JPH01150406A - Rolling apparatus - Google Patents

Abstract

PURPOSE: To enable a large reduction with a small power by swingingly moving a work roll and cradle element around a supporting roll via an arc of movement when the work roll and cradle element in a pair of roll assemblies are revolved around the supporting roll. CONSTITUTION: The roll assemblies 10, 12 which are respectively provided with one of the supporting rolls 14, 16, four of the work rolls 18, 20 and the cradle elements 22, 24 are driven by pinions 56, 58 which engage with gears 60, 62. And when the roll assemblies 10, 12 are revolved so that the work rolls 18, 20 and the cradle elements 22, 24 are revolved around the supporting rolls 14, 16 describing an orbit, respective work rolls 18, 20 and the cradle elements 22, 24 are swingingly moved around the supporting rolls 14, 16 and restored to the initial position via the arc of movement by the gear 48 and a sector gear 50 between respective supporting rolls 14, 16 and cradle elements 22, 24.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rolling apparatus, and particularly to a rolling apparatus capable of relatively large rolling reduction.

[Prior Art and Problems to be Solved by the Invention] Various basic considerations must be taken when designing a stand for a rolling mill. For example, the rolling load is proportional to the width of the product being rolled. Therefore, in the case of wide flat products, very high loads are transmitted via the rolls.

Conflicting design considerations are that for the most efficient reduction of the product being rolled the smallest work roll diameter must be used, and even if the work roll is supported by a backup roll. Even so, the strength of the pressure between the work roll and the backup roll, acting essentially in line contact, can be very high in practice.
This means that cracks can occur at the interface. Although this can be suppressed to some extent by using hard roll materials and smooth roll surfaces, the use of very hard roll materials has the disadvantage that it is highly susceptible to rapid surface degradation due to thermal shock. Introducing the problem of

As a result, rolling mill stand design is focused on using the smallest possible diameter work rolls to achieve the most efficient rolling, and on the work rolls to meet the requirements for entry and strength. There was a constant compromise between the need to increase the diameter. This compromise has often resulted in undesirably high rolling loads and drive torques requiring very large and therefore very expensive equipment.

Various attempts have been made to produce rolling equipment that is capable of relatively large rolling reductions, requires relatively little power, and is capable of operating at relatively low speeds without subjecting the rolls to critical thermal stresses. It has been done. Among these are so-called planetary rolling mills, in which a plurality of relatively small work rolls are successively connected to each other in the form of a planetary gear around each back-up roll. , the upper and lower sets of work rolls move synchronously with each other, and as the workpiece passes through the rolling mill, the multiple relatively small work rolls roll down the workpiece by a very small amount per bite. It is configured to do so.

This type of rolling mill moves very quickly and the rolling loads are relatively small because the rolls roll down the workpiece by a very small amount per bite.

However, such light working loads and high speeds
It has been found that it causes excessive noise and vibration as well as creating serious maintenance problems. Furthermore, the quality of the rolled product was poor. For example, the roll rolls down the workpiece by a very small amount per bite, so that the surface of the workpiece is machined such that the edges are recessed.

To combat this tendency, the edges of the slab needed to be rounded tightly before rolling, and this was cumbersome.

The use of relatively small diameter rolls at relatively high speeds (ie in the region of 3000 r,p,m) creates a dangerous situation. For example, the existence of a scale between work rolls and backup rolls causes many difficulties,
Then, when the scale is rolled onto the surface of the workpiece, the resulting workpiece becomes tr! The more the surface is exposed, the more the surface is adversely affected.

It is an object of the present invention to provide a rolling mill which is capable of relatively large reductions while requiring relatively little power and is capable of operating at relatively low speeds, in order to at least alleviate the above-mentioned difficulties. It is to provide.

[Means for solving problems]

According to the invention, a pair of roll assemblies each comprising a rotatably mounted support roll and a plurality of work rolls, each of which is lined with a cradle element. A rolling apparatus comprising means, the means comprising:
Each work roll and its cradle element are spaced between the roll assemblies as the roll assembly rotates such that the work roll and its cradle element orbit around the respective axes of the support roll. The work roll and the cradle element are first positioned in preparation for biting by the work roll into a supplied workpiece, the work roll and the cradle element being moved through an arcuate movement in which biting into the workpiece takes place. A rolling apparatus is provided, in which the work roll and the cradle element are caused to oscillate about the support roll to their initial positions relative to the support roll. Ru. said means, said means causing each said work roll and said cradle element to rotate when said roll assembly rotates such that said work roll and said cradle element orbit about respective axes of said support roll; A cradle element is first positioned in readiness for bite by the work roll into a workpiece fed between the roll assemblies, and the work roll and the cradle element are positioned for bite into the workpiece. rolling together through an arcuate motion in which the work roll and the cradle element undergo an oscillating motion around the support roll to their initial positions relative to the support roll. The triggering may be constituted by a gear and sector gear drive and a spring return mechanism that returns the work rolls and the cradle elements to their initial positions relative to their respective support rolls. Suitably, deceleration means may also be provided to reduce the speed of the orbital movement of each said work roll when it arrives at the roll entrapment zone, so that the continuous rotation of each said support roll is controlled by said work roll and said cradle element. , causing the workpiece to be drawn between the roll assemblies and rotated such that no direct force is required to feed the workpiece between the roll assemblies. The deceleration means for reducing the speed of the orbital motion of each work roll when it arrives at the roll bite zone reduces the motion of each of the work rolls as it passes through the roll bite zone. This is conveniently done by means of a stop mechanism that in turn locks onto slower moving parts (
can be configured. The stop mechanism may include a pair of reaction members, the reaction members being a pair of recessed gears that are located to the side of the roll assembly but further away from the roll assembly. is also driven at a somewhat slower speed, the reaction member comprising a plurality of springs having respective plungers projecting generally laterally from the sides of each reaction member. each comprising a load stop member, the pair of plungers at opposite ends of the roll assembly contacting a respective ramp at the beginning of their passage through the roll bite zone; A portion of the reaction member is arranged on the outside of the stop member of each of the reaction members against the force of their respective spring with a support link between which each of the work rolls, i.e. the synchronized and A pair of counter-rotating work rolls about to enter the roll entrainment zone is forced into the path of motion of a portion of the support link supporting the work rolls, thereby causing the pair of work rolls to are moved through the roll bite zone at the speed of movement of each pair of reaction members.

The plurality of work rolls are adjustable with respect to their respective cradle elements, so that after a period of use of the rolling mill, unused parts of the work rolls can be put into use.

In this case, a face key may be provided on each cradle extension, such that the work roll has another diametrically opposed end slot formed across the end face of the work roll aligned with the face key. can be rotatably adjusted to do so.

The cradle elements associated with the work rolls may be placed in contact with their respective support rolls by respective pairs of support links, the pairs of support links having respective shaft extensions of the support rolls. It is mounted on the cylindrical surface of the outlet to provide limited rotation. The work rolls and their respective cradle elements may be advantageously arranged longitudinally relative to the support roll by respective circumferential enlargements formed on the cradle elements, the circumferential enlargements comprising: , engages complementary grooves in the surface of the support roll.

The rolling apparatus of the invention may include idler rolls for holding the rolling apparatus under pressure during the moments between roll bites by the work rolls.

〔Example〕

Referring to FIGS. 1-6 of the drawings, the illustrated rolling apparatus includes a pair of roll assemblies, designated by reference numerals 10 and 12, the roll assemblies having a An upright side frame member is mounted in a roll stand, referenced 13.13, for rotation in the direction indicated by the arrow in FIG. The roll assemblies include rotatably mounted support rolls 14 and 16 and a plurality of work rolls 18 and 20.
The work rolls are each backed by fan-shaped cradle elements 22 and 24 and press against their respective support rolls.

According to this configuration, when the roll assembly rotates, the work rolls are sequentially engaged with the workpiece in pairs arranged oppositely, and at this time, the work rolls are engaged with the workpiece in sequence. Only the exposed parts of are used at all times, and therefore only the exposed parts are worn.

As shown in FIG. 5, the plurality of work rolls are adjustable relative to their respective cradle elements, so that after a period of use of the apparatus, unused portions of the rolls are available for use. can be offered. This is because a face key 28 is permanently mounted on each cradle extension 26 so that the work roll has another diametrically opposed end slot 30 formed across the end face of the roll. It may be rotatably adjusted to align with the key. However, it is likely that the work rolls can be rotatably driven by frictional contact between their invisible surfaces and their associated cradle elements when they are engaged with the workpiece. , must be pointed out. key 28
and the end slots 30 act solely as positioning means.

In the illustrated embodiment, four work rolls are spaced apart around each support roll, and the cradle elements associated with the work rolls are arranged in respective link pairs 32, 32.34°. 34.36.36.38.
38 and 40, 40°42.42.44.44,
are disposed in contact with their respective support rolls.

The cradle extension is formed with a stub shaft portion 112 that is supported by a respective journal portion 114 supported by a pair of links.
It is placed inside. The link pair is the support roll 14
and 16 are mounted on the cylindrical surface of each shaft extension 15.15 to provide limited rotation. The cradle elements are maintained in non-slip engagement with their support rolls by respective gears 48 and sector gears 50 (see FIGS. 1 and 3).

The work rolls and their respective cradle elements are longitudinally disposed relative to the support rolls by respective circumferential enlargements 52 formed on the cradle elements, the circumferential enlargements comprising: It engages complementary grooves 54 in the surface of the support roll.

A roll assembly, each comprising one support roll, four work rolls, and their associated cradle elements, includes respective driven gears 60 and 62.
The driven gears are driven entirely by a pair of input pinions 56 and 58 that engage support rolls 14 and 1
It is fixed with a key to the shaft extension 15.15 of 6.

Means are provided for causing each of the work roll and cradle element combinations to rotate relative to a respective support roll during a succession of bites, in other words for rotating the roll assembly. During the process, each of the work rolls and their respective cradle elements are prepared for entrainment of the work roll into the workpiece fed between the roll assemblies: 1. The work roll and the cradle element are first positioned, then the work roll and the cradle element rotate together through an arcuate movement where the biting into the workpiece takes place, and the work roll and the cradle element Returning to their initial position relative to the roll (here a limited rotational movement of the link pair relative to the support roll is required). These means consist of gears 48 and sector gears 50 between the support rolls and their respective cradle elements, and a spring return mechanism, indicated by reference numeral 64 in FIG. They thereby return the work roll and the cradle element to their initial position relative to the support roll. The spring return mechanism 64 is shown in more detail in FIG. 6, from which it can be seen that the pair of links supporting the cradle element are
It can be seen that it is rotatably mounted on the shaft extension by a set of rollers 90. A portion of each link surrounding the associated shaft extension is provided with a partially arcuate aperture 92 and 94, which aperture defines a respective tension spring 96 and a longitudinal direction of the shaft extension. A common stop member 98 extending therein is housed. Each tension spring 96 extends along the associated aperture 92 from a common fixed member 100 upright from the shaft extension to a pivot pin 102 connected to the respective link, as shown. There is. The stop member 98 has a resilient cushioning element 104 on one side as shown.

According to the above arrangement, the link pairs allow limited rotation on the respective shaft extensions of the support rolls as their respective work rolls pass through the roll bite zone. In the situation shown in FIG. 6, a pair of work rolls has just entered the roll entrapment zone. In this case, each spring 96 is at its shortest length and each link is in its initial position relative to its support roll, with the abutment surface 106 of the link against the shoe of the stop member 98. tion element 104 . As the pair of work rolls doing the work pass through a relatively small angular distance as shown in which they rotate while passing through the roll entrainment zone, the support roll passes through a relatively larger angular distance. , so that the spring 96 is fully extended, as shown in phantom.

Furthermore, means are provided for reducing the orbital motion of the six oppositely disposed pairs of work rolls as they enter the roll entrapment zone, so that the continuous rotation of the support rolls is The work roll and cradle element are rotated so that the workpiece is drawn between the roll assemblies. These means are constituted by a stopping mechanism which sequentially slows down the movement of each work roll as it passes through the roll entrainment zone. The zones in which the stop mechanism is engaged and released are shown in FIG. The stop mechanism is shown in FIGS. 3 and 4 and includes paired reaction members 66, 66 and 68, 68 (which are constituted by pairs of large gears); The reaction member is shown abutting the side of the roll assembly, but is driven (by gear means not shown) at a somewhat slower speed than the roll assembly.

The reaction members each include a plurality of spring-loaded stops 70 integrally formed with a respective plunger 72, each of which projects laterally at right angles from a side of the respective reaction member. ing. At the beginning of their passage through the roll bite zone, the pair of plungers at opposite ends of the roll assembly are in contact with the tapered ramps 74, as shown in FIG. , against the force of the respective spring 76, pushes the outer surface of the respective stop member of the reaction member into the path of motion of the journal portion of the link pair, which link pair is connected to the work rolls, i.e., synchronized and A pair of counter-rotating work rolls support each of the rolls entering the roll-engaging zone between them. As a result, during their movement through the roll entrainment zone, the work roll pairs are forced to move at the speed of movement of the respective pair of reaction members. However, from FIG.
It will be appreciated that the unimpeded forward motion of imparts positive rotation to the respective work roll through the arcuate motion performed by the respective cradle element. FIG. 2 shows a pair of opposingly disposed work rolls just entering the roll entrapment zone and about to be secured to the reaction member by engagement of the stop mechanism. is shown as a solid line. The subsequent position of the pair of work rolls, shown in dashed lines, while passing through the roll-biting zone, is such that their associated cradle elements are traversed by the respective cradle elements through an arcuate movement. The manner in which it is rotated by the respective support rolls is clearly shown. This means that, as previously mentioned, during intermittent action of a pair of work rolls, the workpiece requires little or no direct force to feed the workpiece between the roll assemblies. Along with the benefits
This results in being drawn between the roll assemblies. At the end of the movement through the roll biting zone, the respective plungers 72 slide onto the ends of the ramps 74 so that the stop members release their respective springs 76.
, and the work roll is released again from the reaction member (in FIG. 2, the oppositely disposed pairs of roll assemblies and cradle elements It will be appreciated that less than a rotation are shown as returning to their initial position relative to the support rolls; however, this need not be the case and the angular amount of the "return movement" zone is It will be understood that this is not the case at all. The only essential requirement is that the six pairs of work rolls be returned to their initial positions before they re-enter the roll-biting zone. be). The larger angular movement A of the remaining work roll pair while the working work roll pair is passing through the roll entrainment zone is shown in dashed lines in FIG.

The result is a rolling mill that requires relatively little power manpower, yet is capable of relatively large rolling reductions. For example, although the maximum reduction per pass in conventional rolling mills is typically in the range of 30-50%,
A rolling mill embodying the invention is believed to be capable of reducing a slab of steel to one-tenth or less of its incoming thickness in one continuous pass.

As a result, a rolling mill embodying the invention can do the work of five conventional stands working in rows, and requires significantly less power. The apparatus of the invention can also be operated at relatively low speeds, and since the work rolls are exposed to the product for only a relatively short period of time, there is no risk of critical thermal stress on the rolls.

This makes the device of the invention particularly advantageous when used in tandem with continuous thin slab casters. Although the work rolls have a relatively small diameter, they are very strong thanks to being lined by respective cradle elements over their entire length. The load transferred from the work roll to the support roll is due to the line contact between the cradle element and the support roll, respectively, but in this configuration, the rotational support radius of the cradle element is , at least twice the radius of the work roll), and this has the effect of reducing the strength of the pressure at the interface. Furthermore, these surfaces to which rotational loads are transmitted are
Never contact the workpiece or any other surface that has been in contact with the workpiece. As a result of this, it can be expected that these surfaces remain free of scale and in good condition over long periods of time, especially since they are not subjected to thermal shock. The only surface that is likely to wear to any significant degree during use is the surface of the work rolls, and as mentioned above, work rolls tend to wear down over time as unused parts become used. can be readjusted for each cradle element and cradle extension. If the work rolls are reground before being refitted into their cradle elements, they can be refitted using paddles or pressed shell elements so that the roll gap remains unchanged. It remains as it is.

Since the work rolls are fully supported over their entire length and do not appear to undergo significant thermal shock or surface wear, they do not need to be particularly robust when unsupported. It will be appreciated that they are not, so the possibility exists that they could be made of ceramic material. Furthermore, the support rolls and cradle elements do not have a high resistance to thermal shock, since they are not in contact with the product and are therefore not subjected to thermal shock;
Stronger materials may be used for these components. The support roll and cradle element abut each other with a relatively large arc and the strength of the pressure between them is therefore relatively low, making it possible to achieve larger reductions with relatively small diameter work rolls. , which results in lower power requirements.

Various modifications may be made, for example the means for reducing the velocity of the orbital movement of each work roll when it reaches the roll jamming zone may be very different from those already described by way of example. Optionally, it is not necessary to include a spring-loaded stop member that is laterally movable from the reaction member. Other fixing means may also be provided. For example, FIGS. 7-12 show another configuration in which each work roll assembly has one Pair of support plates 7
It is supported between 8.78 and 78. 7, which is similar to FIG. 1 (as can be seen, in this modified configuration each roll assembly is backed by one support roll and a respective cradle element, as in the ring configuration). However, in this case the support rolls are driven at a constant speed by a pair of input pinions 56 and 58 that engage respective driven gears 60 and 62. However, the input pinion is coaxial with the rear pinions 80 and 82, which are always in mesh with the rear driven gears 84 and 86, and the driven gears 84 and 86 are connected to the adjacent support plate. 78.

As shown, pinions 80 and 82 are similar to pinion 56.
and somewhat smaller than 58. The recessed pair of pinions 80 and 82 may be drivingly connected to the pair of input pinions 56 and 58 by respective clutches 88, 88, which may be engaged and disengaged simultaneously. As shown schematically in FIG. 8, each clutch 88 is a hydraulically operated clutch in which the respective input pinion is fixed to an associated pinion on a keyed shaft. It is possible to connect with When the clutch is disengaged, pinions 80 and 82 are free to rotate on the shaft on which they rest.

The operation of the rolling mill with this modified configuration is such that as the support rolls are driven at a constant speed by the pair of input pinions 56 and 58, the work rolls move simultaneously but intermittently around them. It is something. In this case, a spring return mechanism 64 as shown in FIG. 6, although only one is provided for each roll assembly, is provided.
bringing them to a position where the opposed pairs of work rolls are about to enter the roll entrainment zone, as shown in FIG. 9, in which position the clutch is engaged;
This, in turn, slows down the gears 60 and 62 and with them the support plates 78,78. This slows down the orbital motion of the work rolls (all of them together in this modified configuration), so that the continuous rotation of the support rolls
This will rotate the work roll and cradle element. As in the previous embodiment, the workpiece is
It is pulled between the roll assemblies by a pair of work rolls doing work. When the pair of work rolls doing this work escapes from the roll entrapment zone, the clutch 88
．． 88 disengages so that gears 84 and 86 are no longer delayed and spring return mechanism 64
The work rolls are brought to their initial position relative to the support roll, ie, to the position where the next opposing pair of work rolls is about to enter the roll bite zone.

Little or no force is required to feed the workpiece between the roll assemblies during roll engagement (
If the gearing is such that the circumferential speed of rotation of each work roll slightly exceeds the circumferential speed corresponding to the movement of its axis as it passes through the roll bite zone, then the workpiece will be drawn into the gap)
It will be appreciated, however, that the feed roll, which is not shown for clarity in the drawings, is necessary to maintain forward motion of the workpiece during intermittent bites by the work roll. Although the work rolls may appear to be relatively widely spaced around the support rolls, as the work rolls pass through the remainder of their orbital motion around their respective support rolls, The fact that the rolls move more slowly when passing through the roll biting zone than in It will also be appreciated that if desired, the work roll may be brought into contact with the workpiece.This will be readily understood with reference to FIG. An idler roll may be incorporated into the apparatus of the invention for keeping the rolling apparatus under pressure during the moments between roll bites.Such an idler roll may be
It is shown in phantom in FIG. 6 and designated by the reference numeral 108.

Various other modifications may also be made. For example, the cradle element need not necessarily have a separable extension as in the embodiments shown in FIGS. 1-6, as shown in FIGS. 10-12. As such, the cradle elements and their extensions may be manufactured in one piece, and the work rolls are inserted into their fitted position and held securely by a movable holding plate 110 during rolling. . In this method, the work roll can be withdrawn laterally from the cradle element, as shown in phantom in FIG. Wear can be compensated very easily by covering those seats in the interior.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway schematic perspective view of an embodiment of a rolling apparatus according to the present invention, FIG. 2 is a schematic diagram of an end surface thereof, and FIG. 4 is a sectional view taken along line 4-4 in FIG. 3, FIG. 5 is an exploded assembly view, and FIG. 6 is a schematic sectional view taken along line 6-6 in FIG. ,
a diagram showing a spring return mechanism forming part of the rolling apparatus;
and FIGS. 7 to 12 are diagrams showing other embodiments. 10.12... Roll assembly 14.16... Support roll 18.20... Work roll 22.24... Cradle element 64...
・Spring return mechanism agent Patent attorney Yasuo Miyoshi Agent Patent attorney Hidekazu Miyoshi

Claims (10)

[Claims] (1) includes a pair of roll assemblies, each consisting of a rotatably mounted support roll and a plurality of work rolls, each of which is lined with a cradle element; A rolling apparatus comprising means for causing the roll assembly to orbit the work roll and the cradle element about respective axes of the support rolls. When rotating, each work roll and its cradle element are first positioned in readiness for bite by the work roll into a workpiece fed between the roll assemblies, and the work roll and its cradle element are The cradle elements roll together through an arcuate motion where the biting into the workpiece takes place.
and the rolling apparatus, wherein the work roll and the cradle element are caused to swing around the support roll to their initial positions relative to the support roll. (2) the means for each workpiece when the roll assembly is rotated such that the work roll and the cradle element orbit around respective axes of the support roll; A roll and its cradle element are first positioned in readiness for engagement by the work roll into a workpiece fed between the roll assemblies, and the work roll and its cradle element are positioned within the workpiece. Rolling together through an arcuate motion where biting takes place, the work roll and the cradle element undergo an oscillating movement around the support roll to their initial position relative to the support roll. comprising a gear and sector gear drive and a spring return mechanism for returning the work roll and the cradle element to their initial positions relative to their respective support rolls. The rolling apparatus according to claim 1. (3) deceleration means are provided for reducing the speed of the orbital motion of each said work roll when it arrives at the roll entrapment zone, so that the continuous rotation of each said support roll is reduced by the speed of said work roll and said cradle; an element causes the workpiece to be rotated such that the workpiece is drawn between the roll assemblies and no direct force is required to feed the workpiece between the roll assemblies. The rolling apparatus according to claim 1. (4) said deceleration means for reducing the velocity of the orbital motion of each said work roll when it arrives at said roll biting zone; 4. Rolling apparatus according to claim 3, characterized in that the interlocking is constituted by a stop mechanism which fixes the parts moving more slowly in turn. (5) the deceleration means for reducing the velocity of the orbital motion of each work roll upon arrival at the roll entrainment zone is constituted by a stopping mechanism comprising a pair of reaction members, the reaction members comprising: a pair of recessed gears located to the side of said roll assembly but driven at a somewhat slower speed than said roll assembly; a plurality of spring loaded stop members each having a respective plunger projecting generally laterally from a side of the reaction member at opposite ends of the roll assembly; a pair of plungers in contact with a respective ramp at the beginning of their passage through said roll bite zone;
The ramps extend the outer sides of the stop members of each of the reaction members against the force of their respective springs and between them the respective work rolls, i.e. the synchronized pushing a pair of work rolls which are moving and rotating in opposite directions and which are about to enter the roll entrainment zone into the path of motion of a portion of the support link supporting the work rolls, so that the work rolls are 4. The rolling apparatus of claim 3, wherein pairs of rolls are moved through the roll bite zone at the speed of movement of each pair of reaction members. (6) The plurality of work rolls are adjustable with respect to their respective cradle elements, so that after a period of use of the rolling apparatus, unused parts of the work rolls can be put to use. The rolling apparatus according to claim 1. (7) a face key is provided on each cradle extension, such that the work roll has another diametrically opposed end slot formed across the end face of the work roll; 7. The rolling apparatus of claim 6, which can be rotatably adjusted to align. (8) the cradle element associated with the work roll is placed in contact with its respective support roll by a respective pair of support links; 2. The rolling apparatus of claim 1, wherein each shaft extension is mounted on a cylindrical surface to provide limited rotation. (9) the work rolls and their respective cradle elements are arranged longitudinally with respect to the support roll by respective peripheral enlarged diameter portions formed on the cradle elements; 2. The portion of the support roll of claim 1, wherein the portion engages a complementary groove on the surface of the support roll.
The rolling device described in . 10. The rolling mill of claim 1, further comprising an idler roll for holding the mill under pressure during moments between roll bites by the work rolls.