Title of Invention

"A ROLL LOCKING UNIT FOR A COMPOSITE ROLL FOR ROLLING METAL BILLET AND A COMPOSITE ROLL THEREOF"

Abstract

In the present invention there is provided a novel roll locking unit for a composite roll for rolling metal billets and an improved composite roll incorporating the said locking unit. The outer most circular portion of a composite roll, such as a rolling ring, which comes into direct contact with a metal billet being subjected to rolling, is fitted onto the roll core portion or arbor by means of the novel roll locking unit consisting of an annular ring-wedge locking assembly. The annular ring-wedge locking assembly comprises of an inner slit ring, an outer slit ring, two thrust pads from either sides and set of cap screws from either sides, this wedge locking assembly is positioned on the shaft by a spacer sleeve. The novel roll locking unit allows removably mounting a rolling ring onto a composite roll capable of hot rolling of metal billets. The present invention will be particularly useful for providing finishing passes in a rolling mill, where surface finish and accuracy are the main criteria.

Full Text

The present invention relates to a roll locking unit for a composite roll for rolling metal billets and a composite roll thereof. The present invention particularly relates to a novel roll locking unit capable of effectively locking the outer most- circular portion, such as a rolling ring, onto the core of a composite roll for rolling metal billets. The present invention provides a novel roll locking unit for removably mounting a rolling ring onto a composite roll capable of hot rolling of metal billets. The outer most circular portion of a composite roll, such as a rolling ring, which comes into direct contact with a metal billet being subjected to rolling, is fitted onto the roll core portion or arbor by means of the novel roll locking unit, of the present invention, consisting of an annular ring-wedge locking assembly. The present invention will be particularly useful for providing finishing passes in a rolling mill, where surface finish and accuracy are the main criteria. In a rolling mill to flatten a metal billet, the roll that is used is of composite design wherein the arbor or the core jjportion of the roll is provided with a separate surface member, such as a rolling ring, which comes into direct contact with the metal billet being subjected to rolling. This separate circular surface member has to be locked onto the arbor or the core portion of the roll. The strength requirement of a roll has to be such that the inner portion or arbor has to be toughened and shock resistant and the outer surface or ring has to be hardened and wear resistant. The prior art search covering literature, patent data bases and industrial survey reveals that there are a few designs of composite roll. Such rolls have been formed either by shrink-fitting the rolling ring on the arbor or by pouring the metals of the arbor !] and ring separately into a moldas the roll is cast. Reference may be made to U.S. patent no. 3143012, wherein rolls have been formed by shrink-fitting the rolling ring onto the arbor. A major drawback iln this case is that hard wear resistant rolling ring has poor tensile properties and hence, when such a ring is shrink-fitted over an arbor, it is placed under a residual tensile stress which may cause it to break. Reference may be made to U.S. patent no. 517747 and U.S. patent no. 1011430, wherein rolls have been formed by pouring the metals of the arbor and ring separately into a mold as the roll is cast. A major drawback in this case is that when a ring and arbor are cast together of different metals, the ring is metallurgically bonded to the arbor and cannot be separated when vvorn or damaged, making it difficult for maintainability. In the hitherto known prior art composite roll for rolling metal billets are based on locking by epoxy bonding. An embodiment of this is shown in figure 1 of the drawings accompanying this specification, wherein advanced epoxies (1) have been used for driving rolling ring (2) onto merchant mill roll (3). Some of the drawbacks in this case is that mounting of the ring (2) and operating conditions must be perfect for success. Moreover, during hot rolling, the friction from the journal bearings is a source of heat input to the roll shaft (3). Hence, under elevated roll temperature, the epoxy (1) may soften and the bond may fail. In another known prior art, as shown in figure 2 of the drawings accompanying this specification, composite roll for rolling metal billets are based on locking by intermediate tapered sleeve. A rolling ring (4) is mounted by means of a tapered sleeve (5) onto a tapered roll shaft (6). The tapered sleeve design is usually not adequate when more than two rolling rings are required. Each ring requires corresponding taper and also shoulder in the shaft for the ring to butt against. From the hitherto known prior art it is seen that there is a definite need for providing a roll locking unit for a composite roll for rolling metal billets and to provide an improved composite roll. The main object of the present invention is to provide a novel roll locking unit for a composite roll for rolling metalj billets which obviates the drawbacks of the existing composite rolls. Another object of the present; invention is to provide an improved composite roll i incorporating the novel locking unit which obviates the drawbacks of the existing composite rolls. Still another object of the present invention is to provide an improved composite roll having better maintainability, specially replacement of the rolling ring with relative ease. In the present invention there is provided a novel roll locking unit for a composite roll for rolling metal billets and a composite roll incorporating the said locking unit. In the present invention the outer most circular portion of a composite roll, such as a rolling ring, which comes into direct contact with a metal billet being subjected to rolling, is fitted onto the roll core portion or arbor by means of the novel roll locking unit. The novel roll locking unit comprises in combination rolling ring or rings, a roll shaft, spacer sleeve or sleeves and an annular wedge locking assembly consisting of inner slit ring, outer slit ring, left thrust pad, right thrust pad and cap screws. This effectively provides the strength requirement of a roll which is, the inner portion or arbor has to be toughened and shock resistant and the outer surface or ring has to be hardened and wear resistant. The present invention provides a novel composite roll for hot rolling capable of rolling metal billets. The present, invention will be particularly useful for finishing passes of rolling mill, where surface finish and accuracy are the main criteria. In the drawings accompanying this specification, figures 3, 4 and 5 show the various parts and describe the novel roll locking unit for a composite roll for rolling metal billets and an improved composite roll incorporating the said locking unit of the present invention. Figure 3 shows the schematic view of the composite roll with roll locking unit of the present invention. Figure 4 depicts the sectional view of the improved composite roll assembly of the present invention. The various parts (7 to 11) as shown in figures 3 and 4 are as follows: 7: Hardened and wear resistant rolling ring. This is the outer most circular portion of a composite roll which comes into direct contact with a metal billet being subjected to rolling. 8: Toughened and shock resistant roll shaft. 9: Annular ring-wedge locking assembly. The novel roll locking unit consisting of the annular ring-wedge locking assembly is the means by which the outer most circular portion of a composite roll, such as a rolling ring, which comes into direct contact with a metal billet being subjected to rolling, is fitted onto the roll core portion or arbor. 10: Spacer sleeve. 11: Grub screw. Figure 5 shows the schematic view of the annular ring-wedge locking assembly of the present invention. The individual parts (12 to 16) of the locking assembly as depicted in figure 5 are as follows: 12: Inner slit ring provided with double taper at outer surface. 13: Outer slit ring is provided with double taper at inner surface. 14: Left thrust pad is double tapered and provided with multiple number of threaded holes on pitch circle. 15: Right thrust pad is double tapered and provided with multiple numbers of through holes and multiple number of (threaded holes on pitch circle capable of accepting cap screws. 16: Cap screws. Accordingly the present invention provides a roll locking unit for a composite roll for rolling metal billets, which comprises an annular ring-wedge locking assembly (9) characterised in that the said annular ring-wedge locking assembly (9) consisting an inner slit ring (12), an outer slit ring (13), left thrust pad (14), right thrust pad (15) and cap screws (16), wherein the said slit rings (12 & 13) being peripherally separated by the said thrust pads (14 & 15) incorporating a plurality of cap screws (16). In an embodiment of the present invention, the inner slit ring (12) is provided with double taper at outer surface. In another embodiment of ithe present invention, the outer slit ring (13) is provided with double taper at inner surface. In yet another embodiment of the present invention, the left thrust pad (14) is double tapered and provided with multiple number of threaded holes on pitch circle. In yet another embodiment of the present invention, the right thrust pad (15) is double tapered and provided with multiple numbers of through holes and multiple number of threaded holes on pitch circle capable of accepting cap screws (16). In a further embodiment of the present invention, the taper surfaces of the slit rings (12 & 13) engage with corresponding taper surfaces of the thrust pads (14 &15). Accordingly the present invention provides a composite roll incorporating the novel roll locking unit as herein above described, which comprises in combination one or more rolling ring (7), roll shaft (8), one or more spacer sleeve (10), plurality of grub) screws (11) and one or more annular ring-wedge locking assembly (9), wherein the said rolling ring(s) (7) separated by the said spacer sleeve (10) are remoyably fixed onto the said roll shaft (8) by means of the said annular ring-wedge Hocking assembly (9) placed in the annular space between the said rolling ring (7) and the said roll shaft (8). The present invention consisting of a novel roll locking unit for a composite roll for rolling metal billets and an improved composite roll incorporating the said locking unit has been described below with reference to figures 3, 4 and 5 of the drawings: The composite roll assembly consisting of rolling rings (7) are mounted onto a roll shaft (8) by using the annular ring wedge locking system (9) of the present invention, which is placed in the annular space between the rolling ring (7) and the roll shaft (8) as shown in figures 3 and 4. To assemble the total composite roll, steel spacer sleeve (10) is placed at pre-defined position of the roll shaft (8) by means of grub screws (11). The rolling ring (7) and locking system (9) are then assembled with the cap screws (16) tightened lightly and uniformly and the rolling ring (7) aligned. After alignment, the cap screws are tightened evenly. The annular ring-wedge locking assembly (9), as shown in figure 5, consists of inner slit ring (12) with double taper at outer surface, outer slit ring (13) with double taper at inner surface, double tapered thrust pad (14) with multiple numbers of threaded holes on pitch circle, double tapered thrust pad (15) with multiple numbers of through holes and multiple numbers of threaded holes on pitch circle and multiple numbers of cap screws (16). The taper surfaces of the slit rings engage with corresponding taper surfaces of thrust pads. With the equal tightening of screws, the taper surfaces of the thrust pads slide over the taper surfaces of slit rings, which results in elastic contraction of inner slit ring and elastic expansion of outer slit ring, thus producing mechanical shrink fit between roll shaft and rolling ring, this makes the locking action complete. The novelty of the present invention consisting of a novel roll locking unit for a composite roll for rolling metal billets and an improved composite roll incorporating the novel roll locking unit, in comparison with the prior art, resides in that the roll locking unit allows the rolling ring to be removably mounted onto the core shaft, thereby avoiding discarding the entire billet rolling unit. The novelty of the present invention has been achieved by the non-obvious inventive steps of providing in combination the annular ring-wedge locking assembly. This provides means for the rolling ring to sit firmly locked onto the circular core shaft and also whenever needed, can be dismantled for replacement of either / any of the components. Further, it has made possible for the composite rolling shaft, in billet rolling, to be re-used and not discarded after its life is over, by replacement of the outer active part of the roll. The locking mechanism of both the outer ring and the inside shaft is very strongly and reliably secured for longer duration of use, before the next replacement. It is a contribution to better maintainability. The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the present invention. Example 1 The device of present invention is the roll locking unit for composite roll. Multiple grooves are generally used oh the rolling rings for their most economical use. Experimental data have been generated by carrying out torsion test on a laboratory scale model. The various parts used and results obtained were as follows: Outer diameter of the roll - 70 mm Diameter of roll shaft = 25imm Outer diameter of locking assembly = 50 mm Number of tightening screws (M6) = 8 Number of releasing screws (M6)= 4 Tightening torque to each cap screw= 4 N-m Torque carrying capacity of the locking unit=138.5 N-m. Example 2 In another set of experiments the data generated by carrying out torsion test on a laboratory scale model were as fallows: Outer diameter of the roll = 70 mm Diameter of roll shaft = 25 mm Outer diameter of locking assembly = 50 mm Number of tightening screws (M6) = 8 Number of releasing screws (M6)= 4 Tightening torque to each cap screw= 2.5 N-m Torque carrying capacity of the locking unit=97.6 N-m. The main advantages of the present invention are: 1) Increased roll assembly life. 2) Better replacability of rolling rings, in maintenance. 3) Easy assembly and dismantling of locking system. 4) Increased tons of production per groove in the rolling process. 5) Production with high and consistent quality. 6) Reduced scrap in rolling. 7) Lower cost per ton of production. 8) Increased mill utilization. 9) Reduced roll inventory. We claim: 1. A roll locking unit for isa composite roll for rolling metal billets, which comprises an annular ring-wedge locking assembly (9) characterised in that the said annular ring-wedge locking assembly (9) consisting an inner slit ring (12), an outer slit ring (13), left thrust pad (14), right thrust pad (15) and cap screws (16), wherein the said slit rings (12 & 13) being peripherally separated by the said thrust pads (14 & 15) incorporating a plurality of cap screws (16) 2. A roll locking unit for a composite roll as claimed in claim 1, wherein the inner slit ring (12) is provided with double taper at outer surface. 3. A roll locking unit for a composite roll as claimed in claims 1 & 2 wherein the outer slit ring (13) is provided with double taper at inner surface. 4. A roll locking unit for a co'mposite roll as claimed in claims 1-3, wherein the left thrust pad (14) is double tapered and provided with multiple number of threaded holes on pitch circle. 5. A roll locking unit for a co'mposite roll as claimed in claims 1-4, wherein the right thrust pad (15) is double tapered and provided with multiple numbers of i! through holes and multiple number of threaded holes on pitch circle so as to accept cap screws (16). 6. A roll locking unit for a composite roll as claimed in claims 1-5, wherein the taper surfaces of the slit rings (12 & 13) engage with corresponding taper surfaces of the thrust pads (14 & 15). 7. A composite roll incorporating the roll locking unit as claimed in claim 1 which comprises in combination one or more rolling ring (7), roll shaft (8), one or more spacer sleeve (10), plurality pf grub screws (11) and one or more annular ring- wedge locking assembly (9)| wherein the said rolling ring(s) (7) separated by the said spacer sleeve (10) are removably fixed onto the said roll shaft (8) by means of the said annular; ring-wedge locking assembly (9) placed in the annular space between the said rolling ring (7) and the said roll shaft (8). 8. A roll locking unit for a composite roll for rolling metal billets and a composite roll thereof substantially as) herein described with reference to the examples and figure 3, 4 and 5 of the drawings accompanying this specification.

Documents:

496-del-2003-abstract.pdf

496-del-2003-claims.pdf

496-del-2003-complete specification(granted).pdf

496-del-2003-correspondence-others.pdf

496-del-2003-correspondence-po.pdf

496-del-2003-description (complete).pdf

496-del-2003-drawings.pdf

496-del-2003-form-1.pdf

496-del-2003-form-18.pdf

496-del-2003-form-2.pdf

496-del-2003-form-3.pdf