Threaded – headed fastener – or washer making: process and apparat – Process – Making externally threaded fastener – e.g. – screw or bolt
Patent
1994-10-14
1996-08-20
Bray, W. Donald
Threaded, headed fastener, or washer making: process and apparat
Process
Making externally threaded fastener, e.g., screw or bolt
29 65, 723556, 72357, 72411, 470 10, 470 27, B23G 900, B21D 2200
Patent
active
055474241
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a method and an apparatus for making an elongate object, such as a screw or similar fastener, with a head at one end and a point at the other end, wherein a blank is positioned in a die in the form of a through-going channel, following which the head end is subjected to pressure working with or against a tool, while a dolly is kept engaged with the die at its other end.
BACKGROUND
For instance for automatic screwing-in of self-tapping screws it is decisive that the screws are provided with a so-called point, which may e.g. have the shape of a truncated cone at one end of the screw, while the screw head is provided at the opposite end of the screw. Points on screws can have numerous other shapes. It has been found difficult to produce such a point in a simple manner. One reason is that the screw is manufactured from a wire blank having blunt ends which occur as a result of cropping of the blank from rod-shaped or wire-shaped stock. When such a screw is to be made, the material of both blank ends is to be subjected to forming, viz. to a screw head and a screw point, respectively.
Such a point can be made in a known method by means of a constriction of the die, in which the blank is retained while the head is formed by cooperation with the tool. Thus, the through-going channel of the die has a constriction. This means that an ejector pin having a smaller cross-section than the cross-section of the wire blank must be used for ejecting the blank from the die following machining. The cross-section of the ejector pin must necessarily correspond to the narrowest part of the point in order that the ejector pin can be inserted into the die and push the finished blank out. There is a great risk that such a thin ejector pin will bend or break when it is to produce the great force required to eject the blank from the die.
In the prior art there is a transition between un-deformed material in the shank and deformed material in the head, which results in a weakening of the screw at this transition between head and shank.
SUMMARY OF THE INVENTION
The invention provides a simple method of making a point on a screw blank, where there are no constrictions in the die, and consequently an ejector pin having the same cross-section as the blank may be used. Also, e.g. a slot may be made in the head of the screw using a smaller force than needed in the past. This reduces wear on the tool and gives a greater precision of the slot and the geometry of the head.
It has moreover been found that this method results in a reinforcement of the transition between shank and head, which is frequently the weakest point on screws.
Furthermore, this method enables production of many different point types which have been extremely difficult to produce in the past.
This is obtained according to the invention by first providing a pre-formed head on the blank in a manner known per se such that said head has an excess of material with respect to the size of the final head, and using a dolly with a depression opposite the die, and subjecting the blank to pressure working in a manner such that the pressure acting between the tool and the die causes a flow of material in the blank so that blank material flows down into the depression of the dolly.
When the tool forms the head of the screw, the excess material will be pressed down through the shank of the screw, and material will consequently be pressed out into the depression in the dolly. This causes flow of material around the transition from head to shank, which results in reinforcement of this transition. This also means that it is sufficient that the tool presses against the head with a smaller force than ordinarily needed for forming the head.
If a radial, outwardly directed cold flow of a small amount of blank material into a cavity defined at the die is produced during the exertion of the axial pressure, it is assured that the tool will readily let go of the blank after forming the head of the screw. Otherwise there would be a risk that the t
REFERENCES:
patent: 1308629 (1919-07-01), Griffiths
patent: 2036758 (1936-04-01), Johnson
patent: 2102941 (1937-12-01), Cadwallader, Jr.
patent: 2182092 (1939-12-01), O'Leary
patent: 2314390 (1943-03-01), Vellier
patent: 2644178 (1953-07-01), Nielsen
patent: 3126561 (1964-03-01), Orloff
patent: 3188849 (1965-06-01), Wisebaker et al.
patent: 3461470 (1969-08-01), Cochrum
patent: 3466917 (1969-09-01), Eakin et al.
patent: 3477075 (1969-11-01), Putetti
patent: 4033003 (1977-07-01), Marroquin
Bray W. Donald
Enkotec A/S
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