator is relatively low evenwhen the temperature of the refrigerant is about 80C as shown in Fig. 3.
Furthermore, as the refrigerant does not contain water, the refrigerant is hardly absorbed by the material (e.g. plastic) of the projection lens and loss of the refrigerant due to permeation of vapor is very little. As a result, 35 the projection performance (e.g. focussing and/or resolution) is maintained ~, ."
,.
, ' : . ' . ' : , regardless of temperature dependency or secular change.
The invention w~ll now be described further by way of example only and with reference to Figs. 6 and 7 of the accompanying drawings.
Fig. 6 is an exploded view of a video projector according to one 5 embodiment of the invention and Fig. 7 is a sectional view of the assembled video pro;ector shown in Fig. 6. The video projector shown in Figs. 6 and 7 is in this case a monochrome video projector for projecting a video image in either blue, green or red. For a color video projector, three monochrome video projectors as shown in Figs. 6 and 7, respectively projecting a video 10 image of blue) green or red, are used. Hereinafter, one monochrome video projector is described.
In Figs. 6 and 7, the monochrome video pro~ector comprises a CRT 1 for forming video images on a front phosphor screen la which is a single color selected from red, green and blue; a radiator 20 made of metal and having 15 radiating fins ZOa, filling port 16 and diaphragm 5 inserted therein; a spacer 2 disposed between the CRT 1 and the radiator 20 for maintaining the front face of the CRT 1 and the rear face of the radiator 20 a predetermined distance apart; and a proJection lens 4 disposed on the front face of the radiator 20. A rubber gasket 7 has a diameter of about 0.1--0.2 mm, which is 20 wider than the gap A between the outer periphery lb of the CRT 1 and the inner periphery 20b of the radiator 20 as shown in Fig. 7. The rubber gasket 7 is compressed in the gap A and is watertightly bonded by filling the gap with an adhesive 8, such as silicone. At this time, the centers of the CRT 1 and the radiator 20 are aligned. The rear face of outer periphery B of the projection 25 lens 4 is watertightly bonded to front mounting face C of the radiator 20 by the adhesive 8. Thereby, a watertight space 9 is formed by the CRT 1, the radiator 20 and the projection lens 4.
After that, refrigerant 21 is introduced into the watertight space 9 through the injection port 16 until the level of t~e refrigerant reaches a 30 predetermined upper limit. When the required~refrigerant level is reached, the diaphragm 5 (made of fluoro rubber) is inserted into the f~illing port 16, and then the port 16 is covered by a filler cap 6 which is secured to the radiator 20 by screws 17.
When video signals are applied to the CRT 1, the front phosphor 35 screen 12 on the CRT 1 is heated by impingement thereon of electrons. Heat ~ ~ - 4 -.
: ' ; . . :
- from the CRT 1 is conducted to the refrigerant 21 and the refrigerant 21 expands. To accommodate the expanded volume of the refrigerant 21, the diaphragm 5 expands. Thereby, any pressure caused by the expansion of the refrigerant 21 does not adversely act on the CRT 1 and the projection lens 4.
Furthermore, the refrigerant 21 convects in the watertight space 9 and the heat of the refrigerant 21 is radiated and the refrigerant is cooled by the radiating fins 20a of the radiator 20. Therefore, the temperature of the refrigerant 20 is kept below a predetermined level and does not rise above that level.
Furthermore, even when the project~on lens 4 is heated and expanded by the temperature rise of the refrigerant 21, stress is not applied to the projection lens 4 because the adhesive 8 for bonding the radiator 20 and the projection lens 4 i9 an elastic material such as silicone. Accordingly, deformation or breakage of the pro~ection lens 4 is completely avolded.
In the above-men~ioned embodiment, a mixed fluid of ethylene glycol diethylene glycol and glycerine is used as the refrigerant 21. Preferably, the mixture contains 80--50 wt % of ethylene glycol, 40--10 wt % of diethylene glycol and 5--40 wt % of glycerine. The vapor pressure of the mixed fluid of ethylene glycol, diethylene glycol and glycerlne is lower than that of the 20 conventional mi~ed fluid of ethylene glycol and water, because the vapor pressure of diethylene glycol is lower than that of water at a temperature of about 80;C.
A comparison between the mixed fluid consisting of ethylene glycol, diethylene glycol and glycerine of the above-mentioned embodiment and the 25 conventional mixed fluid consisting of ethylene glycol and water, both under conditions that the refrigerant 21 is fully filled in the watertight space 9 and is heated to 80;C, is described below. In the case of the conventional mixed fluid having 80 wt % of ethylene glycol and 20 wt % of water, the vapor pressure of the mixture is very high at about 450 mmHg at 80-C. At that time, 30 the internal pressure of the watertight space 9, which is filled with the mixture was 0.2 Kg/cm2. Such an internal pressure causes expansion of the adhesive 8 for bonding the CRT 1 and the radiator 10 (in Fig. 2) or 20 (in Fig. 7) and for bonding the radiator 10 (in Fig. 2) or 20 (in Fig. 7) and the projection lens 4. ~The distance between the CRT 1 and the projection lens 4 35 is significantly changed as shown in Fig. 4, so that the projection ;
~, ~ ' , , ' .: '' :, ' - ., - ' performance (e.g. focussing and resolution) of the projectiorl lens 4 is adversely affected in the prior art.
On the other hand, in a ~luid mixture having 60 wt % of ethylene glycol, 30 wt % of diethylene glycol and 10 wt % of glycerine, in accordance 5 with the present invention, the vapor pressure of the fluid mixture becomes relatively low at about 50 mmHg. Therefore, the internal pressure of the watertight space 9, which is filled with the mixture of ethylene glycol, diethylene glycol and glycerine, was only 0.02 Kg/cm2. As a result of such low pressure, expansion of the adhesive 8 for bonding the CRT 1 and the 10 radiator 10 or 20 and for bonding the radiator 10 or 20 and the projection lens 4 is very small. The distance between the front face of the CRT 1 and the pro~ections lens 4 ~s changed very little - the displacement being about 0.03 mm as shown in Fig. 4. Accordingly, the projection performance of the pro~ection lens 4 is hardly affected by temperature dependency or temperature 15 drift.
Furthermore, loss of the refrigerant 21 in the watertight space 9 is measured at 80;C because the plastic of the pro~ection lens 4 and the silicone for the adhesive 8 are permeable and vapor from the refrigerant 21 permeates to the pro~ection lens 4 and the adhesive 8. The amount of conventional mixed 20 fluid of ethylene glycol and water which is as much as 9.8 g per 100 g after 4000 Hr as shown by the characteristic curve of loss versus time given in Fig. 5. On the contraryj loss of the fluid mixture consisting of ethylene glycol, diethylene glycol and glycerine in accordance with the present invention is as little as only about 1.2 g per lOO g after 4000 Hr.
As mentioned above, the present invention uses a fluid mixture of 80--50 wt % of ethylene glycol, 10--40 wt % of diethylene glycol and 5--20 wt % of glycerine as refrigerant. The vapor pressure of the mixed fluid is relatively low and the loss due to the permeation through the plastic lens 4 or silicone adhesive 8 is low. Therefore, the mixed fluid directly 30 comes into contact with the projection lens 4. As a result, the video pro~ector can be made compact and inexpensive without adverse influence on its optical performance by temperature dependency or temperature drift.
The 1uid mixture of the present invention further has the advantage that a desired index of refraction thereof can easily be reali~ed by us~ing the 35 feature that the indices of refraction of ethylene glycol (1.4316), diethylene ~ - 6 -. : : ., . :
, . : ,: ~ ~
: ~. . : - :
,, ~ .
: :, 1312~06 glycol (1.4472) and glycerine (1.4746) are different from each other.
When the mixed fluid is, for example, made of only ethylene glycol and glycerine, the inde~ of refraction thereof is in a range of 1.4395 to 1.4477. However, when the mixed fluid is made of ethylene glycoll diethylene 5 glycol and glycerine in accordance with the present invention, the index of refraction thereof is in a range of 1~4361 to 1.4517 as shown in following table 1.
10No. Fluid Mixture Mixing Ratio Index o Refraction 1 ethylene glycol 80 wt % 1.4395 glycerine 20 wt %
152 ethylene glycol 60 wt % 1.4497 glycerine 40 wt %
ethylene glycol 80 wt %
3 diethylene glycol 10 wt % 1.4361 glycerine 10 wt %
ethyIene glycol 50 wt %
4 diethylene glycoI 10 wt % 1.4517 glycerine 40 wt %
`~ Therefore, the performance of the overall optical system of the video pro~ector can widely and easily be changed and the most suitable liquid, e.g.
a liquid having the desired characteri~tics can be obtained. As a result, 30 improvement in the contrast of the~projec~ion lens can be achieved by reduction of reflectance by the refrigerant.
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`~ Therefore, the performance of the overall optical system of the video pro~ector can widely and easily be changed and the most suitable liquid, e.g.
a liquid having the desired characteri~tics can be obtained. As a result, 30 improvement in the contrast of the~projec~ion lens can be achieved by reduction of reflectance by the refrigerant.
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Claims (3)
1. A liquid cooled cathode ray tube apparatus for a video projection system comprising:
a cathode ray tube for making a video image;
a plastic projection lens disposed in front of said cathode ray tube for projecting said video image to a predetermined position;
a radiator disposed between said cathode ray tube and said projection lens; and a transparent refrigerant fluid consisting essentially of a mixture of ethylene glycol, diethylene glycol and glycerine contained in a liquid-tight space defined by said cathode ray tube, said projection lens and said radiator.
a cathode ray tube for making a video image;
a plastic projection lens disposed in front of said cathode ray tube for projecting said video image to a predetermined position;
a radiator disposed between said cathode ray tube and said projection lens; and a transparent refrigerant fluid consisting essentially of a mixture of ethylene glycol, diethylene glycol and glycerine contained in a liquid-tight space defined by said cathode ray tube, said projection lens and said radiator.
2. A liquid cooled cathode ray tube apparatus for a video projection system according to claim 1, wherein said refrigerant fluid consists essentially of 80 to 50 wt % of ethylene glycol, 10 to 40 wt % of diethylene glycol and 5 to 40 wt % of glycerine.
3. A liquid cooled cathode ray tube apparatus for a video projector system according to claim 1, wherein said refrigerant fluid has an index of refraction similar to that of said plastic projection lens.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000599942A CA1312906C (en) | 1989-05-17 | 1989-05-17 | Liquid cooled cathode ray tube apparatus for video projection system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000599942A CA1312906C (en) | 1989-05-17 | 1989-05-17 | Liquid cooled cathode ray tube apparatus for video projection system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1312906C true CA1312906C (en) | 1993-01-19 |
Family
ID=4140065
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000599942A Expired - Fee Related CA1312906C (en) | 1989-05-17 | 1989-05-17 | Liquid cooled cathode ray tube apparatus for video projection system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1312906C (en) |
-
1989
- 1989-05-17 CA CA000599942A patent/CA1312906C/en not_active Expired - Fee Related
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |