GB2247984A

GB2247984A - Liquid cooling device of projection CRT

Info

Publication number: GB2247984A
Application number: GB9114436A
Authority: GB
Inventors: Jaebum Park
Original assignee: Samsung Electron Devices Co Ltd
Current assignee: Samsung SDI Co Ltd
Priority date: 1990-08-21
Filing date: 1991-07-03
Publication date: 1992-03-18
Also published as: KR920005882Y1; MY106810A; DE4123400A1; JP2547339Y2; JPH0499658U; KR920005317U; GB9114436D0

Abstract

A heating coil 8 is provided for the liquid coolant in a projection CRT so that it quickly attains its operating temperature. The liquid cooling device for attaching to the GRT faceplate has a radiator (2) having a space in its inner portion and a transparent plate attached to the front of the radiator to seal a space (4) from the outside. A heating coil (8) is embedded around the inner portion of the space (4) of the radiator, and this heating coil is controlled by a power supply circuit, Fig. 3 (not shown), using a temperature sensor 14 for detecting the temperature of the coolant in order to heat the coolant quickly to a stabilizing temperature of 60 SIMILAR 80 DEG C, thereby shortening the picture appearance time of the projection CRT. When the coolant is heated to the stabilizing temperature, the temperature-control circuit cuts-off the electric power to the heating coil and allows continued heating of the coolant by the heat generated through the action of the projection CRT. <IMAGE>

Description

LIQUID COOLING DEVICE OF PROJECTION CRT BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a liquid cooling device for a projection CRT, and more particularly to a liquid cooling device having a coolant preheating system to quickly bring the coolant to its operating temperature thereby reduc1Ang delay in the appearance of the television picture.

(2) Description of the Prior Art

Since utilization of what is called trinescope method in which red, green and blue monochrome images are optically united to obtain a colored picture, a liquid cooling device interposing projection lenses between the CRT and a screen to magnify the lpicture has been recently put to practical use.

The projection CRT attains a large picture by spreading light. As such, large aperture lenses, a high efficiency screen, and a high-powered monochrome CRT are used to ensure even ligh distribution on the screen.

X AS is well known, a high-powered CRT has such an internal operating temperature that the white balance is difficult to preserve. There is also an implosion hazard.

TO solve the above-mentioned implosion problem, a liquid cooling device is placed at the front panel of the high-powered CRT to provide cooling.

Although the liquid cooling device lowers the operating temperature of the CRT, such problems as an increase in coolant volume caused by heating and an increase in settling or stabilizing time of the picture may occur.

The former problem of volume increase, as described in the Laid-open Japanese Patent Application No. So 61-68842, can be solved by depositing a damper in the outer part of a radiator to absorb the expanded coolant. However, the latter problem of increased picture stabilizing time is caused by the property of the coolant, such as ethylene glycol. Its refraction rate, transmission rate, and reflection rate are temperature -dependent and will stabilize around 60- 800 which is achieved after initia.L 2 activation of the CRT. Therefore, there is one solution: to achieve the stabilizing temperature as fast as possible by heating the coolant.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a liquid cooling device for a Projection CRT which is able to reduce delay in the picture appearance by stabilizing the heated coolant at its normal operating temperature in a minimum time.

For the above-mentioned purpose, the present invention is characterized in that a heating coil is disposed in the inner portion of a radiator of the liquid cooling portion comprising the liquid cooling device of the CRT.

The heating coil quickly heats the coolant to some temperature, for example in 60 ST C. For this purpose, on the Chere is a sensor for detecting the temperature of the coolant and a temperature- control system responsive to the sensor is also included to control the electric power applied to the heating coil.

3 other purposes or advantages of the present invention will be much better understood by way of the following description taken with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a front view of a radiator of a liquid cooling device according to an embodiment of the present invention, Fig. 2 is a side sectional view of the projection CRT mounting for the radiator in Fig. 1, and Fig. 3 is a circuit diagram which illustrates an embodiment of a temperature-control system adaptable to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Fig. 1 is a front view of a radiator according to an embodiment of the present invention. The radiator 2 assumes the form of a square ring having a space 4 in the inner area and includes fins 6 on the periphery for radiating heat into the su-rr6ui- atsii,,) sphere.

A heating coil 8 is embedded in the inner portion of the radiator 2 surrounding the space 4. Two electrical supply terminals 10 of the heating coil 8 extend from one part of the 4 periphery.

Furthermore, there is a cavity 12 in one part of the radiator 2 in which a temperature sensor 14 is inserted.

Fig. 2 is a side sectional view of the projection CRT which includes the liquid cooling device described with Fig.l.

The radiator 2 is attached to the front face of the projection CRT 18 by sealants 16. The radiator 2 is f illed with a coolant in the inner part of the space 4, which coolant is sealed from the outside by a transparent plate 20 tightly attached to the front of the radiator 2 by sealants 16.

The temperature sensor 14 detects the temperature of the coolant conducted through the bottom of the cavity 12, which enables a temperature -control circuit to control the electric power :J to the heating coil.

Fig. 3 is an example of a preferred temperature- control circuit of the present invention in which a thermistor is used as the temperature sensor 14.

A resistance Rl, a diode D1, and electrolytic condenser Cl, and a zener diode ZD comprise a constant voltage circuit to obtain DC current. Resistances R2 and R3, a condenser C2, and transistors Trl and Tr2 comprise a power drive circuit. Inputs to a programmable unijunction transistor (PUT) Q1 serves as a comparator for driving transistor Tr4. The transistor Tr4 and a triac Q2 comprise a power switching circuit for supplying power to the heating coil 8.

Transistors Trl and Tr2 are alternatively turned on, except in case of the zero voltage, to add a power driving alternate signal to the base of the transistor Tr3, whereby the anode of the PUT Q1 is always shunted except when the power is zero. When the electric power is near the zero voltage, the anode of the PUT Q1 increases to the potential fixed as a reference voltage VR.

At this time, when the impedance of the temperature sensor 14 is increased by low temperature of the coolant, the gate potential of the PUT Q1 is low, so a biased signal is added to the base of the transistor Tr4 to turn on the triac Q2.

As a consequence, an electric current is applied to the 6 heating coil 8, whereby the coolant begins to heat.

The coolant is soon heated up to a temperature 60- 800 by the heating coil to achieve rapid stabilizing of the picture in the projection CRT, after which the impedance of the temperature sensor 14 becomes lower, and it causes the gate potential of the PUT Q1 to become higher than the potential fixed at a reference voltage VR.

In the end, the PUT Q1 turns off and the triac Q2 is turned off to terminate power applied to the heating coil 8.

When the temperature of the coolant becomes lower than the stabilizing temperature, power to the heating coil is again applied. However, when already heated to the stabilizing temperature, the heating is only applied to preserve a certain temperature level so that the electric current applied to the heating coil is minimal.

As described above, establishing the heating coil in the liquid cooling device of the projection CRT, thereby quickly heating the coolant to the stabilizing temperature, the present 7 invention has the advantage of lessening the time for a stable picture in a projection CRT.

"; '-,. t ' a claims 1. A liquid cooling device for a projection CRT having a radiator which is attached to the front of the projection CRT to provide a space for a coolant, a transparent plate attached to the f ront of the radiator to seal the coolant f rom the outside, the liquid cooling device further comprising a heating coil embedded around the inner portion of the space and a temperature-control circuit including a temperature sensor for detecting the temperature of the coolant and f or controlling power applied to the heating coil to heat the coolant to a stabilizing temperature.

2. The liquid cooling device as claimed in claim 1, wherein a temperature sensor is attached to the periphery of the radiator.

3. The coo"jl.ing device as claimed in claim 1 or 2, wherein the temperature-control circuit comprises a constant voltage circuit including a resistance, a diode, an electrolytic condenser; a zener diode; a power drive circuit including 9 resistances, a condenser, and transistors; and a switching circuit including a programmable unijunction transistor, a transistor, and a triac.

A liquid cooling device for a projection CRT substantially as herein described with reference to Figure 1 and 2 with or without reference to Figure 3 of the accompanying drawings.

Published 1992 at 7be Patent Office, Concept House, Cardiff Road, Newport. Gwent NP9 I RH. Further copies may be obtained from Sales Branch, Unit 6. Nine Mile Point, Cwmfelinfach, Cross Keys, Newport, NP I 7HZ. Printed by Multiplex techniques lid. St Mary Cray, Kent.