Metal deforming – With cutting – By composite tool
Patent
1997-04-03
1998-11-03
Crane, Daniel C.
Metal deforming
With cutting
By composite tool
72335, 73 54, 73684, 2989435, B21D 2830
Patent
active
058292993
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/NL95/00337, filed Oct. 5, 1995.
The invention relates to a method for making aligned holes in both walls of a double-walled hollow wheel rim.
Such a method is known from EP-A-0 579 525. According to this publication (see FIG. 8), the holes are drilled from one direction through both walls of the double-walled hollow wheel rim. This drilling is an expensive and time consuming method, whereby chips and drilling oil will enter into the hollow space inside the wheel rim, which contamination will have to be washed out.
The costs of drilling and cleaning and the involved production time have hindered the more general use of double-walled hollow wheel rims in bicycles, which rims are now mainly used in more expensive bicycles for instance for racing.
It is a first object of the invention to provide a method for making holes in a double-walled hollow wheel rim in an efficient manner, and to obviate the drawbacks associated with the prior art.
To this end, in the method according to the invention the wheel rim is positioned against a punch die, and a punching tool with a cutting edge is moved in a continuous movement through both walls of the wheel rim and the punch die.
By punching the holes in both walls in a continuous movement of the same tool, both holes are in perfect alignment, while the process is quick and gives no contamination of oil and chips inside the hollow wheel rim.
In a preferred embodiment of the method according to the invention, the diameter of the first made hole is enlarged by passing during the same continuous movement an expansion tool, being part of the punching tool, through the hole, whereby the punching tool is stopped before the expansion tool reaches the wall supported by the punch die.
In this way the holes are made with differing diameters in an efficient manner.
In accordance with another aspect of the invented method, the punching tool is accelerated to a speed of at least 10 m/sec before the cutting edge is moved through the first wall of the wheel rim.
By making use of this high speed it is avoided that near the hole the unsupported first wall bends inwards.
The invention also relates to an apparatus suitable for operating the method of the invention for punching holes in a wheel rim, comprising a rim support with a punching die, a punching tool with a cutting edge which is movable from a start position at a distance from the punching die to a stop position whereby the cutting edge is inside the punching die and drive means for the punching tool.
The apparatus according to the invention is characterized in that in use the drive means can extend such a force on the punching tool that it accelerates from the start position to a speed of at least 10 m/sec before the cutting edge touches a first wall of a double-walled hollow wheel rim which is with its second wall positioned against the punch die.
It is remarked that an apparatus for punching holes in a wheel rim is known per se from U.S. Pat. No. 4,854,201. However, the known apparatus is not suitable for punching holes in an unsupported wall, as is required when punching holes in a double-walled hollow wheel rim.
In the apparatus according to the invention the punching tool will make a hole in the first wall without bending this wall, so that the shape of the wheel rim is maintained.
It is desirable that the apparatus of the invention includes braking means to allow the punching tool to be arrested over a short distance.
This makes it possible to reduce the dimensions of the punching tool.
The invention also relates to a double-wailed hollow wheel rim manufactured according to the invention and provided with aligned holes in each wall whereby the hole with the largest diameter is in the outer wall.
In the wheel rim in accordance with the invention the material around the hole in the outer wall is bent inwards on a curved radius.
This way an air-filled tube resting onto the outer wall of the wheel rim cannot be damaged by the sharp edge of the hole and additional costs for making and placing additi
REFERENCES:
patent: 1697817 (1929-01-01), Kuhn
patent: 1762542 (1930-06-01), Booth
patent: 2848805 (1958-08-01), Brink
patent: 3971275 (1976-07-01), Mach
patent: 4545440 (1985-10-01), Treadway
patent: 4819472 (1989-04-01), Daudi
Crane Daniel C.
Holland Mechanics B.V.
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