Lock nut
TECHNICAL FIELD 
     The invention concerns improvements to rotary equipment such as punchers, slitters, embossers, sealers and the like in which cooperating rotating tools are mounted on cantilever shafts for acting on a work piece that passes between the rotating tools. More particularly, the invention relates to a lock nut useful for minimizing radial and axial run-out of bearings in such equipment. 
     BACKGROUND ART 
     In apparatus such as rotary punchers, slitters, embossers, sealers and the like, which involve the use of a pair of cooperating rotary tools, the tools frequently have been mounted on outboard ends of driven cantilever shafts, to facilitate thread up of the work piece, maintenance of the equipment and the like. A problem with such apparatus has been that the ends of the cantilever shafts tend to deflect or flex slightly. Such deflection can lead to premature wear of the tools; and to incomplete or irregular punching, slitting, embossing or sealing. These problems in turn can require frequent shut down of the apparatus for adjustment, replacement of worn and broken parts and other repairs made necessary by such deflection of the cantilever shafts. One potential source of such deflection is radial and axial run-out of bearings supporting the shafts. 
     One solution attempted for such problems has been to provide, rigidly attached to the frame of the apparatus, an additional rotary support for the free end of each cantilever shaft. Aside from the difficulty of threading up and maintaining such an apparatus, the additional support may over constrain the shaft; so that, errors in alignment can cause high stresses on shafts, bearings and tools, leading ultimately to failures. Another solution is described in U.S. Pat. No. 186,109 which shows half journal bearings mounted inboard of the tools from the ends of the cantilever shafts. This arrangement over constrains the shafts and would be expected to lead to early failure of the half journals. U.S. Pat. No. 4,485,710 shows a paper cutting machine in which movement of noncantilever shafts in low precision bearings is minimized by a bearing unit supported between a pair of non-cantilever shafts. U.S. Pat. No. 4,770,078 shows a cutting and scoring apparatus in which tools mounted on cantilever shafts are prevented from moving by rollers mounted in the frame of the apparatus. This arrangement also results in over constraint of the shafts and tools. 
     Thus, a need has existed for a solution to the problem of controlling movement of tools mounted on cantilever shafts, without over constraining the shafts, tools or supporting bearings. A need has also existed from a solution to the problem of controlling run-out of the supporting bearings, which can contribute to movement of the tools. 
     SUMMARY OF THE INVENTION 
     The primary object of the invention is to provide a technique for minimizing radial and axial run-out of bearings in rotary equipment. 
     This objective is given only by way of an illustrative example; thus other desirable objectives and advantages inherently achieved by the invention may occur or become apparent to those skilled in the art. The scope of the invention is to be limited only by the appended claims. 
     To enable the positions of bearings to be adjusted precisely on their respective shafts, a lock nut may be threaded onto an outboard end of the shaft and engaged with a respective bearing. The lock nut may include a body portion with a central threaded bore, a plurality of circumferentially spaced, threaded through bores essentially parallel to an axis of rotation of the lock nut; and a corresponding plurality of screws in the threaded bores, at least one of the screws being adjustably engaged with the respective bearing. Brass contact plugs may be provided between the screws and the bearings. Since the bearings each have an inner race and an outer race, the lock nut preferably engages the inner race. The lock nut also may include a further plurality of circumferentially spaced, threaded through bores extended radially toward the axis of rotation of the lock nut; a corresponding further plurality of radially movable, threaded shoes; and a corresponding further plurality screws in the further plurality of through bores for pressing the shoes against the shaft. The bearings may include a pair of housings, one housing surrounding each bearing. The lock nut may be used to adjust the positions of the housings to greatly reduce radial and axial runout. 
     The invention provides numerous significant advantages. Because of the presence of the lock nut, bearing run-out can be reduced substantially, which helps to minimize the relative movement of the tools and leads to improved punching, slitting, embossing, sealing and the like. Tool wear is more uniform along the axis of rotation of the tool. Higher speeds of operation frequently are achievable. Existing apparatus may be modified readily by installing the lock-nut outboard of bearings already mounted on shafts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objectives, features and advantages of the invention will be apparent from the following more particular description of the preferred embodiments of the invention, as illustrated in the accompanying drawings. 
     FIG. 1 shows a front elevation view of an apparatus embodying the invention. 
     FIG. 2 shows a sectional view taken along line 2--2 of FIG. 1. 
     FIG. 3 shows a perspective view of a constraint member. 
     FIG. 4 shows a plan view of the lock nut according to the invention. 
     FIG. 5 shows a sectional view along line 5--5 of FIG. 4. 
     FIG. 6 shows a sectional view along line 6--6 of FIG. 4. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following is a detailed description of the invention, reference being made to the drawings in which the same reference numerals identify the same elements of structure in each of the several figures. 
     Referring to FIGS. 1 to 3, the lock nut of the invention is particularly useful in an apparatus 10 which includes a drive module 12 from which extends a pair of cantilever shafts 14, 16 which are rotated by module 12 during operation. In the illustrated apparatus, a rotary tool 18 is fixedly mounted for rotation with shaft 14 and a cooperating rotary tool 20 is fixedly mounted for rotation with shaft 16. Those skilled in the art will understand that the invention may be applied to rotary equipment which includes a wide variety of rotary, cooperating tools, such as those used in punchers, slitters, embossers, sealers, printers, calendaring rolls, web choppers and the like. In the familiar manner, a work piece 26, such as an elongated strip or strips of material, is drawn between the rotating tools to be punched, slit, embossed, sealed or to undergo whatever transformation can be completed with such rotary tools. 
     Rotary tool 18 is provided with a circumferential array of threaded holes 32. A cantilever shaft extension 34, having a circumferentially and radially extending flange 36, is mounted on tool 18 by screws 33 extended into holes 32. Similarly, rotary tool 20 is provided with a circumferential array of tapped holes 38. A cantilever shaft extension 40, having a radially extending flange 42, is mounted to tool 20 by a plurality of screws 44. Alternatively, shafts 14, 16 may be enlarged and extended through tools 18, 20, respectively. To minimize the mass and maximize the resonant frequency of the overall assembly, shaft extensions 34, 40 preferably are provided with respective central bores 46, 48. Shaft extensions 34, 40 include respective shoulders 50, 52. Mounted against the shoulders are bearing assemblies 54, 56, each of which includes a cylindrical housing 58 having a radially and circumferentially extending flange 60 and surrounding a duplex bearing 62. Assemblies 54, 56 are fitted onto the shaft extensions against shoulders 50, 52. A retainer ring 64 is mounted into each housing 58 into contact with the outer race of bearing 62. A plurality of screws 66 secure each ring 64 to its respective housing 58. A hardened washer 68 is positioned on each shaft extension against the inner race of bearing 62. A lock nut 70 according to the invention is threaded onto the end of each shaft extension and into engagement with washer 68. 
     FIGS. 4 and 5 illustrate the features of lock nut 70. Those skilled in the art will appreciate that application of the lock nut of the invention is not limited to the illustrated apparatus. An annular body portion 72 is provided with a central threaded bore 74. Surrounding bore 74 are a plurality circumferentially spaced, threaded through bores 76, each bore 76 extending essentially parallel to the axis of rotation of the nut. In each bore 76 is located a screw 78 which bears upon a metal plug 80 positioned in an unthreaded end portion of bore 76. Preferably, plug 80 is made from a material, such as brass, which is softer than screw 78 and washer 68. At initial installation of lock nut 70, screws 78 are not tightened against plugs 80. Also surrounding bore 74 is a further, conventional plurality of circumferentially spaced, threaded through bores 82, each bore extending essentially radially toward the axis of rotation of the nut. In each bore 82 is located a screw 84 which bears upon a threaded metal shoe 86. Preferably, shoe 86 (shown more clearly in FIG. 6) is made from a material, such as brass, which is softer than the material of shaft extensions 34, 40. After the lock nut has been torqued to the necessary preload, screws 84 are tightened against shoes 86 in the familiar manner to prevent the nut from backing off. 
     After bearing assemblies 54, 56 have been installed and lock nuts 70 have been torqued to the preload required by the bearing manufacturer, the radial runout of each bearing assembly is measured against an outer cylindrical surface 88 of each housing 58; and the axial runout of each bearing assembly is measured against a radially extended surface 90 of each flange 60. Potential causes for such axial and radial runout can include preload forces of the lock nut, lack of squareness between the faces of the lock nut and the axis of rotation of the bearings and similar factors. In an actual application for rotary tools of the type illustrated, the radial and axial runouts at this point during assembly have been measured in the range of 0.0001 to 0.0002 inch (0.0025 to 0.0050 mm). To reduce this amount of runout, screws 78 were tightened against plugs 80. Those skilled in the art will appreciate that pressure from plugs 80 against washer 68 will cause slight changes in geometry, such as very small deflection of shaft extensions 34, 40, which can be adjusted to reduce the amount of runout measured. In the same actual application, use of the lock nut enabled radial and axial runout to be reduced by about a factor of ten, to less than 0.000040 inch (0.001 mm). In this application, the lock nut had an outer diameter of about 2.25 inch (57.2 mm) and an inner diameter of about 1.5 inch (38.1 mm), with bores 76 set 60° apart. Screws 78 had a diameter of about 0.164 inch (4.17 mm); and plugs 80, a diameter of about 0.188 inch (4.78 mm). 
     Once lock nuts 70 have been adjusted to produce the desired runout, a constraint member 92 is installed. As shown in FIG. 3, constraint member 92 comprises an upper, cylindrical body portion 94 having a through bore 96 and a lower cylindrical body portion 98 having a through bore 100. Bores 96 and 100 are sized to have a substantial radial clearance of about 0.002 inch (0.051 mm) to outer cylindrical surfaces 88 of bearing housings 58. At least one flexure 102 is extended between body portions 94, 98, in the illustrated embodiment essentially in a plane containing the axes of bores 96, 100. Flexure 102 has a major width dimension M measured essentially parallel to the axes of bores 96, 100 and a minor width dimension m measure essentially transverse to the axes of the bores. A pair of side flexures 104, 106 may be positioned on either side of central flexure 102. Flexures 104, 106 may be angled toward each other, as illustrated, to ease access to the working nip between tools 18, 20. 
     Those skilled in the art will appreciate, however, that flexures 102, 104, 106 are not limited in geometry and location to the configuration of the illustrated embodiment. The geometry and material of the flexures may be chosen as necessary to enable member 92 to serve as a tuned compliance between the cantilever shafts, as suitable for a particular application. The flexures may be designed to produce a desired spring rate in the direction(s) most suitable for a particular rotary tool pair, to withstand the radial and axial run-out forces expected for the particular application. Thus, run-out motion may be limited in accordance with our invention, without adding excessive strain to the shafts or excessive, damaging loads to bearings, tools, cantilever shafts or shaft extensions. Those skilled in the art accordingly will appreciate that the flexures may have various cross sections, such as square, round, oval and the like, or may be built up from several leaves. As illustrated, constraint member 92 is formed integrally of body portions 94, 98 and flexures 102-106; however, those skilled in the art will appreciate that an assembly of separate parts also may be used. To minimize the weight of the constraint member and to more closely match thermal expansion characteristics of the remainder of the assembly, titanium has been found to be a suitable material. 
     Constraint member 92 is installed by slipping bores 96, 100 over surfaces 88 of the bearing housings until radial surfaces 90 are contacted. Surrounding each bore is a circumferentially extending array of through bores 108 through which a corresponding plurality of screws 110 extend to engage a corresponding plurality of tapped holes in flanges 60. Sufficient clearance is provided between bores 108 and screws 110 for ease of installation. In some applications, slight movement of constraint member will be observed. Radial movement may be limited, if desired, by means such as a ball and spring plunger 111 installed next to die tool 20, as illustrated schematically in FIG. 1. 
     A constraint member having the illustrated geometry, coupled with bearing assemblies and lock nuts of the types previously described, was effective to reduce radial and axial runout of a tool pair from a range of 0.000460 to 0.000480 inch (0.0117 to 0.0122 mm), to a greatly improved range of 0.000090 to 0.000115 inch (0.0023 to 0.0029 mm). Consider the case with a Y-axis transverse to the axes of rotation of the tools, an X-axis transverse to the same axes; and a Z-axis parallel to the same axes. In general, constraint systems of the type illustrated are effective to limit movement of the tools in the Y direction, meaning that good engagement is maintained with the work piece. Some benefit also is realized in the X direction and, to a lesser extent, in the Z direction. Should additional stiffness in the X direction be desired, limited stiffness external braces can be added. 
     PARTS LIST 
     10. . . apparatus embodying the invention 
     12. . . drive module 
     14. . . cantilever shaft 
     16. . . cantilever shaft 
     18. . . rotary tool 
     20. . . rotary tool 
     26. . . work piece, length of photographic film 
     32. . . threaded hole 
     33. . . screw 
     34. . . cantilever shaft extension 
     36. . . circumferentially and radially extending flange on 34 
     38. . . tapped hole 
     40. . . cantilever shaft extension 
     42. . . circumferentially and radially extending flange on 40 
     44. . . screw 
     46. . . central bore in 34 
     48. . . central bore in 40 
     50. . . shoulder on 34 
     52. . . shoulder on 40 
     54. . . bearing assembly mounted on 34 
     56. . . bearing assembly mounted on 40 
     58. . . cylindrical housing of 54 or 56 
     60. . . radially and circumferentially extending flange on 58 
     62. . . duplex bearing within 54 or 56 
     64. . . retainer ring for outer race of 62 
     66. . . screw 
     68. . . hardened washer 
     70. . . lock nut 
     72. . . annular body portion of 70 
     74. . . central threaded bore in 72 
     76. . . axially extending, threaded through bore in 72 
     78. . . screw 
     80. . . brass plug 
     82. . . radially extending, threaded through bore in 72 
     84. . . screw 
     86. . . threaded brass shoe 
     88. . . outer cylindrical surface of 58 
     90. . . radially extended surface of 60 
     92. . . constraint member 
     94. . . upper, cylindrical body portion 
     96. . . through bore in 94 
     98. . . lower, cylindrical body portion 
     100. . . through bore in 98 
     102. . . flexure 
     M. . . major width dimension of 102 
     m. . . minor width dimension of 102 
     104. . . side flexure 
     106. . . side flexure 
     108. . . through bore in 94 or 98 
     110. . . screw 
     111. . . ball and spring plunger 
     While the invention has been shown and described with reference to a particular embodiment thereof, those skilled in the art will understand that other variations in form and detail may be made without departing from the scope and spirit of the invention.