Patent Publication Number: US-2016223065-A1

Title: Rack

Description:
BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates to a rack and, more particularly, to a rack that includes, on each side, an upper lateral face extending from a lower lateral face at an angle. 
     2. Related Prior Art 
     Referring to  FIG. 5 , a conventional rack  9  includes a toothed portion  94  formed on a base  92 . The toothed portion  94  includes teeth  944  separated by valleys  942 . The toothed portion  94  and the base  92  are made of same hardness when the conventional rack  9  is cast or forged. Then, the toothed portion  94  is hardened. Thus, the hardness of the toothed portion  94  gets higher than the hardness of the base  92  that remains. The toothed portion  94  is expect to survive wearing against a toothed portion of a pinion for example. The conventional rack  9  includes two lateral faces  92  both extending to the toothed portion  94  from the base  92 . That is, the toothed portion  94  shares the same lateral faces with the base  92 . However, each lateral face includes an upper portion of higher hardness and a lower portion of lower hardness. Each tooth  944  includes two edges in each lateral face. 
     Referring to  FIG. 6 , each lateral face is ground with a grinding wheel  24 . The grinding wheel  24  is inevitably be worn by the edges of the teeth  944  when the grinding wheel  24  is used to polish the upper portion of each lateral face. Thus, the periphery of the grinding wheel  24  turns far from a true circle. Such a periphery of the grinding wheel  24  inevitably jeopardizes the flatness of the lower portion of the lateral face when the grinding wheel  24  is used to polish the lower portion of each lateral face. 
     Moreover, the upper and lower portions of each lateral face should be ground by different grinding wheels. However, the boundary between the upper and lower portions of each lateral face is unclear. Hence, even if a worker bothers to polish the upper and lower portions of each lateral face with two grinding wheels, respectively, the worker will inevitably polish part of the upper portion of each lateral face with a softer grinding wheel or polish part of the lower portion of each lateral face with a harder grinding wheel. 
     The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art. 
     SUMMARY OF INVENTION 
     It is the primary objective of the present invention to provide a rack that can precisely be finished. 
     To achieve the foregoing objective, the rack includes a base and a toothed portion. The base includes two lateral faces. The toothed portion extends on the base and includes two lateral faces each extending from a corresponding one of the lateral faces of the base at an angle. Thus, there is a fold line extending between each of the lateral faces of the toothed portion and the corresponding one of the lateral faces of the base. 
     An advantage of the rack of the present invention is that the lateral faces of the base can properly be polished with a grinding wheel while the lateral faces of the toothed portion can properly be polished with another grinding wheel. 
     Other objectives, advantages and features of the present invention will be apparent from the following description referring to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present invention will be described via detailed illustration of the preferred embodiment referring to the drawings wherein: 
         FIG. 1  is a partial, perspective view of a rack according to the preferred embodiment of the present invention; 
         FIG. 2  is a front view of the rack shown in  FIG. 1 ; 
         FIG. 3  is a front view of a grinding wheel for finishing the rack shown in  FIG. 2 ; 
         FIG. 4  is a front view of another grinding wheel for finishing the rack shown in  FIG. 2 ; 
         FIG. 5  is a partial, perspective view of a conventional rack; and 
         FIG. 6  is a front view of a grinding wheel for finishing the conventional rack shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring to  FIGS. 1 and 2 , a rack includes a toothed portion  12  formed on a base  14  according to the preferred embodiment of the present invention. The base  14  includes an aperture  142 . The base  14  is formed with two lateral faces  17  that preferably extend parallel to each other. 
     The toothed portion  12  is formed with teeth  120  separated by spaces  126 . Each tooth  120  is formed with a top land  122 . There is a bottom land  124  in each space  126 . The toothed portion  12  Further includes two lateral faces  16  each extending from a corresponding lateral face  17  of the base  14 . 
     There is a fold line  18  extending between each lateral face  16  and the corresponding lateral face  17 . The fold line  18  is clear boundary between each lateral face  16  and the corresponding lateral face  17 . 
     The toothed portion  12  and the base  14  are made of same hardness when the rack is cast or forged. Then, the toothed portion  12  is hardened. Thus, the hardness of the toothed portion  12  gets higher than the hardness of the base  14  that remains. That is, the hardness of the lateral faces  16  is higher than the hardness of the lateral faces  17 . The toothed portion  12  is expected to survive wearing against a toothed portion of a pinion for example. 
     Referring to  FIG. 2  in particular, the top land  122  of each tooth  120  is made of a width A. The width A is the shortest distance between the lateral faces  16 . The base  14  is made of a width B. The width B is the shortest distance between the lateral faces  17 . The width A is smaller than the width B. Each tooth  120  is made of a height L. The toothed portion  12  is made of a height H. The height L is smaller than or identical to the height H. Each fold line  18  extends past the bottom lands  124  where the height L is identical to the height H. 
     There is an angle θ between each lateral face  16  and the corresponding lateral face  17 . The angle θ is larger than 0° and smaller than 20°. The angle θ is preferably 5°. 
     Referring to  FIG. 3 , a grinding wheel  22  is used to polish each of the lateral faces  17 . An axle (not numbered) for rotating the grinding  22  is directed substantially vertically. 
     Referring to  FIG. 4 , a grinding wheel  24  is used to polish each of the lateral faces  16 . An axle (not numbered) for rotating the grinding  24  is tilted, i.e., not directed vertically. 
     The hardness and/or roughness of the grinding wheel  24  are higher than that of the grinding wheel  22 . Advantageously, the lateral faces  17  of the base  14  are properly polished with the grinding wheel  22  while the lateral faces  16  of the toothed portion  12  are properly polished with the grinding wheel  24 . 
     The present invention has been described via the detailed illustration of the preferred embodiment. Those skilled in the art can derive variations from the preferred embodiment without departing from the scope of the present invention. Therefore, the preferred embodiment shall not limit the scope of the present invention defined in the claims.