Method for manufacturing metal material with an intermediate hollow and two solid end portions

Information

  • Patent Grant
  • 6401511
  • Patent Number
    6,401,511
  • Date Filed
    Tuesday, October 10, 2000
    24 years ago
  • Date Issued
    Tuesday, June 11, 2002
    22 years ago
  • Inventors
  • Examiners
    • Larson; Lowell A.
    Agents
    • Troxell Law Office PLLC
Abstract
The method for manufacturing a metal material with an intermediate hollow and two solid end portions includes a step for preparing a first mold for manufacturing a roughly-shaped metal material with a first inner solid end hollow and a lengthwise intermediate hollow of a preset length. A conical portion is formed around am outer end hole of the mold. The outer conical end of the metal material is pressed in the intermediate hollow to form a second outer end portion of the metal material. Thus, a finished product of metal material with two solid end portions and an intermediate hollow is manufactured. Such a method can surely simplify the processes of manufacture, lowing the cost of production, and strengthening the integrated structure of products.
Description




BACKGROUND OF THE INVENTION




This invention relates to a method for manufacturing metal material with an intermediate hollow and two solid end portions, particularly to one possible to simplify manufacture processes, to lower the cost of production and to strengthen the structure of products.




A conventional method for manufacturing a bike crank includes a step for preparing a sand-core embedded in an intermediate hollow in a mold of a crank. Then melted material is filled in the mold, and when the roughly shaped crank is to be taken out, an opening in the end section of the crank is bored for removing the sand core out of the mold. Then, the outer surface of the crank is ground smooth to finish the crank with the intermediate hollow. Such a method for manufacturing the crank is not only complicated in processes, but also increases the cost of production. Besides, boring an opening or a threaded hole for removing the sand core in the crank will weaken its strength.




Another conventional method for manufacturing a crank with an intermediate hollow is to preset a slot in one side surface of a crank body, which is to be closed up with a cover means welded together with the rim of the slot. Such structure of a crank is not integrated as one unit, weakened in its strength, and due to the varied materials of the crank and the cover means as well as possibility of expansion and contraction caused by weather, so the joint section may be liable to split.




SUMMARY OF THE INVENTION




The objective of the invention is to offer a method for manufacturing metal material with an intermediate hollow and two solid end portions. A first step of the method is to prepare a roughly-shaped metal material having a first inner solid end portion, and a bar body having a lengthwise intermediate hollow, and an expanded conical portion set around an open end hole of the bar body. Next, the expanded conical portion is compressed and shrunk to move towards the open end hole of the bar body and closes it up, forming a second solid end portion; then, the intermediate hollow is closed up by the second solid end portion, and a finished crank of metal material with an intermediate hollow and two solid end portions is obtained.




Another objective of the invention is to offer a method for manufacturing metal material with an intermediate hollow and two solid end portions, which is simple in manufacture, quick in shaping, integral as one unit and sure to strengthen the structure of metal material.











BRIEF DESCRIPTION OF DRAWINGS




This invention will be better understood by referring to the accompanying drawings:





FIG. 1

is an exploded perspective view of a first preferred embodiment of a method for manufacturing metal material with an intermediate hollow and two solid end portions, wherein a metal bar material is to be placed in a mold in the present invention:




FIG.


2


(A) is a side cross-sectional view of the first preferred embodiment of the method, wherein the metal bar material placed in the mold is not yet pressed into shape in the present invention:




FIG.


2


(B) if is a side cross-sectional view of the first preferred embodiment of the method, wherein the metal bar material is ready shaped in the present invention:





FIG. 3

is a perspective view of the metal bar material roughly shaped in the present invention:




FIG.


4


(A) is a side cross-sectional view of the first preferred embodiment of the method, wherein the roughly-shaped metal bar material placed in a closed mold in the present invention:




FIG.


4


(B) is a side cross-sectional view of the first preferred embodiment of the method, wherein the roughly-shaped metal bar material placed in the mold and pressed to be shaped in the present invention:





FIG. 5

is a cross-sectional view of the metal material roughly shaped in the first preferred embodiment in the present invention:





FIG. 6

is a perspective view of the metal bar material roughly shaped in a second preferred embodiment of the method in the present invention:




FIG.


7


(A) is a cross-sectional view of the roughly-shaped metal bar material placed in a closed mold in the second preferred embodiment in the present invention:




FIG.


7


(B) is a side cross-sectional view of the roughly-shaped metal bar material placed in the mold and pressed by a press rod to shape in the second preferred embodiment in the present invention:





FIG. 8

is an exploded perspective view of the roughly-shaped metal bar material placed in a press mold in the second preferred embodiment in the present invention:





FIG. 9

is a perspective view of a bike crank formed in the method in the present invention.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




A first embodiment of a method for manufacturing metal material with an intermediate hollow and two solid end portions in the present invention, as shown in

FIG. 1

, includes a mold


10


for making a roughly-shaped metal material, consisting of an upper mold


11


and a lower mold


12


. After combined together, the mold


10


forms an inner semispherical end hollow


13


, an intermediate cylindrical hollow


14


communicating with the inner end hollow


13


. The cylindrical hollow


14


connects with an outer conical open-end hole


15


. Further, the inner end hollow


13


has a larger diameter than that of the intermediate cylindrical hollow


14


, and may have a rectangular, spherical, conical shape or the like.




Further, a metal bar material


20


of a cylindrical solid aluminum alloy is placed in the intermediate cylindrical hollow


14


of the mold


10


, then the upper mold


11


and the lower mold


12


are combined together.




Next, as shown in FIG.


2


(A), the metal bar material


20


placed in the intermediate hollow


14


of the mold


10


is pressed into shape by means of a press device


30


having a press rod


31


, which is actuated to rectilinearly press the outer end of the metal bar material


20


. The outer diameter of the press rod


31


of a preset length is smaller than the inner diameter of the intermediate cylindrical hollow


14


in order to form an annular gap


16


of a preset size between the outer surface of the press rod


31


and the inner wall of the intermediate cylindrical hollow


14


. The press rod


31


presses the metal bar material


20


through the conical hole


15


of the mold


10


, and after a preset time, as shown in FIG.


2


(B), the metal bar material


20


is pressed by the press rod


31


to reach the bottom of the inner semi-spherical hole


13


and filling it up. In addition, due to continual pressing by the press rod


31


, surplus of the metal bar material


20


is pushed along the press rod


31


filling up the annular gap


16


of the intermediate cylindrical hollow


14


and the conical hole


15


of the mold


10


.




In accordance with the first preferred embodiment, the press rod


31


has the largest stroke as to press the solid metal bar material


20


to fill up the whole intermediate cylindrical hollow


13


, pushing it to extend along the annular gap


16


outward to a required length. Then, the press rod


31


is pulled out of the mold


10


, the upper mold


11


is opened, and thus a roughly shaped metal material


40


is acquired.




Furthermore, as shown in

FIG. 3

, the roughly-shaped metal material


40


has a first solid end portion


41


formed in the inner semi-spherical hole


13


and a bar body


43


connected with the first solid end portion


41


has a lengthwise hollow


42


of a preset length formed by the press rod


31


pulled out. The bar body


43


has an integral circumferential wall, and the wall is formed by the annular gap


16


. In addition, the bar body


43


has an outer open hole


44


with an expanded conical portion


45


of a preset size, and the expanded conical portion


45


is formed by the conical hole


15


of the mold


10


.




Next, as shown in FIG.


4


(A), the expanded conical portion


45


is then closed up, forming a second solid end portion


46


; then, the roughly-shaped metal material


40


is placed in a closed mold


50


formed of an upper mold and a lower mold combined together with an inner semi-spherical hollow


51


, an intermediate cylindrical hollow


52


communicating with the inner hollow


51


. And an outer open hole


53


is formed to communicating with the intermediate cylindrical hollow


52


, having a semicircular molding wall


54


. Then, the expanded conical portion


45


of the roughly-shaped metal material


40


is pressed by means of a press rod


55


, as shown in FIG.


4


(B), and pushed to extend towards the outer open hole


53


and then closed up the molding wall


54


, forming a second solid end portion


46


, as shown in FIG.


5


. Thus, a finished product of a dumbbell-shaped metal material with an intermediate hollow and two solid end portions is obtained.




A second preferred embodiment of the method for manufacturing metal material of a bike crank with an intermediate hollow and two solid end portions in the present invention, as shown in FIGS.


7


(A) and


7


(B), includes a mold


50


with an inner spherical or block-shape hollow


51


for forming a first sold end section


71


of a metal bar material with an intermediate cylindrical hollow


72


, and a conical portion


74


formed in one end. Next, the roughly-shaped metal material


70


is placed in the closed mold


50


with the outer open hole


53


to match with the column-shaped press rod


55


, and a molding wall


56


is provided near the open hole


53


of the bar body


52


, as shown in FIG.


7


(B). When the press rod


55


presses the roughly-shaped metal material


70


, the expanded conical portion


74


of the metal material


70


is compressed by the molding wall


56


, and shrunk to a column-shape to form a second solid end portion


75


with the open hole


53


closed up, as shown in FIG.


8


. Thus, a metal material crank


76


with an intermediate hollow


72


and two solid end portions


71


is obtained.




Lastly, the metal material crank


76


with the first solid end portion


71


and the second solid end portion


75


is placed in a press-mold


80


to be shaped finally as a finished product. The press mold


80


consists of an upper mold


81


and a lower mold


82


, having in its central portion a hollow


83


shaped as a bike crank, and the roughly-shaped metal material


70


is compressed and shaped by the press mold


80


, as shown in

FIG. 9

, and, then, a finished product of a bike crank


90


with an intermediate hollow


91


is manufactured.




The technological feature of the method in the invention is a first step of making the roughly-shaped metal material


40


having a first solid end portion


41


, a bar body


43


connected with the first solid end portion


41


and having the lengthwise hollow of a preset length. The circumferential wall of the bar body


43


is made integral, and the other end section of the bar body


43


is the opening


45


having the conical portion


45


of the preset size. Next, the conical portion


45


is compressed and shrunk to move towards the open-end portion of the intermediate hollow, and then closed up, forming the second solid end portion


46


. Thus, a finished product of metal material with the intermediate hollow and the two solid end portions is manufactured.




While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications may be made therein and the appended claims are intended to cover all such modifications that may fall within the spirit and scope of the invention.



Claims
  • 1. A method of manufacturing a bicycle crank having a hollow center portion and solid end portions, comprising the steps of:a) providing a blank mold having a mold cavity including a closed end forming a first enlarged chamber, an open end forming a second enlarged chamber and an elongated cylindrical portion interconnecting and communicating with the first and second enlarged chambers, the cylindrical portion having a cross-sectional dimension smaller than the cross-sectional dimensions of the first and second enlarged chambers; b) placing a solid metal bar in the cylindrical portion of the mold cavity; c) inserting a first press rod into the solid metal bar through the open end of the mold cavity into at least a portion of the cylindrical portion of the mold cavity, the first press rod having a cross-sectional dimension less than the cross-sectional dimension of the cylindrical portion of the mold cavity, whereby the metal material of the metal bar completely fills the first elongated chamber to form an enlarged first solid end portion, fills a space in the cylindrical portion around the first press rod to form a hollow center portion, and at least partially fills the second enlarged chamber; d) removing the first press rod from the mold; and, e) inserting a second press rod into the second enlarged cavity, the second press rod having a cross-sectional dimension greater than the cross-sectional dimension of the elongated cylindrical portion of the mold cavity to compress the metal material at least partially filling the second enlarged chamber so as to form a second solid end portion.
  • 2. The method according to claim 1 wherein the second press rod compresses the metal material in the second enlarged chamber thereby forming an enlarged second solid end portion.
  • 3. The method according to claim 1 wherein the second press rod compresses the metal material in the cylindrical portion of the mold cavity to form the second solid end portion.
  • 4. The method according to claim 1 comprising the additional steps of:a) removing the metal material from the blank mold; b) providing a bicycle crank mold including upper and lower crank mold portions bounding a curved cavity; c) placing the metal material in the curved cavity; and, d) pressing the upper and lower mold portions together to form a curved bicycle crank with first and second solid ends and a hollow center portion.
  • 5. The method of claim 4 wherein at least a portion of the hollow center portion is curved.
US Referenced Citations (2)
Number Name Date Kind
2392175 Norton Jan 1946 A
2748464 Kaul Jun 1956 A