Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD AND APPARATUS FOR MAKING COLD-PILGER-ROLLED TUBES
SPECIFICATION
FIELD OF THE INVENTION
The present invention relates to the manufacture of
tubing. More particularly this invention concerns making cold-
pilger-rolled tubes.
BACKGROUND OF THE INVENTION
A standard apparatus for making a tube has two pilger
rolls rotatable about respective axes to wrap a metal sheet
workpiece moving in a travel direction around a mandrel extending
in the direction between a nip formed between the rolls. The
mandrel is supported upstream of the nip in a thrust block and
has a frustoconically tapered downstream portion extending
through the nip so that as the initially flat workpiece is
wrapped around the mandrel its diameter and wall thickness
decrease. The rolls themselves are each formed with a
substantially semicircular groove to impart the desired
cylindrical outer surface to the workpiece.
With this system, tubes are typically manufactured to
especially stringent size tolerances. Dimensional changes can
however occur in the product during manufacture. Whenever the
tube diameter threatens to depart from the tolerance range, or
had already departed from this range, the rolling mill is shut
down and the size of the roll gap is corrected. Any rapidly
occurring dimensional changes may remain undetected with such
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periodic sampling-type inspections. Confirming that a
dimensional adjustment had been successfully performed was also
possible only after at least one entire additional tube had been
made or unless the rolling mill was again halted to inspect
dimensions. Ultimately, production time was lost during each
dimensional inspection since the rolling mill had to be stopped.
Optical methods such as those using laser light grids
are suitable for measuring the diameter of finished tubes.
The application of nondestructive testing methods for
the cold-pilger-rolling process is, however, not known in the
prior art. Instead, the testing methods used heretofore have
continued to pursue the principle where measurement is performed
after forming and sampling have been completed, and subsequently
individual or multiple forming parameters are then modified based
on the test values, and finally the result of this parameter
modification is then checked once again after a further completed
forming process.
OBJECTS OF THE INVENTION
It is therefore an object.of the present invention to
provide an improved method and apparatus for making cold-pilger-
rolled tubes.
Another object is the provision of such an improved
method and apparatus for making cold-pilger-rolled tubes that
overcomes the above-given disadvantages, in particular that
enable the position of at least one forming die to be adjusted
effected during cold pilger rolling based on measurement data
obtained during the forming process.
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SUMMARY OF THE INVENTION
An apparatus for making a cold-pilger-rolled tube has
two grooved pilger work rolls rotatable in a roll frame about
respective axes to wrap a workpiece moving in a travel direction
around a mandrel extending in the direction between a nip formed
between the rolls and anchored upstream of the nip in a thrust
block. According to the invention an outside diameter of the
workpiece is measured downstream in the direction from the rolls
as the workpiece passes through the nip, and means for displacing
one of the rolls relative the other of the rolls transversely to
the travel direction as the workpiece passes through the nip in
accordance with the measured outside diameter for maintaining a
uniform outside diameter of the workpiece.
According to the invention, the means for displacing is
operatively linked to at least one work roll engaging the tube
from the outside, and the means for displacing is in turn
connected to the measuring device. This is preferably effected
by interconnecting a controller between the means for displacing
and the measuring device, this measuring device being especially
preferably connected to a data memory for the adjustment and/or
operational parameters.
This way, an online apparatus is provided for producing
cold-pilger-rolled tubes that is able to monitor the rolled
product and detect defects that may occur preferably almost
immediately, and preferably to perform appropriate corrective
countermeasures preferably still during the ongoing forming
process.
This not only allows the ongoing forming process to be
monitored continuously; it furthermore also enables any
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corrective and adjustment actions to be tracked and evaluated
almost immediately in order to immediately initiate and effect
any required corrections.
To this end, the means for displacing is connected to
at least one tool or die engaging the tube from outside,
preferably at least one roll, and can thereby effect and adjust
the roll gap setting in the desired manner and preferably online
with the measuring device.
In an advantageous embodiment of the invention,
deviation in the outside diameter of the tube from a specified
set-point value or from a tolerance range is determined during
the forming process. This is especially advantageously effected
by comparing measurement data with specifications and reference
data stored in a controller, and, in particular, in the
controller's memory. An apparatus is thus created that
automatically monitors adherence to the required tolerances
during the entire manufacturing process, and preferably also
ensures that appropriate actions are taken.
The measuring device is preferably optical, such as a
laser sensor that provides nondestructive and reliable online
measurement of the outside diameter of the cold-pilger-rolled
tube using equipment that is especially easy to handle while
achieving especially precise measurement results.
The outside diameter is typically measured not only
when the tube is at one fixed position. Instead, the cold-
pilger-rolling process produces a regular rotation of the tube
about its longitudinal axis. It is therefore possible to provide
measurement coverage over the entire circumference of the formed
tube simply by the preferred fixed positioning of the measuring
device relative to the rotation of the tube relative to the
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measuring device produced during the normal manufacturing
operation. The approach is also preferred whereby not only one
measurement at one specific site on the tube is performed, but a
plurality of measurements is performed while, for example,
maintaining a specified frequency extending over the entire
forming process. As a result, determining the recorded
measurement data also enables the effect of any measurement
errors to be minimized by simple means.
In a preferred embodiment of the invention, the work
roll engaging the tube from the outside is supported in at least
one adjustment position at which the roll gap can be set, and
preferably also secured in this position. This reliably ensures
the ability to readjust the apparatus and readjust the roll gap,
preferably automatically and during the forming process.
3.5 In a first alternative embodiment of the invention, the
adjustment device can include an electrically adjustable
adjustment wedge that can alter the roll gap preferably
steplessly to any appropriate shape and thickness by utilizing
readily controllable and available means.
In a second alternative and similarly preferred
embodiment of the invention, the adjustment device has a
hydraulically adjustable adjustment wedge and in order to supply
the hydraulic fluid a pump for the fluid is preferably disposed
on the roll stand itself. This also provides a stepless
adjustment of roll gap by simple and easy-to-control means. The
preferred positioning of the pump on the roll stand itself
additionally contributes to the compactness of the constructive
design while reducing the length of the hydraulic lines to the
minimum extent necessary.
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In a third alternative and similarly preferred
embodiment of the invention, the adjustment and fixation of the
roll gap is effected by one or more hydraulic cylinders. This
preferred embodiment too enables stepless adjustment of the roll
gap to be ensured by simple and easy-to-control means.
In a fourth alternative and similarly preferred
embodiment of the invention, the adjustment of the roll gap is,
however, implemented by vertically adjusting at least one back-up
roll for the work roll engaging the tube from outside. This
avoids having to adjust the work roll itself that engages the
tube from outside, preferably the one roll, and being connected
thereby to the adjustment device. Instead, the adjustment device
can be connected to the back-up roll, thereby ensuring indirectly
that the roll gap can be adjusted by similarly simple and
reliably controllable means.
The preferred approach in this regard is furthermore
one whereby the transmission of measurement data, and optionally
control data, to the adjustment device(s) is effected through
cables. In an alternative and similarly preferred approach,
however, transmission is possible wireless or by telemetry in
order to thereby minimize the amount of cabling and the
installation space required for this purpose. Using wireless
transmission of measurement and optionally control data, also
obviates the need to encapsulate cables and protect the cables
from the effects of the forming process.
A preferred approach according to the invention is one
where not only the one work roll engaging the tube from outside
is adjustable but also where in addition the rolling mandrel is
also mounted in the rolling mill so as to be adjustable. To this
end, the rolling mandrel is preferably also connected to the
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measuring device and optionally to the controller. This ensures
that all of the tools involved in the forming process can be set
appropriately in their position relative to each other in order
to achieve the best possible forming product. The flexibility of
the apparatus is advantageously enhanced in terms of its ability
to react to deviations from the specified size in wall thickness
and/or the outside diameter of the tube.
In a second aspect of the invention, a method is
provided to produce cold-pilger-rolled tubes by means of a
rolling mill, which method includes a rolling mandrel supported
on at least one mandrel thrust block, and at least two tools
engaging the tube from outside, preferably rolls, as well as a
measuring device to measure the wall thickness of the tube during
the forming process. According to the invention, the means for
displacing the work roll engaging the tube from outside always
adjusts the position when the measuring device connected to it
detects a deviation in the outside diameter of the formed tube
from a specified value or tolerance range.
The means for displacing is preferably connected not
only to the measuring device but also a controller in order to
implement the method according to the invention.
The advantages achieved by the method according to the
invention and realizable effects correspond to those that have
already been described with reference to the first aspect of the
invention.
The method according to the invention provides
preferably fully automatic measurement of the outside diameter of
the formed tube and appropriately corrects any detected
deviations by re-adjusting the roll gap between the rolls.
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The preferred approach in this regard is one where the
outside diameter is measured over the entire circumference of the
tube and over its entire length. To this end at least one
measuring device, preferably exactly one fixed measuring device,
is provided inside the apparatus. The fact that a partial
revolution of the tube about its longitudinal axis is effected in
the rolling mill for each feed motion during the forming process
enables the fixed measuring device to cover the entire
circumference of the formed tube. This is furthermore
implemented by using especially simple means, yet still yields a
reliable measuring result for the outside diameter of the entire
tube.
A preferred approach is finally one where to implement
the method according to the invention not only the rolls but also
an adjustably disposed rolling mandrel are adjusted so as to
counteract deviations in the outside diameter or wall thickness
from a specified value and tolerance range. This enables the
flexibility of the equipment and of the method according to the
invention to be especially advantageously enhanced in terms of
being able to deal with conformity variations of any kind and to
remedy these at any site by the most effective means.
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25011-168
BRIEF DESCRIPTION OF THE DRAWING
The above and other objects, features, and advantages
will become more readily apparent from the following description,
reference being made to the accompanying drawing in which:
FIG. 1 is a side schematic view of a first roll stand
according to the invention;
FIG. 2 is a partly sectional schematic side view of the
first roll stand according to the invention with its control
system;
FIG. 3 and 4 are schematic side view of second and
third roll stands according to the invention;
FIG. 5 is a schematic side view of the third roll stand
according to the invention with its control system;
FIG. 6 through 14 are schematic side view of fourth
through twelfth roll stands according to the invention.
DETAILED DESCRIPTION
As seen in FIG. 1 a roll 4 for the cold-pilger-rolling
of tubes comprises an upper die or work roll 4a and a lower die
or work roll 4b carried in a stationary frame or stand 4 and
defining a roll gap S through which extends a mandrel 8 (FIG. 2)
for the stretch reduction of a tube T into a predetermined cross-
section and predetermined wall thickness. The upper roll 4a can
be moved up and down by an adjustment wedge 7a, thereby enabling
the size of roll gap S to be set appropriately. Adjustment of
adjustment wedge 7a is in turn effected by rotating a spindle 14
that axially fixed at both ends in the frame 4 and threaded to
the adjustment wedge 7a. Rotating the spindle 14 makes the
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adjustment wedge 7a move left or right in a workpiece travel
direction D, with the angled surface of adjustment wedge 7a to
slide relative to the complementary angled surface of adjustment
wedge 7b that is connected directly to the chock for roll 4a that
is mounted in the frame 4 so as to only be movable vertically,
perpendicular to the direction D.
FIG. 2 shows roll stand with the tube T passing between
upper work roll 4a and lower work roll 4b. For the sake of
simplicity, the rolling mandrel 8 used with the also employed the
cold-pilger-rolling method is not shown. The tube T in the
drawing runs in the direction D from left to right passing
through roll gap S between the upper roll 4a and the lower roll
4b, and after forming is complete enters a measuring device 5 in
which the outside diameter of the tube T is measured. The
measurement data from measuring device 5 is fed to a controller 6
that after accessing appropriate operating data issues as
required a control command to adjust the roll gap S by moving the
upper work roll 4a up or down in the direction of an arrow 15.
FIG. 3 is a schematic side view of second embodiment of
the invention where an adjustment wedge 7a can be moved
horizontally in the direction D for shifting the upper roll 4a by
electric or hydraulic motors 16 and 17, in order to adjust roll
gap S in the desired manner.
FIG. 4 is a schematic side view of a third embodiment
of the invention in which, unlike the first and second
embodiments of FIGS. 1 through 3, the lateral movement of
adjustment wedge 7a is effected by hydraulic cylinders 18 and 19.
In this case as well, the horizontal movement of the adjustment
wedge 7a produces vertical movement of the upper work roll 4a and
an adjustment of roll gap S in the desired manner.
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FIG. 5 shows a fourth embodiment that is variant of the
system of FIG. 4 in which a pump 20 driven by a motor 21 controls
the flow of oil to the hydraulic cylinders 18 and 19. In a
preferred approach, both the pump 20 and the motor 21 are
attached in a fixed manner to the roll-stand frame 4 so as to
limit to the necessary minimum the installation space of roll
stand together with all of its ancillary modules.
FIG. 6 is a side schematic view of a fourth roll stand
according to the invention. A vertically effective hydraulic
cylinder 22 functions directly and without the use of adjustment
wedges or the like to shift the upper work roll 4a and thereby
adjust the roll gap S in the desired manner. The vertical
adjustment of the piston inside the hydraulic cylinder 22 is
effected by supplying the hydraulic fluid under pressure P from
is an external source.
FIG. 7 is a schematic side view of a fifth embodiment
of the invention. Adjustment of the roll gap S by adjusting the
vertical position of the upper work roll 4a is effected here by a
spindle 23 that functions as an element supporting the upper work
roll 4a. The spindle 23 is vertically fixed in the stand 4 and
threaded into a large nut rotatable by a motor 24, and thus
effects not only the stepless adjustment of roll gap S by means
of the vertical position of work roll 4a but also the fixation of
upper work roll 4a in the desired position.
FIG. 8 is a schematic side view of a sixth embodiment
of the invention, showing the supply of power to the actuator
itself. It is thus obvious that this embodiment can also be
appropriately combined with the embodiments of FIGS. 1 through 7.
The supply of power to the roll stand is implemented through an
external source 25 to a terminal 26 that is attached in fixed
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fashion to roll 4. The power to the unillustrated actuator for
upper roll 4a is supplied from this terminal via a flexible
cable.
FIG. 9 is a schematic side view of a seventh embodiment
s of the invention, showing as in FIG. 8 the type of electrical
power supply to roll 4 and its unillustrated actuator for the
upper roll 4a. This seventh embodiment of the invention can thus
also be appropriately combined with the embodiments shown in
FIGS. 1 through 7. The supply of power in this case is done
io inductively between a stationary electrical conductor 27 and a
pick-up 28 is connected to the frame 4 and operatively connected
to each other in such a way that a voltage is induced in the
pick-up 28 without contacting the conductor 27, the voltage being
sufficient to supply the unillustrated actuator for the upper
15 roll 4a in order to appropriately adjust the roll gap.
FIG. 10 is a schematic side view of an eighth
embodiment of the invention. This embodiment too involves the
supply of power to the system and, in particular, its
unillustrated actuator for the upper roll 4a. This eighth
20 embodiment can thus also be appropriately combined with the
embodiments shown in FIGS. 1 through 7. The supply of power to
this eighth embodiment is effected hydraulically through a feed
tube that is supplied from outside with hydraulic fluid under
pressure P. The feed tube 29 has two holes on its upper side
25 through which the hydraulic fluid can enter a fluid reservoir 30
that is slidably supported on the feed tube 29. This fluid
reservoir is fixed to the roll frame 4, and has on its lower side
an opening 30a through which the hydraulic fluid can be
transported under pressure P to the unillustrated actuator for
30 upper roll 4a.
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FIG. 11 is a schematic side view of a ninth embodiment
of the invention. This ninth embodiment can also be combined as
required with the embodiments shown in FIGS. 1 through 7. Power
is supplied here electrically and/or hydraulically. An electric
power source 31 and/or a pressure accumulator 32 is attached in
fixed fashion to the roll frame so as to effect the electrical
and hydraulic supply of power.
FIG. 12 is a schematic side view of a tenth embodiment
of the invention. This tenth embodiment involves the
transmission of control and measurement data from the
unillustrated measuring device and/or unillustrated controller to
the unillustrated actuator of the system, in particular, to the
actuator of the upper roll 4a. It is thus obvious that this
tenth embodiment can also be appropriately combined with the
embodiments of the invention shown in FIGS. 1 through 11. The
transmission of control and measurement data is implemented by
means of cables or telemetry, a telemetric non-contact
transmission of data being effected from the unillustrated
measuring device and/or the unillustrated controller through a
transmitter 33 to a receiver 34 carried on the frame 4 of this
tenth embodiment of the invention.
FIG. 13 is a schematic side view of a roll stand in an
eleventh embodiment of the invention. In contrast to the
previously described embodiments, it has a pair of respectively
displace rolls 4a and 4b that are supported by respective back-up
rolls 35a and 35b in the roll frame 4. These back-up rolls 35a
and 35b in turn are supported on respective beams 36a and 36b
that are vertically shiftable in the frame 4 such that an
appropriate vertical and/or angular adjustment of the support
beams 36a and 36b also enables roll gap S to be adjusted between
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the upper and lower rolls 4a and 4b. Particularly in the case of
a roll stand that is displaceably disposed laterally along the
longitudinal orientation of support beams 36a and 36b, this
approach when given an appropriate orientation of support beams
36a and 36b, allows rolling of the back-up rolls 35a, 35b along
the support beams 36a 36b for adjustment, either a constant
setting for roll gap S or, on the other hand, a movable setting
of roll gap S to be adjusted depending on the positioning of the
roll frame 4 along the support beams 36a, 36b. It is of course
obvious for the person skilled in the art that the eleventh
embodiment illustrated here can be combined with the features
described with reference to FIGS. 1 through 12.
FIG. 14 is a schematic side view of a twelfth
embodiment of the invention. In this solution, a pair of gears
37 that are in mesh can slide axially along a fixed drive shaft
38 to which the upper gear 37 is splined. Changes in roll gap S
can be transferred thereby from a fixed motor 39 that rotates the
shaft 38 to an adjustment wedge 7a that is threaded onto a
spindle 40 rotated by the lower gear 37. Thus, no matter what the
position of the frame 4 and gears 37 along the shaft 38, rotation
of this shaft 38 by the motor will rotate the spindle 40 and move
the upper roll 4a up or down as needed
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