Abstract:
A method and apparatus for injecting solid particles such as dry ice into an airstream using an airlock having a spherical valve member with spaced through ports and rotatable between an annular seal on one side of the spherical member for feeding the particles to the fluid stream chamber with an annular seal on the opposite side for sealing a particle feed chamber. The airlock device is useful for sealing fluid stream pressure of about 133 Kg/m 2  and temperatures of about 350° R.

Description:
BACKGROUND 
   The present disclosure relates to devices for feeding solid particles into a fluid stream and particularly a pressurized stream of air such as that employed for blasting or cleaning operations where it is desired to inject solid particles for effecting abrasion on the article to be cleaned by the fluid stream. A particularly widely employed application of such devices is that of feeding solid carbon dioxide or dry ice particles into a pressurized air stream for blast cleaning of particles or items to be cleaned and recycled in a manufacturing or assembly operation. Such devices for introducing particles into a fluid stream are often referred to as “air-lock valves.” Dry ice fluid blasting is widely used for cleaning metal parts to be used in manufacturing or reconditioning of components, these items can be found in the automotive, electrical, nuclear, and printing industries. 
   Heretofore, vane type devices have been employed for feeding dry ice particles into a pressurized air stream; and, problems have been encountered in providing sealing of the pressurized fluid from the feeding chamber for the dry ice particles and particularly as the feeder device is lowered to the temperature of the dry ice of about −110° F. (350° R). Typically, the feeder mechanism is operated by a motor to rotate the vane or disc member for introduction of the dry ice particles into the flow stream. Another type of feeder mechanism employed for feeding dry ice particles into a fluid stream is that of a cylindrical rotary member; however, feeder mechanisms of this type have also encountered problems of sealing about the injection port to the fluid pressure chamber and the cylindrical rotor member at the extremely low temperatures encountered where dry ice is fed into the fluid stream. Heretofore, where increased pressure was applied to the seals for effecting sealing to overcome the contraction of the feeder components, the increased friction required prohibitive increases in power to the motor employed for rotating the vane, disc or rotary cylinder. Thus, it has been desired to provide a feeder device for injecting particles into a fluid stream, particularly for injecting dry ice into a pressurized air stream, in which effective sealing is provided at the extremely low temperatures encountered with dry ice and in such a manner as to eliminate the need for excessive power to the motor for rotating the feeder mechanism. 
   BRIEF DESCRIPTION 
   The present disclosure describes a feeder device for injecting solid particles into a fluid stream, and particularly for injecting dry ice into a pressurized air stream, employing a spherical member having recesses therein for receiving the solid particles from a feeding inlet and having a pair of annular seals disposed on opposite sides of the spherical member which is disposed in a housing for rotation therein. The side of the spherical member opposite the particle feed inlet is disposed over a particle inlet to a fluid pressure chamber and is sealed thereabout by one of the annular seal members. The spherical member is mounted on a shaft journalled for rotation in the housing and may be motor driven for rotating the spherical member to cause the recesses to receive dry particles and rotate them past the seals to the inlet to the fluid pressure chamber. A portion of the annular seal between the spherical member and the fluid pressure chamber has the curvature thereof matched to the curvature of the spherical member for effective sealing. The spherical member and housing may be formed of stainless steel; and, it has been found satisfactory to form the first and second annular seals of polytetrafluoroethylene material filled with glass fiber particularly for service at temperatures of −110° F. The region surrounding this spherical member between the annular seals is vented to the atmosphere to relieve any residual pressure trapped in the recesses as they rotate past the seals. 
   The present device thus provides a spherical rotating member with recesses therein for receiving solid particles and rotating the spherical member to pass the solid particles past annular seals for discharge through an inlet into a pressurized fluid flow chamber for carrying the solid particles in the fluid stream. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The sole drawing is a section view taken through the axis of symmetry of the feeder device of the present disclosure. 
   

   DETAILED DESCRIPTION 
   Referring to the drawing, the feeder device of the present disclosure is indicated generally at  10  and includes a body or housing  12  having a generally hollow cylindrical configuration and has an inlet fitting subassembly indicated generally at  14 , which is disposed in the inner perimeter of housing  12  and which has an opening or inlet  16  for receiving solid particles  18  therein, which may be by gravity flow. The subassembly  14  may be retained in housing  12  by any suitable removable fastening. 
   Housing  12  has a spherical member  20  disposed therein which has a plurality of recesses  22  formed on the surface thereof in a circumferentially spaced arrangement. The spherical member  20  is disposed for rotation within housing  12  and has for this purpose a shaft  24  received therethrough. Shaft  24  is journalled for rotation in bearings  26 ,  28  provided on housing  12 . In one embodiment, member  20  has a diameter of about 4.5 m (114 mm) with about 17 recesses  22  each of about 0.75 m (19 mm) diameter and similar depth. 
   Housing  12  has a fluid pressure chamber  30  formed in the lower end thereof which has an inlet  32  adapted for connection to a source of pressurized fluid, such as air, and an outlet  34  for discharging fluid therefrom. In the present practice, chamber  30  receives air pressurized typically to about 200 PSI (1380 kPa). However, lower measures and high measures may be encountered. Chamber  30  also has a particle receiving opening or port  36  formed therein and which is located to have the surface of spherical member  20  disposed thereover as illustrated in  FIG. 2 . 
   Spherical member  20  is secured to shaft  24  by any suitable expedient as, for example, a set screw  38  threaded through a bore in the spherical member located in one of the recesses  22 . 
   Shaft  24  has an end thereof extending externally of the housing  12  provided with a coupling, indicated generally at  40 , for connection to a motor  42  indicated in dashed outline operative for effecting rotation of shaft  24  and spherical member  20 . Motor  42  may be either electrically operated or an air motor. 
   Spherical member  20  has disposed about the lower hemisphere thereof an annular seal ring  44  which has a portion of the inner periphery thereof configured to match the curvature of the spherical member  20  to effectively seal there against during rotation of the spherical member  20 . Annular seal  44  may have suitable seals such as ring  46 , disposed about the outer surface thereof for sealing against the inner surface of the housing  12 . Optionally, a second seal ring  48  may be provided about annular member  44  and spaced from seal  46  for sealing about the inner cylindrical wall of housing  12 . 
   A second annular seal  50  is disposed about the upper hemispherical surface of spherical member  20 ; and, the seal member  50  may have suitable annular seals, such as seal ring  45  about the periphery thereof for sealing against the inner surface of the housing  12 . It will be understood that suitable generally semi cylindrical recesses  52 ,  54 ,  56 ,  58  are formed respectively in the annular seals  44 ,  50  to provide clearance for shaft  24  and to enable the annular seal  44  to positively seal on the surface of spherical member  20 . 
   The housing  12 , inlet fitting sub-assembly  14  and the surrounding housing structure forming the pressure chamber  30  may be formed of stainless steel or other suitable material resistant to corrosion from moisture in the fluid pressure chamber  30  and on the surface of the spherical member  20 . 
   The region between the upper annular seal  50  and the lower annular seal  44  within the housing is vented by suitable ports  60  provided in the wall of the housing  12  as shown in the broken away central portion of the spherical member  20 . 
   In the exemplary embodiment, a suitable hopper  62  with flange  64  is attached to flange  66  on inlet subassembly  14 , by any suitable expedient, such as screws or bolts (not shown). 
   In operation, as the spherical member  20  is rotated, the solid particles such as dry ice particles (solid CO 2 ) descend through the inlet  16  and are collected in the recesses  22 ; and, as the spherical member  20  continues to rotate, the particles are retained in the recesses by seals  50 ,  44  until passing through the lower seal member  44 . The particles are then discharged by gravity and or compressed fluid into the fluid pressure chamber  30 . As the empty recesses  22  are rotated back up past the sealing surface of seal member  44 , the small amount of compressed fluid from chamber  30  retained in the recess  22  is discharged into the space between the upper and lower seal members  50 ,  44  and vented through vent ports  60 . 
   If desired, a suitable funnel  62  may be attached to the inlet fitting sub-assembly  14  to guide the solid particles into the inlet  16 . In the illustrated exemplary embodiment, for handling dry ice particles in a compressed air stream of about  30  to 200 psi in chamber  30 , the materials for the device must withstand temperature extremes of about −110° F. (350° R) and stainless steel has been found satisfactory for such service. The annular seal members  44 ,  50  may be formed of glass filled polytetrafluoroethylene material or other suitable material capable of sealing on the surface of the spherical member  20  in service temperatures of −110° F. In operation of the exemplary embodiment illustrated, for feeding of dry ice particles to the pressure chamber  30 , the motor  42  may rotate the spherical member  20  at about 70 rpm. 
   The exemplary embodiment may be readily disassembled for seal replacement without special tools. In the exemplary embodiment illustrated, an operator may disassemble, replace parts and reassemble within about one hour, thereby minimizing down time and service cost. 
   The present disclosure thus describes a feeder device for injecting solid particles into a pressurized fluid stream for discharge of the particles in the stream such as, for example, for pressure blast cleaning and the application of blast cleaning with dry ice particles in air has been particularly described. The device utilizes a unique spherical member with recesses in the surface for rotating through annular seals to discharge the particles from a particle inlet to a port in the pressure chamber where the particles may fall by gravity from the recesses in the spherical member. 
   An exemplary embodiment has been described with reference to the drawing. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiment be construed as including all such modifications and alterations and equivalents thereof insofar as they come within the scope of the appended claims.