Patent Publication Number: US-7585207-B2

Title: Throwing wheel assembly

Description:
BACKGROUND OF THE INVENTION 
   The throwing blades must be removable since they wear out and must be routinely replaced. The mounting must provide for accurate location on the wheel radially since varying of the radial position can result in a wheel imbalance when rotated at high speed. Excessive clearance can result in tipping of the blade and irregular performance. 
   The throwing blades must be removable since they wear out and must be routinely replaced. The mounting must provide for accurate location on the wheel radially since varying of the radial position can result in a wheel imbalance when rotated at high speed. Excessive clearance is a result in tipping of the blade and irregular performance. 
   In addition, any clearance spaces can result in abrasive material entering those spaces and make it difficult or impossible to remove the blade for replacement. 
   U.S. Pat. No. 5,476,412 describes a method using a tapered dovetail channel to create a tight fit which wedges to locate the blade radially. However, the tapered dovetail is difficult to form accurately by normal casting processes and accuracy of the radial location of the blade may suffer if there are inaccuracies in forming the double tapered dovetail shape. These radial location variations are problematic as described above. 
   Another approach which is described in U.S. Pat. No. 3,869,289 involves the use of springs to force the blade axially out to bring dovetail wings on the blade into engagement with the dovetail shaped channel sides in the wheel. This requires separate spring elements which can get broken and lost. Proper locking sometimes is not achieved with this design. 
   It is an object of the present invention to provide a throwing blade mounting to the throwing wheel which does not require precision forming of a double tapered wedge shape in a dovetail but rather uses a simpler shape which is easier to machine and to obtain accurate radial location of the blades on the wheel side plates. 
   SUMMARY OF THE INVENTION 
   The above recited object and other objects which will be understood upon a reading of the following specification and claims are achieved by a throwing blade having a parallel dovetailed feature which is configured to engage sides of channels having dovetailed sides. In order to lock the blades in engagement with the dovetailed sides of a mating channels, a slot is formed into the bottom of each channel and a corresponding downwardly projecting cam ramp feature is formed on the base of each blade projecting below the dovetailed feature. The axially sloping bottom surface of the slot and the ramp top surface feature engage with each other to cam the dovetail base on the blade into tight engagement with the dovetailed channel sides to tightly lock the blade to the throwing wheel. With a simple ramp engagement, more accurate radial location of the blades can be achieved while using only conventional casting processes. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a pictorial view of a throwing blade according to the present invention. 
       FIG. 2  is a pictorial view of a wheel having radial channels configured to receive blades according to the invention. 
       FIG. 3  is a pictorial view of the wheel shown in  FIG. 2  with a number of blades shown in  FIG. 1  installed therein. 
       FIG. 4  is an enlarged view of the section  4 - 4  taken in  FIG. 3 . 
       FIG. 5  is a view of a horizontal section through an installed blade, with a fragmentary view of portion of the throwing wheel. 
       FIG. 6  is an end view of the blade and wheel portions shown in  FIG. 4 . 
   

   DETAILED DESCRIPTION 
   In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims. 
   Referring to the drawings and particularly  FIGS. 1 and 2 , a throwing blade  10  according to the invention is shown adapted to be mounted to a throwing wheel  28  rotated about a central axis in the well known manner. The throwing blade  10  is comprised of a generally rectangular steel casting having an upper and lower edges formed with flanges  12 ,  14  and a web  16  defining the throwing surfaces. The web  16  is tapered as per conventional practice (as shown in  FIG. 5 ), being thicker at a radially outer end  18  than at a radially inner end  20  of the blade  10 . 
   According to the present invention, a dovetailed feature  22  is formed extending along the base of the blade  10  for approximately one half the length of the blade  10 . 
   The dovetailed feature  22  has sides extending radially and parallel to each other although angled towards each other in the conventional manner. 
   Projecting in an axially direction from the flat bottom of the dovetailed feature  22  is a camming cam ramp  24  which extends outwardly from the radial inner end  20  of the blade  10 , and terminates at a radial outer end at the lower flat surface  26  of the dovetail feature  22 . The cam ramp  24  slopes in an axial direction, i.e., the top surface  24 A varies in height above the flat surface in the axial direction. 
   The throwing wheel  28  is annular in shape, having a central hole  30  on the axis of rotation which receives the blades  10  when they are being installed on the wheel  28 . 
   A series of radial channels  32  are formed into one face of the throwing wheel  28 . 
   Each channel  32  includes a pair of dovetailed sides  34  complementary to the dovetail feature  22  on each blade  10  but somewhat larger to allow an easy slidable fit therein. 
   The bottom of each channel  32  is formed with a bottom sloping surface  36 A of a slot  36  matching the top surface  24   a  of the cam ramp  24  extending radial out from the central hole. 
   Each blade  10  is installed by placing the dovetail feature  22  at the radial inside end of a channel  32  with a flat ramp surface  26  resting on a flat surface  38  defining the bottom of the dovetail channel  32 . 
   The blade  10  is then slid radially out, bringing the sloping bottom of the slot  36  into engagement with the top surface  24   a  of the cam ramp  24 . This lifts the blade  10  normally to the channels, (i.e., in an axial direction) by a camming action between the engaged surfaces  36 ,  24 A as the blade  10  is advanced radially in a receiving channel  32  until the sides  40  of the dovetail feature  22  are wedged against the sides of the dovetail channel  32  as seen in  FIGS. 3 ,  4  and  6 . 
   This securely holds the blade  10  in position as seen in  FIG. 4  where the cam ramp  24  extends most of the length of the dovetailed  22  which itself extends most of the length of the channel  32 . The ramp angle being is sufficiently shallow, i.e., 6°-8° to achieve self-locking of the blades  10  in the channels  32 . 
   This engagement will prevent blade tilting and excessive variations in radial location, yet can be manufactured using ordinary processes. 
   Removal can be reliably achieved since the clearance between the dovetails are restored by driving the blade  10  to be removed back down the ramp.