Milling device for working, and in particular for trimming the edges of sheet metal strips, sheet metal plates or the like

A milling device for working, and particularly for trimming the edges, of sheet metal strips, sheet metal plates, and the like. The workpiece is movable in any desired shape or direction in relation to the working position between guide rollers. The milling device has a cutter head which can be turned by a motor. The rotational axis of the cutter head is located approximately parallel to the plane of the workpiece and approximately vertical to the direction of advancement of the device. The device is provided with at least one cutter element provided with a cutting edge inclined at an angle to the normal plane of the cutter head.

FIELD OF THE INVENTION 
The invention relates to a milling device for working, and in particular 
trimming the edges of sheet metal strips, sheet metal plates or the like. 
The workpiece is movable in any desired shape or direction in relation to 
the working postion between guide rollers, having a cutter head which can 
be turned by a motor, the rotational axis of which is located 
approximately parallel to the plane of the workpiece and approximately 
vertical to the direction of advancement and which has at least one cutter 
element provided with a cutting edge inclined at an angle to the normal 
plane of the cutter head. 
BACKGROUND OF THE INVENTION 
A device for the milling of longitudinally extending areas, particularly of 
the edges of continuous metal strips or long rods, is known from German 
Published Application DE-AS No. 15 02 100, where the axis of a cutter head 
equipped with hard alloy cutters is inclined by an angle .gamma. in 
relation to the plane of the strip to be trimmed. The hard alloy cutters 
are also disposed inclined by the same angle .gamma. in relation to the 
normal plane of the cutter head. However, in this known device the 
individual cutting edges are formed in a straight line and by themselves 
cannot define a plane, i.e. no cutting edge plane can be defined in the 
sense of the subject of the present application. Furthermore, it is of 
importance that the inclination of the flank of a straight cutting edge 
such as in the device in accordance with DE-AS No. 15 02 100 cannot have 
any influence on the shape of a cutting arc. The shape of the elliptical 
cutting arc is determined by the angle .gamma. or, respectively, the 
rotational cone of the cutting generatrix of the cutting tool, the size of 
which can be different, depending on the radial distance of the point of 
contact of the cutting edge in reference to the rotational axis. 
SUMMARY OF THE INVENTION 
It is an object of the invention to improve a milling device for trimming 
the edges of sheet metal strips, plates, or the like, where the workpiece 
is movable in any desired shape or direction relative to the working 
position between guide rollers in such a way that a simple and 
cost-effective treatment of the edges of sheet metal strips, sheet metal 
plates or similar workpieces becomes possible while, at the same time, 
ensuring a large cutting output combined with small stresses on the 
cutting edges, self-sharpening effects on the cutting edges and a long 
edge life, as well as making possible the working of very hard austenitic 
materials. 
This object is obtained by means of the device of the present invention. 
In the milling device in accordance with the invention, the shape of the 
non-elliptical cutting arc is decisively influenced by the shape of the 
elliptical cutting generatrix. It is also possible to determine the shape 
and position of the activated arcuate generatrix of the cutting edge. 
Since the cutting directions of the individual cutting edge points 
practically have such small deviations in relation to the cutting edge 
plane, use of the cutting edge plane as flank is not possible. It follows 
from this that in the subject of the application the cutting edge plane 10 
cannot be defined as the "flank of the round cutting insert". 
Considerable differences from the known device are a result of the 
invention, not only in a structural view, but also--e.g., with the same 
dimensions of the cutter heads--in view of milling properties. During the 
working of the edges of sheet metal, for example, it is known that the 
direction of the milling forces should have only slight deviations from 
the sheet metal plane, because otherwise a plastic deformation of the 
edges may be caused by bending or the heavy vibrations may lead to 
breaking of the cutting edge. In a milling device according to the 
invention such disadvantages have been avoided from the start because of 
the constant direction of the milling forces, while in the subject of 
DE-AS No. 15 02 100 the direction of the milling forces can change 
depending on the angle of contact 2 .phi. of the cutting edges, resulting 
in the disadvantages described above. 
In contrast thereto, long contact arcs with practically only small changes 
of the direction of the milling forces are made possible by means of the 
device of the present invention. With it considerably longer cutting edges 
can be used, thus resulting in considerably longer life with identical 
cutting speeds because of the smaller specific load. 
A further advantage of the present invention resides in the fact that the 
contact point of the cutting edge is located at a comparatively small 
radial distance from the rotational axis, thus this cutting edge contact 
point will make contact with the material with less kinetic energy. During 
the subsequent work process, the cutting edge, which is in the form of a 
circular cutter, for example, is accelerated to a multiple of the contact 
speed of up to three-quarters of the length of the cut, after which it 
slows down again. In this manner, extraordinarily high average speeds can 
be attained during cutting. 
In contrast to that, the circumferential speed of the contact point in the 
device according to DE-AS No. 15 02 100 is considerably higher, so that 
the attainable cutting speed is limited in relation to the dynamic load 
capacity of the operating cutting edge. This results in the disadvantages 
in regard to the productivity of the known device mentioned above. 
The invention is described by means of an exemplary embodiment with the aid 
of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIGS. 1, 2, a milling device for working a sheet metal edge 9 of a sheet 
metal strip 1 is shown being advanced in one direction, which is brought 
into the working position between guide rollers 2. Milling is performed 
with a cutter head 3, the rotational axis 4 of which is located 
approximately parallel to the plane of the sheet metal strip 1 as well as 
approximately vertical to the direction of advancement V. The cutter head 
3 is rotated unidirectionally by means of an electric motor 5 and a drive 
unit 6. The cutter head 3 is equipped, via a fixed screw connection 7, 
with a cutting element 8, the cutting edge plane 10 of which is disposed 
inclined by two small angles .alpha. and .beta. in relation to the 
rotational plane NN being perpendicular to the cutter head rotational axis 
4. The face of the cutter element 8 has a particular radius, and the 
center of the cutter edge face 10 is preferably located less than the 
distance of the particular radius from the rotational axis 4. As viewed in 
the direction of travel of strip 1, the face 10 forms an angle .alpha. 
with the plane N--N. As viewed perpendicularly to the direction of travel 
from above, the face 10 forms an angle .beta. with the plane N--N. In 
regard to the disposition of the cutter head 3 it is of advantage if the 
rotational axis 4 is disposed above or below the sheet metal plane by an 
amount corresponding to the cutter radius. 
In this milling device the arcuate cutting edge 11 of the cutting element 8 
contacts the sheet metal edge 9 with a contact arc .phi. constituting a 
large arc. The cutting edge becomes operational between a contact point E 
and a contact point A. In this manner a cutting edge segment S of the 
cutting element 8 can be brought to bear which corresponds to 
approximately one-half of the circumference. Because of the drawing cut 
thus created, a small load on the cutting edge and, at the same time and 
because of the large contact arc .phi., a large milling cut is achieved. 
A particular milling advantage can also be achieved by the operational 
cutting edge, the contact point E of which is located near the rotational 
axis 4, having a slow speed. Thus a sudden load on the cutting edge 11 can 
be considerably reduced. 
Further advantageous features can be achieved by using the cutter head 3 at 
small cutting depths. The amount of optimal milling thickness can be 
considered to be the advantageous cutting depth. It is possible in this 
manner to achieve high milling efficiency, that is, great comma factors, 
with particularly small milling devices. In order to make use of these 
features it is advantageous if greater cutting depths are worked in 
several milling stages. In order to eliminate the reactive milling forces 
acting on the workpiece, it is advantageous if the milling stages can be 
used alternatively running in the same and then in the opposite direction. 
Use of a circular cutter, i.e. a cutting element having a single, convexly 
curved cutting edge 11, will also result in the advantage of being able to 
use the entire circumference of the cutting edge by loosening and 
advancing the used edges. In this way the circular cutter results in the 
optimal relationship between the desired small size of the cutter size and 
the long cutting edge. 
Additionally, instead of one circular cutter on the cutting element 8, a 
pluraity of arcuate or nearly arcuate cutting edge elements can be 
provided, the cutting edge planes 10 of which are inclined by two small 
angles and which each are defined by an entry point E and exit point A. In 
this embodiment all cutting segments of the cutting element 8 can 
advantageously have a shape identical to each other. 
It is to be understood that the above described exemplary embodiments have 
been given by way of example only and that other embodiments and 
improvements are possible within the scope of the invention. 
The foregoing description of the specific embodiments will so fully reveal 
the general nature of the invention that others can, by applying current 
knowledge, readily modify and/or adapt for various applications such 
specific embodiments without departing from the generic concept, and 
therefore such adaptations and modifications are intended to be 
comprehended within the meaning and range of equivalents of the disclosed 
embodiments. It is to be understood that the phraseology or terminology 
employed herein is for the purpose of description and not of limitation.