Abstract:
An apparatus for bisecting a CRT is disclosed. The device separates the funnel portion of the CRT, which is composed of a leaded glass, and panel portion of the CRT, which is composed of an unleaded glass, for recycling purposes. The apparatus consists of a lateral track along which the CRT moves. Opposing sides of the CRT are cut by circular saws disposed on opposite sides of the track. The CRT is then rotated 90 degrees and a second set of saws cuts the remaining opposing sides of the CRT.

Description:
GOVERNMENT INTEREST  
       [0001] This invention was developed under a contract with the Department of Defense, United States Federal Government Contract No. 00372.228.ED.10D.GLS. As a result, the U.S. Government may have certain rights in this invention. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention pertains to the field of recycling and, in particular, to the recycling of glass of the type commonly found in cathode ray tubes, of which a portion is an unleaded glass and a portion is a leaded glass. The invention describes an apparatus for separating the leaded glass from the unleaded glass of the cathode ray tubes.  
         BACKGROUND OF THE INVENTION  
         [0003]    This invention is directed to the recycling of used cathode ray tubes (CRTs), which are used mainly in computer monitors and television sets. The typical cathode ray tube is constructed of two glass portions. The first portion is the funnel portion, which is composed of leaded glass which is approximately 21-25% by weight lead oxide. The lead oxide in the glass is used for containing the radiation produced by the electron gun of the CRT, which is positioned at the small, rear end of the funnel portion and which shoots electrons from the rear of the funnel to the front of the panel, where they impact, activating phosphors on the front panel of the CRT to create the image. The front panel, or display area of the CRT, is typically manufactured with an unleaded glass. During the manufacturing process the panel portion and the funnel portion are fused together to form the body of the CRT. The electron gun is then affixed to the rear of the funnel and a vacuum is drawn in the CRT by expelling the air. The panel portion and the funnel portion of the CRT are typically fused or fluxed together with a lead oxide frit, using heat. The lead frit is composed of approximately 75-80% lead oxide. The joint between the panel and the funnel of the CRT is referred to as the frit line.  
           [0004]    Due to the lead content in the CRT and the frit, some states have enacted or are considering enacting land fill ban laws, which would ban the disposal of CRTs in the land fills. Therefore, there is a need to provide an alternate disposal method for CRT glass and, in particular, the funnel and frit line portions of the CRT, which contain the lead oxide. To avoid the disposal of the CRTs in land fills, it is desirable to be able to recycle the glass into new CRTs. However, to recycle the glass it is necessary to separate the portion of the CRT containing the lead (i.e. the funnel and frit joint) from the portion of the CRT containing no lead or low lead glass (i.e. the panel). After the glass types are separated, they can be further processed to produce furnace ready cullet, which can be recycled. The recycled glass (i.e. the cullet) is typically used to manufacture new CRT screens. While the leaded glass is able to tolerate some contamination with the low lead or unleaded glass from the panel portion of the CRT, there is near-zero tolerance for contamination of the panel glass with leaded glass from the frit or funnel portion of the CRT. Therefore, it is necessary to separate the two portions of the CRT.  
           [0005]    Due to the lead oxide content of the CRT and the glass itself, separation of the two portion of the CRT can be hazardous. Typical risk factors include sharp saw blades, jagged glass edges, phosphor dust, lead dust and high voltage. Therefore, it would be desirable to have a way of separating the two portions of the CRT that lessens the degree of risk of exposure to both the operator and the environment. Secondly, because of the low tolerance for contamination of the unleaded glass panel portion with the leaded glass from the funnel portions, it is desirable that no funnel glass or leaded frit remain with the panel glass after the separation of the two parts of the CRT. Lastly, it is desirable that the separation of the two portions of the CRT be accomplished in a reasonable time cycle to make the recycling of the glass economical.  
         SUMMARY OF THE INVENTION  
         [0006]    The invention disclosed herein is a cutting apparatus which is able to separate the panel portion and the funnel portions of the CRT using a plurality of saws, which cut the CRT at a point on the panel side of the frit line. As stated previously, it is desired that the frit line remain with the funnel portion of the CRT because of its high lead content. The apparatus utilizes a plurality of small circular saw blades to cut the four sides of a typical CRT screen. The device is adjustable to accommodate varying sizes of CRT screens and in the primary embodiment, shown in FIG. 1, utilizes four circular saw blades, one of which cuts each sides of the CRT. In an alternative embodiment, eight circular saw blades are used, each of which cuts half of the thickness of the glass from one side of the CRT, to avoid overheating of the saw blade as the glass is cut, and to increase the cutting speed. The apparatus is enclosed in a housing to lessen the risk from contamination., and the process of positioning the CRT with respect to the saw blades is semi-automatic.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 shows a top plan view of a first embodiment of the invention utilizing four circular saw blades.  
         [0008]    [0008]FIG. 2 is an elevational view of the embodiment of FIG. 1.  
         [0009]    [0009]FIG. 3 is a second embodiment of the invention utilizing eight circular saw blades. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0010]    The preferred embodiment of the invention is best described with reference to FIG. 1, which shows the device in a top plan view. CRT  1  is mounted using vacuum cup  20  on actuator  18 , which is moveable along track  16  through longitudinal axis of the apparatus. Actuator  18 , with CRT  1  mounted thereon starts in home position  40  and passes from the left of FIG. 1 towards the right of FIG. 1 along track  16 , coming to rest in end position  48 . At position  42 , CRT  1  encounters circular saw blades  12 , driven by drivers  11 . Circular saw blades  12  are adjustable along rails  13 , supported by motor supports  8  to facilitate the accommodation of CRTs of various sizes. Blades  12  are preferably 6″ diameter diamond saw blades capable of cutting through the glass of CRT  1 , which is typically approximately ⅜″ thick. As CRT  1  moves from position  40  through position  42 , blades  12  come in contact with opposing sides A and C of CRT  1  and these sides are cut. After passing through saw blades  12  at position  42 , CRT  1  enters center position  44 , where it is rotated  90 ° by a rotary device on actuator  18 . As actuator  18  moves CRT  1  through position  46 , CRT  1  encounters saw blades  14 , which are positioned along rails  15  to cut the remaining sides B and D of CRT  1 . Note that both blade sets  12  and  14  are adjustable along rails  13  and  15  respectively to accommodate varying sizes of CRTs. After passing through position  46 , all four sides of CRT  1  are now cut, and funnel portion of CRT  1  can now be removed from the panel portion at end position  48 . The vacuum is then released from vacuum cup  20 , allowing the panel portion to be removed and placed separately from the funnel portion.  
         [0011]    To enhance the safety of the operation and, in particular, of the operator, the apparatus is enclosed in housing  10 , which is a sealed cabinet which will capture glass fragments and phosphor particles which are present in the CRT and which may be liberated during the cutting process. In addition, any lead oxide dust generated by the cutting of the CRT is contained by the saw blade coolant and confined to cabinet  10 .  
         [0012]    As each of the saws contacts the CRT to make the cut, the blades  12  and  14  are sprayed with a water-based coolant or cutting fluid, via a set of nozzles mounted in close proximity to the blades (not shown). The nozzles and cutting fluids are commercial, off the shelf components, well known in the prior art. The cutting fluid serves to dissipate the friction of the heat generated by the cutting of the glass with the diamond blades to avoid the warping of blades  12  and  14  during the cutting process and to contain dust particles.  
         [0013]    In the primary embodiment, shown in FIGS. 1 and 2, motors  11  are preferably air-powered. Blades  12  and  14  are preferably 4″-7″ masonry, lapidary or stainless saw blades which are rotated by motors  11  at approximately 1200 RPM. Although air motors are preferred, motors of any type capable of rotating the blades at the appropriate speed can be used.  
         [0014]    In operation, the operator opens a door in cabinet  10  located near the home position  42 , and positions the CRT  1  panel side down on vacuum cup  20 . Preferably vacuum cup  20  is positioned in the center of the panel portion of CRT  1 . A plurality of positioning stops, shown in FIG. 1 as  21   a ,  21   b  and  21   c  are locked in place and contact CRT  1  to aid the operator in positioning CRT  1  squarely on vacuum cup  20 . Position stops  21   a ,  21   b  and  21   c  are adjustable depending on the size of the CRT.  
         [0015]    Next, the operator must vertically position CRT  1  such that the blades contact CRT  1  at the appropriate level. In the preferred embodiment, the CRT is positioned such that the saws will contact the CRT approximately ¼″ below the frit line. One or more detector are used to assist the operator in the leveling of the CRT. In the preferred embodiment, the detector are laser pointers of the type commonly known in the art. The laser pointers are energized and CRT  1  is positioned such that the laser illuminates the point of contact with the blades on CRT  1 . The position of CRT  1  can be adjusted vertically by adjusting the height of track  16 , using adjustment members  22  shown in FIG. 2.  
         [0016]    After CRT  1  is properly positioned, the operator activates a manual valve which allows air to power the vacuum generator for vacuum cup  20 , which captures CRT  1  in position. The doors are then closed on cabinet  10 , and the system is started. Preferably, safety interlocks will be present on all doors of housing  10  to prevent the apparatus from being operated while the doors are in the open position.  
         [0017]    When actuator  18  is at home position  40 , the first two motors  11  will be started, rotating saw blades  12 . Saw blades on opposing sides of CRT  1  preferably rotate in opposite directions. Actuator  18  moves CRT  1  through position  42  and opposing sides A and C of CRT  1  contact saw blades  12 . After opposing sides A and C of CRT  1  have been cut by blades  12 , actuator  18  reaches center position  44  and CRT  1  is rotated 90° to facilitate the cutting of the uncut sides B and D. As CRT  1  is being rotated, saw blades  12  are powered down, and the second set of saw blades  14  are powered up. Actuator  18  then moves CRT  1  through position  46  where the uncut sides B and D of CRT  1  are cut by saw blades  14 . When complete, actuator  18  moves to end position  48  and the saw blades  14  are powered down, whereupon the operator opens a second door in housing  10  near end position  48  and removes the separated pieces of CRT  1 . The operator then closes the door and resets the apparatus, which will move actuator  18  back to home position  40 , whereupon the apparatus is ready to repeat the process.  
         [0018]    A second embodiment of the invention is shown in FIG. 3. In this embodiment, the four blades have been replaced by eight blades. In this version, the blades are preferably 4″ lapidary blades and may be rotated at a speed of up to approximately 3000 RPM. To cut sides A and C of CRT  1 , blades  12   a  and  12   b  are used. Each set of blades  12   a  and  12   b  are positioned to cut approximately ½ the thickness of the glass wall of CRT  1 . Because the glass of CRT  1  is approximately ⅜ of an inch thick at the cutting point, blades  12   a  will be positioned to cut the first {fraction (5/16)}″ of glass, while blades  12   b  will be positioned inwardly by approximately {fraction (5/16)} of an inch and will cut the remainder of the thickness of the glass wall of CRT  1 . While the glass itself is only ⅜″ thick, it is necessary to cut ⅝ of an inch total in order to produce a complete separation at the corners of the CRT  1 , because of the curvature of the outer perimeter of the panel. When CRT  1  is moved to position  46  to cut sides B and D, blade sets  14 a and  14   b  perform as do  12   a  and  12   b ; that is, blades  14   a  cut the first {fraction (5/16)}″ of the thickness of the glass while blades  14   b  are positioned inwardly to cut the second {fraction (5/16)}″ of the thickness of the glass and the corners. To support the additional weight of the motors  11  in the second embodiment, additional motor supports  8  have been added.  
         [0019]    The modifications in the second embodiment result in less wear and tear on the blades and produce less heat during the cutting operation. As a result, the blades can be rotated at a higher RPM, preferably about 3000 RPM, and the cutting operation cycle can be completed faster than with the primary embodiment.  
         [0020]    The apparatus disclosed herein has been described with reference to specific sizes and operating parameters which are exemplary only and should not be taken as a limitation to the invention, the scope of which is defined by the claims which follow.