Patent Abstract:
A jackscrew nut and/or bolt head assembly includes a bottom washer that is interlocked via circumferentially arrayed castle extensions and recesses. Spherical faces at the washer top are thereby held in alignment with corresponding spherical jackscrew bottoms, which assures evenly distributed contact pressures during out of angle elastic jackscrew displacement during jackscrew loading. The bottom washer interlock may provide further for a transfer of a primary pre tightening torque exerted onto the main body of the nut and/or bolt head via a tool that concurrently accesses all jackscrew heads extending above the main body. The assembly may be initially tightened via the primary torque whereby secondary jackscrew actuation and displacement is greatly reduced. The jackscrews are thinned in reverse for maximum contact area at their spherical bottoms.

Full Description:
CONTINUATION IN PART 
       [0001]    The present invention is a Continuation in Part of the U.S. patent application Ser. No. 13/898,674 titled “Dual Actuated Jackscrew Nut And/Or Bolt Head” filed on May 21, 2013 of the same inventor. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates to jackscrew nuts and bolt heads. 
       BACKGROUND OF INVENTION 
       [0003]    Jackscrew nuts and bolt heads circumvent the need for high power torque wrenches, especially with larger bolt diameters. Instead of having to tighten one nut or bolt head with high torque and big tool to bring the respective central thread connection to the required load, a number of circular arrayed jackscrews that are screwed in the nut and/or bolt head are sequentially tightened with comparatively low torques requiring only comparatively small tools. The jackscrews thereby lift off and the nut and/or bolt head from their flange position as is well known in the art. 
         [0004]    The single actuation of nut and/or bolt head via jackscrews commonly requires extensive repetitive actuation of the individual jackscrews to induce the overall loading lift off. A substantial portion of that overall loading lift off is commonly needed in comparatively low overall nut and/or bolt load range, which would require relatively low tightening torque on the nut and/or bolt head. This in turn would substantially reduce overall jackscrew actuations. Therefore, there exists a need for a jackscrew nut and/or bolt head that provides for a dual actuation such that low load displacement may be accomplished by tightening the nut and/or bolt head directly and such that the final loading may be provided via the jackscrews. The present invention addresses this need. 
         [0005]    During final tightening of jackscrews, contact pressures between the jackscrew bottom and the opposing washer or flange commonly cause galing between the surfaces. This substantially increases friction in the interface. In addition to load related elastic deformations and due to necessary loose thread connections, the jackscrews are forced out of their natural assembly direction. This causes edge contact of the jackscrew bottom, which increases local peak stresses and galing even more. In the prior art it has been attempted to reduce this issue by making the jackscrew bottom slightly spherical. Nevertheless a spherical surface pressing against a planar surface causes again high peak stresses and galing. Therefore, there exists a need for a nut and/or bolt head jackscrew assembly incorporating a load washer with spherical faces that are held in alignment with spherical jackscrew bottoms. The present invention addresses also this need. 
         [0006]    Jackscrew nuts and/or bolt heads commonly need to be utilized at radially tight locations, while at the same time providing pre tightening and an interlocking between the nut and/or bolt head and a washer. The present invention addresses also this need. 
       SUMMARY 
       [0007]    A jackscrew nut and/or bolt head assembly includes a circumferentially and radially interlocked load washer. Spherical faces at the washer top are thereby held in alignment with corresponding spherical jackscrew bottoms. The spherical-to-spherical jackscrew-washer interface assures evenly distributed contact pressures during out of angle elastic jackscrew displacement and minimizes galing. 
         [0008]    The circumferential and radial interlocked load washer provides further for a transfer of a primary torque exerted onto the main body of the nut and/or bolt head via an assembly torque access, which may be a standardized outside spline such as well known triple square, twelve spline or the like. The assembly torque access may be incorporated at the top and/or circumference of the nut and/or bolt head. In case it is incorporated at the circumference, the assembly torque access may also be incorporated into the load washer in a fashion such that load washer and nut and/or bolt head may have the primary torque concurrently applied. 
         [0009]    The washer interlock may be provided by a castle shaped top of the load washer that interlocks with corresponding recesses at the bottom of the nut and/or bolt head. In addition, the jackscrews may be reversed thinned with a bottom diameter larger than a central thread diameter, which in turn is larger than a jackscrew top diameter. The top diameter may be provided by a top shaft that is guided in a corresponding top guide hole of the nut and/or bolt head. At the same time a bottom guide shaft of the jackscrew is guided in bottom guide hole within either a washer castle or the nut and/or bolt head. This keeps the jackscrew thread free of tilting forces that may occur during elastic deformation of the nut and/or bolt head during tightening. Also, the larger bottom diameter maximizes area contact and minimizes contact pressures with the load washer. The jackscrew heads may have radial recesses for applying torque to the jackscrew. Circumferential portions of the jackscrew heads may have a continuous diameter such the circular arrayed jackscrew heads may be together accessed by pre tightening tool. An overall outside diameter of the nut and/or bolt head may be kept to a minimum while providing a more centralized tool access to the individual jackscrew heads. This may be of particular advantage in tight applications of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0010]      FIG. 1  is a front perspective view of a first embodiment of the invention in a nut configuration. 
           [0011]      FIG. 2  is a partial cut view of  FIG. 1 . 
           [0012]      FIG. 3  is a bottom perspective view of a partial assembly of  FIG. 1 . 
           [0013]      FIG. 4  is a front perspective view of a second embodiment of the invention in a nut configuration 
           [0014]      FIG. 5  is a front perspective partial cut view of a third embodiment of the invention in a bolt head configuration. 
           [0015]      FIG. 6A  is front perspective partial cut view of a fourth embodiment of the invention in nut configuration with a pre tightening tool above . 
           [0016]      FIG. 6B  shows a jackscrew of the fourth embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    According to a first embodiment of the invention and referring to  FIGS. 1-3  a jackscrew tightening assembly  1000  may feature a central thread  1002  with a thread axis  1005 . In case of the jackscrew tightening assembly  1000  being a nut, the central thread  1002  may be an internal thread. In case of the jackscrew tightening assembly  1000  being a bolt head, the central thread  1002  may be an external thread as shown in  FIG. 5 . Parts of the jackscrew tightening assembly  1000  are a main body  1008 , jackscrews  1026 , a load washer  1035  and a washer interlock  1044 . The main body  1008  is extending radial outward with respect to the central thread  1002  as is well known for jackscrew nuts and/or bolts. The main body  1008  has a main top  1011 , a main bottom  1014  that is opposite the main top  1011  in axial direction with respect to the central thread axis  1005 , through holes  1017  with a through hole axis  1020  that is in an offset to the central thread axis  1005 , and a secondary thread  1023  at least along a portion of the through hole  1017 . The jackscrews  1026  are extending through respective through holes  1017 , and engaging via their jackscrew threads  1027  with the respective secondary threads  1023 . The jackscrews  1026  have jackscrew heads  1029  facing away from the main bottom  1014  and spherical bottoms  1032  facing away from the main top  1011 . The jackscrews  1026  are preferably arrayed in a number around the central thread  1002  such that upon even tightening of all jackscrews  1026  the axial sum of all their individually exerted axial loads is transferred onto the central thread  1002  in a balanced fashion via the main body  1008  as may be well appreciated by anyone skilled in the art. 
         [0018]    The load washer  1035  is adjacent the main bottom  1014  and surrounding the central thread  1002 . The load washer  1035  has a washer top  1038  that is facing the main bottom  1014  and a number of spherical faces  1041  that are formed into the washer top  1038 . The spherical faces  1041  are matching their respective spherical bottoms  1032  and are in substantial axial alignment with them and rotationally symmetric with respect to the central thread axis  1005 . The load washer  1035  is at least circumferentially but preferably also radial held with the main body  1008  via a washer interlock  1044  that includes a first interlock feature  1047  provided by the load washer  1035  and a second interlock feature  1050  that is at least circumferentially but preferably also radial mating the first interlock feature  1047  and that is part of the main body  1008  such that the spherical faces  1041  are held in alignment with respective spherical bottoms  1032 . The first interlock feature  1047  may be an internal spline that is axially extending through a central through hole  1039  of the load washer  1035 . The second interlock feature  1050  may be an external spline axially extending from the main bottom  1014 . According to  FIGS. 1 ,  2 , the second interlock feature  1050  may be a body contour  1062  axially extending from the main bottom  1014  towards the main top  1011  and the first interlock feature may be one or more protrusions axially extending above the washer top  1038 . 
         [0019]    Further part of the jackscrew tightening assembly  1000  may be an assembly torque access  1053  via which a primary torque may be externally applied to the jackscrew tightening assembly  1000 . The assembly torque access may be part of at least one of the main body  1008  and the load washer  1035  such that the primary torque that is applied to at least one of the main body  1008  and the load washer  1035  is also applied via the washer interlock  1044  to one other of the main body  1008  and the load washer  1035  while the spherical bottoms  1032  remain in substantial axial alignment with their respective spherical faces  1041 . The assembly torque access  1053  may be a body outside contour  1063  that at least in part corresponds to a well known twelve spline, triple square standard or the like. The body outside contour may also serve as the second interlock feature  1050 . Part of the assembly torque access  1053  may also be a load washer contour  1065  that is axially substantially collinear with the body outside contour  1063  such that the primary torque may be concurrently applied to both the main body  1008  and the load washer  1035  with the same tool as may well appreciated by anyone skilled in the art. 
         [0020]    According to  FIG. 3 , the assembly torque access  1053  may be a body top spline  1068  protruding from the main top  1011 . The body top spline  1068  may have jackscrew access recesses  1071  that are radial recessed into it such that the jackscrew heads  1029  are accessible while the body top spline  1068  radial extends in between the jackscrew heads  1029 . 
         [0021]    Referring to  FIG. 5 , the main body  1008  and the load washer  1035  may be circumferentially and radial held together via interlock shafts  1074  of the jackscrews  1026  engaging with receptacles  1077  formed into the load washer  1035 . Receptacle disks  1080  featuring the spherical faces  1041  may be placed inside and preferably at the bottom of the receptacles  1077 . Their small size provides for a cost effective fabrication of them with superior hardness of at least their spherical faces  1041 , which may further reduce risk of galing in the interface as may be well appreciated by anyone skilled in the art. At the same time, the load washer  1035  may be fabricated from a less hard and brittle material making it less susceptible to cracking due to out of balance peak loading from the jackscrews  1026  as may also be well appreciated by anyone skilled in the art. 
         [0022]    The interlock shafts  1074  may be accessed via the axial gap between the main body  1008  and the load washer  1035  by a hook tool  700  having a hook  702  corresponding to the diameter of the interlock shafts  1074 . By use of the hook tool, the primary torque may be applied for initially tightening the main body  1008 . 
         [0023]    The hook tool  700  provides torque transfer with only partial circumferential access to the main body  1008 , which may be advantages in tight locations. 
         [0024]    At least one of the jackscrews  1026 , the load washer  1035 , the main body and the receptacle disks  1080  may be permanently magnetic to assist in keeping the jackscrew tightening assembly  1000  together during its installation and handling. The through hole axes  1020  may be in an angle to the central thread axis  1005  such that the jackscrew heads  1029  are closer to the central thread axis  1005  than the spherical bottoms  1032 . This may advantageously provide for a more centralized access to the jackscrew heads  1029  with a tightening tool, while at the same time keeping the most outward diameter of the main body  1008  to a minimum. 
         [0025]    In case the load washer  1035  is configured as a well known lock washer with one directional serrations on its bottom or other features preventing the load washer  1035  from being rotated in loosening direction of the main body  1008 , the jackscrews  1026  may be loosened to the extent that the jackscrew shafts  1074  disengage from the receptacles  1077  and the main body  1035  rests directly on the washer top  1038  prior to loosening the main body  1008 . That way, the locking load washer  1035  may remain stationary while the main body  1035  slides on the washer top  1038 . To provide still a gap for hook tool  700  access, the main body  1008  may have a central circular rim extending downward from the main bottom  1014 . 
         [0026]    Referring to  FIGS. 6A and 6B , in a fourth embodiment of the invention the main body  1008  features top guide holes  1022  that are extending from the main top  1011  concentric with respect to their through hole axes  1020 . The secondary threads  1023  are adjacent and below the top guide holes  1022  and concentric with respect to their respective top guide hole  1022 . Recessed into the main bottom  1014  are a number of castle recesses  1058  and preferably circumferentially evenly arrayed. Bottom guide holes  1024  are extending from the main bottom  1014  and are also concentric with their respective top guide holes  1022 . 
         [0027]    The jackscrews of the fourth embodiment have preferably each a top guide shaft  1072  in addition to the bottom guide shaft  1074 . Each top guide shaft  1072  is adjacent the jackscrew head  1029  and in between the jackscrew head  1029  and the spherical bottom  1032 . The top guide shafts  1072  are guided in respective top guide holes  1022 . The load washer  1035  has a number of castle extensions  1057  that extend above the washer top  1038 . Castle guide holes  1078  are recessed into the castle extensions  1057  and have spherical faces  1041  formed at their bottom preferably horizontally leveled with the spherical faces  1041  that are formed into the washer top  1038 . While the load washer  1035  is in mating contact with the main body  1008 , the castle extensions  1057  are interlocking with the castle recesses  1058  axially with respect to the central thread axis  1005 . The bottom guide shafts  1074  are preferably guided circumferentially alternating in either the bottom guide holes  1024  or the castle guide holes  1078 . 
         [0028]    The bottom guide shaft  1074  has a bottom diameter BD that is preferably larger than the jackscrew thread  1027  diameter THD. The top guide shaft  1072  has a top diameter TD that is smaller than the jackscrew thread  1027  diameter THD. The jackscrew heads  1029  may have circumferentially continuous circle portions that are circumferentially interposed with a radial torque access recess. This provides on one hand torque access to individual jackscrews  1026  with correspondingly shaped nuts as is well known in the art. On the other hand, the jackscrews  1026  may be concurrently accessed with a jackscrew assembly tightening tool  800  that has an array of jackscrew head access holes  802  on its tool bottom  803 . The jackscrew head access holes  802  are preferably circumferentially arrayed and are matching the jackscrew head  1029  pattern on above the main top  1011 . The jackscrew head access holes  802  are close to an outer tool diameter TOD that is preferably smaller than an outer main body diameter BOD. This greatly improves access clearance especially in tight situations, which is made possible due to the even load transfer over a large number of jackscrew heads  1029  and their top guide shafts  1072  that hold the jackscrew heads  1029  rigid against out of axis bending, which may be well appreciated by anyone skilled in the art. A tool access  801  on the tool top  804  may be a square hole for coupling with a hydraulic torque wrench as is well known in the art. 
         [0029]    During tightening of the jackscrews  1029  the main body  1008  may come under load and elastically deflect radially outward at the main bottom  1014 . To keep the castle guide holes  1078  raidally aligned with top guide holes  1022  in that case, a castle spacing between adjacent castle extensions  1057  may have an outer castle spacing CLO that is less than an inner castle spacing CLI. In that way, the castle recesses  1058  are radially opposed by the castle extensions  1057  while the main bottom  1014  may elastically deform in direction away from the central thread axis  1005 . 
         [0030]    In the fourth embodiment, the jackscrews  1029  are screwed in from the main bottom  1014  and from the castle recesses  1058 . The load washer  1035  is than mated with the main body  1008  and the spherical bottoms  1032  brought into contact with spherical faces  1041 . Main body  1008  and load washer  1035  are together screwed on and/or in at their assembly location. Then the pre tightening tool  800  may be coupled with the jackscrew tightening assembly  1000  by mating its jackscrew head access holes  802  with the jackscrew heads  1029 . The pre tightening tool  800  may be coupled to a hydraulic torque wrench via its tool access  801  and a pre tightening torque conveniently applied to the main body  1008  via the jackscrew heads  1029 . The top guide shafts  1072  assist thereby to transfer the pre tightening force onto the main body  1008 . After removing the pre tightening tool  800 , the individual jackscrew heads  1029  may be accessed to bring the jackscrew tightening assembly  1000  up to final loading. Loosening of it may be performed in reverse as may be clear to anyone skilled in the art. 
         [0031]    Accordingly, the scope of the Figures and the Specification above is set forth by the following claims and their legal equivalent:

Technology Classification (CPC): 5