Abstract:
An improved method and machine for safely and properly crushing fluorescent lamps or tubes of various types, various sizes and various configurations is described. The inventive system discloses a machine comprising a housing which can be placed in a building or facility such a hardware store or other retail establishment which is easily accessible to the public. Rewards may be provides to the party/person disposing the fluorescent tubes such as redeemable coupons, etc, The machine thus encourages the public to safety crush and dispose fluorescent lamp tubes and thereby tends to increase the rate of recycling of fluorescent tubes. the invention also proves heating means for more quickly and safely reducing the hazardous mercury vapor contained in the crushed tubes.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application claims the rights to the filing date of U.S. provisional application Ser. No. 61/575,373 filed on Aug. 19, 2011 in the name of Troy W. Livingston, the same inventor herein, and this application having the same Title as said provisional application. 
         [0002]    This invention relates to the disposal of chemical wastes, and particularly to the collection, storage, crushing and disposal of fluorescent lamps and the processing of mercury vapors emitted from said fluorescent lamps, and rendering said mercury vapors to a non toxic state as per Federal and Sate requirements. 
         [0003]    Fluorescent lamps are of many shapes and sizes including elongated bulbs/tubes of several feet in length as well as coiled bulbs and compact bulbs. One universal type is a compact fluorescent lamp (CFL) that is about 2-8 inches in length and has a tube body diameter of 2-4 inches, another common type of fluorescent lamp comprises an elongated tube four feet in length and tube body which is 1-2 inches in diameter, and a third common type is in the form of a circle 4-12 inches wide and the tube body which is 1-2 inches in diameter. 
         [0004]    All of the fluorescent lamps contain mercury and toxic mercy vapor as well as a mix of exotic and common metals in a powdered phosphorescent coating inside a glass tube. Modern four feet long fluorescent tubes have 8-10 mg of mercury. Older tubes may have several times that amount of mercury. The phosphor in a common “cool white” bulb is a complex mixture containing mercury and various exotic metal and common metals. During the working life of a fluorescent bulb or lamp the mercury is gradually absorbed into the phosphor. At the end of the lamp&#39;s useful life up to 98% of the mercury has been absorbed. This makes the phosphorescent powder dangerously toxic and must be contained. 
         [0005]    In one current practice of recycling spent lamp tubes/bulbs, the tubes are placed in corrugated boxes and shipped a disposal center. Shipping the spent tubes from one site to another often results in tube breakage, or damage and opening of the container thus exposing workers in the vicinity to the toxic mercury vapors. Further, such supping practice is expensive to the party disposing the lamps and hence is not conducive to improving the recycling rate. 
         [0006]    There are commercially available fluorescent lamp disposable devices which appear to comprise modified 55 gallon cans with various entry ports to accept various types of fluorescent lamps. Since these prior devices are operated by employees, no provisions have been made or components provided, to distinguish and separate fluorescent bulbs from unacceptable objects, nor to protect the crushing components from damage by unacceptable objects, nor to provide components for automatically separating fluorescent lamp bulbs from other waste. 
         [0007]    In the USA the recycling rate for fluorescent lamps is quite low in the 25% range. Basically this means that fluorescent tubes are disposed in or with the same garbage as all the other household garbage, or with recycled nontoxic and useable materials such as paper or cardboard or plastics. 
         [0008]    In Europe the recycling rate for fluorescent lamps is about 80%. The present invention is intended to make recycling of fluorescent lamp tubes easier, safer, and importantly to promote and raise the rate of recycling in the USA and throughout the work such as by rewarding the party/person disposing the lamps with redeemable coupons or merchandise credits. 
     
    
     SUMMARY OF THE INVENTION 
       [0009]    A basic object of the present invention is to provide an improved fluorescent lamp bulb/tube crushing and disposal method and system. More particularly, the present invention provides an improved method and machine for safely and properly crushing fluorescent lamps or tubes of various types, various sizes and various configurations. The inventive system discloses a machine comprising a housing which can be placed in a building or facility such a hardware store or other retail establishment which is easily accessible to the public thereby encouraging the public to safely crush and dispose fluorescent lamp tubes and thus increase the rate of recycling of fluorescent tubes. As one incentive to dispose of the fluorescent bulbs, rewards such as redeemable coupons may be offered to the party disposing the fluorescent bulbs in the inventive machine. The invention discloses a unique crushing system having two cooperating crushing wheels positioned adjacent one another. One of the crushing wheels is pivot able and spring biased to a closed position to crush fluorescent tubes. Should an object that is inserted to be crushed is of a hard damaging material, the pivoting wheel is forced outwardly by the hard material. The pivoting wheel opens against the spring bias and allows the hard object to drop through the open spacing between the wheels thereby preventing damage to the machines and the other components of the machine. The invention also provides heating means for quickly and safely reducing the volatility of the crushed tubes. Further, the invention provides means for separating fluorescent lamps/tubes residue and non fluorescent waste. 
         [0010]    The foregoing features and advantages of the present invention will be apparent from the following more particular description of the invention. The accompanying drawings, listed herein below, are useful in explaining the invention. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is an isometric of the housing of the present invention; 
           [0012]      FIG. 2  is a side section view of the inventive fluorescent lamp crusher machine to show the components of the machine mounted in a mercury vapor sealed housing; 
           [0013]      FIG. 3  is a view of the crushing wheels of the fluorescent lamp crushing machine and the supporting components; 
           [0014]      FIG. 4  is a view of the crushing wheels in the process of crushing a compact fluorescent bulb; 
           [0015]      FIG. 5  is a view of the crushing wheels useful in explaining the function of the blades attached to the wheels; 
           [0016]      FIG. 6  is a view of the crushing wheel depicting the open or pivoted position of one wheel that protects the pair of wheels from damage; 
           [0017]      FIG. 7  is an isometric view to show die heating band provided for the fluorescent bulb residue container and the clamping mechanism for the band; 
           [0018]      FIG. 8  is a top view of the container of  FIG. 6  with the clamping mechanism in a closed mode; 
           [0019]      FIG. 9  is a top view of the combiner of  FIG. 7  showing the clamping mechanism in an open mode; 
           [0020]      FIG. 10  shows an alternative embodiment of the crushing wheels shown in the previous figures; 
           [0021]      FIG. 11  show a second alternative embodiment of the crushing wheels; and, 
           [0022]      FIGS. 12A and 12B  show graphs of the heating cycle for the mercury vapors released by the fluorescent lamp tubes/bulbs. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0023]      FIG. 1  is an isometric view of the noosing  11  of the inventive fluorescent lamp/tube crushing machine  10  and depicts the general configuration of the housing. The overall dimensions of one embodiment of housing are: 4.5 ft wide by 5 ft high by 3.5 ft in depth. The indicated bulb opening  24  is long enough to conveniently accept the common elongated fluorescent tubes that are four feet in length. Also the bulb opening  24  is wide enough to accept compact fluorescent tubes, but is narrow enough to limit the size of large objects that can he inserted through the opening, as a safety precaution. A control panel  2 , including suitable know type start button, ready lights and a cancel button are mounted on housing  11 . Service doors  3  for accommodating the insertion and removal of a container for fluorescent bulb residue are conveniently mounted in front of the housing  11 . 
         [0024]      FIG. 2  is a side view partly in section of the housing  11  depicting the inventive fluorescent lamp crushing machine/crusher  10 . The machine  10  is intended to be positioned in a location easily accessible to the public on the floor of a retail store or adjacent an entrance to a store to receive fluorescent lamps that are to be crushed. The machine is electrically powered and includes internal controls which are activated in response to the opening of a lamp receiving door (as will be described), and a start button and other button commands from the party/person disposing a fluorescent lamp or lamps. 
         [0025]    As depicted in  FIG. 2 , the inventive fluorescent lamp bulb crushing machine  10  comprises an enclosed rectangular housing  11  including various panels, doors, channels and mounting support surface as will now be described. 
         [0026]    To initiate the machine operation, the person (the user) disposing a fluorescent lamp bulb  12  pushes lamp receiving door  24  open. The top of door  24  is hinged to the housing  11  and is mounted to be pivotable about hinge  22  point biased to be closed as by suitable spring means, not shown. The door can be pushed open by a user to move to the dotted position indicated in  FIG. 2  to provide an elongated opening to receive a fluorescent bulb  12  as long as four feet or a CFL (compact fluorescent bulb), or a circular bulb. The bulb  12 , depicted in  FIG. 2  is a CFL. The opening of door  24  causes a “ready” light to be illuminated. Also a vacuum motor  38  starts immediately upon the opening of the door  24  and runs for at least fifteen seconds (even if no bulb is inserted through door) Next the user drops the bulb  12  into bulb receiving tray  32  and then pushes start button  45  to initiate the bulb crushing operation. After a four second timed delay, the crushing operation starts. This four second delay is provided to give the user an opportunity to assure that she/he has inadvertently dropped a non intended object such as car keys into the tray. A cancel button  46  is provided for the user to stop (abort) any further operation and to retrieve any non-intended object, or to stop operation of the machine for any other reason. After the four second delay period, the machine operation will proceed and the cancel button  46  will not stop operation of the machine. 
         [0027]    Bulb  12  now rests on receiving tray  32  which is triangular in shape and is formed by a panel  19  and a crushing chamber access door  23 . As stated above, tray  32  is sufficiently long to accept a common forty-eight long fluorescent tube. Further tray  32  is sufficiently wide and deep to accept the universal CFL (compact fluorescent luminescent) tubes and the common circular types of fluorescent tubes. When the receiving door  24  closes, and a tube  12 , the air cylinders  20 , mounted adjacent tray  32 , are energized to drive plungers  21  of spaced air cylinders  20  to strike and break the luminescent tube(s) in the tray. At least two identical air cylinders  20  are mounted in spaced relation adjacent tray  32 . As can be appreciated, the various cylinders  20  operate in concurrent relation and are particularly useful for breaking elongated fluorescent bulbs which may be up to four feet in length. The plungers  21  of air cylinders  20  effectively break the elongated bulb into manageable pieces for subsequent crushing by the crushing wheels. When the door  23  is closed it forms part the angled bottom of tray  32 . Door  23  is hinged to a bracket  54  and is controlled to open and close by an air cylinder  55 . After a three second delay from the time the air cylinder plunger  33  extends to close receiving door  24 , an air cylinder  55  is energized to move crushing chamber access door  23  to open to the position indicated by the dotted lines. When door  23  opens the bulbs or other objects in tray  23  fall down. The panel  19  forming the other part of the bottom of tray is also angled downwardly to assure that when door  23  is opened, any luminescent tube parts drop down and out of tray  32 . (Two seconds after door  23  opens, the plunger of cylinder  55  closes door  23 ). 
         [0028]    Concurrently with the opening of chamber door  23 , the crushing wheels  50  and  51  are energized to start rotating. The bulb  12  or broken pieces of bulb  12  fall into chamber  61  and onto the rotating crushing wheels  50  and  51  where the bulb  12  and any pieces of tube are crushed. 
         [0029]    Note that the timing for closing and opening of the doors is necessary to ensure that the housing  11  is fully sealed from the outside atmosphere so that no mercury vapors are released to the ambient air. 
         [0030]    As shown in FIGS.  2  and  3 - 6 , crushing wheels  50  and  51  each have outwardly extending crushing teeth, generally labeled as  52 , on their periphery. The wheels are of the same size and are seven inches in diameter and ten inches in axial length. In one embodiment, the teeth of the wheels are frusto conical is shape and are about one inch high. (The term frusto-conical is used herein to refer to a pyramidal shaped object that has Its peak cut off and made flat and thus is parallel to a flat bottom). 
         [0031]    Wheel  50  is driven by a suitable electric rector, not shown. Wheel  50 , in turn drives wheel  51  via chain  55 , see  FIG. 6 . The chain is shown in  FIG. 6 , but for purposes of clarity of the other components in the drawings the chain is not shown in  FIGS. 2-5 . The connection of chain  55  between the wheel  50  and  51  causes the wheels to rotate in opposite directions, i.e., wheel  50  rotates in a counter clockwise direction and wheel  51  rotates in a clockwise direction. The teeth of one wheel are interleaved with the teeth of the other wheel. Flat ended teeth are selected in order to properly crush the bulb  12  and the broken pieces of bulb without digging into and getting caught in the broken pieces which might result in possible clogging of the teeth and wheels. 
         [0032]    Note also that the crushing wheels  50  and  51  are mounted to have about a three-quarter inch spacing between the teeth of wheel  50  and the teeth of wheel  51 . The separation between the teeth results in the crushing of the bulbs without grinding or pulverizing the bulbs or bulb pieces. Additional smaller teeth may be provided on wheels  50  and  51  to crush fluorescent tubes of small diameter. 
         [0033]    The crushed bulb  12  and bulb pieces fall down past wheels and are directed by pivoting diverter plate  49  to a fluorescent bulb residue container/barrel  90  made of steel. Suitable sensors  43  control the positioning of diverter plate  49 . The sensors  43  control an air cylinder  42  that has its plunger  41  affixed to plate  49  to position the plate to guide the fluorescent residue to container or barrel  90 . When the sensors  43  detect an object that is not a fluorescent tube, air cylinder  42  is activated to move plate  42  to the position indicated by the dotted line to guide the object to a non fluorescent waste container  12 . 
         [0034]    An important and unique feature of the crushing assembly  47  is that wheel  50  is mounted on a stationary axle while wheel  51  is mounted on an axle that can swing or pivot from a first or closed position and a second or open position, indicated by the dotted lines in  FIGS. 1 and 6 . The purpose of the aforementioned swing is to protect the wheel from damage should hard unacceptable objects such as hard non crushable objects are dropped through door  24  into tray  32 . As will be described in detail herein after, when such a non crushable object engages the wheels, wheel  11  will swing out to the dotted line position and the object will drop down between the wheels into a trash bin  44 . Note that when wheel  11  swings out and air cylinder  42  will be energized to move diverter plate  43  to position indicated by the dotted lines to guide the unacceptable object to a non fluorescent bulb waste container  44 . 
         [0035]    Another important feature of the invention is that all breaking and crushing of the fluorescent bulbs occurs in a folly closed and safe environment and also meets State and Federal Regulations. Refer now to  FIG. 2  and particularly to the heavy arrow lines thereon. Dotted arrow line  27  depicts the ambient air entering the machine housing  11  via filter  29 . The filtered air moves through channel SB past the one way air valve  35  into the interior of the housing  11 . The open position of valve  35  is indicated by the dotted lines. The filtered air also moves down channel  59  through a second air input valve  36  to the bulb crushing chamber  61 . Both air valves  35  and  36  are mounted in horizontally hinged position to housing  11  to close by gravity when the machine  10  is in a passive or none operating mode. 
         [0036]    As stated above as soon as the receiving door  24  is pushed open, the vacuum pump  38  starts and air indicated by arrow line  39  is exhausted from housing  11  by the pump  38  and concurrently as air is drawn into housing  11 , as described above. 
         [0037]    As stated above soon as the user opens the bulb receiving door  24 , the vacuum pump motor is energized for a period of 15 seconds. After the user places or drops the spent fluorescent bulb in the tray  32 , and the receiving door  24  is closed, she/he presses the start button  45  to initiate the crushing cycle, and the vacuum pump continues to run. Thus the vacuum pump  38  has now been activated to exhaust air from the housing  11  and particularly from the tray chamber  32  and crushing chamber  68 , and to draw ambient air into the housing via channels  58  and  59 . As indicated by the dashed line  34 , exhaust air from chamber of tray  32  is drawn up through channel  71  and one way ball valve  73 , through channel  74  as indicated by dashed line  34 , air filter  53 , and through activated charcoal filter  63  to filter out the mercury vapor. The filtered and cleaned air indicated by the solid line  39  thence exits through channel  75  and vent  48  of housing  11  to the atmosphere. Mercury vapors created by the breaking and crushing of the fluorescent bulbs are fully filtered out of the exhaust air by charcoal filter  63 . 
         [0038]    Also as depicted in  FIG. 2 , by the heavy dashed lines  67  and  69  air is also drawn from the crushing chamber  61  as soon as the vacuum pump  38  is activated. Ball valve  73  is a one way valve positioned to allow flow of air upward and outwardly from crushing chamber  61 . Thus as soon as vacuum pump  38  is activated air is caused to be drawing the crushing chamber  61  via ball valve  72 , through channel  71 , ball valve  73  and channel  74 . Valves  72  and  73  are mounted in series, and as air ix exhaust via channel  71  both valves  72  and  73  are open to enable a full flow of exhaust air. When the machine is in a passive mode, both ball valves  71  and  72  are closed by gravity and ambient air is prevented from entering the housing  11 . As indicated by the line  34  the exhaust air is expelled via the paths previously described to pass through activated carbon filter  63  immediately upon opening door  24  and continues throughout the machine operation. 
         [0039]      FIGS. 3-5  are additional detailed view of the overall crushing assembly  47  wheels  50  depicting various modes of the crushing cycle. Refer to  FIG. 3  which depicts the crushing of a CFL (compact fluorescent tube)  12 .  FIG. 3  shows a CFL tube  12  at a point just prior to failing into the rotating crushing wheels  50  and  51 .  FIG. 4  depicts the crushing of bulb  12  by the teeth  52  of wheels  50  and  51 . Note that as depicted in  FIG. 4 , the teeth  52  of the two wheels do not engage each other and hence the bulb  12  is crushed hut not ground down. The bulb  12  is crushed into small pieces that are guided into the bulb collection container by diverter plate  49 . 
         [0040]    The function of blades  16 , on wheels  50  and  51  is depicted in  FIG. 5  showing a box  12 A that gets fed to the crushing wheels  50  and  51 . When a relatively light box  12  A is struck by the flat teeth  32  of the wheels, the box may tend to bounce and “float” above the rotating teeth and the object will not be engaged and crushed. However, blades  16  which extend outwardly of the flat teeth  12  and are somewhat flexible will engage and push box  12 A downwardly to be fed to the passage between the wheels and the box  12 A will be crushed. 
         [0041]    As shown in  FIGS. 3-5 , wheel  51  is biased to a closed position by the force of spring  77  connecting through arms  87  and  85 . As depicted in  FIG. 6 , when the teeth  52  of the rotating wheels  50  and  51  engage a non crushable object very high forces will be generated to push the wheels apart. The spring  77  force tending to hold wheel  51  in a closed position will be overcome and wheel  51  will move (swing, pivot) outwardly. The passageway between wheels  50  and  51 , indicated by the arrow line  81 , will widen and the non crushable object  12 B will drop through the passageway into the non fluorescent waste container  44 . Swinging or pivoting wheel  51  thus provides the important function of protecting the wheels  50  and  51 , as well as the overall machine  10  against damage. 
         [0042]    Refer now to  FIG. 6  for an additional detailed explanation of the operation of swinging/pivoting wheel  51 . The motor drive shaft rotates wheel  50 . In turn, a chain  55  connects sprocket  60  on wheel  50  to drive sprocket  61  on wheel  51 . As the wheel  51  pivots outwardly and opens the spacing between the two wheels (as described above) provision must be made to assure that the chain remains in a tight engaging configuration around both wheels to properly and synchronously drive wheel  51 . The crushing wheel assembly  47  depicted in  FIGS. 3-6  has been developed to assure that the chain  55  remains taut and does not sag in either the closed or open mode. A vertically extending arm  85  has its lower end mounted to the axle of wheel  51 . The upper end of arm  85  is mounted to pivot on pin  88  that in turn is affixed to the lower end of arm  87 . The upper end of arm  87  is affixed to tension spring  77 . Arm  87  pivots about stationary pin  86 . An idler wheel  53  is mounted on the pin. An angled extension  89  is provided for arm  85 . An idler wheel  54  is mounted on the distal end of extension  89 . 
         [0043]    As depicted in  FIG. 6 , drive wheel  50  is mounted to rotate in a counter clockwise to move the non crushable object  12 B downwardly. The path of the chain  55  goes from the bottom of sprocket  60  to the top of sprocket  61  in a configuration to drive wheel  51  in a clockwise direction to thus cooperate with wheel  50  to move object  12 B downwardly. The path of the chain  55  continues from the top wheel  51  down and around idler wheel  54 , up and around the top of idler wheel  53 , and thence down and around drive wheel  50 . 
         [0044]    As wheel  51  is moved outwardly, arm  85  pivots on pin  88  and moves arm  87  about pin  86  to overcome the tension force of spring  77 . Idler wheel  54  which is mounted on angled extension  89  is positioned to adjust or “take-up” any slack in chain  55  as it is moved outwardly and back to its initial lamp crushing position This pivoting movement functions to maintain the chain  55  in a taut condition throughout the complete movement of wheel  51  from its initial bulb crushing position to its open position, and the return of wheel  51  from its initial bulb crushing position to its open position, and the return of wheel  51  to its initial position. The tension of spring  77  returns the wheel  51  to its initial position, as soon as the non crushable object  12 A drops past the wheels  50  and  51  and the force effected by the object  12 A is removed. As stated above, the moving or swinging action wheel  51  provides the important function of protecting the wheels  50  and  51 , as well as the overall machine  10 , against maliciously intended damage. 
         [0045]    Refer now to  FIGS. 2 and 7 .  FIG. 7  is an isometric view of the fluorescent bulb residue container  90  which is depicted in section in  FIG. 2 . Mercury evaporation from the residue of a fluorescent lamp takes approximately two weeks at room temperature for the mercury vapor contamination to fall below the hazardous levels. Data has shown that the mercury vapor volatilization rate varies with temperature. 
         [0046]    Refer now to the graphs shown in  FIGS. 12A and 12B . The graph of  FIG. 12A  shows vaporization rates when the mercury residue is heated to 185 degrees F. and when the residue is heated to 210 degrees F. The higher heated mercury evaporates at a faster rate. In the inventive system the fluorescent residue is heated to about 185 degrees F. to decease the time period to reduce die toxicity of the mercury vapor to non hazardous levels from two weeks to approximately one hundred and ten minutes, that is to essentially 0.005 mg of mercury per cubic meter, well below Federal and State requirements. While it has been found that if the temperature is increased to 210 degrees F., the mercury vapor can be rendered less toxic in a shorter period, as shown in graph of  FIG. 12A , unpleasant odors begin to emanate when the fluorescent tamp residue is heated to a temperatures above 185 degrees F. Therefore, and as shown in  FIG. 12B , heating the residue to 185 degrees F. has been found preferable, and basically it requires only a few minutes longer to render the residue non hazardous. 
         [0047]    Thus, one embodiment of the heating assembly of the invention includes an electric heater  92  to heat container  90  and the fluorescent lamp residue to 185 degrees to accelerate rate of volatilization of the mercury vapor. Refer now to FIGS.  2  and  7 - 9 .  FIG. 2  shows a steel barrel container  90  for the luminescent bulb residue mounted on the floor of housing  11 . The container  90  is mounted on a platform that may be rolled out of housing  11 , so that the residue container can is easily inserted and removed. The housing  11  includes suitable doors  14  for accommodating the insertion and positioning of container  90  in housing  11 . An electric powered heating band  91  is mounted to surround a portion of the barrel  90  to heat the barrel and any contained luminescent bulb residue. The heating band  91  has a conductive heating coil  92  embedded therein. In one embodiment band  91  is about five inches wide extends about ¾ of the circumference of the barrel  90  and is powered to heat barrel  90  and the contained fluorescent lamp residue to about 185 degrees F. for the purpose described above. 
         [0048]      FIGS. 7-9  show a clamp type assembly  93  that positions band  91  around barrel  90 . Downwardly extending rods generally labeled  94  are affixed to the floor of housing  11  to support the clap assembly  93  around barrel container  90 . Barrel  90  has to be removed front housing  11  when it is full of luminescent tube residue, and reinserted and positioned within housing to be in position to receive additional residue. The platform is mourned on rollers and enables convenient positioning and the barrel allows for easy removal and reinsertion. The clamp assembly  93  serves the foregoing purpose. 
         [0049]      FIGS. 10 and 11  show alternative embodiments of the crushing wheels. The size and operation of the alternative embodiments  50 A of  FIGS. 10 and 50B  of  FIG. 11  are essentially the same as those of wheel  50  of  FIGS. 2-6 . Note of course that wheels  50  and  51  are identical. Wheel  50 A of  FIG. 10  is constructed to have the crushing teeth formed as tubes  106  mounted in spaced relation on the periphery of a round end plates  107  that have an opening  108  to mounted on the wheel axle. Wheel  50 B of  FIG. 11  is constructed to have the crushing teeth formed as gear-like protrusions  109  formed on the periphery of a solid cylinder  110 . A center opening in cylinder receives the wheel axle. As stated above the size and operation wheels  50 A and  50 B are identical to those of wheel  50 . These alternative embodiments appear to be somewhat more inexpensive to manufacture. 
         [0050]    While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.