Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DESCRIPTION OF PRIOR ART
This invention relates to improvements in plate
rolling and particularly to improvements in a method of
rolling steel plate into substantially cylindrical form,
viz, a pipe.
Plate rolling methods have been described in the
inventor's earlier Patent viz, U.S. Patent 3,879,994.
The earlier patent specification described a
novel method of plate rolling more particularly to form
- substantially cylindrical pipes simply by bending a plate
about a rotatable mandrel.
Thus steel plate is rolled by engaging an edge of
the plate under a flange of a rib extending axially on the
cylindrical surface of a mandrel. The mandrel is turned to
advance and curve the plate. Complete pipes are formed by
curving plate about the mandrel through 180 then engaging
the opposite edge of the plate with the mandrel and curving
the remaining 180.
One problem that has been experienced in the per-
formance of the invention is the maintenance of the plate in
a dynamically stable relationship on the rotatable mandrel.
Instability does occur during the final stages of curving of
the plate through the full 360 unless adequate precautions
are taken. This instability is brought about by the moments
and forces which are exerted on the plate leading to a tend-
ency for the almost completely circular plate to "spin out"
from the mandrel gripper during the final stages of rolling.
The problem has to date been met by the Applicant
by the use of frictional devices such as a slipper device
similar to that described in the above-mentioned earlier
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patent or the use of other braking devices imparting frict-
ion to the external plate surface.
Referring to the inventor's U.S. Patent 3,879,994
the slipper member 41 bridges the gap between the pressure
rolls 17,18 and the rolled plate thus ensuring that the
plate is held against the mandrel 20 thereby enabling
complete formation of the pipe. The use of the slipper and
other external braking devices have proved workable in pract-
ice, however, unfortunately they are cumbersome and tend to
damage the surface of the workplate.
DESCRIPTION OF INVENTION
It has been found that the same results can be
achieved in a simple manner according to the invention in
a method of rolling a plate to form a cylindrical article
which comprises engaging an edge of the plate by gripper
; means mounted on a cylindrically formed mandrel mountedrelative to pressure means adapted to engage said plate,
turning the mandrel to advance and curve said plate, revers-
ing the plate to engage its opposite edge to complete the
curving process to form a cylinder, said mandrel and said
pressure means being relatively movable such that the relat-
ionship between said plate and said pressure means can be
controlled.
In one aspect of the invention there is provided a
method of rolling a plate to form a substantially cylindric-
al article on apparatus comprising a support bed for the
plate, a rotatable mandrel with a gripper means for engaging
an edge of the plate, pressure means adjacent said mandrel
adapted to engage said plate, including the steps of engag-
;ng an edge of the plate by said gripper means, turning the
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mandrel to advance said plate past said pressure means to
curve said plate into a cylinder shape characterized in that
said mandrel and said pressure means are relatively movable
to create a force on said advancing plate at least during
thé final stages of rolling to prevent relative movement of
the plate and said mandrel.
There is also provided according to the present
invention an apparatus for carrying out the method described
in the preceding paragraphs comprising a mandrel rotatable
above a plate support bed, pressure roller means mounted
adjacent said mandrel for contacting and supporting said
plate, said mandrel and said pressure roller means being
relatively movable during a plate rolling operation at least
during the final stages of said operation to apply a force
against said plate as it is advanced.
Thus contact is maintained between said plate and
said pressure means at least during the final stages of roll-
ing whereby additional lateral forces are generated and
applied to said plate thereby preventing lateral movement
and rotation of the plate relative to said mandrel. Said
lateral forces may or may not include frictional forces
brought about for example by contact between the internal
surface of the plate and said mandrel.
Conveniently the pressure means includes a pair
of supporting rollers mounted on either side of centre below
the mandrel and are relatively movable to the mandrel or
vice versa. It is a simple matter to provide such relative
movement such as by adjustable mechanical linkages or hy-
draulic cylinders thus eliminating additional mechanisms
such as slippers or friction brakes engaging the external
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surface of the plate.
BRIEF DESCRIPTION OF DRAWINGS
The invention will be described in greater detail
having reference to the accompanying drawings in which:-
Figure 1 is a side elevational view of part of theapparatus showing an end view of the mandrel;
Figure 2 is an end elevational view of part of the
apparatus showing a side view of the mandrei; and
Figures 3 to 5 are schematic views showing various
stages of rolling according to the invention.
DETAILED DESCRIPTION OF INVENTION
Referring firstly to Figures 1 and 2 there is
shown therein plate rolling apparatus comprising a horizont-
al framework 11 embodying supporting rollers 12 or other
like ~eans upon which steel or other plate 13 may be advanc-
ed horizontally at a convenient height. The framework 11
has a well 14 through which a massive supporting I-beam 15
extends in a direction at right-angles to the direction of
advancement of the plate 13 with i~s flanges horizontal.
The upper flange 16 supports two horizontal rollers 17 and
18 the axes of which extend in the longitudinal direction of
the I-beam 15 at an appropriate height for the upper surface
of the rollers 17 and 18 to be at the same height as the
upper surfaces of the rollers 12. Thus flat plate advanced
along the rollers 12 also contacts and runs upon the rollers
17 and 18. The lengths of the rollers 17 and 18 are suffic-
iently great to engage the full width of the plate 13. The
rollers 17 and 18 are shown supported by end brackets 19
fixed on the flange 16 and it is to be understood that as
many intermediate supporting brackets may be provided along
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the rollers 17 and 18 as are deemed necessary to prevent
significant flexing.
The flange 16 is provided with means for support-
ing a mandrel 20 with its axis above the web of the I-beam
15 centrally spaced between the rollers 17 and 18 but above
them. As shown by Figure 2 the supporting means comprises
two hydraulic cylinders 21 and 22. One cylinder 21 is fixed
in position with a shaft bearing 23 mounted on the upper end
of its pis~on rod 24. The other cylinder 22 also has a
piston rod 25 with a shaft bearing 26 mounted on its end,
but instead of being fixed to the flange 16 it is connected
by a pivot pin 27 to a bracket 28 fixed on the flange 16.
The cylinder 22 is pivotally connected to the piston rod 29
of a further hydraulic cylinder 30 pivoted to the web of the
I-beam 15 so that by retraction of the piston rod 29 into
the cylinder 30 the cylinder 22 together with its piston rod
25 and bearing 26 can be swung downwardly from the full line
position shown in Figure 2 into the position shown in dotted
lines in which it is entirely below the path of movement of
the plate 13.
With the cylinder 22 in its erect position shown
in full lines in Figure 2, its bearing 26 and the bearing 23
provide support for the shaft 31 of the mandrel. Mandrels
of different diameters can be used with appropriate raising
or lowering of the piston rods 24 and 25. Suitable drive
means is provided for the shaft 31 comprising a motor 32 and
reduction and reversing gear box 33, both mounted on the
I-beam 15 with a double universal drive connection 34 extend-
ing from the gear box 33 to the shaft 31.
The mandrel 20 may be in the form of a cylindrical
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drum as shown in Figures 1 and 2, in which case for the sake
of rigidity it i5 desirably provided with internal discs or
other suitable supporting means, not shown. However, it is
not essential for the mandrel to have an enclosing periph-
eral surface which is a complete cylinder. In addition the
power cylinders 21 and 22 are actuatable to move the mandrel
up or down during an actual plate bending operation. This
will be described in greater detail later.
An essential aspect of the mandrel is the provis-
ion thereon of a gripper 36 which consists of a continuous
rib extending in an axial direction at the peripheral region
of the mandrel. The gripper 36 projects radially away from
the mandrel for a short distance and has two flanges 37
which extend in the circumferential direction, one at each
side. The flanges 37 provide between themselves and the
periphery or the partial peripheral surface of the mandrel a
recess which is slightly greater in width than the thickness
of the plate with which the mandrel is to be used.
The gripper 36 on mandrel 20 applies a moment to
the edge of the plate 13 when the mandrel is rotated in the
direction of arrow A, equal to the plastic moment of the
plate and a vertical force equal for most of the time to the
roller force applied against the plate by rollers 17,18.
Figures 3 to 5 show schematically the various stages of com-
pletion of formation of a pipe according to the present
invention using the apparatus described in Figures 1 to 2.
It will be understood that the torque applied to
the mandrel, which is constant for practically the full form-
ing cycle, and equal to the plastic moment (MPL) of the
plate 13, is in fact applied to the plate edge via the
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gripper 36. The mandrel 20 acts as guide and there is con-
tact but little pressure between the mandrel 20 and the
plate 13. Whilst the plate is in contact with the mandrel
there exists all around the plate a bending moment equal
to the plastic moment (MPL).
In the closing stages shown in Figures 4 and 5
near the completion of bending, the moment applied at the
gripper 36 will cause the plate to escape or spin away from
the mandrel in the direction of rotation of the mandrel
- unless preventative means are employed.
The preventative means are essentially those which
will apply a horizontal retarding force or component of
force to the plate in addition to the roller force Fr which
ff acts vertically until the closing stage.
At the closing stages viz. Figures 4 and 5 MPL
(the gripper moment) is opposed by an equal and opposite
moment comprising the sum of moments caused by externally
applied roller forces HFr1, HFr2 and the internal frictional
es t~Frl, ~LFr2.
According to the invention, the opposing moments
are generated by lowering the mandrel by operation of power
cylinders 21,22 in the direction of arrow B or raising the
rollers (by means not shown) until both rollers are engaged
by the plate thereby creating lateral forces Fr1 and Fr2.
The action of the forces creates a horizontal component of
force HFr2 and HFr2, which give rise to said opposing
moments. These opposing moments are sufficient to prevent
slippage or spinning of the bent plate away from the mandrel.
It has been found that sufficient lateral force
can be created to prevent slippage of the curved plate with-
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out the imposition of any external frictional component as
hitherto used.
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