US3861190A

US3861190A - Rolling mills

Info

Publication number: US3861190A
Application number: US322191A
Authority: US
Inventors: Jack Maltby; Dennis Stubbs
Original assignee: British Steel Corp
Current assignee: British Steel Corp
Priority date: 1972-01-27
Filing date: 1973-01-09
Publication date: 1975-01-21
Anticipated expiration: 1992-01-21
Also published as: FR2169298B1; GB1385494A; FR2169298A1; DE2303467A1; JPS4884072A; SE376554B; ZA73139B; CA962864A; IT977672B; AU465545B2; AU5104073A

Abstract

A four-high rolling mill stand for rolling metal bar stock. Each work roll is carried by a work roll arm pivotably mounted about a first axis and each support or back-up roll is carried by a separate support roll arm, each support roll arm being pivotally mounted about a second and third axis respectively positioned on opposite sides of the first axis. The position of one or each of the second and third axes is adjustable to permit adjustment of the axes of the associated support or back-up rolls towards and away from the stock pass line.

Description

United States Patent [191 Maltby et al.

[54] ROLLING MILLS [75] Inventors: Jack Maltby; Dennis Stubbs, both of Sheffield, England [73] Assignee: British Steel Corporation, London,

England [22] Filed: Jan. 9, 1973 [21] Appl. No.: 322,191

[30] Foreign Application Priority Data Jan. 27, 1972 Great Britain 3887/72 [52] US. Cl. 72/247 [51] Int. Cl B21b 31/18 [58] Field of Search 72/237, 247, 244

[56] References Cited UNITED STATES PATENTS 1,900,032 3/1933 Worthington 72/247 [4 1 Jan. 21, 1975 3,613,428 10/1971 Townsed et a1 72/237 Primary Examiner-Milton S. Mehr Attorney, Agent, or Firm-Bacon & Thomas [57] ABSTRACT A four-high rolling mill stand for rolling metal bar stock. Each work roll is carried by a work roll arm pivotably mounted about a first axis and each support or back-up roll is carried by a separate support roll arm, each support roll arm being pivotally mounted about a second and third axis respectively positioned on opposite sides of the first axis. The position of one or each of the second and third axes is adjustable to permit adjustment of the axes of the associated support or back-up rolls towards and away from the stock pass line.

4 Claims, 5 Drawing Figures PATENTED JAN 21 I975 sum 1 [IF s PATENTED JANE] I975 SHEET 30F 5 PATENTED 1975 3,861,190

SHEET 5 0F 5 ROLLING MILLS This invention relates to rolling mills and particularly to four or more high cantilever rod or bar or strip stock rolling mills.

British Pat. Specification No. 1,240,658 discloses and claims such a mill and particularly describes a mill wherein each work roll together with its associated support roll is carried for rotation in an individual arm pivotally mounted in the mill frame, the two arms being mounted for pivotal movement about a single fixed pivot axis. This arrangement leads to substantial design complexity in the neighbourhood of that pivot axis, to consequent possible mechanical weaknesses under heavy load, and to difficulty of access for repair and maintenance of the parts of the mill near the pivot axis. This is particularly true where an eccentric pivot pin arrangement is utilised as disclosed and claimed in pending Pat. Application No. 125,678, filed Mar. 18, 1971, now U.S. Pat. No. 3,750,448.

Furthermore the mutual bearing surfaces of both the work rolls and the support rolls wear in use, and the work rolls also need re-dressing on occasion. Consequently the diameter of fresh rolls is significantly greater than the diameter of rolls completing their last service. The pivot mounting of the two arms must accommodate these diameter reductions on all four rolls as well of course as the relatively slight movement involved in roll gap modulation to ensure the rolled product has the desired diameter. It will be appreciated that pivotal movement of one arm relative to the other about any axis changes the angle between the axis of the rolls carried by those two arms. Consequently a scrubbing action will occur on the product between these two rolls whenever their axes are not precisely parallel, the severity of the scrubbing depending upon the magnitude of the angle.

An object of the present invention is to provide an improved mill design taking into account the above and other factors.

According to the present invention there is provided a rolling mill stand including two work rolls drivably carried in a mill frame, each work roll being backed up by a support roll, at least one of said work rolls being rotatably carried by an arm pivotable about a first axis for adjustment of the work gap between said work rolls, the support roll associated with said one work roll being rotatably carried on another arm mounted in the frame for pivotal movement about a second axis spaced apart from said first mentioned axis, for adjustment of the gap between said support rolls, the pivot axes being substantially perpendicular to the axes of the rolls.

Preferably each work roll is carried by a separate work roll arm pivotable about said first axis, and each support roll is carried by a separate support roll arm pivotable respectively about said second axis and a third axis, said second and third axes being spaced apart on opposite sides of said first axis.

The work roll arms are preferably carried in individual arms pivoted together to form a sub-assembly, the sub-assembly being releasably and removably mounted to the frame. Such arrangements are disclosed in our co-pending US. Application Ser. No. 323,123, now US. Pat. No. 3,818,742 of even date entitled Improvements in Rolling Mills.

The sub-assembly may extend between, and substantially perpendicular to, the two spaced apart support roll arm pivot axes.

Preferably means is provided for adjusting the effective position of one or each of said second and third axes whereby to permit adjustment of the axes of the associated support rolls towards and away from the stock pass line. Preferably the means for adjusting the effective position of said axis or axes includes graduation marks so that the effective position of said axis (axes) can be preselected.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a general elevation of a close coupled twin stand four high bar or rod rolling mill according to the invention;

FIG. 2 is a part sectional side elevation of one stand of the mill shown in FIG. 1;

FIG. 3 is a part sectional rear elevation of the stand of FIG. 2 shown in two positions to either side of the vertical centre line;

FIG. 4 is a sectional view on the line IV-lV of FIG. 2; and

FIG. 5 is a part sectional front elevation of the stand of FIG. 2 shown in two positions to either side of the vertical centre line.

Referring now to the drawings there is shown in FIG. 1 a close coupled twin stand fourhigh cantilever rod or bar mill viewed along the stock pass line 9. The two stands 10, 11 have a common basic frame 12 including standards l3, l4 and upper and lower cross beams l5, 16 for each stand. The stands are driven, for example, by

individual motors

17, 18 and are arranged in a no twist mode so that the rolled stock need not be twisted between the two passes. The stands are similar and one is shown in FIGS. 2, 3 and 5 turned through 45 for ease of illustration.

Each stand comprises a pair of

work rolls

20, 21 backed up by

respective support rolls

22, 23. The work rolls are releasably mounted to the free ends of work

roll drive shafts

24, 25 which are rotatably carried in respective

work roll arms

26, 27 and are driven through

couplings

28, 29 by the

motors

17, 18. The two

arms

26, 27 are pivotally mounted one to the other about a first axis at pivot 30 to form a sub-assembly which is releasably held in the frame by an off-set pin 31. Attention is directed to our above referance co-pending Application of even date for a further disclosure of this sub-assembly.

The support rolls 22, 23, are rotatably mounted to and carried by upper and lower

support roll arms

35, 36. Each arm comprises a central web 37 with upper and

lower flanges

38, 39 and secured to a massive forward chock 40. Each

arm

35, 36 is mounted at its rearward end for pivotal movement about a respective second and third axis at pivot pins 41 by means of an eccentric pivot pin arrangement described later in relation to FIG. 4.

Each chock 40 has a stub axle 42 secured thereto and the support roll is mounted thereby by means of a selfaligning spherical roller bearing indicated schematically at 43 so that the support rolls are aligned on their associated work rolls. This bearing is stabilised against the unwanted rotation about a horizontal axis by means of a flat sided guide 43a projecting forwardly from the axle 42 and slidable to a limited extend vertically in vertical slot 43b in a circular plate 44. A collar 45 secured to the support roll rotates concentrically about stationary plate 44 by means of a simple ball race bearing 46.

Referring now to FIGS. 2, 3 and 4 it will be seen that each support roll pivot pin 41 may be withdrawn from the frame by means of handle 47, normally latched, to permit ready installation and removal of each entire support roll and support roll arm sub-assembly forwardly through the opening between the frame standards. The pivot pin 41 works in bores 48 in massive cross frame members 49 secured to the basic frame 12.

Pivot pin 41 mounts an eccentric 50 having an external cylindrical surface 51 centred on axis 52 which is off set from the axis 53 of the pivot pin 41. Surface 51 works within a bore in the rearward end of the support roll arm. It will thus be appreciated that movement of eccentric 50 in an are relative to pin 41 will cause movement in an arc of the position of the effective pivot axis 52 of the appropriate support roll arm. The eccentric is arranged so that in its centre position of its travel the two

axes

52, 53 are side by side as seen in FIG. 2 so that movement of the eccentric from its centre position causes the effective pivot axis 52 to move substantially vertically up or down, at least at the start of its travel, as viewed in FIG. 2.

Adjustment of the position of the eccentric is effected by slackening

lock nuts

55, 56 and moving rod 57 substantially axially through an aperture in boss 58 which is secured to the web 37. Rod 57 is pivotally attached at 59 to the arms 60 of the eccentric 50. Graduations 61 marked on the eccentric opposite a mark on the web 37 assist in adjusting the eccentric to a desired position. The lock nuts are then tightened.

Referring now mainly to FIG. it will be seen that the forward ends of the support roll chocks 40 are a close sliding fit between the

standards

13, 14 of the mill frame. The upper chock has depending side members 70 and the lower chock has upper side members 71. Member 71 houses piston and cylinder devices 72 which can be pressurised to separate the two chocks 40 from their closest position seen on the left hand side of FIG. 5 to their most widely spaced normal operating positions seen on the right hand side of FIG. 5. These devices 72 are also pressurised when the mill is in use to preload the mill as will be described below.

It will also be seen from FIG. 5 that the forward end of the work roll arms present bearing blocks 80 which are a sliding fit between the

side members

70, 71 of the associated support roll chocks 40. The lower block 80 houses piston and cylinder devices 81 which can be pressurised to separate the two chocks 80 from their closest position seen on the left hand side of FIG. 5 to their most widely spaced position seen on the right hand side of FIG. 5. These devices are also pressurised when the mill is in use to pre-load the mill. A piston and cylinder device 96 mounted in the lower chock 40 serves when extended to separate the lower work roll 21 from the support roll 23.

Referring to FIGS. 2, 3 and 5 the lower support roll arm 36 is supported on the basic frame 12 by virtue of its chock 40 resting on an adjustable wedge device 82, the position of the wedge 83 thereof being controlled by handles 84.

The rolling force between the work rolls is provided by a massive hydraulic piston and cylinder device 85 having a line of action coincident with that of the wedge device and with the centre line between the frame standards. Device acts on the chock 40 of the upper support roll of arm 35 and is adapted to accommodate for the slight angular mis-alignments which occur in operation due to the fact that the rolls are all carried by arms movable about pivot axes within a finite distance from the stock pass line. A preferred form of the device 85 is disclosed in our co-pending British Pat. Application No. 20649/72 entitled Hydraulic Actuators.

The operation of the rolling mill will now be described. Assume that the mill stand has just been re assembled for use with fresh support rolls and fresh work rolls and also that the maximum work roll gap (e.g. 4mm) is to be used. Starting with the loading device 85 and the work roll arm separating devices 81 depressurised, but with the devices 72 pressurised to hold the support roll arms apart, the wedge device 82 is adjusted to raise, or lower, the top line of the lower work roll 21 into correct relationship with the stock pass line (e.g. 2mm below it in this case). It will be appreciated that work roll 21 rests on support roll 23 and is carried up or down therewith. The eccentric 50 associated with the lower support roll arm 36 is adjusted, if necessary, so that the lower support roll axis is adjusted towards or away from the associated work roll axis to maintain the axis of the support roll as closely parallel to the work roll axis.

The separating devices 81 are actuated to raise or lower the upper work roll arm relative to the lower arm so that the work roll gap is the correct vertical height. Eccentric pivot pin arrangement can then be operated if necessary to adjust the axial roll groove alignment as described in our above referenced co-pending Application. The devices 72 are relaxed so that the upper support roll arm 35 descends to bring the upper support roll 22 to rest on its associated work roll 20.

Finally the loading device 85 is pressurised and at the same time the

devices

72 and 81 are pressurised so that all the slack between the four arms themselves and between the arms and the frame, and the resilience of the frame itself is taken up. All surfaces in the load path are thus pre-stressed. During rolling, control of the pressure applied to device 85 controls the work roll gap. This condition of the four rolls is shown on the right hand side of FIG. 5. The device 85 is acting at an extreme angle of about 23 minutes in this condition.

As rolling proceeds the work rolls wear and at intervals need redressing. Similarily the support rolls wear. In order to re-dress the work rolls the loading device 85 is relaxed, and separating

devices

72, 81 and 96 operated to maintain an open gap between the work rolls and open a gap between the work rolls and the support rolls. The work rolls may then be released from the ends of their drive shafts and fresh or re-dressed rolls mounted thereof. A similar procedure is followed for removal and replacement of the support rolls. When the mill is operating with the minimum diameter work and support rolls the

devices

72 and 81 will be in their most retracted positions shown on the left hand side of FIG. 5, and the eccentrics 50 will also have been adjusted to near the other ends of their travel. At the same time the device 85 will be acting at an extreme angle of up to about 37 minutes. The eccentrics 50 may need to be adjusted at a support roll change operation but would not normally need adjustment for work roll changes.

On occasion, it may be desired to replace the entire sub-assembly of both work arms. The device 85 is then de-pressurised, wedge device 82 adjusted to its lowest possible position and devices 72 operated to their fullest extent. The piston and cylinder device 96 is pressurised to lift the lower work roll just clear of the lower support roll to avoid rubbing. The drive shafts are decoupled and the sub-assembly and then be removed forwardly between the frame standards by means of a porter bar.

It has been mentioned that the loading device 85 has to act at one extreme angle for maximum diameter rolls and maximum roll gap, and the other extreme angle for minimum diameter rolls and minimum roll gap. The angular difference between these extremes is reasonably small in magnitude and the device can be designed to accommodate for this in a number of ways, even in view of the extreme magnitude of the operational loads present in a rolling mill. The angular difference between these two extreme positions can be reduced by removing the second and third pivot axes 52 further apart to bring them nearer level with devices 85 and the wedge device 82 respectively. However as these axes are moved apart, so the problem of scrubbing of the support roll from the work rolls becomes more severe. The latter problem is more serious and so the best compromise position for the pivot axes is chosen for each particular practical design of mill. Bearing also in mind the advantages of having the work roll arms as a removable sub-assembly as described in our co-pending U.S. Application, Ser. No. 322,123 the chosen position for the pivot axes in the illustrated embodiment is as close to one another as reasonably possible whilst still leaving space therebetween to accommodate the removable sub-assembly. It will be appreciated that the scrubbing problem can be minimised, if not entirely removed, by correct adjustment of the eccentric 50 for each rolling situation as discussed, though this will not always be necessary in practice. Another advantage of this arrangement is that a single pivot pin can be used for each support roll arm, rather than needing the complexity of having one pivot each side of the stand for each arm. This eases the problem of correct alignment and contact between chock 40 and

frame opening walls

13 and 14. Moreover, accessability to the movable parts is greatly improved. The removability of the subassembly has been discussed, but also each support roll arm carrying its support roll and eccentric arrangement can be removed as a whole. By use of the graduations 61 near the eccentrics, a support roll can be replaced as is reasonably practical, the relative positions illustrated being sufficient to reduce to a practical minimum the discussed angular changes in position of the four arms during various conditions of use of the mill.

We claim:

1. A rolling mill stand including:

a mill frame,

two drivable work rolls,

two work roll arms mounted in the mill frame, each arm carrying a respective work roll,

a first pivotal mounting means to which both work roll arms are mounted to permit pivotal movement of the work roll arms in a plane substantially parallel to a plane containing the axis of the work rolls, for adjustment of the gap between the work rolls,

two support rolls backing up the work rolls,

two support roll arms mounted in the mill frame,

each arm carrying a respective support roll,

and a second pivotal mounting means to which one of said support roll arms is mounted, said second pivotal mounting means being spaced from said first pivotal mounting means and permitting pivotal movement of said one support roll arm in a plane substantially parallel to the plane of movement of the work roll arms for adjustment of the gap between the support rolls.

2. A rolling mill stand according to claim 1 including a third pivotal mounting means spaced from both the first and the second pivotal mounting means and to which the other support roll arm is mounted, thereby permitting pivotal movement of both support roll arms independently of one another in a plane substantially parallel to the plane of movement of the work roll arms.

3. A rolling mill stand according to claim 1 in which means are provided for adjustment of the second pivotal mounting means whereby to permit adjustment of the axis of the associated support roll towards and away from the stock pass line.

4. A rolling mill stand according to claim 2 in which means are provided for adjusting the second and third pivotal mounting means whereby to permit adjustment of the axis of the associated support rolls towards and away from the stock pass line.

Claims

1. A rolling mill stand including: a mill frame, two drivable work rolls, two work roll arms mounted in the mill frame, each arm carrying a respective work roll, a first pivotal mounting means to which both work roll arms are mounted to permit pivotal movement of the work roll arms in a plane substantially parallel to a plane containing the axis of the work rolls, for adjustment of the gap between the work rolls, two support rolls backing up the work rolls, two support roll arms mounted in the mill frame, each arm carrying a respective support roll, and a second pivotal mounting means to which one of said support roll arms is mounted, said second pivotal mounting means being spaced from said first pivotal mounting means and permitting pivotal movement of said one support roll arm in a plane substantially parallel to the plane of movement of the work roll arms for adjustment of the gap between the support rolls.