Abstract:
A throwing wheel assembly including a rotatable wheel and one or more throwing blades each removably positionable on the face of the wheel in a throwing position, the throwing blades having holding structures projecting therefrom and the improvement comprising one or more retainers which are removably positionable in a recess provided in the wheel face and which and are adapted for removably receiving and retaining the blade holding structures.

Description:
FIELD OF THE INVENTION 
   The present invention relates to throwing wheel assemblies for blasting machines. 
   BACKGROUND OF THE INVENTION 
   Centrifugal blasting machines are commonly used in the art to strip or clean metal castings and other items. Centrifugal blasting machines typically employ a throwing wheel assembly comprising a plurality of throwing elements, referred to as throwing blades, mounted on the face of a rotator, runnerhead, or other rotatable wheel element. The throwing blades are adapted for receiving a stream of abrasive particulate material and throwing the particulate material radially outward from the wheel at an appropriate discharge point. 
   Because of the action of the abrasive material within the centrifugal blasting apparatus, the throwing blades will commonly undergo considerable wear and must be replaced periodically. To avoid having to replace the entire throwing wheel assembly, the blades must be removably mounted on the throwing wheel. Unfortunately, in order to provide a sufficiently secure attachment for the blasting operation, the blade attachment assemblies used heretofore typically have not allowed the blade elements to be quickly and easily removed and replaced. The removal and replacement of the blade elements often requires special tools, as well as the extensive disassembly of other parts of the device. 
   A more recent prior art throwing wheel assembly  10  which both (a) provides for the secure attachment of the blades to the throwing wheel and (b) allows the blades to be quickly removed and replaced, is depicted in  FIGS. 1–4 . The prior art assembly  10  can be used with any length or width of blade, does not require the machining and close tolerances characteristic of previous devices, reduces the number of costly machined parts required for attaching the blades, allows the use of bi-directional throwing blades, and requires no tools for removing or installing the blades. 
   The prior art assembly  10  comprises: a throwing wheel  13  having an axis of rotation  11 ; a hub or rotor  12  affixed to throwing wheel  13 ; a plurality of throwing blades  14  which are removably mounted on, and are perpendicular to, the face  9  of throwing wheel  13 ; and an impeller  23  centrally mounted on hub  12  between the inlet ends  16  of the throwing blades  14 . The blades  14  generally extend radially away from the impeller  23 . 
   The impeller  23  is rotatably affixed to hub  12  for receiving a stream of abrasive particulate blasting material from a spout  20  and feeding the abrasive material to the throwing blades  14 . The impeller  23  is provided with openings  24  for delivering the abrasive material through a discharge opening  25  provided in the impeller case  21 . The abrasive material is received on the inlet ends  16  of the blades  14  as the blades  14  rotate past the opening  25 . The abrasive material moves outwardly along the throwing surface  15  of the blade  14  and is thrown from the distal end  17  of the throwing surface  15  at a desired discharge point. 
   Each of the throwing blades  14  comprises: an inner lateral side  30  positionable on the face  9  of wheel  13 ; an outer lateral side  29  opposite side  30 ; a first holding structure  26  which projects laterally outward from the lower end of side  30 ; and a second holding structure  27  which projects laterally outward from the upper portion of side  30 . The blade  14  is a one-piece component with holding structures  26  and  27  being integral features thereof. The upper holding structure  27  is a rigid lug or arm which is receivable in a corresponding detent  40  provided in the periphery of the throwing wheel  13 . A bore  45  extends radially inward from detent  40  for receiving a spring or other biasing element  95 . The upper holding structure  27  includes a cavity or recess  90  in the bottom thereof for receiving and engaging the upper end of the biasing element  95 . 
   The lower holding structure  26  of blade  14  includes outer lip portions  50  which hook or project upwardly toward the upper discharge end  17  of the blade  14  and are adapted to engage corresponding counter lip structures  51  formed in the face  9  of wheel  13 . The counter lip structures  51  are contained within a lower detent  53  formed in face  9 . The biasing element  95  continuously acts against the upper holding structure  27  to urge the blade  14  radially outward so that the lips  50  or other locking features of the lower holding structure  26  are held in locking engagement with the corresponding lips  51  or other locking features provided detent  53 . 
   In the prior art assembly  10 , each blade  14  can be easily attached to the throwing wheel  13  by placing the upper holding structure  27  in one of the outer detents  40 , pushing the blade downward to compress the biasing element  95 , pivoting the bottom of the blade  14  inward to place the lower holding structure  26  in the detent  53  and to align locking features  50  with locking features  51 , and then releasing the compressive force applied to biasing element  95  so that the biasing element  95  acts to urge the blade  14  radially outward to thereby hold the lower holding structure  26  in locked engagement with the wheel  13 . The blade  14  can be easily removed from wheel  13  by simply reversing this procedure. 
   Thus, the locking mechanism of the prior art assembly  10  holds the blades  14  securely during operation but allows the blades to be quickly and easily removed and replaced without the use of special tools and without any significant disassembly of the blasting machine. Unfortunately, however, the lower detents  53  and/or the locking features  51  formed in the face  9  of wheel  13  for receiving and retaining the lower holding structure  26  of blades  14  are exposed to significant abrasive contact and can be highly susceptible to wear. Whenever significant erosion at one or more of these attachment sites occurs, the entire throwing wheel  13  must be replaced. 
   Consequently, a need exists for an improved throwing wheel assembly which provides all of the benefits of the prior art assembly  10  but alleviates the wheel erosion problems. A need particularly exists for an improved throwing wheel assembly of this type which would further extend the life and reduce the cost of the wheel, eliminate the need to perform extensive millwork on the wheel, and allow the wheel to be formed from materials which are more highly abrasion resistant. 
   SUMMARY OF THE INVENTION 
   The present invention satisfies the needs and alleviates the problems discussed above. In one aspect, there is provided an improved throwing wheel assembly including a rotatable wheel and a throwing blade removably positionable on a face of the rotatable wheel in a throwing position, the throwing blade having a holding structure projecting therefrom. The improvement comprises: (a) the face having a recess therein and (b) the throwing wheel assembly further comprising a retainer which is removably positionable in the recess and is adapted for removably receiving the holding structure such that the retainer will retain the throwing blade in the throwing position. 
   In another aspect, there is provided an improved throwing wheel assembly including a rotatable wheel having an axis of rotation and a plurality of throwing blades, each of the throwing blades being removably positionable on a face of the rotatable wheel in a throwing position and each of the throwing blades also having a holding structure projecting therefrom. The improvement comprises (a) the face having a recess therein extending around the axis of rotation and (b) the throwing wheel assembly further comprising a plurality of retainers removably positionable in the recess, each of the retainers being adapted to removably receive the holding structure of a corresponding one of the throwing blades such that the retainers will retain each of the throwing blades in the throwing position. 
   Further aspects, features, and advantages of the present invention will be apparent to those skilled in the art and upon examining the accompanying drawings and upon reading the following detailed description of the preferred embodiments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cutaway elevational view of a prior art throwing wheel assembly  10 . 
       FIG. 2  is an elevational view of the face  9  of a throwing wheel  13  employed in prior art assembly  10 . 
       FIG. 3  is a cutaway elevational side view of the throwing wheel  13  as seen from perspective I—I shown in  FIG. 2 . 
       FIG. 4  is an elevational view of the inner lateral side  30  of a throwing blade  14  employed in prior art assembly  10 . 
       FIG. 5  is a perspective view of an inventive improved throwing wheel assembly  100 . 
       FIG. 6  is a front elevational view of inventive assembly  100 . 
       FIG. 7  is an elevational face view of inventive assembly  100  without any throwing blades positioned thereon. 
       FIG. 8  is a front elevational face view of a modified throwing wheel  13  employed in inventive assembly  100 . 
       FIG. 9  is a cutaway elevational side view of the modified throwing wheel  13 . 
       FIG. 10  is a cutaway elevational side view of a novel retainer element  104  installed within the recess  102  of the modified throwing wheel  13 . 
       FIG. 11  is a plan view of retainer  104 . 
       FIG. 12  is a cutaway elevational side view of retainer  104 . 
       FIG. 13  is a bottom view of retainer  104 . 
       FIG. 14  is an elevational outer end view of retainer  104 . 
       FIG. 15  is a plan view of a spacer  106  employed in inventive assembly  100 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An embodiment  100  of the inventive improved throwing wheel assembly is depicted in  FIGS. 5–15 . The embodiment  100  of the improved inventive assembly is essentially identical to the prior art assembly  10  except that, rather than forming lower detents  53  and locking features  51  in the face  9  of the throwing wheel, the inventive improvement comprises: (a) a circular recess  102  which is formed in face  9  and extends around the axis of rotation  11  of throwing wheel  13  and (b) one or more retainers  104  which are removably secured in recess  102 . If a plurality of retainers  104  are used, the improved throwing wheel assembly  100  can also optionally include one or more spacers  106  positioned in recess  102  between the retainers  104 . 
   The embodiment  100  of the improved throwing wheel assembly shown in  FIGS. 5 and 6  includes six retainers  104  and blades  14  with a corresponding number of spacers  106  positioned between the retainers  104  such that the retainers  104  and spacers  106  form a ring around the axis of rotation  11 . The retainers  104 , spacers  106 , and recess  102  are all preferably configured and sized such that the forward outer faces  108  and  110  of the retainers  104  and spacers  106  either do not protrude from the face  9  of wheel  13  or do not protrude from the wheel face  9  to any great degree (i.e., preferably not more than ¼ inch, and more preferably not more than 0.2 inches, beyond the outer peripheral surface  112  of wheel face  9 ). 
   Each of the retainers  104  preferably comprises: a cavity  114  formed in the outer face  108  of the retainer  104  for receiving the lower holding structure  26  of a throwing blade  14 ; lip structures  116  or other locking features within cavity  114  which correspond to, and mate with, the upwardly projecting lip structures  50  or other locking features of the lower holding structure  26 ; a sloped interior channel  118  formed between the interior lips  116  for receiving the sloped gusset feature  46  of the lower holding structure  26 ; a bore  120  formed through the bottom of cavity  114  for alignment with a corresponding bore  122  formed in wheel  13 ; and an outer recessed portion  124  of cavity  114  which allows the wide initial portion  126  of lower holding structure  26  to be substantially fully received in cavity  114  such that the holding structure  26  will be substantially flush with the outer face  108  of the retainer  104  and the inner lateral side  30  of the blade  14  will lie substantially flat against the outer peripheral surface  112  of the wheel face  9 . 
   Each retainer  104  is preferably held in place in recess  102  by a flathead bolt  126  which extends through the cavity bore  120  and into a corresponding bore  122  formed in wheel  13 . During operation, the bolt  128  is covered by the blade holding structure  26  so that the bolt is shielded from the abrasive material. To further assist in holding the retainer  104  in place, a groove  130  can be formed across the back of retainer  104  for receiving a circular rim  132  formed on wheel  13 . The retainer groove  130  includes an upwardly projecting lip  134  which mates with a corresponding lip  136  formed on rim  132  to prevent the retainer  104  from moving radially outward. 
   The inventive throwing wheel assembly  100  can be adapted to accommodate either a single throwing blade  14  or a plurality of throwing blades  14 . To maximize the number of throwing blades  14  used, the recess  102  of wheel face  9  can be filled with a desired number of retainers  104  having no spacers  106  positioned therebetween. To reduce the number of throwing blades  14  employed, spacers  106  will preferably be positioned between retainers  104  and the width of the spacers  106  will be selected as necessary to accommodate the desired number of throwing blades  14  and to provide the desired spacing therebetween. The spacers  106  protect the wheel  13  and the retainers  104  from abrasive contact and also assist in holding the retainers  104  in fixed position. The recess  102  will preferably be filled with retainers  104  or with a combination of retainers  104  and spacers  106  so as to form a ring around the axis of rotation  11 . 
   Each spacer  106  has an arcuate inner edge  140  and an arcuate outer edge  142  which match the size and curvature of recess  102 . A groove (not shown) is formed in the back of each spacer  106  to receive and accommodate the circular rim  132  projecting from the wheel face  9 . To hold the spacers in place, each spacer preferably has beveled sides  146  which diverge toward the wheel face  9 . The inwardly diverging sides  146  of the spacers  106  are received under corresponding, outwardly diverging sides  148  of the retainers  104  so that the bolted retainers  104  will hold the spacers  106  in place. 
   With the desired number of retainers  104  and spacers  106  secured within the wheel recess  102 , the inventive improved throwing wheel assembly operates in the same manner as the prior art assembly  10 . The upper holding structures  27  projecting from the blades  14  are removably positionable in the outer peripheral detents  40  formed in the wheel  13  such that the biasing elements  95  positioned in bores  45  will urge the blades  14  radially outward and thereby hold the lower holding structures  26  of the blades  14  in locked engagement with the retainers  104 . As with assembly  10 , the blades  14  of the inventive assembly  100  can be removed and replaced by simply pushing the blades  14  radially inward to temporarily depress the biasing elements  95 . 
   Although the inventive throwing assembly  100  has been described as used in conjunction with the throwing blades  14  of the prior art assembly  10 , it will be understood that the inventive assembly could alternatively be used with throwing blades having other configurations. Each of the throwing blades  14  of the prior art assembly  10  is a bi-directional blade having a flat front throwing surface  15  and a flat rear surface  9 . In addition, the sides  29  and  30  of the blades  14  diverge slightly in the direction of flow such that the front and rear surfaces  15  and  19  are flared. However, the inventive throwing wheel assembly could alternatively be used, for example, with blades which are unidirectional (i.e., have only one throwing surface) and/or have a curved rather than flat throwing surface and/or have throwing surfaces which are straight rather than flared. 
   In addition, although the retainer cavities  114  of the inventive throwing assembly  100  have been formed to accommodate and correspond to the configuration of the lower holding structures  26  of the blades  14 , it will be understood that the retainer cavities  114  can be adapted and configured to receive and retain generally any other type of holding structure configuration. Similarly, other types of biasing structures and elements can be employed for urging the projecting blade-holding structures  26  toward locked engagement with the retainers  104 . 
   The inventive improved throwing wheel assembly  100  provides several advantages over the prior art assembly  10 . The removable retainers  104  and spacers  106  employed in the inventive assembly shield the throwing wheel from abrasive contact. In the event that erosion occurs in the inventive locking mechanism, the user can simply replace the affected retainer  104  rather than replacing the entire throwing wheel. The present invention also eliminates the requirement for extensive millwork on the wheel and allows the wheel to be formed of more highly abrasion-resistant materials. Such materials have not typically been used heretofore for forming the throwing wheel because they are not readily machinable. The replaceable retainers  104  of the inventive assembly, on the other hand, can be formed from different materials which may be less expensive or better suited for the particular production and machining requirements of the retainers  104 . 
   Thus, the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes and modifications will be apparent to those skilled in the art. Such changes and modifications are encompassed within the spirit of this invention as defined by the appended claims.