Patent Publication Number: US-2007096458-A1

Title: Exhaust Pipe for a Flat Lamp

Description:
FIELD OF THE INVENTION  
      The present invention relates to an exhaust pipe, and more particularly, to an exhaust pipe being adapted as an interface of pumping/exhausting gas into/out of a flat lamp therethrough, whereas the flat lamp is serving as a back light of liquid crystal display.  
     BACKGROUND OF THE INVENTION  
      In the recent information oriented society, importance of visual display devices has increased. Requirements for large-sized display devices having low power consumption, thin thickness, light weight and high picture quality have to be satisfied. Because of the maturity of liquid crystal display (LCD) technology, the characteristics of LCD devices are capable of satisfying all those conditions and are suitable for mass-production and thus various new LCD products have been rapidly developed. Among those LCD devices, LCD TV is considered to be the star display device for the future digital TV system.  
      LCDs are nonemissive light devices, which means they do not produce any form of light. Instead they block/pass light reflected from an external light source provided by a back light module. Currently, it is common to use a back light module with multiple thin cold cathode lamps as the light source of illumination to give the display sufficient contrast and brightness and thus satisfy the demands of high brightness LCDs. However, in order to providing uniform illumination across the LCD surface and luminance that is high enough to produce good contrast in a day environment, the back light module with multiple thin cold cathode lamps must have a diffuser that is thick enough to takes the numerous points of light and uniformly spreads it out over the entire area of the display. Moreover, the brightness decay of each cold cathode lamp is speeding up after long-hour operation while the speed of the decaying is varied from one cold cathode lamp to another that it is common for a large-sized high brightness LCD to suffer the phenomenon of uneven illumination. Therefore, flat fluorescent lamps become a preferred option to be used as the back light of liquid crystal display.  
      Please refer to  FIG. 1 , which is an exposed perspective view of lo a flat lamp disclosed in U.S. Pat. No. 4,920,298. As seen in  FIG. 1 , the flat lamp  1  is substantially a flat fluorescent lamp, which is primarily comprised of an upper glass plate  13 , a lower glass plate  14 , a first side frame  11 , a second side frame  12 , Phosphors and electrodes. Since the lighting of the flat fluorescent lamp  1  is caused by the principle of gas discharging, it is required to fill the lamp  1  with an inert gas and thus a process of gas pumping/exhausting is required for the manufacturing of the lamp  1 . The flat fluorescent lamp  1  is produced by removing air from the interior of the lamp through the tip tube  15  and then introducing an inert gas into the same through the tube  15  and sealing off the outer end of the tip tube  15  by fusion. In  FIG. 1 , the tip tube  15  is fitted in the cutout  121  formed on the second side frame  12 .  
      Although the tip tube  15  is being fitted on the cutout  121  of the second side frame, it is noted that the thickness of the flat lamp  1  will not be increased thereby. Nevertheless, since the outer end of the tip tube  15  is not specially designed for the fused-to-seal process and the glass wall of the tip tube  15  is thin as the diameter of the tip tube  15  is enlarged as much as possible for the maximum flux, the condition that a portion of the glass wall of the tip tube  15  is melt while another portion is not will be caused as the tip tube is being fused at an improper position or the temperature control of the fuse-to-seal process is not appropriate. The aforesaid partial melting condition of the tip tube  15  is going to cause the leakage of the lamp  1  or enable outeside air to enter the lamp, in which case, the illuminating quality of the lamp  1  is adversely affect. In addition, since the overall tube diameter of the tip tube  15  is approximately equal to the thickness of the second glass side frame  12  of the lamp  1  while the thickness of the flat lamp  1  should be very small to be used as the back light of LCDs, the overall tube diameter of the tip tube  15  is even smaller that cause the mechanical strength of the tip tube  15  to be relatively weak and thus the tip tube  15  is prone to be break during the pumping/exhausting process.  
      Therefore, it is in great need to have an improved exhaust pipe that is free from the foregoing problems.  
     SUMMARY OF THE INVENTION  
      The primary object of the invention is to provide an exhaust pipe for a flat lamp to be adapted as an interface of pumping/exhausting gas into/out of the flat lamp therethrough, in that the exhaust pipe is composed of tubes of different diameters for enhancing the mechanism strength at the joint of the exhaust pipe and the flat lamp.  
      It is another object of the invention to provide an exhaust pipe for a flat lamp capable of reducing the leakage of the flat lamp caused by the exhausting pipe being fused to seal partially, in that the exhaust pipe has a neck arranged at a position of the exhaust pipe specified for sealing the same by fusion and the diameter of the neck is shrunk for enabling the same to be smaller than that of the exhaust tube.  
      To achieve the above objects, the present invention provides an exhaust pipe, being adapted to be arranged at a side of a flat lamp for pumping/exhausting gas therein/therefrom, which comprises: an inner tube, fitted to a side frame of the flat lamp while enabling the same to be in communication with a discharge space formed inside the flat lamp; and an outer tube, being adapted to communicated with the inner tube while being connected to a pumping/exhausting device.  
      In a preferred embodiment of the invention, a notch is formed on the side frame of the flat lamp for insetting the inner tube, wherein a portion of the inset inner tube is protruding out of the side frame by a length ranged between 3 mm to 5 mm as the length of the protruding portion of the inner tube is smaller than that of the portion of the inner tube insetting in the notch.  
      Preferably, the external diameter of the inner tube is smaller than the thickness of the side frame.  
      Preferably, the outer tube is arranged to ensheathe the inner tube, and the internal diameter of the outer tube is larger than the external diameter of the inner tube by 0.3 mm.  
      Preferably, the outer tube has a tapered joint arranged at an end thereof to be used for connecting the same to the inner tube, and the outer tube and the inner tube can be integrally formed.  
      Preferably, the inner tube is a round-shaped tube.  
      In another preferred embodiment of the invention, the inner tube further comprises a square head to be fitted and embedded into a notch formed in the side frame of the flat lamp.  
      Preferably, a neck is formed on the outer tube at a position proximate to the square head of the inner tube.  
      Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the present invention.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an exposed perspective view of a flat lamp disclosed in U.S. Pat. No. 4,920,298.  
       FIG. 2A  is a top view of an exhaust pipe adapted for a flat lamp according to a first preferred embodiment of the invention.  
       FIG. 2  is a side view of an exhaust pipe adapted for a flat lamp according to a first preferred embodiment of the invention.  
       FIG. 3  is a top view of an exhaust pipe adapted for a flat lamp according to a second preferred embodiment of the invention.  
       FIG. 4A  is a top view of an exhaust pipe adapted for a flat lamp according to a third preferred embodiment of the invention.  
       FIG. 4B  is a side view of an exhaust pipe adapted for a flat lamp according to a first preferred embodiment of the invention.  
       FIG. 5A  is a schematic diagram showing an exhaust pipe with shrinking neck according to the present invention.  
       FIG. 5B  is a schematic diagram showing another exhaust pipe with shrinking neck according to the present invention.  
       FIG. 5C  is a schematic diagram showing yet another exhaust pipe with shrinking neck according to the present invention.  
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
      For your esteemed members of reviewing committee to further understand and recognize the fulfilled functions and structural characteristics of the invention, several preferable embodiments cooperating with detailed description are presented as the follows.  
      Please refer to  FIG. 2A  and  FIG. 2B , which are respectively a top view and a side view of an exhaust pipe adapted for a flat lamp according to a first preferred embodiment of the invention. As seen, the flat lamp  2  is comprised of four side frames  21 ,  22 ,  23 ,  24 , a top glass plate  28  and a bottom glass plate  29 . Wherein, the four side frames  21 ,  22 ,  23 ,  24  are bonded to the peripheral edges of the top and bottom glass plates  28 ,  29  while being sandwiched thereby, by which the formation of the four side frames  21 ,  22 ,  23 ,  24 , forms the side wall of the flat lamp.  
      In  FIG. 2A  and  FIG. 2B , an exhaust pipe  25  is adapted to be arranged at a side of the flat lamp  2  an is in communication with an discharge space formed inside the flat lamp  2 . The exhaust pipe  25  comprises: an inner tube  251 , fitted to a notch  241  formed on the side frame  24  of the flat lamp  2  while enabling the same to be in communication with the discharge space of the flat lamp  2 ; and an outer tube  252 , being adapted to communicated with the inner tube  251 ; wherein the diameter of the outer tube  252  is larger than that of the inner tube  251 . Moreover, the gap that is formed as the inner tube  251  being fitted into the notch  241  can be filled by a glass paste for ensuring airtight during pumping/exhausting gas into/out of the flat lamp  2  through the exhaust pipe  25  so as to prevent leakage.  
      Furthermore, a portion  2511  of the inset inner  251  tube is protruding out of the side frame  24  and the external diameter of the inner tube  251  is smaller than the internal diameter of the outer tube  252  so that the mechanism strength at the joint of the exhaust pipe  25  and the flat lamp  2  can be enhanced by ensheathing the outer tube  252  onto the protruding portion  2511  of the inner tube  251 . It is noted that the external diameter of the outer tube  252  should not exceed the overall thickness of the flat lamp  2 , i.e. the total thickness including those of the top plate  28 , the bottom plate  29  and the side frames. In this first preferred embodiment of the invention, the internal diameter of the outer tube  252  is larger than the external diameter of the inner tube  251  by about 0.3 mm, however, the difference between the two being 0.3 mm is preferred but not limited by thereby. In order to enhance airtight while preventing leakage, it is preferred to have the external diameter of the outer tube  252  to be small than the thickness of the side frame  24 . Yet, the length of the protruding portion  2511  of the inner tube  251  is preferred to be in the range of 3 mm to 5 mm, that is, if the protruding portion  2511  is too short, not only the outer tube  252  is difficult to ensheathe and fix itself onto the inner tube  251 , but also the mechanism strength at the joint can not be enhanced as preferred; and if the protruding portion  2511  is too long, not only will cause trouble while ensheathing the inner tube  251  by the outer tube  252 , but also the inner tube  251  is ease to be break during the ensheathing process. Moreover, the length of the protruding portion  2511  of the inner tube  251  should be smaller than that of the portion of the inner tube  251  insetting in the notch  241 , otherwise, the inner tube  251  might be tilted by instable median point thereof during the manufacturing of the flat lamp  2 . In addition, the length of the portion of the inner tube  251  insetting in the notch  24  should not larger than the width of the side frame  24 , otherwise, the insetting portion of the inner tube will invade the illuminating area of the flat lamp  2  and thus cause unwanted shadows.  
      Please refer to  FIG. 3 , which a top view of an exhaust pipe adapted for a flat lamp according to a second preferred embodiment of the invention. The integrally formed exhaust pipe  26  of  FIG. 3  is also capable of being fitting to a side of a flat lamp  2 , and further it is not going to cause the overall thickness of the flat lamp to increase after the integrally formed exhaust pipe  26  is fused to seal the flat lamp  2 . In  FIG. 3 , the outer tube  263  has a tapered joint  262  arranged at an end thereof to be used for connecting the same to the inner tube  261  fitted in the notch  241 , and the outer tube  263  and the inner tube  261  can be integrally formed. The advantage of the exhaust pipe  26  of  FIG. 3  is that the portion of the exhaust pipe  26  resides and remains in the flat lamp  2  is comparatively smaller after it is being fused to seal the lamp  2  and it is preferably to be fused at the position marked by the dotted line  90  shown in  FIG. 3 . However, it is also because of the tube diameter of the exhaust pipe  26  is tapered at the joint of the exhaust pipe  26  and the flat lamp  2 , the mechanical strength of the joint is weakened so that the exhaust pipe is easy to break as it is being used to pump/exhaust gas into/out of a large-sized flat lamp. Therefore, the exhaust pipe  26  of  FIG. 3  is suitable to be used for smaller flat lamps.  
      Please refer to  FIG. 4A  and  FIG. 4B , which are respectively a top view and a side view of an exhaust pipe adapted for a flat lamp according to a third preferred embodiment of the invention. The exhaust pipe  27  in this embodiment is integrally formed, whereas the inner tube thereof  271  further comprises a square head to be fitted and embedded into a notch  241  formed in the side frame  24  of the flat lamp  2 , and the square head is channeled at the center thereof to be in communication with the outer tube  272  of the exhaust pipe  27 . It is preferred that the thickness of the square head is the same as that of the side frame  24 . The exhaust pipe  27  of this embodiment can help to improve the sealing of the flat lamp  2  since the notch  241  formed is usually a square that can match with the square head of the inner tube  271  and thus the gap formed around the notch  24  and the square hand is smaller to be seal by a small amount of glass paste.  
      Since the aforesaid tip tube is not specially designed for the fused-to-seal process and the glass wall of the outer tube is comparatively thinner as the diameter of the outer tube is enlarged as much as possible for the maximum flux, the condition that a portion of the glass wall of the outer tube is melt while another portion is not will be caused as the outer tube is being fused at an improper position or the temperature control of the fuse-to-seal process is not appropriate. The aforesaid partial melting condition of the outer tube is going to cause the leakage of the lamp or enable outside air to enter the lamp, in which case, the illuminating quality of the lamp is adversely affect. Therefore, it is intended to design the outer tube of an exhaust pipe specifically for the problem. Please refer to  FIG. 5A , which is a schematic diagram showing an exhaust pipe with shrinking neck according to the present invention. The outer tube  252   a  of the exhaust pipe shown in  FIG. 5A  has a neck  2521  being arranged at a position to be fused. It is noted that the diameter of the outer tube  252   a  is shrunken at the neck portion thereof so that the fuse-to-seal process is easier to be perform at the neck without causing leakage. In  FIG. 5C , the tapered outer tube similar to that shown in  FIG. 3  also are formed with a neck  264 . In  FIG. 5C , a neck  273  is formed on the outer tube of an exhaust pipe similar to that shown in  FIG. 4A .  
      To sum up, it is noted that the residue of the fused exhaust pipe attached on the flat lamp will not cause the thickness of the flat lamp to increase, and the design of the exhaust pipe of the invention will help to increase the mechanism strength at the joint of the exhaust pipe and the flat lamp.  
      While the preferred embodiment of the invention has been set forth for the purpose of disclosure, modifications of the disclosed embodiment of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.