Patent Publication Number: US-9403207-B2

Title: Spiral bevel gear forging apparatus

Description:
FIELD OF THE INVENTION 
     The invention relates to a forging apparatus, more particularly to a forging apparatus for forging a blank into a spiral bevel gear. 
     BACKGROUND OF THE INVENTION 
     Conventional spiral bevel gears are formed by using a mechanical cutting process. However, such a processing method will waste a lot of material, and requires complicated processing and lengthy processing time, so that the efficiency thereof is low. Moreover, because metal fibers are cut off and are, thus, discontinuous during the cutting process, the structural strength of the finished product is rather weak. Manufacturers mostly use a forging method for pressing and molding. However, because a spiral bevel gear has spiral teeth with a negative draft angle, it cannot be directly stripped from the mold. A cutting tool must be additionally used, thereby resulting in the aforesaid drawbacks of the cutting process. 
     At present, there are two suggested methods of directly stripping from mold for forging. One method is to use a rotatable punch rod for pushing the processed and completed spiral bevel gear out of the mold. The rotatable punch rod rotates following tooth grooves inside the mold core. However, the punch rod of this method must be provided with a transmission component, such as a gear, and must coordinate with components, such as a motor, a rack bar, or a chain, so that this method is complicated and may destroy the strength of the punch rod. Another method is to rotate the mold core instead of the punch rod so that there is no need to process the punch rod which may destroy the strength thereof. In this method, the mold core is rotated, and the punch rod is used to push the spiral bevel gear out of the mold. Although this method can maintain the strength of the punch rod, the mold core must undergo the process of boring holes and grooves, thereby destroying the strength and the sealing effect of the mold core. Hence, there is still room for improvement. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of this invention is to provide a spiral bevel gear forging apparatus that is capable of overcoming the aforesaid drawbacks of the prior art. 
     According to this invention, a spiral bevel gear forging apparatus for forging a blank comprises a first mold unit and a stripping unit. The first mold unit includes a first mold core having a mold cavity for receiving the blank, and a first punch rod inserted movably into the first mold core and having a positioning end extending into the mold cavity for releasable engagement with a bottom of the blank. The stripping unit includes at least one push mechanism capable of driving the first mold core to rotate about the first punch rod, and a drive mechanism operable to move between a non-ejecting position and an ejecting position. When the drive mechanism is operated to move from the non-ejecting position to the ejecting position, the push mechanism is actuated by the drive mechanism to drive the first mold core to rotate about the first punch rod, and the first punch rod is actuated by the drive mechanism to move relative to the first mold core such that the positioning end of the first punch rod is moved out of the mold cavity for ejecting the blank out of the first mold core. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the invention will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which: 
         FIG. 1  is an exploded sectional view of a spiral bevel gear forging apparatus according to the embodiment of the present invention; 
         FIG. 2  is a schematic top view, illustrating relations between a first mold core and a push mechanism of the embodiment; 
         FIG. 3  is an enlarged sectional view of the encircled area (A) in  FIG. 1 ; 
         FIG. 4  is an assembled sectional view of the embodiment; and 
         FIG. 5  is a sectional view of the embodiment, illustrating how a finished blank may be ejected from the mold. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT 
     Referring to  FIGS. 1 to 5 , a spiral bevel gear forging apparatus  1  according to the embodiment of the present invention is installed in an upright manner for convenience of illustration, and is shown to comprise a first mold unit  2 , a second mold unit  3 , and a stripping unit  4 . 
     The first mold unit  2  includes a first mold seat  21 , a first mold core  22  mounted in the first mold seat  21 , a first punch rod  23  inserted movably into the first mold core  22 , a first elastic member  24  sleeved on the first punch rod  23 , and three rotary members  25  disposed between the first mold seat  21  and the first mold core  22  for reducing friction therebetween. The first mold core  22  has a mold cavity  222  for receiving a blank (B) to be forged, and includes two diametrically opposed tooth-shaped portions  221  projecting from an outer periphery of the first mold core  22 , as shown in  FIG. 2 . The mold cavity  222  has a gear configuration and a negative draft angle. The first punch rod  23  has a positioning end  231  extending into the mold cavity  222  for releasable engagement with a bottom of the blank (B), and an enlarged end  232  opposite to the positioning end  231 . In this embodiment, the positioning end  231  has a rectangular shape. Alternatively, the positioning end  231  may have an oval, triangular, rectangular, or any other shape. The first elastic member  24  has two opposite ends respectively abutting against the enlarged end  232  of the first punch rod  23  and the first mold core  22 . Each of the rotary members  25  is a bearing. 
     The second mold unit  3  includes a second mold seat  31  matable with the first mold seat  21 , a second mold core  32  disposed in the second mold seat  31  and matable with the first mold core  22 , a second punch rod  33  disposed in the second mold seat  31  and extending into the second mold core  32 , and a second elastic member  34  sleeved on the second punch rod  33  and having two opposite ends respectively abutting against the second mold seat  31  and the second mold core  32 . 
     The stripping unit  4  includes a drive mechanism  41  and two push mechanisms  42 . The drive mechanism  41  includes an ejector plate  411  disposed in the first mold seat  21  and connected to and supporting the first punch rod  23 , an ejection lever  412  fixed to the ejector plate  411  and extending through the first mold seat  21  in a direction away from the first punch rod  23 , and two restoring elastic members  413  each of which has two opposite ends respectively abutting against the first mold seat  21  and the ejector plate  411 . The ejection lever  412  is connected to a power source (not shown), such as an air or oil cylinder, and is movable upward and downward relative to the first mold seat  21 . 
     Each of the push mechanisms  42  includes a first slide block  421 , a second slide block  422 , and a spring-loaded member  423 . The first slide blocks  421  of the push mechanisms  42  are parallel to and spaced apart from each other, as best shown in  FIG. 2 . The first slide block  421  of each push mechanism  42  includes a body portion  424  having opposite inner and outer ends, a rack portion  425  disposed on the inner end of the body portion  424  and meshing with a respective one of the tooth-shaped portions  221  of the first mold core  22 , and a first inclined surface  426  provided on the outer end of the body portion  424 . The second slide block  422  of each push mechanism  42  has one end provided with a second inclined surface  427  slidably abutting against the first inclined surface  426 , as best shown in  FIG. 3 , and another end opposite to the second inclined surface  427  and abutting against the ejector plate  411 .  FIG. 3  is an enlarged sectional view of the encircled area (A) in  FIG. 1 . The spring-loaded member  423  of each push mechanism  42  includes a headed shank  4231  extending through the first mold seat  21  and fixed to the first slide block  421 , and a spring  4232  sleeved on the shank  4231  and having two opposite ends respectively abutting against the head of the shank  4231  and an outer side of the first mold seat  21 . 
     With reference to  FIGS. 1 and 4 , the operating steps of this invention are as follows: First, the blank (B) is placed in the mold cavity  222  of the first mold core  22 , after which the second mold unit  3  is moved down to mate with the first mold unit  2 . At this time, the first and second mold seats  21 ,  31  are mated, the first and second mold cores  22 ,  32  are also mated, and the first and second punch rods  23 ,  33  are respectively disposed on the bottom and top of the blank (B). Next, the second mold unit  3  is actuated to press downward, so that the second punch rod  33  presses downward against the blank (B) and cooperates with the first punch rod  23 , which presses upward against the blank (B), to squeeze and deform the blank (B) until the blank (B) uniformly fills the gear-shaped mold cavity  222  of the first mold core  22 , thereby forming a forged blank (B′) which is a spiral bevel gear. During the downward pressing of the second mold unit  3 , the second elastic member  34  is compressed by the second mold seat  31  to generate a biasing force that biases the second mold core  32  to tightly abut against the first mold core  22 . As such, the first and second mold cores  31 ,  32  abut tightly against each other and are tightly closed during the forging process. 
     With reference to  FIGS. 2, 3 and 5 , after the forging process is completed, the second mold unit  3  is moved upward to restore to its original position, and the power source (not shown) is activated to move the drive mechanism  41  from a non-ejecting position shown in  FIG. 4  to an ejecting position shown in  FIG. 5 . During this movement, the ejection lever  412  of the drive mechanism  41  pushes upward the ejector plate  411 , which in turn pushes upward the second slide blocks  422  and the first punch rod  23 . Through this, the second inclined surfaces  427  of the second slide blocks  422  respectively push the first inclined surfaces  426  of the first slide blocks  421  to move the first slide blocks  421  toward each other. Because the rack portions  425  of the first slide blocks  421  are respectively meshed with the tooth-shaped portions  221  of the first mold core  22 , as the first slide blocks  421  move toward each other, the first mold core  22  is pushed to rotate about the first punch rod  23 . Because the positioning end  231  of the first punch rod  23  is engaged with the bottom of the forged blank (B′), and because of the shape of the positioning end  231 , the forged blank (B′) is prevented from rotation. In coordination with the rotation of the first mold core  22 , the first punch rod  23  pushes the forged blank (B′) out of the first mold core  22 , thereby stripping the forged blank (B′) from the first mold core  22 . During movement of the drive mechanism  41  from the non-ejecting position to the ejecting position, the first elastic member  24 , the restoring elastic members  413  and the spring-loaded members  423  are all compressed. After the stripping operation is completed, the first elastic member  24  restores the first punch rod  23  to its original position, the restoring elastic members  413  restore the ejector plate  411  to its original position, and the spring-loaded members  423  restore the first slide blocks  421  to their original positions. This positioning mechanism can prevent the first mold core  22  from being unable to rotate back to its original position during rotation, and can directly proceed with the next processing operation without the need for re-calibration. Hence, the processing accuracy is enhanced, and the processing time is saved. 
     This invention uses a mechanism that rotates for stripping, so that only a single operation is needed to produce a forged article having a complicated shape and a precise size. The issue of difficulty in stripping the forged blank having a negative draft angle from the mold can thus be resolved. Further, there is no need for additional cutting processes so that the material can be saved, the processing operation can be minimized, and the cost can be reduced. Moreover, during forging, the first and second mold cores  22 ,  32  are in a closed state, so that formation of burrs on the forged blank (B′) can be greatly reduced. In addition, metal flow lines can be distributed along the contour of the forged blank (B′), thereby preventing the flow line edge of the forged blank (B′) from being exposed. The mechanical properties of the forged blank (B′) can thus be improved. 
     In sum, by using the linkage between the first slide blocks  421  and the second slide blocks  422 , the first mold core  22  is rotatable about the first punch rod  23 , and the forged blank (B′) can be ejected out of the first mold core  22 , thereby completing the stripping operation. The integrities of the first punch rod  23  and the first mold core  22  are not destroyed so that their strengths and precisions are enhanced, and the issue of stripping from the mold with difficulty is resolved. Therefore, the object of this invention is achieved. 
     While the invention has been described in connection with what is considered the most practical embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.