ROLLING MILLS
United States Patent 3818742
A four-high rolling mill stand for rolling metal bar stock. The work rolls are carried in work roll arms pivotally mounted to one another about a pivot axis and forming a mill sub-assembly. An adjusting device is provided for adjusting the effective position of the pivot axis relative to one of the work roll arms. The sub-assembly is removably mounted to the frame by a pin passing through a bore in the frame and a bore in the sub-assembly. The support or back-up rolls are rotatably mounted in the frame, the axis of rotation of the support rolls being movable with respect to the frame for alignment to support rolls on their associated work rolls.
US Patent References:
Sheet-metal working machine
Hahnemann - September 1931 - 1822697
Bar mill
Worthington - March 1933 - 1900032
Rolling mill
Wood - July 1952 - 2601793
/3587267.html
Townsend - June 1971 - 3587267
/3613428.html
Townsend et al. - October 1971 - 3613428
Sheet-metal working machine
Hahnemann - September 1931 - 1822697
Bar mill
Worthington - March 1933 - 1900032
Rolling mill
Wood - July 1952 - 2601793
/3587267.html
Townsend - June 1971 - 3587267
/3613428.html
Townsend et al. - October 1971 - 3613428
Inventors:
Maltby, Jack (Sheffield, EN)
Stubbs, Dennis (Sheffield, EN)
Stubbs, Dennis (Sheffield, EN)
Application Number:
05/322123
Publication Date:
06/25/1974
Filing Date:
01/09/1973
View Patent Images:
Export Citation:
Assignee:
British Steel Corporation (London, EN)
Primary Class:
Other Classes:
72/247, 72/237
International Classes:
B21B13/00; B21B31/08; B21B31/00
Field of Search:
72/247,241,237,238
Primary Examiner:
Mehr, Milton S.
Attorney, Agent or Firm:
Bacon & Thomas
Claims:
I claim
1. A rolling mill stand including,
2. A rolling mill stand according to claim 1 in which the latch means includes a lug extending from one work roll arm, said lug having a first bore extending substantially perpendicular to the axis of said work roll arm,
3. A rolling mill stand according to claim 1 including a guide plate mounted on the frame, and extending between one work roll arm and the frame, which in use guides the sub-assembly into its position in the stand.
4. A rolling mill stand according to claim 2 in which said first bore is chamferred to permit movement of at least the roll end portion of the work roll arms to a limited extent in a direction parallel to the stock pass line, and a load sensing device is disposed between said roll end portion of the work roll arms and the frame to provide in use a signal embodying a measure of the tension in the stock adjacent the mill stand.
5. A rolling mill stand according to claim 1 in which the means for pivotally mounting the two work roll arms comprises a pivot pin having an axis extending normal to the axis of the work roll arms.
6. A rolling mill stand according to claim 5 in which said pivot pin includes two eccentric surfaces and the work roll arms are pivotally mounted with one on each eccentric surface.
7. In a four-high rolling mill stand having a frame and two spaced apart, rotatable support rolls, a sub-assembly adapted to be positioned in said frame between said support rolls and releasably latched to said frame, said sub-assembly comprising two drivable work rolls, a work roll arm operably secured to each on said work rolls,
1. A rolling mill stand including,
2. A rolling mill stand according to claim 1 in which the latch means includes a lug extending from one work roll arm, said lug having a first bore extending substantially perpendicular to the axis of said work roll arm,
3. A rolling mill stand according to claim 1 including a guide plate mounted on the frame, and extending between one work roll arm and the frame, which in use guides the sub-assembly into its position in the stand.
4. A rolling mill stand according to claim 2 in which said first bore is chamferred to permit movement of at least the roll end portion of the work roll arms to a limited extent in a direction parallel to the stock pass line, and a load sensing device is disposed between said roll end portion of the work roll arms and the frame to provide in use a signal embodying a measure of the tension in the stock adjacent the mill stand.
5. A rolling mill stand according to claim 1 in which the means for pivotally mounting the two work roll arms comprises a pivot pin having an axis extending normal to the axis of the work roll arms.
6. A rolling mill stand according to claim 5 in which said pivot pin includes two eccentric surfaces and the work roll arms are pivotally mounted with one on each eccentric surface.
7. In a four-high rolling mill stand having a frame and two spaced apart, rotatable support rolls, a sub-assembly adapted to be positioned in said frame between said support rolls and releasably latched to said frame, said sub-assembly comprising two drivable work rolls, a work roll arm operably secured to each on said work rolls,
Description:
This invention relates to rolling mills and particularly to four or more high cantilever rod or bar or strip stock rolling mills.
British Patent 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 although of advantage for small work rolls or with preloaded work roll thrust bearings 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 our co-pending Patent Application No. 125,678, filed Mar. 18, 1971.
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 axes of the rolls carried by those two arms. Consequently a scrubbing action will occur on the product being rolled 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 a frame, two work rolls drivably carried in individual arms pivotally mounted one to the other to form a mill sub-assembly, whereby said arms are pivotally movable relative to one another to permit adjustment of the work gap, said sub-assembly being removably mounted to the frame, and support rolls backing up the said work rolls, said support rolls being rotatably mounted in said frame so that the axes of rotation of the support rolls are movable with respect to the frame for alignment of the support rolls on their associated work rolls.
The two work roll arms are preferably pivotally mounted one to the other for pivotal movement about an axis which extends substantially parallel to and spaced apart from the stock pass line. The work rolls are preferably secured co-axially to the free ends of work roll drive shafts journalled in the respective arms and the pivot axis then extends perpendicular to and spaced apart from these shafts, and preferably also passes between the axes of the two drive shafts, substantially equi-distant therefrom.
Preferably means is provided for adjusting, relative to at least one of the arms, the effective position of the pivot axis of the mounting of the arms one to another, whereby to permit adjustment of the axial position of the work rolls relative to one another.
The support rolls are preferably rotatably carried in arms pivotally mounted in the frame and these support roll arms are desirably mounted to the frame for pivotal movement about individual spaced apart axes. Such arrangements are disclosed in our co-pending Patent Application No. 3887/72 of even date entitled "Rolling Mills."
The sub-assembly is preferably removably mounted to the mill frame in a manner permitting movement of at least the roll end portion of the arms to a limited extent in a direction parallel to the stock pass line, and a load sensing device being provided between said portion and the frame to provide in use a signal embodying a measure of the tension in the stock adjacent the mill stand. Attention is drawn to Patent Specification 1,240,657 in considering such arrangements.
The sub-assembly is preferably removably held in the frame by a pin movable in a bore in the frame and in a bore in the sub-assembly. Preferably the pin is offset with respect to a line passing through the pivot axis and between the work rolls.
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 part sectional side elevation of one stand of a close coupled twin stand four high rolling mill according to the invention,
FIG. 2 is a longitudinal part sectional view of the upper work roll arm;
FIG. 3 is a top plan view of the sub-assembly of the two work roll arms,
FIG. 4 is a view similar to FIG. 1 showing the sub-assembly partly removed from the mill, and
FIG. 5 is a part sectional rear elevation of the stand of FIG. 1 shown in two positions to either side of the vertical centre line; and
FIG. 6 is an enlarged fragmentary view of the sub-assembly latch pin.
Referring now to the drawings there is shown in FIG. 1 one stand of a close coupled twin stand four high cantilever rod or bar rolling mill. The two stands of the mill are arranged in the non twist mode as more fully described and illustrated in our above referenced co-pending Application. The two stands have a common basic frame including a pair of frame standards 13, 14 and upper and lower cross beams 15, 16. The standards are secured to the side frame webs 17, 18 which are in the shape of right angle isosceles triangles and each have a rearward flange 18 and a base flange 19 for securing to the basic frame of the mill.
Each stand comprises a pair of work rolls 20, 21 backed up by respective support rolls 22, 23. The work rolls are releasably secured to the free ends of drive shafts 24, 25 which are rotatably carried in respective work roll arms 26, 27 and driven through couplings 28, 29 by electric motors (not shown). The two arms 26, 27 are pivotally mounted one to the other by pivot pin 30 to form a sub-assembly described more fully below.
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 secured to a massive forward chock 40. Each arm is mounted at its rearward end for pivotal movement about a respective pivot pin 41 by means of an eccentric pivot pin arrangement 100. The mounting of the support rolls, the eccentric pin arrangement and other details concerning the support rolls and support roll arms are more fully disclosed in our co-pending Application of even date. For the present purpose it may be observed that the two pivot pins 41 are spaced apart by the minimum practicable distance necessary to allow the work roll sub-assembly to pass freely there between as illustrated in FIGS. 1 and 4. This minimises scrubbing between the work rolls and support rolls.
The work roll sub-assembly will now be described. The two arms 26, 27 are generally similar in shape, except that at the rearward end the upper arm 26 (see FIGS. 2 and 3) has depending spaced apart lugs 50 and the lower arm 27 has upwardly extending lugs 51. Lugs 50 are a close sliding fit between lugs 51, (as seen in FIG. 3.) The lugs are bored to accommodate an eccentric pivot pin 30. The lower arm is provided at its rearward lower end with an additional lug 52 having a bore 53. The bore 53 has chamferred ends 54, as shown in the enlarged scrap view of FIG. 6.
When the sub-assembly is in position, as shown in FIG. 1, the bore 53 registers with a bore 55 in a bracket 59 secured to the side frame web 17, and a single latch pin 56 having a chamferred tip 57 is received in the bores 53, 55 to hold the sub-assembly in position in the mill. The chamferred ends 54 of bore 53 permit limited movement on the latch pin 56 of at least the roll end portion of the work roll arms in a direction parallel to the stock pass line.
The eccentric pivot pin 30 has two end lengths having an outer surface centered on a first axis 60 and a central length centered on a second axis 61. The lengths centered on axis 60 are those working in the bores of the lugs 51, and the lengths centered on axis 61 is that working in the bores of the lugs 50. A lever arm 62 secured to one end of pin 30 and a drive arm 63 is pivoted to the remote end of arm 62. Arm 63 can be adjusted substantially axially by slackening, rotating, and retightening, control handles 64 which lock on either side of a bracket 65 secured to the mill frame. It will be appreciated that axial movement of arm 63 causes rotation of pin 30 through a small arc. The axes 60, 61 are aligned above one another as seen in FIG. 2 when the drive arm 63 is in the centre of its travel. Accordingly rotation of pin 30 to either side of its centre position causes the work roll arms 26, 27 to move substantially axially relative to one another with minimum vertical movement whereby to permit adjustment of the axial positions of the work rolls to avoid ovality in the rolled stock.
Referring to FIG. 2, the upper work roll drive shaft 24 is rotatably mounted within its arm 26 by means of a rearward thrust and radial bearing arrangement 66 and a forward radial bearing arrangement 67. A sleeve 68 is engaged between the bearings to transmit axial thrust from the forward to the rearward bearing. The work roll 20 is releasably secured to the free end of the work roll drive shaft 24 by means of a hydraulically expandable bolt 69 extending through an axial bore 70 in the roll and threadedly received in a threaded bore 71 in the end of the shaft. The use of such a bolt ensures very secure mounting of the roll, with good axial position accuracy and ready releasability. Attention is drawn to Patent Specification 1,240,656 in this connection. The lower work roll drive shaft is mounted in its arm in a similar manner and the lower work roll mounted to its shaft in a similar manner.
Referring now to FIG. 3 the upper arm 26 is provided with two electro mechanical transducers, such as linear variable differential transformers, 74, 75 secured thereto in the angles of the outer surface of the arm immediately behind the forward bearing block 76 thereof. These transducers have plungers extending from sealed housings and acting on adjustable mechanical stocks, (not shown) in the corresponding situations on the lower work roll arm. The stocks are adjusted so the plunger contacts the stock level with the stock pass line as seen in FIG. 1. Electrical connections 77 extend to the transducers. This mounting position gives good protection to the transducers against incidental mechanical damage and dirt and in addition they are desirably close to the stock pass line. It will be appreciated that, in use, signals from these transducers represent the work gap between the work rolls, and that these signals are used in controlling, or modulating, the work gap during a rolling operation.
FIG. 3 also illustrates, schematically, a lateral piston and cylinder loading device 80 disposed centrally of the height of the bearing block 76 and housed in a recess therein. Two load cells 81 (only one is visible in FIG. 3) are disposed one above the other in a recess in the opposite side face of bearing block 76. The bearing block of the lower arm 37 is similarly equipped with a device 80 and two cells 81. In the installed position of the sub-assembly, the bearing blocks 76 are a close fit between the two frames standards 13, 14. In use the loading device 80 is pressurised substantially to take up the lateral clearance so that the sensors of the load cells 81 are pre-loaded against stops 82. It will be appreciated that, in use, signals from the load cells represent the tension, positive or negative, in the stock adjacent the mill stand.
FIG. 3 also shows in dotted outline the location of two piston and cylinder devices 84 which are housed within the bearing block 76 of the lower work roll. When pressurised the devices 84 act against the upper bearing block to force the blocks apart. During use of the mill this pre-loads the work rolls against the support rolls, and these devices may also be used to separate the work rolls for access thereto during work roll changing operations.
For a fuller description of pre-loading the mill and the above and other piston and cylinder devices reference is directed to our co-pending Application of even date. Mention is briefly made here however of the main piston and cylinder self-aligning loading device 86 which applies the actual rolling load on the work rolls by acting on the chock 40 of the upper support roll arm, and the adjustable wedge device 87 which supports the chock 40 of the lower support roll arm to withstand the rolling load and is adjustable to maintain a constant pass line in the mill.
Referring now to FIG. 4 the rolling mill stand is shown with the sub-assembly in the course of removal from its installed position. In order to remove the sub-assembly the single off-set latch pin 56 is withdrawn by handle 101, the drive shafts 24, 25 un-coupled, and the eccentric drive arm 63 un-coupled from lever arm 62. The sub-assembly is then free of all mechanical connection to the remainder of the mill and can be withdrawn as a whole forwardly through the gap defined by the support rolls and the standards 13, 14. A counter balanced porter bar and crane would be used for this operation, which is characterised by its relative speed and simplicity.
In order to guide the sub-assembly during its insertion and withdrawal operation, a guide plate 90 is welded on to housing side member. Lateral radiused cheeks (not shown) are provided secured to the frame webs 17, 18 one at each side of the sub-assembly towards the rearward end thereof to guide the rear end of the sub-assembly into its final installed position. The chamferred end of latch pin 56 facilitates its insertion to lock the sub-assembly in position. This pin does not need any substantial strength since all operational loading as between the work roll arms is taken up by pin 30. As described, the forward end of the sub-assembly is laterally located by the fit of the blocks 76 as shown in FIG. 3.
It will be appreciated on review of FIGS. 1 and 4 that the two support roll arms may have to be pivotally moved to their most widely separated position in order to permit removal of the sub-assembly. This is accomplished by pressurisation of the piston and cylinder separating devices (not shown) which act directly between extensions of the forward support roll chocks 40 (described in our co-pending Application). The loading device 86 is de-pressurised and the wedge device 87 retracted.
The advantage of the described arrangement of pivoting the two work roll arms direction to one another is that this greatly simplifies and enhances the stiffness as between the two work roll arms. In other words the axial stiffness path from one work roll to the other through the pivot 30 is reasonably short, direct and simple. This stiffness is important for accuracy of the rolled stock. The arrangement would be more stiff if the pivot axis were closest to the stock pass line, but this would tend to decrease the pass shape accuracy and increase scrubbing between the rolls and their support rolls due to the pivot action of the arms when different diameter rolls are used. Proper adjustment of the eccentric pivot pin 30 serves to align the work roll grooves.
The described arrangement also uses a single pin 30 instead of two opposite pins, and moreover the pin 30 is disposed schematically between the two work roll axes, which again aids accuracy in the rolled stock. The described arrangement wherein the support roll arms are pivotally mounted above and below the sub-assembly also serves to reduce the number of lateral clearances and consequent complexity and lack of stiffness in the neighbourhood of the pivotal mountings.
British Patent 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 although of advantage for small work rolls or with preloaded work roll thrust bearings 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 our co-pending Patent Application No. 125,678, filed Mar. 18, 1971.
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 axes of the rolls carried by those two arms. Consequently a scrubbing action will occur on the product being rolled 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 a frame, two work rolls drivably carried in individual arms pivotally mounted one to the other to form a mill sub-assembly, whereby said arms are pivotally movable relative to one another to permit adjustment of the work gap, said sub-assembly being removably mounted to the frame, and support rolls backing up the said work rolls, said support rolls being rotatably mounted in said frame so that the axes of rotation of the support rolls are movable with respect to the frame for alignment of the support rolls on their associated work rolls.
The two work roll arms are preferably pivotally mounted one to the other for pivotal movement about an axis which extends substantially parallel to and spaced apart from the stock pass line. The work rolls are preferably secured co-axially to the free ends of work roll drive shafts journalled in the respective arms and the pivot axis then extends perpendicular to and spaced apart from these shafts, and preferably also passes between the axes of the two drive shafts, substantially equi-distant therefrom.
Preferably means is provided for adjusting, relative to at least one of the arms, the effective position of the pivot axis of the mounting of the arms one to another, whereby to permit adjustment of the axial position of the work rolls relative to one another.
The support rolls are preferably rotatably carried in arms pivotally mounted in the frame and these support roll arms are desirably mounted to the frame for pivotal movement about individual spaced apart axes. Such arrangements are disclosed in our co-pending Patent Application No. 3887/72 of even date entitled "Rolling Mills."
The sub-assembly is preferably removably mounted to the mill frame in a manner permitting movement of at least the roll end portion of the arms to a limited extent in a direction parallel to the stock pass line, and a load sensing device being provided between said portion and the frame to provide in use a signal embodying a measure of the tension in the stock adjacent the mill stand. Attention is drawn to Patent Specification 1,240,657 in considering such arrangements.
The sub-assembly is preferably removably held in the frame by a pin movable in a bore in the frame and in a bore in the sub-assembly. Preferably the pin is offset with respect to a line passing through the pivot axis and between the work rolls.
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 part sectional side elevation of one stand of a close coupled twin stand four high rolling mill according to the invention,
FIG. 2 is a longitudinal part sectional view of the upper work roll arm;
FIG. 3 is a top plan view of the sub-assembly of the two work roll arms,
FIG. 4 is a view similar to FIG. 1 showing the sub-assembly partly removed from the mill, and
FIG. 5 is a part sectional rear elevation of the stand of FIG. 1 shown in two positions to either side of the vertical centre line; and
FIG. 6 is an enlarged fragmentary view of the sub-assembly latch pin.
Referring now to the drawings there is shown in FIG. 1 one stand of a close coupled twin stand four high cantilever rod or bar rolling mill. The two stands of the mill are arranged in the non twist mode as more fully described and illustrated in our above referenced co-pending Application. The two stands have a common basic frame including a pair of frame standards 13, 14 and upper and lower cross beams 15, 16. The standards are secured to the side frame webs 17, 18 which are in the shape of right angle isosceles triangles and each have a rearward flange 18 and a base flange 19 for securing to the basic frame of the mill.
Each stand comprises a pair of work rolls 20, 21 backed up by respective support rolls 22, 23. The work rolls are releasably secured to the free ends of drive shafts 24, 25 which are rotatably carried in respective work roll arms 26, 27 and driven through couplings 28, 29 by electric motors (not shown). The two arms 26, 27 are pivotally mounted one to the other by pivot pin 30 to form a sub-assembly described more fully below.
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 secured to a massive forward chock 40. Each arm is mounted at its rearward end for pivotal movement about a respective pivot pin 41 by means of an eccentric pivot pin arrangement 100. The mounting of the support rolls, the eccentric pin arrangement and other details concerning the support rolls and support roll arms are more fully disclosed in our co-pending Application of even date. For the present purpose it may be observed that the two pivot pins 41 are spaced apart by the minimum practicable distance necessary to allow the work roll sub-assembly to pass freely there between as illustrated in FIGS. 1 and 4. This minimises scrubbing between the work rolls and support rolls.
The work roll sub-assembly will now be described. The two arms 26, 27 are generally similar in shape, except that at the rearward end the upper arm 26 (see FIGS. 2 and 3) has depending spaced apart lugs 50 and the lower arm 27 has upwardly extending lugs 51. Lugs 50 are a close sliding fit between lugs 51, (as seen in FIG. 3.) The lugs are bored to accommodate an eccentric pivot pin 30. The lower arm is provided at its rearward lower end with an additional lug 52 having a bore 53. The bore 53 has chamferred ends 54, as shown in the enlarged scrap view of FIG. 6.
When the sub-assembly is in position, as shown in FIG. 1, the bore 53 registers with a bore 55 in a bracket 59 secured to the side frame web 17, and a single latch pin 56 having a chamferred tip 57 is received in the bores 53, 55 to hold the sub-assembly in position in the mill. The chamferred ends 54 of bore 53 permit limited movement on the latch pin 56 of at least the roll end portion of the work roll arms in a direction parallel to the stock pass line.
The eccentric pivot pin 30 has two end lengths having an outer surface centered on a first axis 60 and a central length centered on a second axis 61. The lengths centered on axis 60 are those working in the bores of the lugs 51, and the lengths centered on axis 61 is that working in the bores of the lugs 50. A lever arm 62 secured to one end of pin 30 and a drive arm 63 is pivoted to the remote end of arm 62. Arm 63 can be adjusted substantially axially by slackening, rotating, and retightening, control handles 64 which lock on either side of a bracket 65 secured to the mill frame. It will be appreciated that axial movement of arm 63 causes rotation of pin 30 through a small arc. The axes 60, 61 are aligned above one another as seen in FIG. 2 when the drive arm 63 is in the centre of its travel. Accordingly rotation of pin 30 to either side of its centre position causes the work roll arms 26, 27 to move substantially axially relative to one another with minimum vertical movement whereby to permit adjustment of the axial positions of the work rolls to avoid ovality in the rolled stock.
Referring to FIG. 2, the upper work roll drive shaft 24 is rotatably mounted within its arm 26 by means of a rearward thrust and radial bearing arrangement 66 and a forward radial bearing arrangement 67. A sleeve 68 is engaged between the bearings to transmit axial thrust from the forward to the rearward bearing. The work roll 20 is releasably secured to the free end of the work roll drive shaft 24 by means of a hydraulically expandable bolt 69 extending through an axial bore 70 in the roll and threadedly received in a threaded bore 71 in the end of the shaft. The use of such a bolt ensures very secure mounting of the roll, with good axial position accuracy and ready releasability. Attention is drawn to Patent Specification 1,240,656 in this connection. The lower work roll drive shaft is mounted in its arm in a similar manner and the lower work roll mounted to its shaft in a similar manner.
Referring now to FIG. 3 the upper arm 26 is provided with two electro mechanical transducers, such as linear variable differential transformers, 74, 75 secured thereto in the angles of the outer surface of the arm immediately behind the forward bearing block 76 thereof. These transducers have plungers extending from sealed housings and acting on adjustable mechanical stocks, (not shown) in the corresponding situations on the lower work roll arm. The stocks are adjusted so the plunger contacts the stock level with the stock pass line as seen in FIG. 1. Electrical connections 77 extend to the transducers. This mounting position gives good protection to the transducers against incidental mechanical damage and dirt and in addition they are desirably close to the stock pass line. It will be appreciated that, in use, signals from these transducers represent the work gap between the work rolls, and that these signals are used in controlling, or modulating, the work gap during a rolling operation.
FIG. 3 also illustrates, schematically, a lateral piston and cylinder loading device 80 disposed centrally of the height of the bearing block 76 and housed in a recess therein. Two load cells 81 (only one is visible in FIG. 3) are disposed one above the other in a recess in the opposite side face of bearing block 76. The bearing block of the lower arm 37 is similarly equipped with a device 80 and two cells 81. In the installed position of the sub-assembly, the bearing blocks 76 are a close fit between the two frames standards 13, 14. In use the loading device 80 is pressurised substantially to take up the lateral clearance so that the sensors of the load cells 81 are pre-loaded against stops 82. It will be appreciated that, in use, signals from the load cells represent the tension, positive or negative, in the stock adjacent the mill stand.
FIG. 3 also shows in dotted outline the location of two piston and cylinder devices 84 which are housed within the bearing block 76 of the lower work roll. When pressurised the devices 84 act against the upper bearing block to force the blocks apart. During use of the mill this pre-loads the work rolls against the support rolls, and these devices may also be used to separate the work rolls for access thereto during work roll changing operations.
For a fuller description of pre-loading the mill and the above and other piston and cylinder devices reference is directed to our co-pending Application of even date. Mention is briefly made here however of the main piston and cylinder self-aligning loading device 86 which applies the actual rolling load on the work rolls by acting on the chock 40 of the upper support roll arm, and the adjustable wedge device 87 which supports the chock 40 of the lower support roll arm to withstand the rolling load and is adjustable to maintain a constant pass line in the mill.
Referring now to FIG. 4 the rolling mill stand is shown with the sub-assembly in the course of removal from its installed position. In order to remove the sub-assembly the single off-set latch pin 56 is withdrawn by handle 101, the drive shafts 24, 25 un-coupled, and the eccentric drive arm 63 un-coupled from lever arm 62. The sub-assembly is then free of all mechanical connection to the remainder of the mill and can be withdrawn as a whole forwardly through the gap defined by the support rolls and the standards 13, 14. A counter balanced porter bar and crane would be used for this operation, which is characterised by its relative speed and simplicity.
In order to guide the sub-assembly during its insertion and withdrawal operation, a guide plate 90 is welded on to housing side member. Lateral radiused cheeks (not shown) are provided secured to the frame webs 17, 18 one at each side of the sub-assembly towards the rearward end thereof to guide the rear end of the sub-assembly into its final installed position. The chamferred end of latch pin 56 facilitates its insertion to lock the sub-assembly in position. This pin does not need any substantial strength since all operational loading as between the work roll arms is taken up by pin 30. As described, the forward end of the sub-assembly is laterally located by the fit of the blocks 76 as shown in FIG. 3.
It will be appreciated on review of FIGS. 1 and 4 that the two support roll arms may have to be pivotally moved to their most widely separated position in order to permit removal of the sub-assembly. This is accomplished by pressurisation of the piston and cylinder separating devices (not shown) which act directly between extensions of the forward support roll chocks 40 (described in our co-pending Application). The loading device 86 is de-pressurised and the wedge device 87 retracted.
The advantage of the described arrangement of pivoting the two work roll arms direction to one another is that this greatly simplifies and enhances the stiffness as between the two work roll arms. In other words the axial stiffness path from one work roll to the other through the pivot 30 is reasonably short, direct and simple. This stiffness is important for accuracy of the rolled stock. The arrangement would be more stiff if the pivot axis were closest to the stock pass line, but this would tend to decrease the pass shape accuracy and increase scrubbing between the rolls and their support rolls due to the pivot action of the arms when different diameter rolls are used. Proper adjustment of the eccentric pivot pin 30 serves to align the work roll grooves.
The described arrangement also uses a single pin 30 instead of two opposite pins, and moreover the pin 30 is disposed schematically between the two work roll axes, which again aids accuracy in the rolled stock. The described arrangement wherein the support roll arms are pivotally mounted above and below the sub-assembly also serves to reduce the number of lateral clearances and consequent complexity and lack of stiffness in the neighbourhood of the pivotal mountings.