Abstract:
A locking ring assembly retains a bearing to a shaft rotatably supported on a first axis of rotation. Guide pins or rods extend axially from an annularly shaped bearing retainer slideably disposed on the shaft towards the pressure ring, also slideably disposed on the shaft. The heads of the guide pins are slideably disposed and captured in adjusting apertures of the pressure ring. A multi part pressure screw assembly are provided in the adjusting apertures of the pressure ring. Such pressure screws translate axially in the apertures of the pressure ring when rotated, with the thrust pads engaging the heads of the guide pins to displace the pressure ring from the bearing retainer. The pressure ring reacts against a reactive element or ring disposed on the shaft opposite the bearing retainer to develop an axial pressure load against the bearing.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to the bearing retainer art and more particularly to an expandable bearing retainer or locking device construction which is particularly applicable for use on mill roll necks, shafts and the like.  
         [0003]     2. Description of the Prior Art  
         [0004]     Locking ring assemblies particularly applicable for use on mill roll necks, shafts and the like are available in a wide variety of configurations. These devices are disclosed and claimed in patents which issued to Romolo B. Bianco including U.S. Pat. No. 4,136,989 issued Jan. 30, 1979 entitled “Expandable Annular Cam-Type Locking Device For a Shaft”; U.S. Pat. No. 4,189,251 issued Feb. 19, 1990 entitled “Expandable Annular Locking Device For a Shaft”; and U.S. Pat. No. 4,200,407 issued Apr. 29, 1980 entitled “Bolted Annular Locking Collar For a Shaft”. In addition, the Edward P. Bianco, et al U.S. Pat. No. 5,411,337, issued May 2, 1995 entitled “Axially Guided Locking Ring Assembly” is also directed to a locking device which retains a bearing on a mill roll shaft.  
         [0005]     Structures typical of the prior art have a portion or an element disposed in an annular groove of the shaft with an adjusting mechanism disposed between the groove and a bearing to be retained on the shaft. The bearing is typically pressed by the adjusting mechanism against a shoulder of the shaft such as is shown in U.S. Pat. No. 5,411,337.  
         [0006]     Mill roll shafts and retainer bearings mounted thereon are complicated by the large size of the associated components and the resultant high axial thrust loads required to maintain the bearings in their desired positions. The construction of the locking ring assemblies for mill roll shafts is further complicated by the dirty, harsh operating environment in which the locking ring assemblies are employed. The intrusion of dirt and contaminants into undesired locations within a locking ring assembly can potentially affect its ability to maintain the required thrust load against the bearing.  
         [0007]     There is also a need in the bearing retainer art to maintain pressure on the bearing and to allow for axial movement of the bearing, which is necessary for the bearing to seat properly on the shaft. It is also necessary to have space for thermal expansion of the bearing. Normal requirements of the bearing manufacturers for this bearing movement to occur ranges from 0.010 inch to 0.050 inch, more or less. The prior art devices including U.S. Pat. No. 5,411,337 do not compensate sufficiently for thermal expansion and thus does not provide for axial movement of the chock bearing. Thus, there is a need to provide an axially guided locking ring assembly containing a plurality of adjustable pressure screw assemblies allowing for controlled axial clearance or end play movement of the chock bearing due to thermal expansion.  
       SUMMARY OF THE INVENTION  
       [0008]     In one aspect of the invention, a locking ring for retaining a chock bearing to a shaft which is rotatably supported on a first axis of rotation is disclosed comprising the retaining ring or reaction means, a pressure ring, a bearing retainer and a plurality of guide pins. The retaining ring engages a circumferential slot in the shaft. The pressure ring is slideably located on the shaft between the retaining ring and the bearing. The pressure ring has a plurality of apertures parallel to the first axis of rotation. Each aperture has a threaded portion and a non-threaded guide portion, with the guide portion disposed towards the bearing. The bearing retainer is disposed between the pressure ring and the chock bearing and has a loading face on a first side of the bearing retainer for contacting the bearing. The guide pins are fixed to the second side of the bearing retainer and are arranged parallel to the first axis of rotation. The first end of the guide pins has a head slidably disposed and captured in the guide portion of the aperture of the pressure ring. A novel multi part pressure screw assembly is threaded into the threaded portion of each pressure ring aperture and engages the guide pin.  
         [0009]     In another aspect of the present invention, each pressure screw assembly comprises a general cylindrical body having a pair of end faces and a longitudinally extending axis extending through the cylindrical body and the end faces. The body has first, second and third concentric interconnected cylindrical bores between the end faces. The first bore adjacent one of the end faces is larger in diameter than the other bores. The second bore adjacent to the other of the end faces is larger in diameter than the third bore and is internally threaded. The third bore connects the first and second bores. The cylindrical body has external threads throughout the major portion of its length and includes a leading thread and a trailing thread. The remaining portion of the length of the cylindrical body is provided with an external polygonal shaped head between the other end face and the trailing thread. A floating annular thrust pad is received in the first bore and has a centrally located threaded bore extending partway therethrough. Each pressure screw assembly has a bolt having threads on one end and a head on the other end, with the threaded end and the head end of the bolt being separated by a cylindrical portion. The bolt is located in the three concentric bores of the pressure screw body with the head in the second bore, the cylindrical portion in the third bore and the threaded end threaded into the threaded bore of the thrust pad. A biasing means is received in the second bore and abuts the head of the bolt. An adjustable externally threaded adjusting screw is threaded into the second bore of each pressure screw assembly and engages the biasing means for varying the bias thereof.  
         [0010]     In still another aspect of the present invention is that the prior art one-piece solid pressure screw is now made in multiple pieces or parts thus allowing for controlled axial clearance or end play movement of the chock bearing. With such a construction, a multiple piece pressure screw assembly will maintain pressure on the chock bearing and will allow for axial movement of the chock bearing, which is necessary for the bearing to seat properly and to have space for thermal expansion.  
         [0011]     Yet another aspect of the present invention is that the multiple piece pressure screw assembly contains five components including a main pressure screw cylindrical body, a floating thrust pad, a thrust pad bolt, a thrust pad pressure spring and a thrust pad pressure spring adjusting screw.  
         [0012]     When the present invention is used, the pressure spring adjusting screw is tightened to allow for no movement of the floating thrust pad. As a result, the main pressure screw assembly components are tightened to provide a solid locking of the pressure ring, retaining ring and the bearing retainer to the chock bearing, thereby locking the chock, bearing and roll into one assembly. The procedure used with the present invention further provides for backing off of the adjusting screw a predetermined number of turns, normally two turns. This backing off of the adjusting screw will relax the spring tension and will provide for axial movement of the chock bearing while still maintaining some tension. This permits the bearing to float and provides for axial clearance. Dimensional changes to the components of the pressure screw assembly will allow for a wide range of axial clearance.  
         [0013]     Another aspect of the present invention is that the size of the pressure screw and components will be determined by the size of the pressure ring. In use, there will be a minimum of four pressure screw assemblies per pressure ring up to ten or twelve, again depending on the size of the pressure or locking ring. The larger the bearing locking ring housing, the larger the pressure or locking ring and the larger the pressure screw assembly. Thus, the provided clearance and tension will be determined by the bearing design and size and by the requirements of the bearing manufacturer.  
         [0014]     Finally, a further feature of the present invention is to provide a novel pressure screw assembly primarily for use in an axially guided locking or pressure ring which permits control axial clearance movement of the chock bearing of a mill. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a sectional axial end view of a mill roll shaft with a locking or pressure ring assembly mounted thereon.  
         [0016]      FIG. 2  is a diagrammatic sectional view of the locking or pressure ring assembly looking in the direction of arrows  2 - 2  of  FIG. 1 .  
         [0017]      FIG. 3  is a sectional view taken in the direction of arrows  3 - 3  of  FIG. 1  and illustrating a locking mechanism for the pressure screw of the locking or pressure ring assembly.  
         [0018]      FIG. 4  is a sectional view taken on the line  4 - 4  of  FIG. 2 .  
         [0019]      FIG. 5  is a fragmentary sectional view taken on the line  5 - 5  of  FIG. 2 .  
         [0020]      FIG. 6  is a sectional view through the locking or pressure ring looking in the direction of arrows  6 - 6  of  FIG. 4 .  
         [0021]      FIG. 7  is a sectional view through the locking ring looking in the direction of arrow  7 - 7  of  FIG. 4 .  
         [0022]      FIG. 8  is a fragmentary view of a part of the locking or pressure ring of  FIG. 4  within the circle numbered  8 .  
         [0023]      FIG. 9  is an exploded isometric view of the five component parts of the pressure screw assembly. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]     Referring now to the drawings and in particular  FIGS. 1 and 2 , a conventional mill roll shaft is designated by the numeral  10 . The shaft  10  has a longitudinally extending axis referred to herein as the first axis of rotation  12 . The shaft  10  has a plurality of cylindrical portions on which are disposed the pressure or locking ring assembly  14  and the chock bearing  16 . The pressure or locking ring assembly  14  and bearing  16  are mounted on opposite portions of the shaft as best shown in  FIG. 2 . Shaft  10  has a first cylindrical portion  18 , followed by a second cylindrical portion  20  which is smaller in diameter than the first cylindrical portion  18 . A third cylindrical portion  22  is located to the immediate right of the second cylindrical portion  20  and has a diameter at least as large as the first cylindrical portion  18 . The shaft  10  further includes a fourth cylindrical portion  24  located to the immediate right of the third cylindrical portion  22 . The fourth cylindrical portion has a diameter larger than the third cylindrical portion  22 . The shaft  10  further includes a fifth and final cylindrical portion  26  located to the immediate right of the fourth cylindrical portion  24 . The fifth cylindrical portion  26  is larger in diameter than the adjacent cylindrical portion  24  as illustrated in  FIG. 2 .  
         [0025]     The chock bearing  16  is disposed on the fourth cylindrical portion  24  and abuts a shoulder  28  of the fifth cylindrical portion  26 . An annular bearing retainer  32  is disposed on the third cylindrical portion  22  of the shaft  10 . Bearing retainer  32  has a loading face  34  on a first side disposed against the adjacent face or side of the chock bearing  16 . The loading face  34  is configured so as to contact only the annular inner race  36  of the bearing  16  and to avoid contact with the outer race  38 . The bearing retainer  32  has a beveled or inclined surface  40  adjacent the loading face  34 . With such a construction, the loading face  34  avoids contact with the fifth cylindrical portion  28  of the mill roll shaft  10 .  
         [0026]     The inner race  36  of the chock bearing  16  is press fit over the fourth cylindrical portion  24 . The bearing retainer  32  has an annular opening  42  sized to provide a clearance fit over the third cylindrical portion  22  of the mill roll shaft  10 . The bearing retainer  32  has a front or first side  44  in which is provided a plurality of non-threaded apertures or cavities  46  which extend from the first face  44  a predetermined depth into the solid body  47 . The cavities  46  are circumferentially spaced apart with respect to the first axis of rotation  12 .  
         [0027]     The bearing chock or housing  50  of the mill is disposed over the outer race  38  of the bearing  16 . An annular seal plate  52  is fixed to the bearing chock  50  and together with the bearing retainer  32  forms an annular labyrinth seal  54 . The annular seal plate  52  is provided with a plurality of cavities  56  concentrically aligned with openings  58  for receiving threaded fasteners  60  which extend through the seal plate  52  into threaded engagement with the aligned threaded cavities  60  provided in the chock housing  50 .  
         [0028]     The mill roll shaft  10 , when worn out, can be removed from the entire mill assembly and replaced with a new shaft  10  without removing the bearing  16 , chock block or housing  50 , bearing retainer  32  and the pressure or locking ring assembly  14 . The bearing  16  and the bearing retainer  32  are retained by the bearing chock  50  and the seal plate  52 . It is only necessary to remove the reaction means or retaining ring  68  which is disposed on the second cylindrical portion  20  of shaft  10  between the circumferential notch or undercut  70  in the flange  71  of the pressure ring  72  and a shoulder  73  of the first cylindrical portion  18  of the shaft  10 . Thus, only the retaining ring or reaction member  68  needs to be removed to allow the shaft  10  to be pulled from the mill for repair, reconstruction or replacement. The retaining ring  68  is manufactured in multiple parts to facilitate installation and removal from shaft  10  as is known in the art.  
         [0029]     The chock housing  50 , seal plate  52  and bearing retainer  32  may expand to the left when viewed in  FIG. 2  upon thermal expansion of the chock bearing  16 . The amount of thermal expansion or movement permitted is determined by the setting or strength of the pressure screw assemblies  80  carried by the annular pressure ring  72 . Each pressure screw assembly  80  consists of five component parts which will hereinafter be identified. The pressure screw assemblies  80  are effective in conjunction with the axially extending guide pins or rods  84  which are anchored in the cavities  46  of the bearing retainer  32  for allowing for controlled-axial clearance or end play movement of the chock bearing  16 . The adjusting pressure screw assemblies  80  will maintain pressure on the chock bearing  16  while still permitting axial movement of the chock bearing  16  which is required for the chock bearing  16  to seat properly on the shaft  10  and also to provide space for thermal expansion of the chock bearing  16 . The chock bearing manufacturers recommend a range of movement for the chock bearing of 0.010 inch to 0.050 inch, more or less.  
         [0030]     The pressure ring  72  may have any number of pressure screw assemblies  80 , as an example, four pressure screw assemblies  80  per ring up to ten or twelve pressure screw assemblies per pressure ring, depending on the size of the chock bearing. The larger the bearing chock housing, the larger the pressure or locking ring and therefore the larger the pressure screw assemblies.  
         [0031]     Referring now to  FIGS. 2 and 9 , each pressure screw assembly  80  consists of five components namely the pressure screw cylindrical body  90 , a floating thrust pad  92 , a thrust pad bolt  94 , biasing means, as an example, in the form of a coil spring  96  and a spring adjusting screw  98 .  
         [0032]     The pressure screw assembly  80  and the cylindrical pressure screw body  90  has a longitudinally extending axis  100  parallel to and spaced from the shaft axis or first axis of rotation  12  of the mill shaft  10 . The cylindrical body  90  has a pair of end faces  102  and  104 . The longitudinally extending axis  100  extends through the body  90  and the end faces  102  and  104 . The cylindrical body  90  further includes three concentric interconnected cylindrical bores located between the end faces  102  and  104 . The first bore  106  is located adjacent the end face  104 . The second bore  108  is elongated and is located adjacent the other end face  102 . The second bore  108  has an internal first annular abutment surface  110  which is parallel to the end face  102 . Located between the first annular bore  106  and the second annular bore  108  is a third annular bore  110 . The bores  106 ,  108  and  110  are interconnected as illustrated in  FIG. 2 , with the first annular bore  106  being larger in diameter than the other bores  108  and  110 . The second bore  108  is larger is diameter than the third bore  110  which is smaller in diameter than both of the bores  106  and  108 . The second bore  108  is internally threaded so as to receive the threaded adjusting screw  98 . The outer end of the adjusting screw  98  is provided with a hex socket, not shown, to receive or to accommodate a hex-shaped drive tool for rotating the adjusting screw  98 . The cylindrical body  90  has a leading thread  114  and a trailing thread  116 . The threads on the cylindrical body  90  extend throughout the major portion of its length. The remaining portion of the length of the cylindrical body  90  is provided with an external polygonal shaped head  120  between the end face  102  and the trailing thread  116 .  
         [0033]     The floating annular thrust pad  92  has a centrally located threaded bore  126  extending part of the way therethrough as best shown in  FIG. 2 . The floating annular thrust pad  92  is received in the first bore  106  with clearance therebetween and is engageable with the first abutment surface  104 . The bolt  94  has a head  130  at one end and a threaded stem  132  on the other end. The 94 bolt further includes cylindrical portion  134  which separates the head  130  from the threaded end or stem  132 . The cylindrical portion  134  of the bolt  94  provides an annular third abutment surface  136 . The bolt  94  enters the annular cylindrical body  90  through the front face  102  and the second bore  108  where the head  130  is contained in the second bore  108 , the cylindrical bolt portion  134  is retained in the third bore  110  and the threaded stem  132  is threaded into the threaded cavity  126  of the thrust pad  92  which is located in the first bore  106  of the adjusting screw body  90 .  
         [0034]     Biasing means in the form of a coil spring  96  is inserted into the second bore  108  and has one end abutting the head  130  of the bolt  94 . The adjustable externally threaded adjusting screw  98  is threaded into the second bore and has a leading end thereof engaging the other end of the coil spring  96  and urging the spring  96  against the head  130  of the bolt  94 .  
         [0035]     The pressure ring  72  and its annular flange  71  are also slidably disposed over the shaft  10 . The ring  72  has a first side  150  disposed towards the bearing retainer  32  and an oppositely facing second side  152  in which is located a plurality of adjusting apertures  153  extending parallel to the first axis of rotation  12 . Each of the adjusting apertures  153  has a threaded portion  155  between the second side  152  and a point between the first side  150  and second side  152 . Another portion of the apertures  153  defines or provides a substantially smooth guide portion  156  between the threaded portion  155  and the first side  150  of the pressure ring  72 .  
         [0036]     As mentioned previously, the second side of the bearing retainer  32  is provided with a plurality of circumferentially extending cavities  46  which are opposite and spaced from the adjusting apertures  153  in the pressure ring  72 . Each of the cavities  46  of the bearing retainer  32  is provided with an elongated guide pin or rod  84  mounted on one end in the cavity and retained therein by an adjusting screw  154 . The other end of the guide pin  84  is provided with a generally cylindrical head  158  which is received in the opposing smooth guide portion  156  provided in the first side  150  of the pressure ring  72 . It should be noted there is a slight space between the opposing head  158  of the guide pin  84  and the floating pad  92  as best illustrated in  FIG. 2 . This space is eliminated upon the tightening of the adjusting screw  98  and the moving of the bolt  94  and pad  92  to the right as viewed in  FIG. 2 .  
         [0037]     In operation, each of the adjustable externally threaded adjusting screws  98  are tightened to urge the pad  92  against the head  158  of the corresponding guide pin  84  which will prevent any further movement of the thrust pad  92 . Each pressure screw assembly  80  is tightened to provide a solid locking pressure ring  14 , retaining ring  68  and the bearing retainer  32  with the chock bearing  16  thereby locking the chock bearing  16  and shaft  10  into one assembly. Once all of the pressure screw assemblies  80  have been tightened so as to connect all of the component parts mounted on the shaft  10  into one assembly, it is then necessary to provide for thermal expansion of the bearing  16  by backing off each of the adjusting screws  98  a predetermined number of turns, as an example, two turns. This will relax the tension in the coil spring  96  and will thereafter provide for axial movement of the chock bearing  16  while still maintaining some tension on the coil spring  96  providing for some axial clearance which will permit the bearing  16  to float. With this novel construction, the new pressure screw assemblies  80  provide axial clearance for the bearing  16  and bearing housing  50 . Each pressure pad  92  after adjustment is under some constant spring tension. If there is any thrust movement or thermal expansion of the chock bearing  16 , then the bearing  16  will apply some force through the bearing retainer  32  and the guide pins or rods  84  against the floating pressure pads  92  allowing for some clearance or movement of bearing  16 .  
         [0038]     The size of the pressure screw and components will be determined by the size of the pressure or locking ring. The larger the chock housing, bearing and related components, the larger the pressure ring and pressure screw assemblies. The provided clearance and tension will be determined by the bearing design and size and by the requirements of the bearing manufacturer.  
         [0039]     A plurality of annular guide pin or rod retainers  170  are secured to the first side  150  of the pressure ring  72  over each of the adjusting apertures  153 . A central opening  172  is aligned with each of the adjusting apertures  153  and is sized to provide a slidable piloting relationship with the stem of the guide pin or rod  84  as shown in  FIG. 2 . The sliding relationship of the head  158  to the guide portion  156  together with the sliding relationship between the retainer&#39;s primary opening  172  and the cylindrical shank of the guide pin or rod  84 , maintains the locking pressure ring assembly  14  coaxial with the bearing retainer  32 . The guide pin retainers  170  are made of hardened steel to minimize potential wear, providing longer service life without appreciable deterioration of alignment accuracy. Each retainer  170  is located on the side  150  of the pressure ring body  72  by a pair of dowel pins  176 . Socket head screws  178  are used to secure each retainer  170  to the first side  150  of the pressure ring  72 . The guide pin or rod retainer  170  can be integrated into the main body of the pressure ring  72  by providing a blind bore therein from the second side  152  of pressure ring  72  and providing a hole through the first side  150  equal in diameter to the primary opening  172 .  
         [0040]     A plurality of screw lock assemblies  180  are circumferentially spaced and disposed in the body of the pressure ring  72  as shown in  FIGS. 1 and 3 . Each screw lock assembly  180  has a lock aperture  182  in the pressure ring  72  normal to the corresponding pressure screw assembly  80 . A part of the aperture  182  is threaded at  183 . The screw lock assembly  180  includes a steel ball  184 , a spring  186  and a set screw  188 . The ball  184  is disposed in the lock aperture  182  against the externally threaded pressure screw body  90 . The spring  186  is located in the lock aperture  182  between the steel ball  184  and the set screw  188  which threadingly engages the threaded portion  183  of the lock aperture  182 . Tightening of the set screw  188  increases the force from the spring  186  against the steel ball  184 , thereby increasing the torque required to turn the pressure screw body  90 . Thus, the screw lock assemblies  180  maintain the position of the pressure screw bodies  90  in the threaded adjusting apertures  153  located in the pressure ring  72 .  
         [0041]     The pressure ring assembly  72  is installed on the mill roll shaft  12  as follows: a guide pin or rod retainer  170  is slipped over the shank portion of each of the guide pins or rods  84 . Assembled guide pins or rods  84  and retainers  170  are aligned with each of the guide portions  156  of the adjusting apertures  153 , with the heads of the guide pins  84  disposed in guide portions  156 . Dowel pins  176  are installed to position the retainers  170  relative to the adjusting apertures  153 . The socket head screws  178  are then installed to fix the guide pin retainers  170  to the first side  150  of the pressure ring  72 .  
         [0042]     The bearing retainer  32  is then slipped over the mill roll shaft  12  with its loading face  34  disposed toward the chock bearing  16 . The seal plate  52  is slipped over the retainer  32  and fixed to the bearing chock housing  50 . The labyrinth seal  54  formed between the seal plate  52  and the bearing retainer  32  substantially prevents dirt and contamination from reaching the bearing  16 . The pressure ring  72  is next slipped over the mill roll shaft  10  with the extending guide pins  84  directed toward the bearing retainer  32 . The pressure ring  72  is pushed towards the bearing retainer  32 . The primary apertures  172  are aligned with the cavities  46  and the bearing retainer  32 . Each of the axially extending portions of the guide pins  84  are inserted into the cavities  46  of the bearing retainer  32 . The end of each rod  84  bottoms out against the bottom of the cavity  46  as best shown in  FIG. 2 . Thereafter, the set screws  154  are adjusted to retain the rods  84  in cavities  46 .  
         [0043]     The pressure screw assembly  80  are threaded into the threaded portion of the adjusting apertures  153 . The steel balls  184  are deposited one by one in each of the lock apertures  182  and backed up by the springs  186  and set screws  183  which are also installed in the lock apertures  182 .  
         [0044]     The retaining ring or reaction member  68  is slipped into the groove  70 , over the second cylindrical portion  20 . The adjusting screws  98  are then turned so as to tension the spring against the thrust bolt  94  and in turn moves the floating pad  92  against the head  158  of the guide pin or rod  84 . The adjusting screw  98  is tightened to allow no movement of the thrust pad  82 . The tightening of the main pressure screw assembly  80  provides solid locking of the pressure ring  72 , retaining lock ring  68  and bearing retainer  32  to the chock bearing  16  thereby locking the chock  50 , bearing  16  and roll  10  into one assembly.  
         [0045]     It is then necessary to back off the adjusting screws  98  a predetermined number of turns, as an example, two turns. This will relax the tension in the coil springs  96  and will provide for axial movement of the chock bearing  16 , while still maintaining some tension that will allow the bearing  16  to float and provide axial clearance for thermal expansion.  
         [0046]     Throughout the travel of the adjusting pressure screws  98 , the guide pins  84  are maintained in an axial orientation by the cooperation of the guide pin flanges or retainers  170  and the primary apertures or openings  172  with the cylindrical shank portions of the rods  84 . The desired level of thrust load against the chock bearing  16  is then developed by the pressure screws  98  acting against the heads  158  of the guide pins or rods  84 . When the pressure screws  98  are fully installed, they are nearly flush with the second side of the pressure ring  72 . The set screws  188  of the screw lock assemblies  180  are tightened to prevent any loss of thrust load against the bearing  16  during operation of the mill. The pressure screw assemblies  80  are prevented from backing out or loosening by the pressure exerted on them by the screw lock assemblies  180 .  
         [0047]     The force applied against each pressure screw assembly  80  by the steel ball  184  is variable, depending on the amount of the spring  186  that is compressed by the set screw  188 . The set screws  188  can, of course, be partially unthreaded to reduce the force against the pressure screw assemblies  80  to allow their adjustment. After adjusting the pressure screw assemblies  80 , the set screws  188  can be retightened against the springs  183  to relock the pressure screw assemblies  80 .  
         [0048]     With the interface between the multi part pressure screw assembly  80  and the head  158  of the guide pin or rod  84  being effectively sealed off and protected from contaminants within the adjusting aperture  153 , a highly reliable and sustainable bearing retaining load is achieved with the present locking ring assembly.  
         [0049]     Other aspects, objects, features and advantages of the present invention can be obtained from a study of the patent drawings, the disclosure and the appended claims which follow.