Abstract:
An expanding hub assembly for a capstan drive for a steel mill comprising a modified spline having a large cylindrical surface area for mating with an installed mill roll. The cylindrical surface is interspersed with a series of evenly spaced shallow axial troughs formed therein for mating with a series of shallow projecting splines on a mounted mill roll. The hub is hollow and an expansion device is present in the hollow hub for expanding the mating surface of the hub.

Description:
This application relates to an improvement of U.S. Pat. No. 5,700,233 entitled SLEEVELESS CANTILEVER DRIVE FOR HIGH TORQUE APPLICATIONS, the inventor of which is M. Fabris and the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The process of reducing steel by rolling is a well developed art in the manufacture of steel products. The above mentioned U.S. Patent is capable of providing a method of mounting a roll on a driving capstan in a swift and efficient manner such that the roll and capstan rotate concentrically. The apparatus described above will function perfectly well within certain torque and roll diameter limitations. 
     As designers of steel mills call for increased capacity, the demand for a method of mounting a large reduction roll on a large capstan in such a manner as to transmit a large driving torque to the roll is a trend which will not be deterred. 
     Not only must the rotating capstan transmit torque to the reduction roll during a rolling operation with no slippage, but the roll must be capable of being mounted on the capstan in a swift and efficient manner in such a way that the roll mounted on the capstan rotates concentrically with the capstan. Also when the surface of a roll has deteriorated to the point where it must be refurbished, the roll must be capable of being quickly demounted from the capstan drive in preparation for replacement with a new or refurbished roll. This particular method of mounting a roll on the driving capstan lends itself to preserving the surface integrity of the two mating surfaces i.e. the roll and the capstan. Because the surface of the capstan is in its normal unexpanded state during the roll demounting and mounting operations, there is substantial clearance between the mating surfaces of the roll and capstan, hence little or no surface abrasion occurs during these operations. 
     The above U.S. Patent is perfectly capable of providing such a method of quickly demounting a used roll and remounting a new or refurbished roll on a capstan such that the capstan and the newly mounted roll rotate in a concentric relationship. It is only when certain torque and roll diameters are exceeded beyond certain prescribed limits that an alternate method of mounting and demounting must be found. 
     The success enjoyed by U.S. Pat. No. 5,700,233 is generally thought to have been achieved by the use of a wedge plug which is threaded into the internal cavity in the hub of a rotating capstan such that once a roll is mounted on the hub, the threaded plug is moved axially within the hub to expand the entire circumference of the hub on which the roll is mounted. 
     There are distinct advantages to this method of mounting a reduction roll: 
     1) rolls are easily mounted on the driving capstans while the capstan is in its unexpanded state, 
     2) when the capstan is expanded the entire circumference of the capstan is expanded uniformly under the mounted roll to provide a stable concentric mounting arrangement for the roller on the driving capstan. 
     3) The level of skill required to remove and replace a reducing roll with another roll which is concentrically mounted on the capstan shaft is not as great as with prior art mounting techniques. 
     4) Because of the simplicity of method of mounting the reducing roll on the capstan, and the reduction of components in the driving interface between the capstan and the roller, it is possible to speed up the change over time for roll replacement and thus increase the rolling capacity of the mill. 
     5) Wear of the mating surfaces of the roll and capstan is minimized during the life time of the capstan, because of the method of mounting the roll on the capstan and the shape of the surfaces. which eliminates roll slip on the capstan. 
     SUMMARY OF THE INVENTION 
     This invention provides a novel method of mounting and demounting rolls on a capstan drive which is ideally suited to rolls of a prescribed size wherein large driving torques and substantial reduction forces are imparted to the rolls by the driving capstans. The method of mounting the roll on the capstan of this invention includes the presence of a suitable spline drive system in the interface between the roll and the capstan. 
     The spline drive provides for a positive placement of the roll on the capstan mating face and the spline interface assures a positive drive with no slippage. After mounting a roll on the splined capstan the surface of the capstan mating interface is expanded, preferably by the use of a wedging plug similar to the one shown in FIG. 5 of the aforementioned patent. 
     Ideally it will be found that this invention will produce the best results if the projecting splines on the roll are about half the width of the upstanding intermeshing splines on the capstan. This configuration assures the easy interchange of rolls on the unexpanded interface of the capstan drive while allowing sufficient area of expansion of the capstan interface (by the wedge plug) to preserve concentricity during a rolling operation. 
     The presence of any infinitesimal wear which may occur on the surface of the capstan or rolls over a lifetime of the capstan in a steel mill is easily offset by the expandable surface of the capstan. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective partial sectional view of the complete. assembly of this invention. 
     FIGS. 2 and 2A show the capstan in elevation and end views. 
     FIG. 2B shows a sectional view of the mounting hub of the capstan. 
     FIGS. 3 and 3A show the roll in section and elevation. 
     FIGS. 4 and 4A show the wedge plug in elevational and end views. 
     FIG. 5 shows a perspective of a release bolt. 
     FIGS. 6,  6 A and  6 B show various views of the end cap. 
     FIG. 7 shows a cap for the bolt of FIG.  5 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a partial perspective sectional view of the capstan and roll showing the complete mounting assembly  10 . Capstan  12  includes two spaced bearing surfaces  14  and  16  for mounting bearings (not shown) of a steel mill drive. Gear  18  is integrally formed on capstan  12  between bearings  14  and  16  to permit the capstan to be rotationally  10  driven. 
     A brief description of the parts of the complete assembly shown in FIG. 1 will now be given before the detailed description of each individual part is given. 
     A flinger  28  is shown mounted on capstan  10  between capstan shoulder  30  and the face  32  of roll  20 . 
     A roll  20  is next shown mounted on capstan  12 . Roll  20  has a pair of work engaging grooves  22  and  24  formed in the working surface thereof for shaping the steel product being reduced by the roll  20 . Roll  20  is mounted on interface  26  of roll  20  and capstan  12 . 
     A cap  34  is positioned on capstan  10  at interface  36 . Bolts  38  are threaded into cap  34  and are able to press against surface  41  of roll  20  to press the roll  20  and flinger  28  against the shoulder  30 . 
     A bolt  40  is threaded into capstan  10  at counter bore  42 . The description of bolt  40  will be described later. 
     A wedge plug  44  having a shallow external buttress thread at capstan interface  46  is provided in the hollow cavity in capstan  12 . 
     Locking cap  48  is provided to prevent accidental twisting of bolt  40 . Three compression screws  39  are located in threaded holes in cap  34 . 
     The various parts will now be described separately and in greater detail. 
     The expanding hub  50  of capstan  10  is shown in more detail in FIGS. 2,  2 A and  2 B. In FIG. 2 the expandable hub  50  is shown having shallow recesses or troughs  52  which resemble a series of shallow keyways formed in the cylindrical surface  54 . The end  56  of the hub  50  is threaded at  58  to receive cap  34 . 
     The hub  50  of capstan  10  contains a hollow cavity  60  as shown in FIG.  2 B. The cavity  60  is provided with an internal buttress thread  62  for threadably receiving plug  44 . Counter bore  42  at the remote end of cavity  60  is provided with internal threads to receive bolt  40 . 
     Roll  20  is shown in detail in FIGS. 3 and 3A. FIG. 3 shows roll  20  in section, having grooves  22  and  24  in the work engaging surface. The central bore  70  comprises a cylindrical surface  72  interspersed with evenly spaced inwardly protruding shallow splines  74  which will ultimately engage troughs or depressions  52  on hub  50  of capstan  10  when roll  20  is fitted on the capstan. 
     Plug  44  is shown in more detail in FIGS. 4 and 4A. Plug  44  is essentially a cylindraceous member having surface  80  threaded with a buttress type screw thread to match threads  62  on the interior of cavity  60  of hub  50  of capstan  10 . The end  82  of plug  44  is provided with a hex head  84  for twisting plug  44  into cavity  60  of the capstan  10 . Plug  44  is provided with a central bore  86 . 
     Bolt  40  is shown in perspective in FIG.  5 . One end  90  of bolt  40  is threaded into threaded bore  42  of capstan  10 . A conical enlargement  92  having annular surface  94  is provided on bolt  40  adjacent threaded end  90 . Shank portion  96  of bolt  40  is of such size as to be received in bore  86  of plug  44  in a sliding fit. Adjacent hex head  88  is threaded surface  90  of bolt  40 . 
     End cap  34  is shown in more detail in FIGS. 6,  6 A and  6 B. Cap  34  is provided with a cylindraceous recess  96  the interior surface  94  of which is threaded with buttress threads  98 . Cap  34  has a central bore  100  which is surrounded by an annular recess  102  in surface  104  of the cap  34 . Three threaded bores  106  are provided in recess  102  for receiving bolts  39  (shown in FIG.  1 ). 
     A series of eight evenly spaced threaded bores  108  are provided in face  104  of cap  34 . Each bore is provided with an enlarged recess  110  near the surface  104 . Bolts  38  will be received in bores  108 . 
     Four evenly spaced cylindrical blind bores  112  are provided in the peripheral surface  114  of cap  34  for reception of a torquing tool used in twisting cap  34  on hub  50 . 
     The device is assembled as follows: 
     Bolt  40  is threaded into bore  42  of capstan  10  until conical surface  92  of bolt  40  rests against the mating conical surface of capstan  10 . 
     Wedge plug  44  is threaded into cavity  60  of capstan  10  until it reaches the position shown in FIG.  1 . 
     Flinger  28  is placed on hub  50  of capstan  10  until it rests against shoulder  30 . Roller  20  is next placed on hub  50  of capstan  10  with splines  74  of roll  20  engaging the recesses  52  of hub  50 . 
     Bolts  38  are “backed off” in cap  34  to a retracted position and cap  34  is placed on the end of capstan  10  and twisted on threads  58  until it reaches its home position. The recesses  112  in the periphery of cap  34  provide means for the insertion of a tool to tighten (or loosen) cap  34  on capstan  10  to its torqued position. 
     When cap  34  is tightened to its specified torque on capstan  10 , bolts  38  are tightened against surface  41  to a specified torque to press roll  20  and flinger  28  against shoulder  30  of capstan  10  with a predetermined force. Bolts  39  in threaded bores  106  of cap  10  are next advanced until the ends of bolts  39  engage the surface  82  of wedge plug  44 . The bolts  39  are then torqued to a predetermined torque to force plug  44  to move axially in the buttress threads  62  of cavity  60  to wedge the capstan surface of hub  50  (comprising cylindrical segments  54  and depressions  52 ) outwardly so that the outer surfaces  54  of the hub  50  engage surfaces  72  of the central bore of roll  20  to positively center roll  20  on hub  50 . When this predetermined expansion of the splined hub  50  of capstan  10  has been reached, cap  48  is threaded on bolt  40  and is advanced until it engages the surface  103  of recess  102  and is locked in place. Cap  48  prevents any access to the hex head  88  of bolt  40  during operation of the capstan. 
     In order to remove roll  20  from capstan  10  the opposite procedure is followed, that is cap  48  is removed from bolt  40 , bolts  39  are loosened in cap  34  and cap  34  is removed by unscrewing it from threads  58  on capstan  10 . Bolt  40  is now unscrewed from its home position until surface  94  engages the end plug  44  remote from hex head  84 . Bolt  40  is unscrewed to push plug  44  laterally in threads  62  of capstan  10  to permit the hub surface  50  of capstan  10  to contract from its expanded size. Roll  20  may now be conveniently removed with ease. 
     The configuration of the spline drive has been deliberately chosen to maximize the cylindrical surface of the shaft (which has the depression formed therein) to enhance the ability of the hub to provide a concentric drive and reduce surface wear. The width of the splines on the roll (which corresponds to depression  52  on the hub) is about ½ the width of surfaces  54  of hub  50 . 
     Because of clearances required between splines  74  on roll  20  and depressions  52  on hub  50  most of the force required for concentricity arises from surfaces  54  of hub  51 . 
     The presence of splines  74  and recesses  52  assures that shaft torque is applied to roll  20 . 
     The method of expanding hub has been explained using only one of the methods described in U.S. Pat. No. 5,700,233. Of course other methods will be obvious. The shape of the engaging surfaces of the hub with the roll is important. It will be found that a large portion of the hub surface is formed into the cylindrical mating surface of the hub so that concentricity is assured between the hub and the roll. 
     Because of the frequency of roll replacement in modern steel mills, this method of mounting and demounting the rolls on the driving capstan is swift and easy and is accomplished with a minimum inconvenience and few tools. Surface wear of the roll-capstan interface is practically non-existent and any small amounts of wear at the interface is easily compensated for by the expanding capstan. 
     Other advantages of this mounting technique and apparatus is the shortening of the overhanging portion of the capstan which reduces forces applied to capstan bearings and reduces fatigue of capstan drive shaft. 
     The diameter of the mating surface of the capstan and roll is much larger than similar prior art devices thus the strength of the shaft is drastically increased; similarly the bore size in the roll is increased thus reducing roll weight.