US 3101636 A
Description (OCR text may contain errors)
1963 R. A. SCHULTZ 3,101,636
BREAKER-BLOCK SYSTEM FOR MILL ROLLS Filed Sept. 25, 1960 36 IIVI/EIVTOR ROBERT A. SCHULTZ Aflorney United States Patent Office 3,101,636 Patented Au g. 27, was
3,101,636 BREAKER-BLOCK SYSTEM FUR MILL ROLLS Robert A. Schultz, Penn Hills Township, Allegheny County, Pa., assignor to United StatesSteel Corporation, a corporation of New Jersey Filed Sept. 23, 1960, Ser. No. 57,943
Claims. (Cl. 8057) This invention relates to a hydraulic system including breaker blocks between the screws and chocks of a rolling mill and, in particular, to a system which will relieve the load on both blocks whenever one of them is overloaded.
Breaker blocks :have been used individually at the two ends of a mill roll. Patent No. 2,612,798 shows one example. Difficulty has been experienced therewith, however, because, on failure of one block under overload,
- the other remains effective and this results in a continued reduction of the workpiece, such as a slab, on only one side. Slewing or jamming of the piece may ensue but, in any case, the piece is spoiled for further reduction. It is accordingly the object of my invention to provide a system which immediately releases the pressure in one block upon an overload on the other, thus preventing the spoiling of the partially reduced piece.
In a preferred embodiment, I employ a relief cylinder and piston connected to breaker blocks placed between the screws and chocks, respectively, at both ends of the roll. The relief cylinder incorporates a shear disc adapted to fail when the pressure on the piston indicates that excessive load is being applied to either breaker block. On such occurrence, the piston of the relief cylinder moves immediately to relieve the pressure in both breaker blocks simultaneously.
A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawing illustrating the present preferred embodiment. The single FIGURE of the drawing is a diagrammatic representation of my system as applied to a rolling-mill stand, including the relief cylinder which is shown in central vertical section.
Referring now in detail to the drawing, a mill stand comprises housings 11 in the windows 12 of which roll chocks 13 and 14 are disposed. Screws 15 threaded through the tops of the housings determine the spacing between upper and lower rolls 16 and 17, and the reduction effected in the thickness of the piece 18 being rolled. Between the upper chocks 13 and screws 15 are disposed hydraulic breaker blocks 19. Each of these is simply a liquid-filled cylinder having a piston resting on the body of liquid. These cylinders are connected by flexible pipe or hose lines 20 to the top of a relief cylinder 21. Each line 20 includes a check valve 22 adjacent cylinder 21 and the two lines are connected by an equalizer 23 havin-g valves 24 therein adjacent the junctions between it and lines 20. A branch 25, from between valves 24 of the equalizer, extends to the top of cylinder 21.
Cylinder 21 comprises an upper head 26, an expan sion cylinder 27 extending downwardly therefrom, and a piston 28 reciprocable in a bore in head 26. A fluidcushion cylinder 29 is attached below cylinder 27 at the bottom of which is a lower head 30. A plate 27a separates cylinders 27 and 29. Tothe bottom of the latter is screwed a cup enclosure 31. A piston rod 32 is reciprocable in cylinder 29, the upper end of which is the piston 28, already mentioned. The rod has lands '33 and 34 thereon which fit snugly in cylinders 27 and 29, respectively. A connection 35 extends from cylinder 27 to a source of fluid pressure, and includes a control valve (not shown).
Lower head 30 has a bore in its bottom face adapted to receive a load-sustaining shear disc 36 of steel or aluminum, larger in diameter than piston rod 32 and secured to the lower end thereof by a screw 37. A bushing 38 is screwed into the bore in the bottom of head 30. and is dimensioned so the application of load to piston 28 places disc 36' in single shear. A by-pass connection 39 extends from the upper end of cylinder 27 to branch 25 and contains a valve 40.
In explaining the operation of the system described, it will be assumed that the parts are in their illustrated positions, that valves 22, 24 and 40 are closed and that cylinders 19, lines 20 and the bore in head 26 above piston 28 :are filled with a liquid only slightly compressible such as 011. Under such conditions, the entrance of slab 18 between rolls 16 and 17 normally applies substantially equal pressure to the oil in breaker blocks 19 and unit pressure is applied to the piston 28. So long as the total rolling load exerts a pressure on the fluid system below the strength of disc 36 in shear, normal rolling operations continue. If the loads on breaker blocks 19 are not equal, the pressure in the more heavily loaded will be transmitted to head 26 but not the other blocks 19, because of check valves 22, which permit the flow of oil from the breaker blocks to head 26 but not in the reverse direction. Piston 28 is subject to the higher of the two pressures existing in breaker blocks 19 and the pressure remains at the highest value developed, after the rolling load is reduced, thus eliminating the possibility of fatigue failure of disc 36.
If the load on piston 28 is increased above the shear strength of disc 36, as by a hard spot in the slab, the resulting failure of the disc results in immediate downward movement of the piston. Prmsure relief for both breaker. blocks ensues instantaneously and the initial relief is greatly increased when the piston 28 leaves the bore in head 26 admitting liquid to expansion cylinder 27. Downward movement of the rod which may initially accelerate to high instantaneous velocity, is checked by compression of the fluid in cylinder 29.
Restoration after failure may be quickly effected by removal of cup 31, bushing 28 and screw 37 and the replacement of disc 36. Tihereupon, after opening valves 24 and 40, admission of fluid under pressure to cylinder 27 through connection 3-5 raises the piston rod 32. Oil above land 33 flows through by-pass connection 39 back to the breaker block-s. Equal pressure in the two blocks is insured by connection 23. When restoration has been effected, valves 24 and 40 are closed and the system is again ready for operation under normal load.
It will be evident that my invention is characterized by numerous advantages. In the first place, it operates instantaneously to relieve both breaker blocks upon the occurrence of an overload on either one. Theoverload relief occurs in response to the failure of a disc in single shear which can be accurately predetermined. The disc, on failure, is not free to travel but is restrained and is kept out of contact with the fluid which is compressed under normal loads. The system may be quickly restored to normal after a failure of the disc; The loadsustaining .fluid is not lost on failure but is preserved and re-used repeatedly. The moving piston rod is cushioned to decelerate it gradually after a failure.
Although I have disclosed herein the preferred embodiment of my invention, I intend to cover as well any change or modification therein which may be made without departing from the spirit and scope of the invention.
I claim: 3
1. An overload-relief system for a mill roll comprising hydraulic breaker blocks, one at each end of the roll, subject to the load on the roll, a relief cylinder and piston apart from the roll, said cylinder having a head at each end, pipe connections between the breaker blocks, respectively, and one end of said cylinder, a check valve in each pipe connection preventing hack flow from said cylinder to said breaker blocks, the head at the other end of said cylinder having a shear disc on which said piston bears and means securing the rim of the disc to said lastmentioned head;
2. The system defined by claim 1, characterized by the head at said one end of the cylinder having a bore therein in which said piston fits snugly.
3. The system defined hy'claim 2, characterized by said cylinder including a portion of enlarged diameter adjacent the head at said other head and a land on said piston closely fitting said portion.
4. The system defined lay claim 1, characterized by a restoring cylinder coaxial with said piston and a land on said piston fitting snugly therein, eifective to return the piston after fiailure thereof.
5. The system defined by claim 4, characterized by said restoring cylinder inclirding a portion of enlarged- UNITED STATES PATENTS Bailey Oct. 7 1952 Norton Aug. 24, 1954 FOREIGN PATENTS Great Britain Dec. 3, 1952