Metal deforming – By pulling workpiece through closed periphery die – Utilizing specified work moving means
Reexamination Certificate
2002-05-09
2004-04-06
Tolan, Ed (Department: 3725)
Metal deforming
By pulling workpiece through closed periphery die
Utilizing specified work moving means
C072S278000, C072S287000, C072S405020, C072S430000, C226S004000, C226S112000
Reexamination Certificate
active
06715332
ABSTRACT:
SPECIFICATION
1. Field of the Invention
Our present invention relates to a drawing unit for a drawing machine and to a method of drawing an elongated metallic workpiece and suitable for use in a drawing machine.
2. Background of the Invention
Metallic workpieces such as rods, bars and tubes can be drawn by applying a linear pull to the workpiece to draw through a die which reduces the cross section and thus provides a draft in the workpiece, and in part a shape or profile thereto.
Drawing machines of this type can include at least one drawing carriage with a drive for imparting a linear displacement to the carriage. The carriage can be displaced back and forth in a machine frame. The carriage may be provided with jaws capable of engaging and disengaging from the workpiece. The machine used for this purpose can operate continuously on the workpiece and thereby produce a workpiece at limited length or can be a discontinuously operating machine such as a drawing bench.
An example of a continuous linear drawing machine is the machine described in DE OS 28 52 071. This patent publication discloses a carriage-type drawing machine with a drawing unit having two drawing carriages displaceable in guides of a machine frame which run parallel to the drawing direction. The drawing carriages move counter to one another and, in their back and forth movement, draw the workpiece in an endless fashion by a hand-to-hand pulling of the workpiece through the die. The displacement of the carriages is effected by double-arm levers and a double-curved cam which displaces the same.
Another drive system which can be used is that of EP 0 371 165 A1 which has a rotating drum with a cam on its surface formed by a rib and producing opposite movements of two carriages in the back and forth sense.
The strokes of these carriages are relatively small and, as a consequence, the carriages are mostly either in an accelerating or braking mode. So that high mean drawing speeds can be achieved, therefore, they must operate at relatively high stroke frequencies. However, the frequencies at which they can operate is not unlimited since at the points at which reversal of travel direction occur, high inertial forces must be overcome.
OBJECTS OF THE INVENTION
It is, therefore, the principal object of the present invention to provide an improved drawing apparatus which can overcome the drawbacks of these earlier systems and permit optionally longer strokes of the carriages and higher mean carriage speeds than has been possible heretofore.
It is also an object of the invention to provide a drawing unit or apparatus which is free from drawbacks of prior art systems.
A further object is to provide a method of operating a drawing machine or an improved method of drawing elongated metallic workpieces whereby disadvantages of earlier techniques can be avoided.
SUMMARY OF THE INVENTION
These objects and others which will become apparent hereinafter are achieved, in accordance with the invention, in a drawing unit for a drawing machine capable of drawing an elongated metal workpiece and having at least one die through which the workpiece is drawn. According to the invention the drawing unit comprises:
a machine frame forming an elongated path along which the workpiece is drawn;
at least one drawing carriage provided with a workpiece gripper and displaceable back and forth linearly along the path to draw the workpiece through the die; and
a controlled linear motor complex assigned to the drawing carriage and acting upon the respective drawing carriage for independent displacement of the drawing carriage along the path.
The method of the invention can comprise displacing at least one drawing carriage of a drawing apparatus and preferably a plurality of drawing carriages by respective linear motor complexes so that the pattern of movement of the respective drawing carriage can be flexibly adjusted as required by control of the respective linear motor. In a preferred mode of operations, for each pull of the workpiece through the die, at least one pair of such carriages simultaneously engage and displace the workpiece under the control of the linear motor complexes driving the carriages of the pair.
Advantageously the drives for the respective linear motors are individually controlled and regulated and thus the individual linear motor complexes are individually controlled for the respective drawing carriages to provide movement patterns of the drawing carriages which are independent of one another.
By comparison with the drive system of the prior art, the movement pattern of the individual carriages are substantially more flexible. The linear motors allow the stroke lengths, the displacements and the locations of the strokes and displacements of the individual carriages along the path to be selected in a variable manner which is no longer limited by a fixedly located cam.
The linear motors can be controlled with precision and provide a rapid acceleration and rapid braking. They can provide especially long strokes, even where they are used to create back and forth movement of the carriage and thus can provide average drawing speeds which are significantly greater than those attainable heretofore since the acceleration and braking segments can be proportionately shorter. In addition, the respective carriages can have different and controllable speeds for the forward and rearward strokes. As a consequence, the displacement of a carriage backwardly to engage the workpiece can be greater than has been possible heretofore and thus the time consumed in the rearward travel can be reduced and the productivity of the apparatus enhanced. In addition, since a complex mechanical drive below the carriages is not required, the overall height of the drawing machine can be significantly reduced.
Preferably the linear motor complex for a pulling carriage or slide encompasses one or more linear motor units assembled in a modular fashion by appropriate selection of the number and/or drive force of the linear motor units. Starting from a basic carriage which either has no linear motor unit or a unit of low power, the power applied to a carriage can be built up by assembling additional motor units therewith.
In a first embodiment of the invention the primary part or primary parts of the linear motor unit or units constitute movable members on a carriage and are assembled in a modular construction whereas the secondary part or parts are stationary elements which are disposed along the machine frame as metal tracks or rails for the carriage. The guide of the carriage along the path may utilize separate guide rails.
In a preferred second embodiment there is kinematic reversal and the primary part or parts of the linear motor unit or units are formed as stationary elements along the machine frame whereas the secondary part or parts are movable elements connected to the respective carriage and displaceable along the primary parts. The secondary parts of the linear motor units are thus applied to the carriages while the primary parts are mounted on the machine frame.
The predrawing of the end of the workpiece which is required to enable the workpiece to be gripped by the jaws of the drawing carriages can be effected with a separate predrawing carriage which can have either a linear motor drive or a hydraulic drive, or as a combined predrawing and drawing carriage. The latter is preferably provided with a linear electric motor drive although it can have a mechanical, e.g. hydraulic, drive.
Such a combined predrawing and drawing carriage, referred to herein as a “combi-carriage”, can have two clamping jaw pairs with the first pair engageable with the stem of the workpiece which is fitted through the die to commence the drawing process while the second pair engages the outer periphery of the workpiece, e.g. a tube behind this stem.
One drawing unit has only one such carriage, namely a combination predrawing and drawing carriage, forms the first unit for a basic unit for a drawing apparatus or line. A tube, for example, can be drawn with such a unit discontinuousl
Häusler Karl-Heinz
Klingen Hermann-Josef
Zillekens Norbert
Dubno Herbert
SMS Meer GmbH
Tolan Ed
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