Abstract:
A method and apparatus is disclosed for recovering the rubber content of rubber containing goods such as vehicle tires. The goods are purged of air and immersed in a bath of liquid heated to a temperature sufficient to melt the rubber. The rubber being insoluble in the bath and of less density than the bath, it rises to the surface of the bath and is removed. The process employs a perforated process tube in which the goods are passed in the bath.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates generally to the recovery of the rubber content of manufactured goods, and particularly to methods and apparatuses for reprocessing rubber tires.  
         BACKGROUND OF THE INVENTION  
         [0002]    Heretofore the rubber content of used vehicle tires has been recovered rather than incinerated or scrapped. This has been done by mechanically chopping the tires and grinding them and then separating the rubber and metal with a gravity air classifier or centrifuge. In other cases tires have been frozen, as with nitrogen, and then ground. These recycling processes however have been inefficient and very costly. The present invention provides a new method and apparatus for recovering the rubber content of used vehicle tires that is substantially more efficient and less costly to perform.  
         SUMMARY OF THE INVENTION  
         [0003]    In a preferred form of the invention goods comprised of both rubber and heavier than rubber material are processed to recover their rubber content. The method comprises the steps of immersing the goods in a bath of liquid having a density greater than the density of the rubber and in which the heavier than rubber is insoluble and has a greater density than the bath. The bath is at a temperature elevated above the melting point of the rubber. This causes the rubber to become molten, to separate from the non rubber material, and rise to the top of the bath. The molten rubber and the heavier materials are then removed from the bath separately.  
           [0004]    In another form of the invention apparatus for use in recovering the rubber content of goods that comprise rubber and heavier than rubber material comprises a separation tank, means for heating the separation tank, and a process tube that extends into and out of the separation tank. The process tube has perforations in its mid-portion that are located within the separation tank. The apparatus also has means for pushing the goods in the process tube to the mid-portion where their rubber content may be melted and flow out of the tube through the tube perforations and for pushing the residual non molten content of the goods out of an end of the tube located beyond the perforations. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0005]    [0005]FIG. 1 is a schematic illustration of apparatus that embody principles of the invention in its preferred form and which may be used in performing a preferred inventive method of the invention.  
     
    
     DETAILED DESCRIPTION  
       [0006]    With reference in more detail to the drawing there is shown apparatus that may be used to recover the rubber content of used or recycled vehicle tires. The apparatus comprises a hopper  11  into which tires may be deposited. Preferably the hopper is mounted on a scale for volume intake rate control. The hopper  11  is mounted over a first tubular chamber  12  from which it is isolatable by an unshown process block or gate valve. One end of the first chamber  12  is in communication with a second tubular chamber  13 . These two chambers are also isolatable by another unshown process block or gate valve. Chamber  12  is provided with an hydraulic piston-like ram schematically as shown by arrows  15  for pushing discrete loads of material out of the chamber  12  and into the second chamber  13 . The chamber  13  is provided with an unshown purge means for purging the chamber with a inert gas such as nitrogen or carbon dioxide. The second chamber  13  has a lower end mounted in communication with an intake end  17  of a process tube  20 . The second chamber is also equipped with an hydraulic ram schematically shown by arrows  19  for use in pushing materials into the process tube through another unshown gate valve. All of the chambers are preferably made of a high impact resistant material such as steel.  
         [0007]    The process tube  20  is seen to extend through a separation tank  21  which has a service port  22 . The tank is provided with unshown means for heating it to operating temperatures in the range of 750° F. to 1000° F. This may be in the form of fuel-fired burners or electric heaters. Its intake end  17  is seen to be outside of the tank  21  as is its outlet end  18 . It too is provided with an hydraulic ram shown schematically by arrows  26 . Each of these ends are seen to be inclined and to straddle a bowed mid section  24  that is located inside the tank. The midsection is seen to have a number of perforations in the form of slots that are preferably circumferential arcs of some 30° to 45° each. The slots are in different quadrants of the process tube so that all quadrants have some slots.  
         [0008]    The outlet end  18  of the process tube communicates with a collection drum  28  through another unshown gate valve into which metallic materials, such as steel belt and valve debris are delivered. This essentially non-rubber debris can be emptied out the bottom of the drum onto a conveyor as indicated by arrow  29 . The collection drum  28  is equipped with an unshown hydraulic ram that is extendable from its top nozzle  31  to its bottom nozzle  32 .  
         [0009]    Finally, the apparatus includes a recovery tank  33  that is in fluid communication with the top of the tank  21  by a conduit shown schematically by arrows  34 . This tank is used to receive rubber separated from non-rubber material in the separation tank  21  along with any gases. These gases can be flashed off as schematically indicated by arrow  35 . Both the conduit  34  and recovery tank  33  are heated. From tank  33  rubber may be discharged in molten form as indicted by arrow  36 .  
         [0010]    For operation the separation tank  21  is filled with a liquid in which rubber is insoluble and which has greater density and thus is heavier than rubber. The heaters are energized to bring the apparatus up to operating temperature. If high density rubber is to be processed it may be preheated. Rubber tires are then deposited it the hopper  11 . The tires may be whole or severed. Once a batch of preselected weight has been deposited, the batch is introduced into the first chamber  12  by opening the gate valve at the bottom of the hopper. The hopper gate valve is then closed and the batch transferred to the second chamber  13  by opening the gate valve between these two chamber and cycling the ram  15 . The second chamber is then purged of air with the inert purge gas. From the second chamber  13  the batch is forced, air free, into the intake end  17  of the process tube  20  by synchronized operation of the ram  19  with the gate valve at the bottom of chamber  13  open and the gate valve between chambers  12  and  13  now closed.  
         [0011]    Once the batch has been introduced into the process tube it is pushed by the ram  26  into the slotted midsection  24 , the ram being sufficiently flexible to traverse the arcuate tube. With the batch now submerged in the hot liquid bath, the rubber melts. Being lighter than the bath, as the rubber melts it flows out of the process tube through the slots to the surface of the bath. As the separation tank is operated substantially filled with liquid, this surface is at or near the top of the interior of the tank. Conversely, the relatively heavy material, principally the metal debris from steel belts and valves, remains in the tube. This heavy debris being mostly larger than the slots, most of it does not pass out of the tube through the slots and onto the floor of the separation tank. What does fall to the floor is accumulated and periodically removed from the tank during periodic servicing and maintenance accessed via the service port  22 .  
         [0012]    From the surface of the bath the molten rubber is driven through the conduit  34  and into the recovery tank  33 . It is driven by the volumetric displacement force provided by the continuous generation of gases in the heated separation tank. From here the rubber is periodically discharged in molten form as shown by arrow  36  while accompanying gases are outgassed and flashed as indicted at  35 . As this is occurring the heavier debris is cyclically removed by the ram  26  from the process tube  24  into the collection drum  28  from which it is periodically dumped as shown at  29 . This debris may include glass, solder, low melting alloys, metallic oxides and slags, and molten salts in addition to the debris from steel belts and valves. To insure that the outlet remains open, and that any bridged debris can be dislodged, an unshown hydraulic operated puller may be mounted in the outlet end  18 .  
         [0013]    As previously stated, the preferred operating temperature range is 750° F. to 1000° F. Below this range incomplete melting may occur; above this range high temperature degradable can become coke and gases. Although the method and apparatus is primarily designed for use in processing used vehicle tires it may, of course, be used to recover rubber from other types of manufactured goods.  
         [0014]    Though the invention has been described in its preferred form it should be understood that modifications may be made thereto without departure from the spirit and scope of the invention as set forth in the following claims.