Note: Descriptions are shown in the official language in which they were submitted.
1056707
This invention relates to a method and a machine for bending
flat strip to a cylindrical shape, use being made of a rolling mill
comprising at least three rolls.
Such bending machines for implementing said method are already
included in the art. These bending machines, however, have the disadvantage
that it is never possible to obtain a true cylindrical shape, at least
not with the embodiments of such bending machines hitherto known.
This is caused by the fact that a flat strip, fed into the
rolling mill, is bent at the front end of the strip with a radius of
curvature that differs slightly from that of the next part of the strip,
which is supported by the three rolls in a different manner than was the
case for the front end of the strip.
At a given moment following the introduction of the strip, the
strip is flush, along a tangent line, with the first two rolls, while the
strip end butts against the third roll.
At this third roll, the strip end can at first be inclined,
within certain limits, at a relatively random angle to a tangent line at
the point of contact with this roll. Once the strip has passed all of
the three rolls, however, contact at all rolls takes place along a tangent
line. As a result, the front end of the bent strip has a radius of
curvature which varies from that of the greater part of the rounded strip.
This also applies to the rear end when this is sheared or cut off the
strip stock and then passed through the rolls.
According to the invention, the aforementioned drawback is met
by implementing the method in such a way that the strip part is rolled
to a cylindrical shape over a length, measured in peripheral direction,
which is greater than the circumference of the cylinder, the bent strip
part being elastically deflected outwards during rolling, a portion then
being separated from the bent strip the length of which is exactly equal
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to the circumference of the desired cylinder, so that a true cylindrical
shape is formed after the elastic recovery of the separated deflected
portion.
The invention also provides a bending machine for bending flat strip
to a cylindrical shape by means of a rolling mill comprising at least three
rolls, and an element which elastically deflects the rounded strip end in a
direction which causes the radius of curvature of the rounded strip part to
become greater than the radius of curvature which this strip part has in the
released state, characterized in that means are provided for separating
from the strip which is being fed a bent strip portion having a length
equal to the circumference of the desired cylinder.
It has thus become possible to roll with the three rolls more than
360 deg. of the cylindrical bent strip, these 360 deg. being measured along
the circumference of the cylindrical shape which results when the elastic
deflection is released.
Preferably, means are provided for fixing exactly the length of
the strip part which is fed per operation into the rolling mill, so as to
be fully independent of any linear dispensing by the rolls. In such case,
roll slippage along the strip could result in the impossibility of exactly
maintaining the size of the cylinder eventually formed.
It has been found in practice that a highly favourable solution
consists in the use of at least two strip clamps which are each alternately
opened and closed, in such a way that one clamp is opened while the other is
closed, and conversely, not more than one clamp having a fixed position on
the machine and at least one clamp being capable of performing a translating
motion in the feed direction of the strip.
The separating means can be constituted by a sawing machine, a
cutter, a flame cutter, shears, etc. The only condition in this respect is
that such a machine for separating the greater part of the bent strip
transversely to the length of the
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strip which is being fed must be capable of performing a translating
motion with respect to this strip. The same effect can naturally be
obtained if the strip can perform a translating motion with respect to the
separating machine. After the bending process, it is furthermore necessary
for the bent portion of the strip to be conveyed to the machine which
performs the separation of the cylinder produced.
To this end, it is possible, for example, to provide at least
one roll axially displaceable transversely to the feed direction of the
stripO This allows such a roll to be entirely removed from the loop of
the bent strip, so that the latter can be freely conveyed to a separating
machine. For this purpose, the rolling mill can be housed in a support
which is slidably mounted on the machine in the direction of feed of the
strip.
The element which elastically deflects the rounded strip part
can be designed as a curved, substantially half-moon guideway which is
located inside the bent strip part and which partially encircles one of
the rolls, one end of the guideway being provided near the roll surface
and the other end being at the required distance from the roll surface.
In case the thickness and the diameter of the material to be
bent should cause the separated cylindrical part to close about a roll,
use can be made of a guideway comprising at least two guideway components,
one guideway component of which occupies a fixed position with respect
to the roll which is located inside it, the other guideway component being
capable of performing a swivelling movement, so that the remote end of
the guideway can move toward and away from the roll surface.
The separated cylindrical part is thus received removably, since
it is prevented from locking on the guideway. Accordingly, the formed
cylindrical part can be conveniently removed from the bending machine,
for example through a discharge chute on the underside of the machineO
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Some embodiments of the invention will now be described, by way
of example, with reference to the accompanying drawings~ in which:
Figure 1 is a side view of the supply strip at the start of the
bending operationO
Figure 2 shows the same supply strip at the end of the bending
operation.
Figure 3 shows the cylindrical product formed, likewise as a
lateral view.
Figure 4 is a diagram of a bending machine in a vertical partial
section~ at the start of the bending operation.
Figure S shows the same machine as Figure 4, but at the end
of the bending operation.
Figure 6 shows another embodiment of a bending machine.
Figure 7 shows an element for deflecting the bent strip.
Figure 8 shows a variant of the element of Figure 7.
In Figure 1, the strip 1 which is being supplied is shown in a
side view. The portion 2 has already been partially bent in the rollers
(not shown). Portion 3, just like portion 4, is a strip part which has
been properly dispensed for the bending operationO This means that the
length of the strip portions between the points 5, 6, 7 and 8 is equal,
or equalized, during the feeding operation by the aforementioned dispensing
device.
Figure 2 is a schematic side view of the situation when the
bending operation for producing a new cylindrical part has been completed.
The strip part 2 has now been fully bent into the shape 12, the strip
part 3 having advanced to the position 13, and the strip part 4 to the
position 14. The number 19 indicates an element which applies such a
force to the end 15 of the strip part 12 that this is bent open outwardly
over such a distance that the elastic limit of the material is not exceeded.
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This means that, when the element 19 no longer applies force to the end
15, the strip part 12 will spring back fully elastically and assume the
shape imparted to it by the rolls of the rolling mill (not shown). The
number 17 indicates a cutting apparatus, such as, for example, a circular
saw. This saw is so arranged as to be able to cut through the strip part
12 at point 16. This point 16 had the position 6 in Figure 1.
When the sawing machine 17 has severed the strip part 12, the
true cylindrical shape 22 is formed as shown in Figure 3. The ends 26
and 25 of the rounded strip are here drawn at a small distance from each
other for greater clarity. Actually, the gap 27 left between the ends
25 and 26 can be made as small as desired by a proper adjustment of the
dispensing operation and of the rollers of the bending machine. If
required, therefore, the gap 27 can be made equal to 7eroO
Figure 4 shows a bending machine 28 into which a strip 29 is fed.
The number 30 indicates a clamp which is slidably mounted on the machine
and which can be opened and closed. Three rolls 31, 32 and 33 are housed
in a support 34 of the machine. A second clamp 35 is mounted inside this
support and can likewise be opened or closed, as requiredO The number 36
indicates a cutting mechanism.
Figure 5 illustrates the same machine at the moment at which the
operation of bending the strip end has been completedO The sliding clamp 30
has now come very close to the support 34, clamp 30 having been closed
and clamp 35 opened during the bending operation.
The strip part 38 has remained bent open under the action of
the element 37. The bent cylindrical part, having been cut off by the
cutting mechanism 39, rolls down as a true cylinder 40 through the discharge
chute 41 of the machine.
Figure 6 shows a variant of the bending machine described
hereinabove, in which the strip is not bent downwards but upwards. The rolls
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again bear the reference numbers 31, 32 and 33, and are again housed in
the support 34. The cutting mechanism 42 now occupies a slightly higher
position and the drive unit 43 of the machine is shown in slightly more
detail. ~s distinct from the machine of Figure 4, the clamp 44 is here
mounted in a fixed position on the machine, while the clamp 45 can perform
a translation along the machine under the driving action of the traversing
mechanism 46 which is in turn driven by the drive unit 43.
It is naturally possible to vary the bending machine in many
ways within the scope of the invention. It is possible, for example, to
displace the support 34 along the machine bed and to mount the clamp 30
(see Figure 4) in a fixed position on the machine. The support 34 (see
Figure 5) can furthermore be displaced along the machine bed for the
purpose of removing the rolling mill while the cutting mechanism is severing
the cylinder. This is shown schematically in Figure 5 by dotting the lower
roll, which in the dotted form bears the reference number 47. This means
that this roll has been transversely removed from the loop 38, so that
the support with the rolls can be displaced along the machine bed, whereupon
the severing operation can be performed with the aid of the cutting
mechanismO
Figure 7 shows the shape which a deflecting element 48 can have
to cause the bent part 38 of the strip 29 to be deflected outwardly.
This element is a guideway of which the front end 49 is placed
as near as possible to the outer surface of the roll 33. This part 49 is
furthermore tapered, so that the front part of the bent strip 38 can be
conveniently passed along the outer surface 51 of the guideway 48.
Figure 8 illustrates a variant of Figure 7, according to which
the guideway is composed of a fixed component 52 and a movable component
53, in such a way that 53 can turn on a pivot 54. The end 55 of the
guideway component 53 rests against a fixed stop 58 and is held down by
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a ~pring 56 which is supported on a fixed part 57 of the machine. Since
the component 53 can spring inwardly, the severed strip part 38 is
prevented from locking on to the guideway assembly 52-53.
