Patent Application
20100139075
The present invention relates to a metal fabrication method and particularly to a fabrication method to produce oil seal sleeves at desired specifications by punching.
Referring to
While the semi-finished product of the oil seal sleeve thus made has a rough form of the finished product, its roundness and surface roughness still do not meet required standards. Hence follow-on lathing and polishing processes are still needed to get the desired roundness and surface roughness to meet the required standards. These processes are tedious, and take a lot of time and are costly. They also make mass production difficult.
Therefore, the primary object of the present invention is to provide a punching method that does not require follow-on fabrication processes to make oil seal sleeves to meet required specifications.
The punching method according to the invention aims to form an oil seal sleeve. The method includes steps of: preparing a mold which has an upper mold and a lower mold couplable to form a desired gap therebetween, preparing a sheet material at a selected thickness greater than the gap of the mold, preparing a punching machine which has a movable upper chassis to hold the upper mold and a still lower chassis to hold the lower mold, disposing the sheet material between the upper mold and the lower mold, moving the movable upper chassis towards the still lower chassis to couple the upper mold and the lower mold and compress and extend the sheet material to form the oil seal sleeves.
The gap in the mold is smaller than the selected thickness of the sheet material. Hence during the forming process a compression and extension effect can be achieved. As a result, the dimension precision of the oil seal sleeve is higher and the surface roughness of the oil seal sleeve is smaller, thus the roundness and the surface roughness of the oil seal sleeve can meet required specifications.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.
Please refer to
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As the gap D is smaller than the selected thickness E, during the forming process a compression and extension effect is generated. Hence the finished oil seal sleeve 10 is formed at a dimension more precise, and the roundness of the oil seal sleeve 10 is enhanced, and the surface roughness thereof is reduced.
The punching machine 40 can be driven by a motor (not shown in the drawings) to move the movable upper chassis 41. The rotation speed of the motor can be reduced to slow the moving speed V of the movable upper chassis 41 towards the still lower chassis 42 so that the forming speed is slower and material strain also is lower to further enhance the roundness and reduce the surface roughness of the finished oil seal sleeve 10. For instance, by reducing the rotation speed of the motor from 800-900 RPM to 600-700 RPM, the final surface roughness can reach 0.2-0.9 μm.
Moreover, the upper mold 21 may have an annular flange 23 extended from the perimeter to increase the thickness of the upper mold 21, then deformation of the upper mold 21 can be reduced during the forming process to further improve the roundness of the oil seal sleeve 10. The lower mold 22 may have an annular sever portion 24 on the lateral side to incorporate with the upper mold 21 to cut off the extra portion of the sheet material 30 on the periphery. Such a structure can facilitate automatic feeding of a strip type sheet material 30. Moreover, an annular mold release ring 25 may be provided between the sever portion 24 and the lower mold 22 to push the formed oil seal sleeve 10 upwards to be separated from the lower mold 22 after the forming process is finished and prevent the oil seal sleeve 10 from stuck to the lower mold 22.
As a conclusion, the method of the invention, by having a smaller gap in the mold 20, can provide a compression and extension effect during the forming process. In addition, by reducing the moving speed of the upper mold 21, the forming speed is slower. And by increasing the rigidity of the upper mold 21, the finished oil seal sleeve 10 has an enhanced roundness and desired surface roughness to meet the required specifications. Thus the follow-on lathing and polishing processes required in the conventional techniques are no longer needed in the invention. Moreover, mass production is possible and production cost is lower.
