Hydraulic mills

[57] ABSTRACT

The disclosure of the present invention relates to a rolling mill having hydraulic piston cylinder assemblies for controlling the gap of the work rolls of the mill. Linear INDUCTOSYNS (the term INDUCTOSYN being a registered United States trademark of the INDUCTOSYN CORPORATION) are arranged in openings provided in the pistons of the piston-cylinder assemblies for measuring accurately the relative movement of the pistons and cylinders as a function of changes in the roll gap caused by rolling variations. Because of the inherent capabilities of INDUCTOSYNS, they require no additional adjustment features, even though relatively large adjustments are required to maintain a fixed mill passline.

Claims, 5 Drawing Figures

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Patented Sept. 11, 1973

3,757,553

Sheets-Sheet i

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PASS LINE

INVENTOR JOSEPH I. GREENBERGER BY

HENRY C. WESTIN ATTORNEY

Patented Sept. 11, 1973

3,757,553

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INVENTOR JOSEPH I. GREENBERGER BY HENRY C. WESTIN

ATTORNEY

Patented Sept. 11, 1973

3,757,553

Sheets-Sheet 3

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FIG. 4

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JOSEPH I. GREENBERGER

FIG. 5 ^BY

HENRY C. WESTIN ATTORNEY

3,757,553

HYDRAULIC MILLS

In present day rolling mills of the type employed to roll metal strip, such as, for example, cold rolled annealed carbon steel, there is a great need for improving the accuracy, reliability and performance of present methods and devices employed for measuring changes in roll gap of the rolling mill during the rolling operation. Such mills of the hydraulic type, as well as hydraulic hot strip mills, have used load meter devices or other direct position indicators, both of which have been found to possess a number of serious limitations. For one thing, the accuracy and acceptable range within which they are capable of working are not adequate in many cases. In mills where passline is to be maintained at a fixed elevation, even though rolls of different diameters are to be employed, a separate special adjustment device is required to reposition the load meter device or position transducer to be operative within their narrow working range.

The great majority of such devices and transducers, moreover, have been employed in sets of two for each cylinder assembly in order to eliminate effects of tilting of the cylinder components. Such an arrangement greatly adds to the complexity and expense of the gap control equipment in addition to increasing mainte- 25 nance problems.

The present invention provides a method and apparatus of controlling the gap of a rolling mill or like apparatus wherein a linear INDUCTOSYN is employed to produce accurately a signal representative of the ³⁰amount of change in the roll gap. Such a device has an inherent accuracy through a relatively large range of linear motion so that in a mill requiring a fixed passline, no additional means is required to reposition the INDUCTOSYN when different-sized rolls are employed.

It is a further object of the present invention to provide linear INDUCTOSYNS in a mill having a pair of fluid piston-cylinder assemblies for controlling roll gap, wherein a single linear INDUCTOSYN is provided for each piston-cylinder assembly arranged to measure relative movement of the piston and cylinder for each assembly as a function of a change in the roll gap of the mill.

It is a still further object of the present invention to provide in hydraulic rolling mills a linear variable differential transformer (LVDT) position transducer for each hydraulic cylinder in combination with a special electrical motor for repositioning the LVDTs to be in their optimum range of accuracy after the rolls have been reset for passline control.

Another object of the present invention relates to an hydraulic mill wherein an opening is provided in the piston of the piston-cylinder assembly employed for gap control of the mill and into which opening a position transducer is mounted in a manner to be carried by the piston and adapted to measure the displacement of the piston relative to the cylinder as a function of change of roll gap of the mill.

These objects, as well as other novel features and advantages of the present invention, will be better understood when the following description is read along with the accompanying drawings of which:

FIG. 1 is an elevational view, partly in section, of a rolling mill incorporating the features of the present invention in which the left-hand portion indicates the position of the illustrated components of the mill when the mill employs maximum diameter rolls; whereas, the right-hand portion of the drawing illustrates the position of the components when minimum diameter rolls are being employed,

FIG. 2 is an enlarged view of the lower portion of the 5 rolling mill illustrated in FIG. 1,

FIG. 3 is an end view of FIG. 2,

FIG. 4 is a sectional view of a second embodiment of the position transducer illustrated in previous figures, and •θ FIG. 5 is an electrical diagram of the INDUCTOSYN and associated control elements.

In referring first to FIG. 1, there is illustrated the window of one of two identical housings of a 4-high cold rolling mill for rolling strip material constructed gener¹⁵ ally in accordance with well-known designs. There is shown one of the upright mill housings 10 having an elongated vertical window 11 through which there are received, with reference to a passline 12, opposed 20 ^{baCkUp roPs} 13 and 14 which support, in the customary manner, smaller diameter work rolls 16 and 17. The backup rolls are rotatably carried by bearing chock assemblies 18 and 19 which are received in the window 11. An upper work roll chock 22 is provided with an opening 24 for receiving in a nested relationship a lower work roll chock 23. In accordance with wellknown practice, each backup chock 18 is engaged by a pair of roll balance hanger bars 26 of a balance cylinder assembly, not shown. Each backup chock 18 is also engaged indirectly at its top portion in the customary manner by the mill screw 27.

At the bottom of the mill the backup chock 19 rests on a horizontal platform that forms part of the backup roll changing sled 29 which, in turn, is supported by the cylinder 31 of a piston-cylinder assembly 32, the piston thereof being identified as 33, in which arrangement the cylinder moves relative to the stationary piston 33. In accordance with general practice, the sled 29 is adapted to rest on a pair of rails 35 and 36 when in its 40 roll changing position. Since FIG. 1 is designed to depict the rolling position of the components, there is Clearance between the sled 29 and rails 35 and 36.

As noted previously, the right-hand side of FIG. 1 illustrates the condition with minimum diameter rolls, 45 whereas the left-hand side illustrates the condition with maximum diameter rolls, which explains the difference in the elevational disposition of the cylinder 31, with reference to the left and right-hand sides of FIG. 1, with respect to the passline 12. In other words, when the mill ⁵⁰ is employing minimum diameter rolls, it is necessary to lift the lower work roll 17 and the lower backup roll 19 so as to place the upper peripheral surface of the work roll tangentially to the passline 12. As previously noted, it is the requirement that the rolls be so positioned with ⁵ respect to the passline that led to the discovery of the present invention. In this connection, it will be noted with respect to the piston-cylinder assembly 32 that there is inserted within the piston 33 and connected to the cylinder 31a position transducer 37 designed to detect changes in the relative positions between the piston 33 and the cylinder 31. Such changes will represent changes in the gap between the work rolls 16 and 17, which gap changes will result in error in the gage being ₆₅ rolled and necessitate a correction in the gap in order that constant gage material may be rolled.

As noted previously, the second spaced-apart housing, not shown, will also employ a piston-cylinder as3,757,553 sembly similar to the assembly 32 which will have a position transducer similar to the transducer 37.

FIGS. 2 and 3 represent an enlargement of the piston-cylinder assembly 32 illustrated in FIG. 1, in which connection it will be noticed that at its upper portion it takes the form of a vertical movable plunger 41 which includes a projecting stem 42 which, through the means of a nut 43, is secured to the cylinder 31. Accordingly, in this construction the plunger 41 will move with the cylinder 31. At the lower end of the plunger 41 there is provided, as best shown in FIG. 3, a clip 45 which is open radially to receive and fit under a button 46 of a vertical rod 47 that protrudes from the position transducer 37. The position transducer itself is received in a radial opening 49 which, as shown in FIG. 2, takes the form of a narrow slot formed in the piston 33 of the cylinder assembly 32. As shown in FIGS. 2 and 3, the position transducer 37 rests on the bottom of the piston 33 and is supported by the piston. Unit 37 can be removed quickly from its operative position for maintenance purposes by simply disconnecting the electrical connection and moving the unit towards the left as one views FIG. 3, during which movement the button 46 will slide out of the clip 45.

Before leaving FIG. 2 it will be noted that between the plunger 41 and the piston 33 there are provided sealing rings 51 that prevent the fluid from escaping from the piston-cylinder assembly 32.

It is a particular feature of the present invention to provide an INDUCTOSYN, as the position transducer 37. As noted before, this term is a registered trademark of Inductosyn Corporation and has been selected for use in the rolling mills in view of its inherent capabilities of measuring very small displacement of elements very accurately over a large linear motion. This allows its utilization, even though adjustment of the lower rolls for passline control may vary up to 5 inches.

FIG. 5 shows diagrammatically the stationary and moving windings 50α and 50b, respectively, of the INDUCTOSYN 37. A single-phase voltage is applied to the scale 50b, which is the linear equivalent of the rotary INDUCTOSYN rotor, and sine and cosine voltages appear on the two-phase windings of the slider or stator. The receiver slider, not shown, is energized by the transmitter slider 50α and the receiver scale output is the error voltage, which becomes zero when the transmitter and receiver are in alignment. The error signal in the case of passline adjustment and control is produced by a digital summer and for roll gap control by an analog summer, the summers and required amplifier being indicated at 50c. The error signal is fed to a servo-motor 50d that operates the piston-cylinder assembly 32. Thus, the INDUCTOSYN inherently can accommodate large linear motions for passline adjustments in which the repetitive discrete cycles of the windings on relative movement thereof are digitally summed, and yet can be extremely accurate and sensitive for fine roll gap changes, during which only a fraction of a cycle is measured in an analog manner.

The present invention is not limited to the use of INDUCTOSYNS and, as illustrated in FIG. 4, other forms of position transducers, such as an LVDT (linear variable differential transformer), can be employed; for example, as manufactured by Schaevitz Engineering of Pennsauken, New Jersey, U. S. A., and described in their Technical Bulletin AA-lb, Copyright 1955. However, in view of the fact that such devices do not have the linear motion range within the accuracies required, it is necessary to provide an adjustment device to compensate for a change in rolls in order to maintain the lower work roll 17 on passline 12. It will be appreciated that the position transducer and associated parts shown in FIG. 4 are meant to be a substitution of the unit 37 illustrated in FIGS. 1, 2 and 3 so that FIG. 4 shows the bottom portion of the plunger 41 engaged by a button 53 which is held against the plunger 41 by the clip 45 associated with the plunger 41. The button 53 forms the top portion of a rod 54 of a position transducer 55 that takes the form of an LVDT unit. It will be appreciated that the rod 54 moves relative to the LVDT 55 and that such movement is measured by the LVDT as a function of a change in the gap between work rolls 16 and 17. The unit 55 is connected by a bracket 57 to a precision ball screw unit 58 which, in turn, is connected to an electrical stepping motor 59, the motor itself being fixed to a shelf 56 of the total enclosure 70. The stepping motor may take the form of the type manufactured by Superior Electric Company of Bristol, Connecticut, U. S. A., known by their registered trademark as SLO-SYN. In this arrangement the physical linear travel of the position transducer 55 will be related to the maximum adjustment that must be made with reference to the different roll sizes, which adjustment is made through the operation of the stepping motor 59. Once the passline change has been made and the LVDT is electrically nulled with reference to its midpoint, the stepping motor ceases to function and the short stroke and extremely sensitive and accurate LVDT will then measure gap changes.

It will be appreciated by those skilled in the art that the actual mode of control of the mill with reference to obtaining gap control may vary in accordance with well-known technology. One of the advantages of the two embodiments disclosed is that they lend themselves very well to various forms of mill control. By way of example only, the two arrangements can be employed to measure very accurately the change in the gap between the work rolls 16 and 17 to produce a signal of such change, which signal can be utilized in accordance with the control method set forth in U. S. Pat. No. 3,492,056 which issued on Jan. 20, 1970 to J. W. O’Brien and U. S. Pat. No. 3,496,743 which issued on Feb. 24, 1970 to M. D. Stone.

The two embodiments of the present invention can be employed also to allow the operator of the mill to reposition the roll gap specific amounts with respect to a calibrated zero position. One example of such a mill would be where it is possible and desirable to make a periodic recalibration of the true gap condition with respect to a calibrating rolling pressure.

In accordance with the provisions of the patent statutes, I have explained the principle and operation of my invention and have illustrated and described what I consider to represent the best embodiment thereof.