Metal deforming – By use of closed-die and coacting work-forcer – Cup or shell drawing
Patent
1983-05-09
1985-02-19
Gilden, Leon
Metal deforming
By use of closed-die and coacting work-forcer
Cup or shell drawing
72349, B21D 2200
Patent
active
044997507
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a drawing device for presses with mechanically driven drawing ram and with a sheet metal holder exerting its holding force, acting on the sheet metal and counteracting the drawing direction, by way of a pressure plate by means of a die cushion piston, supporting the pressure plate and being under the effect of a pressure medium, in a fixed die cushion cylinder.
During the working stroke of the drawing ram of such a press, the sheet metal is first urged by the drawing die against the sheet metal holder and is subsequently shifted together therewith against the pressure force acting in the die cushion cylinder; during this step, the sheet metal held between the sheet metal holder and the drawing die is deformed at the same time by the drawing punch of the tool fixedly mounted on the press platen. The drawing ram shifts the sheet metal holder against the pressure force acting on the die cushion piston, the drawing ram having to overcome additionally the force of the mass moment of inertia caused by the acceleration of the movable sheet metal holder and die cushion masses. The sheet metal holder, supported on the die cushion piston, forms in this arrangement a rigid system with a large, coherent mass that must be suddenly accelerated from the rest position to the impact velocity of the drawing ram. If the sheet metal holder force is produced hydraulically in the die cushion, then the force of the mass moment of inertia of the pressure fluid must be additionally overcome during acceleration of the system at rest.
In a conventional drawing device of the type discussed above (German Pat. No. 1,452,943), a resilient member is disposed between the sheet metal holder and the movable masses of the die cushion. Thereby the movable mass of the die cushion is accelerated, as seen in time, after the mass of the sheet metal holder so that the forces of inertia of the entire system are not cumulative. The resilient member effects a constant increase in velocity of the die cushion piston up to the velocity of the drawing ram. The effective force of the mass moment of inertia of the die cushion piston is reduced by this constant velocity increase of the die cushion piston. Yet, the drawing ram, with its velocity given within this range of movement, hits the sheet metal disposed, at rest, on the sheet metal holder so that an undamped impact results.
It is an object of the invention to avoid this impact shock in a drawing device of the type described above, or at least to reduce such impact shock.
This feature has been attained according to this invention by providing that a piston having a working surface which is acted upon in the drawing direction is attached to the pressure plate; and that a control means operating in dependence on the ram stroke is included making it possible to accelerate the sheet metal holder, before the drawing ram comes into contact with the latter, by exposing the working surface to a pressure medium, to a movement in the drawing direction.
On account of these measures, the sheet metal holder with the sheet metal lying thereon is already in motion in the drawing direction when the drawing ram impinges on the sheet metal; the relative velocity between drawing ram and sheet metal is thus lower than in case of an impingement on the stationary sheet metal. The impact shock is thereby mitigated or entirely avoided.
An especially simple constructional design of the drawing device is obtained if the working surface is formed at the die cushion piston.
An especially sensitive adaptation of the sheet metal holder movement to the drawing ram movement can be attained by providing that the control means influences the exposure of the working surface to pressure medium by way of a proportional valve.
Advantageously, the movement of the sheet metal holder in the drawing direction can be accelerated to a speed equal to or not much lower than the speed of the drawing ram when impinging on the sheet metal holder.
It is therefore an object of the invention to produce an improved drawing devic
REFERENCES:
patent: 1550626 (1925-08-01), Nelson
patent: 1884700 (1932-10-01), Hothersall
patent: 3296850 (1967-01-01), Fiore
patent: 3453848 (1969-09-01), Williamson
patent: 3456478 (1969-07-01), Alexander
patent: 3460500 (1969-08-01), McCoy
patent: 3636748 (1972-01-01), Hall et al.
patent: 3817076 (1974-06-01), Wallace
patent: 3967482 (1976-07-01), Kubacki et al.
Adam Klaus
Gerber Heinz
Horn Heinz
Gilden Leon
L. Schuler GmbH
LandOfFree
Drawing device for presses with mechanically driven drawing ram does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Drawing device for presses with mechanically driven drawing ram, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Drawing device for presses with mechanically driven drawing ram will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-606496