Patent Publication Number: US-7594842-B2

Title: Cassette assembly for manufacturing fluorescent lamps

Description:
CLAIM OF PRIORITY 
   This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from applications earlier filed in the Korean Intellectual Property Office on 9 Sep. 2005 and 18 Oct. 2005 and there, duly assigned Serial Nos. 10-2005-0084244 and 10-2005-0098059, respectively. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a cassette assembly for manufacturing fluorescent lamps, which can effectively carry and handle a plurality of glass tubes for the fluorescent lamps, and more particularly, to a cassette assembly for manufacturing fluorescent lamps, which can allow inner walls of a plurality of glass tube for fluorescent lamps to be simultaneously coated, thereby improving the productivity. 
   2. Description of the Related Art 
   Generally, a fluorescent lamp is produced by coating fluorescent substance exciting ultraviolet rays on the inside wall of a thin long glass tube, injecting light emitting gas and mercury in the glass tube, and sealing the glass tube. According to the position of electrode installed at opposite ends of the glass tube, the fluorescent lamps are classified into a cold cathode fluorescent lamp (CCFL) and an external electrode fluorescent lamp (EEFL). The EEFL has better light quality, longer lifetime, and less electric consumption as compared with the CCFL. Also, the EEFL can be produced to a compact size. Therefore, the EEFL has been widely used as a backlight of a liquid crystal display (LCD). 
   A typical method of manufacturing the EEFL includes a process of coating fluorescent substance the inside wall of the glass tube, a process of calcinating the coated fluorescent substance, a process of injecting light emitting gas and mercury into the glass tube, a process of sealing opposite ends of the glass tube, and a process of forming electrodes on the opposite ends of the glass tube. 
   Among the processes described above, the coating process and the injecting process are conventionally conducted with 3-5 glass tubes inserted in holes formed along a circumferential edge of a disc-shaped stage rotating horizontally. 
   However, in the conventional method of manufacturing the fluorescent lamp, since the coating, injecting and sealing processes are performed in a state where the small number of glass tubes are loaded to the size limited disc-shaped stage, it is difficult to improve the productivity. 
   In addition, since each glass tube has to be connected or disconnected one by one to a chamber in every process of the manufacturing procedure, the manufacturing process is complicated and consequently time-consuming. 
   Obviously, when the glass tubes are individually loaded on the stage or connected to a chamber, it is difficult to handle a lot of glass tubes during the manufacturing process, and therefore the working efficiency and the productivity are further deteriorated. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in an effort to solve the above-described problems of the prior art. 
   It is an object of the present invention to provide a cassette assembly, by which a plurality of glass tubes for fluorescent lamps can be loaded and processed simultaneously, thereby improving the productivity. 
   In one exemplary embodiment of the present invention, A cassette assembly includes a housing defining a process chamber and having a plurality of holes in which glass tubes for the fluorescent lamps are inserted to communicate with the chamber, a carrying unit including two or more porous plates through which the glass tubes are fitted, a plurality of ring members disposed on the porous plates to preliminarily fix the glass tubes to the carrying unit by allowing the outer circumferences of the glass tubes to contact, and a locking unit for changing the glass tubes from the preliminary fixing status to a lockup status by varying contact pressure applied between the ring members and the glass tubes. 
   In another exemplary embodiment of the present invention, a method of manufacturing fluorescent lamps includes loading a plurality of glass tubes on porous plates; washing and wetting the glass tubes; coating the glass tubes with fluorescent substance simultaneously; brushing the glass tubes coated with the fluorescent substance; unloading the glass tubes from the porous plates; baking the unloaded glass tubes; sealing the baked glass tubes; forming electrodes on the sealed glass tubes; and aging the glass tubes. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the present invention and many of the attendant advantages thereof, will be readily apparent as the present invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
       FIG. 1  illustrates a fluorescent lamp manufacturing apparatus to which a cassette assembly according to an embodiment of the present invention is applied; 
       FIGS. 2 and 3  illustrate a process for coating fluorescent substance using a coating unit depicted in  FIG. 1 ; 
       FIG. 4  illustrates a process for drying the fluorescent substance using the coating unit depicted in  FIG. 1 ; 
       FIG. 5  illustrates the cassette assembly depicted in  FIG. 1 ; 
       FIG. 6  illustrates a guide unit of the cassette assembly depicted in  FIG. 5 ; 
       FIG. 7  illustrates a locking unit of the cassette assembly depicted in  FIG. 5 ; 
       FIGS. 8 and 9  illustrate an operation of the locking unit depicted in  FIG. 7 ; 
       FIGS. 10 and 11  illustrate a variety of modified examples of the locking unit; and 
       FIG. 12  is a flowchart illustrating a method of manufacturing fluorescent lamps according to an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The invention may, however, be embodied in may different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be through and complete, and will fully convey the concept of the invention to those skilled in the art. Throughout the drawings, like reference symbols indicate the same or similar components. 
     FIG. 1  is illustrates an overall structure of a cassette assembly according to an embodiment of the present invention. 
   Referring to  FIG. 1 , the symbol M is a coating unit for conducting a process of coating fluorescent substance. The coating unit includes a chamber C. 
   A chamber C is defined in a box-shaped housing  2 , and a plurality of holes H 1  are bored on the bottom of a housing  2  to detachably couple the upper ends of a plurality of glass tubes G to a chamber C. 
   A plurality of ring members  4  are installed inside of the holes H 1  respectively to ensure a gas tight connection between the upper ends of glass tubes G and a chamber C. 
   As shown in  FIG. 1 , the housing  2  is disposed on a workbench D horizontally, and a container  6  containing the fluorescent substance W that will be coated on the inside wall of the glass tubes G is placed on the bottom of the workbench D. The container  6  is designed to vertically move by a cylinder F 1  to immerse the lower ends of the glass tubes G into the fluorescent substance W stored in the container  6 . 
   A variety of units such as a vacuum pump for supplying drying air A 2  and a blower B 2  for supplying negative pressure A 1  are connected to the chamber C to coat the fluorescent substance W on the inside walls of the glass tubes G. 
   The vacuum pump B 1  is connected to a port P 1  formed on the housing  2  to make the internal pressure of the glass tubes be equal to or less than the atmospheric pressure. When the negative pressure A 1  is generated by the vacuum pump B 1 , the fluorescent substance W is sucked into the glass tubes G as shown in  FIG. 2 . When the negative pressure is released, the sucked fluorescent substance W flows down in the glass tubes Gas shown in  FIG. 3 . Accordingly, the fluorescent substance W is coated on the inside walls of the glass tubes G. 
   The blower B 2  is connected to a port P 2  formed on the housing to supply air heated up to about 150° C. into the chamber C, thereby drying the coated fluorescent substance W. The air can be heated by a separate heating unit. 
   The glass tubes are detachably coupled with a chamber C with maintaining loaded status on a carrying unit  8 . The carrying unit  8  includes more than two supporting plates. Referring to  FIG. 5 , the carrying unit  8  includes three porous plates porous plate T 1 , T 2 , and T 3  that are spaced apart from each other in the vertical direction and face each other horizontally. The plate T 1 , T 2  and T 3  are fixed on a frame  10 . 
   The frame  10  functioning to securely fix the porous plates porous plate T 1 , T 2 , T 3  may be formed by connecting pipes or bars that may be formed of light metal or synthetic resin that is robust and corrosion-resistant. 
   The porous plates T 1 , T 2  and T 3  are provided with a plurality of fixing holes H 2  through which the glass tubes G are inserted and fixed. 
   Each of the holes H 2  has a diameter the glass tube G can pass. The holes H 2  have same arrangement as the holes H 1  of the chamber C. 
   The material for the porous plates T 1 , T 2  and T 3  is selected from synthetic resins having predetermined mechanical strength, heat-resistance and corrosion-resistances and not scratching the glass tubes G. 
   The carrying unit  8  is loaded on a lift  12  installed inside of the workbench D and, is detachably mounted on the bottom of the housing  2  while vertically moving by the lift  12 . 
   The lift  12  may be formed of a metal plate provided at a central portion with an opening  14  smaller than the lowest porous plate porous plate T 3  so that the lower ends of the glass tubes G can be penetrated through the opening  14  when the carrying unit  8  is loaded on the lift  12 . 
   A plurality of cylinders F 2  installed on the bottom of the workbench D can be used as a drive source for drying the lift  12 , and piston rods of the cylinders F 2  move vertically the lift  12  with maintaining horizontal position so that the upper ends of the glass tubes G can be detachably connected to the chamber C. 
   The cassette assembly according to the present invention includes a guide unit for guiding a connection position of the glass tubes G to the chamber C. 
   According to this embodiment, as shown in  FIG. 6 , more than two guide projections  16  are installed on the top porous plate porous plate T 1 , and guide grooves  18  in which the guide projections  16  are inserted are formed on the bottom of the housing  2  to guide the docking positions of the glass tubes G on the housing  2 . 
   The guide projections  16  is installed upright on the top porous plate T 1  in the carrying unit  8  and can be positioned at more than two different places. The guide grooves  18  are formed at the bottom of the housing  2  to correspond to the positions of the guide projections  16  with enough opening size to accept the guide projection therein. 
   Also, the guide projections  16  protrude to be longer than the upper ends of the glass tubes G in the upward direction. 
   The guide projections  16  may be pin member formed of metal such as SUS. The guide projections  16  may be detachably and integrally fixed on the top porous plate porous plate T 1  in the carrying unit  8 . 
   The edges of openings of the guide grooves  18  are cut to be rounded or inclined for the easy insertion of the guide projections  16 . 
   A hook member  20  such as eyebolt is installed on more than two places of the frame  10  of the carrying unit  8 . Jigs (not shown) that can be hooked on the hook members  20  are installed on a robot arm (not shown) so that the glass tubes G can be conveyed easily with maintaining desired positions in a process region in which the fluorescent lamp can be manufactured. 
   A plurality of ring members  22  are installed on the carrying unit  8  to preliminarily fix the glass tubes G using contact pressure. 
   As shown in  FIG. 5 , the ring members  22  are located in the holes H 2  of the top porous plate porous plate T 1  in the carrying unit  8 . 
   The multiple ring members  22  can be made of rubber or silicon material that has elastic property and frictional force. The multiple ring members  22  are fixedly fitted on stepped seat portions  24  formed at the top edges of holes H 2 . Inner diameters of the ring members  22  are large enough for the glass tubes G to be forcedly fitted through the ring members  22 . When glass tube G is fitted through the ring member  22 , the ring member applies predetermined contact pressure to the outer circumference of the glass tube G. The diameter of the stepped seat portion  24  is identical to the outer diameter of the ring member  22 . When the ring members  22  are installed on the stepped seat portions  24 , the ring members  22  protrude above the top surface of the top porous plate T 1 . 
   The ring members  22  fix preliminarily the glass tubes G penetrating the holes H 2  of the porous plates porous plate T 1 , T 2  and T 3  in the carrying unit  8  as the outer circumference of the glass tubes G contacts the inner circumference of the ring members  22 . 
   The preliminary fixing status prevents the glass tubes G from slipping down when the glass tubes G are inserted through the holes H 2  of the porous plates porous plate T 1 , T 2  and T 3 . Also, in the preliminary fixing status, it is preferable that the glass tubes G can be separated from the porous plates porous plate T 1 , T 2  and T 3  only when outer force higher than a predetermined level is applied to the glass tubes G. 
   A locking unit is installed in the cassette assembly to switch the glass tubes G loaded in the carrying unit  8  from the preliminary fixing status to a complete lockup status. 
   In this embodiment, as shown in  FIG. 7 , a pressing plate  26  is used as the locking unit. The pressing plate  26  is disposed to face the top porous plate T 1  with the ring members  22  interposed therebetween. When the pressing plate  26  is operated to move toward or away from the top porous plate T 1 , the ring members  22  is pressed down to be changed into the complete lockup status. 
   The size of the pressing plate  26  is almost same as that of the top porous plate T 1 . The, and, for the glass tubes G to penetrate through, holes H 3  corresponding to the holes H 2  of the top porous plate T 1  are formed on the pressing plate  26 . 
   The pressing plate  26  is vertically guided by the guide projections  16  formed on the top porous plate T 1  in a state where it is fitted around the guide projections  16 . For the material of the pressing plate  26 , it is desirable to utilize metal or synthetic resin for the pressing plate  26  not to be bent or deformed during the pressing process. 
   The pressing plate  26  presses down the ring members  22  by clamping action. That is, as shown in  FIG. 7 , more than two clamping members  28  are installed on the top porous plate T 1  so that the clamping members  28  presses down the ring members  22  while approaching horizontally toward the top porous plate porous plate T 1 . 
   The clamping members  28  may be formed in a typical hook structure having a fixing end rotatably fixed at the top porous plate T 1  and a free end detachably hooked to the pressing plate  26  to that the clamping can be realized by force applied downward. However, the clamping members  28  are not limited to this typical hook structure. Any structures can be utilized as long as it can be move the pressing plate  26  toward the top porous plate T 1  by the clamping action. 
   Elastic members  30  such as compressing coil springs can be placed between the pressing plate  26  and the top porous plate T 1 . These elastic members  30  enable the pressing plate  26  to return opposite direction when clamping action is released after pressing. 
   The locking unit changes the status of the glass tubes G from the preliminary fixing status to the lockup state by moving the pressing plate  26  toward the top porous plate T 1  as shown in  FIG. 8 . The ring members  22  pressed down by the pressing plate  26  are deformed to reduce the inner diameter thereof and thus contact pressure between the ring members  22  and the outer circumferences of the glass tubes G increases. Therefore, the deformed ring members  22  enable to lock up the glass tubes G. 
   The lockup status prevents the glass tubes G loaded in the carrying unit  8  from changing their positions or slipping down when the carrying unit  8  is conveyed together with the glass tubes G. 
   In this embodiment, the pressing plate  26  is passively operated by the clamping members  28 . However, the present invention is not limited to this case. For example, as shown in  FIG. 10 , the pressing plate  26  can be coupled to the piston rods of the cylinders F 3 . Alternatively, as shown in  FIG. 11 , the locking unit can be installed with penetrating screws coupled with a shaft of a driving motor F 4  so that the pressing plate  26  can be pressed down by the linear or rotating motion of the screws. 
   The locking unit can be installed in response to one or more of the porous plates T 1 , T 2  and T 3  in the carrying unit  8  when the ring members  22  are located on porous plates T 1 , T 2  and. 
   A method of manufacturing the fluorescent lamp using the above-described cassette assembly will be described hereinafter. 
   Referring to  FIG. 12 , the glass tubes G are glazed (S 1 ) to make the ends of the glass tubes G rounded by heating the ends of the glass tube G using a torch. The glazing is a fundamental process for manufacturing high quality lamps. 
   Then, the glass tubes G are loaded on the carrying unit  8  (S 3 ). As described above, the porous plates are utilized for setting the glass tubes G, and the glass tubes G are locked up by the pressing plate  26 . 
   When the glass tubes G are locked up, the manufacturing method is followed by washing, wetting, coating, and brushing processes. At each process, the glass tubes G are performed simultaneously. 
   That is, the washing and wetting processes for the insides of the glass tubes are performed in a state of the glass tubes G are locked up (S 5 ). The wetting of the glass tubes G is for keeping uniform humidity or dryness after washing them to produce uniform quality of the products. 
   After the glass tubes G are washed, the glass tubes G are coated with fluorescent substance W stored in the container  6  by generating negative pressure in the glass tubes G, followed by passing hot air through the glass tubes G to dry the coated fluorescent substance S 7 . 
   After the above, the brushing process is conducted to remove the coated fluorescent substance from the ends of the glass tubes S 9 . In the brushing process, the glass tubes maintain their lockup status on the porous plates. 
   Then, the glass tubes G are unloaded S 11  from the carrying unit  8  and a baking process is conducted to securely fix the fluorescent substance on the inside walls of the glass tubes. 
   Next, a forming process for forming the glass tubes is followed and a first sealing process for sealing a first end of each glass tube is conducted (S 15 ). The first sealing process is conducted by melting the first end of the glass tube using a torch. 
   After the first end of each glass tube G is sealed, the inside of each glass tube is exhausted. Then, discharging gas such as argon or neon is injected into the glass tubes, after which a second sealing process is performed (S 17 ). After then, the glass tubes are heated to generate mercury vapor, after which a third sealing process is performed (S 19 ). 
   Then, the glass tubes G are loaded again on the porous plates and electrodes are installed on opposite ends of each glass tube (S 23 ), after which an aging process is performed (S 25 ). The aging process is for stabilizing the glass tubes G by generating initial discharge. In this aging process, the plurality of glass tubes are simultaneously processed. 
   After the aging process is finished, the glass tubes are unloaded from the porous plates (S 27 ). 
   According to the present invention, the glass tubes can be simultaneously conveyed easily to the chamber in which the processes are performed in a state where the glass tubes are loaded in the carrying unit. The elastic ring members enable to prevent the glass tubes from slipping down or changing their positions during conveying multiple glass tubes. Therefore, this invention improves the working efficiency and productivity of the fluorescent lamps. 
   In addition, since many fluorescent lamps are simultaneously manufacture using the porous plates and thus this invention provides an advantage of manufacturing large volume of fluorescent lamps. 
   Although exemplary embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concept taught herein still fall within the spirit and scope of the present invention, as defined by the appended claims.