Threaded – headed fastener – or washer making: process and apparat – Apparatus for making headed fastener – e.g. – nail – rivet – etc. – Having reciprocating die and heading means
Patent
1994-10-14
1997-05-06
Larson, Lowell A.
Threaded, headed fastener, or washer making: process and apparat
Apparatus for making headed fastener, e.g., nail, rivet, etc.
Having reciprocating die and heading means
B21K 144
Patent
active
056265220
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a method and an apparatus for making a head on an elongate blank, wherein a blank is moved into a die having a bottom stop such that part of the blank extends outside the die end opposite the bottom stop. The protruding part of the blank is then formed by a pre-upsetter which has a pre-upsetting bushing positioned in extension of the die, and a punch capable of being displaced in the pre-upsetting bushing, said pre-upsetter and said die being moved away from each other during part of the forming procedure.
BACKGROUND OF THE INVENTION
For pre-upsetting of a head on an elongate blank it is known to place a wire blank in a die having a bottom stop, e.g. in the form of an ejector pin, following which the blank is formed by means of a punch in a pre-upsetter.
To obtain optimum quality of the head and to avoid deflection of the blank during the upsetting process, it is of decisive importance that the free length of the wire blank between the die and the pre-upsetter is sufficiently small. Since, however, a large volume in the head is frequently desired, this distance is usually increased to the maximum length. It is frequently desired at the same time that pre-upsetting proceeds to a great diameter, which increases the load on the pre-upsetter pin. These circumstances limit the maximum upsetting ratio that can be achieved, said upsetting ratio being the length of the wire outside the retention of the die divided by the wire diameter. It is desirable to achieve an upsetting ratio as great as possible.
It is known to improve the upsetting ratio by allowing the pre-upsetter to move away from the die during the process. This results in the short distance at the start of the process, while the length is increased with a simultaneous corresponding increase of the diameter during the process, whereby the blank remains stable. This takes place in the prior art by spring loading the pre-upsetter so that it is pressed away from the die as the head is formed. This prior art is mentioned e.g. by Billigmann/Feldmann: "Stauchen und Pressen", 1973. However, this process has the drawback that it is difficult to optimize the process, because the movement of the pre-upsetter away from the die is only controlled by a spring, and this restricts the size of upsetting ratios that can be achieved.
In this prior art, the punch follows the forced movement of the forming mechanism from e.g. a crank mechanism.
SUMMARY OF THE INVENTION
The object of the invention is to provide a method and an apparatus making it possible to obtain considerably greater upsetting ratios than has been possible till now. Where the maximum upsetting ratio achievable in the past was about 5, it has been found possible to achieve a considerably higher upsetting ratio with the invention.
This is achieved in that the movement of both the punch and the pre-upsetter with respect to the die is positively controlled so that the pre-upsetter and the die are moved away from each other at the end of the forming procedure, while the punch continues to press in a direction toward the die. When the movement of the individual parts with respect to each other is positively controlled in this manner, it is possible to optimize the upsetting process much better than has been possible till now.
In one embodiment of the invention, the punch movement is controlled by a cam disc having pre-calculated curve paths. These curve paths are calculated precisely so that the upsetting process will be optimum, because the movement of the punch does not follow the movement of the forming mechanism.
An apparatus for performing the method comprises means which can positively control the movement of the punch as well as the pre-upsetter with respect to the die, so that the pre-upsetter is moved away from the die at the end of the working procedure, while the punch continues to press in a direction toward the die.
A particular embodiment of the apparatus comprises a cam disc having pre-calculated curve paths for controlling the movement of the
REFERENCES:
patent: 3127626 (1964-04-01), Friedman
patent: 3253287 (1966-05-01), Friedman
patent: 3359580 (1967-12-01), Osman et al.
patent: 3471878 (1969-10-01), Herpich
Enkotec A/S
Larson Lowell A.
Schoeffler Thomas C.
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