Optical cable installation with mini-bend reduction

Abstract

A cable straightener removes mini-bends from cable as it is unwound from a reel for installation in an underground duct, providing improved blowing performance for any cable with non-negligible stiffness and that exhibits reel-set or shape memory recovery, for example cables enclosed within small diameter tubular steel jackets, cables enclosed within aluminum laminated polymer sheets, and cables enclosed within hard polymer tubing. Residual stresses induced in such cables are reduced by first and second sets of straightener rollers prior to pushing/blowing installation.

1 . A method for installing a cable in a duct comprising the steps: 
 unwinding the cable from a reel, reducing bends in the cable, and then inserting the cable into the duct.    
     
     
         2 . A method for installing a cable in a duct comprising the steps: 
 uncoiling the cable from a length of coiled cable, laid in “figure-eights” on the ground or stored in a coiling device, reducing bends in the cable, and then inserting the cable into the duct.    
     
     
         3 . A method for installing a cable in a trajectory duct comprising the steps: 
 receiving the cable from a previous tandem duct section, reducing bends in the cable, and then inserting the cable into the trajectory duct.    
     
     
         4 . A method according to claims  1 ,  2  or  3 , where the step of reducing bends in the cable is performed by advancing the cable through one or more sets of straightener rollers.  
     
     
         5 . A method according to claims  1 ,  2  or  3 , where the step of reducing bends in the cable is performed by advancing the cable through first and second sets of straightener rollers, including the step of reducing cable bends along a first plane in the first roller set and reducing cable bends along a second plane in the second roller set, where the second plane extends transversely with respect to the first plane.  
     
     
         6 . A method according to claims  1 ,  2  or  3 , where installing the cable is performed by pushing and/or blowing with compressed gas fed into the duct with a speed at least higher than the installation speed of the cable.  
     
     
         7 . A method according to claims  1 ,  2  or  3 , where inserting the cable is performed by pushing and/or blowing with compressed gas fed into the duct, the compressed gas exerting a pushing force on a piston device attached to the end of the cable.  
     
     
         8 . A method according to claims  1 ,  2  or  3 , where inserting the cable is powered by a pushing force developed by gripping the cable between a set of rotatable tractor treads.  
     
     
         9 . A method according to claims  1 ,  2 , or  3 , where inserting the cable is powered by a pushing force developed by gripping the cable between a set of rotary wheels.  
     
     
         10 . A method according to claims  1 ,  2  or  3 , where inserting of the cable is performed by pushing and/or flowing with liquid pumped into the duct at a flow speed at least higher than the installation speed of the cable.  
     
     
         11 . A method according to claims  1 ,  2  or  3 , where inserting of the cable is performed by pushing and/or flowing with liquid pumped into the duct, the liquid exerting a pushing force on a piston device attached to the end of the cable.  
     
     
         12 . Apparatus for installing a cable in a duct which comprises a chamber with an inlet for the cable, an inlet for gas or liquid and an outlet for the gas or liquid coupled to the duct, with mechanically driven wheels or tractor treads to push the cable into the duct, characterized by a straightener roller set engageable with the cable for reducing cable bends before the cable is introduced into the duct.  
     
     
         13 . Apparatus according to  claim 12  where the chamber, the gripping wheels or tractor treads and the straightener roller set are integrated.  
     
     
         14 . A method for installing a cable in a cable duct, comprising: 
 introducing a fluid under pressure into the cable duct at an inlet end thereof;    supplying a length of cable to be installed;    straightening the cable; and    feeding the cable into the cable duct through the inlet end thereof.    
     
     
         15 . A method according to  claim 14 , including the steps: 
 supplying the cable to be installed from a reel; and    rotating the reel as the cable is unwound and fed into the duct.    
     
     
         16 . A method according to  claim 14 , wherein the straightening step is performed before the cable is fed into the duct.  
     
     
         17 . A method according to  claim 14 , including the step: 
 providing the cable with a core of one or more optical fibers and enclosing the core within a tubular metal jacket.    
     
     
         18 . A method according to  claim 14 , including the steps: 
 supplying the cable to be installed from a coiling device; and    advancing the cable through a curved guide loop duct of about one turn.    
     
     
         19 . A method for installing a cable of the type including a core of one or more optical fibers, comprising the steps: 
 increasing the stiffness of the cable by enclosing the core within a small diameter tubular metal jacket;    straightening the cable; and    installing the straightened cable, by blowing and/or pushing, in a tubular duct.    
     
     
         20 . A method for installing a cable in a trajectory duct comprising the steps: 
 coiling the cable from a reel into a coiling device via a looped guide duct of about one turn, uncoiling the cable from the coiling device and advancing it through the looped guide duct, and pushing and/or blowing the cable into the trajectory duct.    
     
     
         21 . An improved cable coiling apparatus of the type including a frame, a coiling basket mounted on the frame, a fixed guide arm mounted on the frame, a spinning guide arm mounted for rotation on the frame and multiple pairs of guide wheels mounted on the fixed guide arm and on the spinning guide arm for engaging a length of cable and guiding the cable during cable coiling and uncoiling operations, wherein the improvement comprises: 
 the fixed guide arm including a curved arm portion leading to the frame and multiple pairs of guide wheels mounted on the curved arm portion for engaging a length of cable and guiding the cable during coiling and uncoiling operations; and    multiple pairs of guide wheels mounted on the frame and extending along a curved path forming a guide loop of about one turn for engaging a length of cable and guiding the cable into and out of the coiling basket during coiling and uncoiling operations.    
     
     
         22 . Improved cable coiling apparatus according to  claim 21 , wherein the frame includes a substantially circular frame member and the multiple guide wheels defining the guide loop are mounted on the circular frame member.  
     
     
         23 . Improved cable coiling apparatus according to  claim 21 , wherein the guide wheels of each pair are separable to allow initial placement and loading of the length of cable along the guide loop.  
     
     
         24 . Improved cable coiling apparatus according to  claim 21 , wherein the coiling basket has a coiling radius and the radius of curvature of the guide loop is substantially equal to the coiling radius.  
     
     
         25 . Improved cable coiling apparatus according to  claim 21 , wherein the coiling basket has a coiling radius and the extended portion of the fixed guide arm is curved so that the multiple pairs of guide wheels mounted on the curved arm portion define a curved guide loop having a radius of curvature that is substantially equal to the coiling radius.  
     
     
         26 . Cable installation apparatus comprising, in combination: 
 a cable coiling apparatus for storing a length of cable to be installed in a duct;    a cable insertion unit with mechanically driven wheels or tractor treads for pushing the cable into the duct; and    a cable straightener disposed between the cable coiling apparatus and the cable insertion unit, the cable straightener including a straightener roller set engageable with the cable before it enters the cable insertion unit.    
     
     
         27 . Cable installation apparatus according to  claim 26 , and further including apparatus forming a guide loop of about one turn disposed between the cable coiling apparatus and the cable straightener.  
     
     
         28 . Cable installation apparatus according to  claim 27 , wherein the guide loop apparatus comprises a tubular duct having a first open end and a second open end through which the cable to be laid is extended, and the tubular duct is arranged along a curved path.  
     
     
         29 . Cable installation apparatus according to  claim 27 , wherein the cable coiling apparatus includes a curved frame member and the guide loop apparatus comprises multiple pairs of guide wheels mounted on the curved frame member.  
     
     
         30 . Cable installation apparatus according to  claim 27 , wherein the guide wheels constrain the cable to follow along a cable guide path having a radius of curvature that is substantially equal to the coiling radius of the cable coiling apparatus.  
     
     
         31 . A method for installing a cable in first and second tandem trajectory ducts comprising the steps: 
 supplying a first length of the cable to be installed from a reel;    installing the first length of the cable by pushing and/or blowing the cable into the first trajectory duct;    coiling a second length of the cable from the reel into a coiling device via a looped guide duct of about one turn;    uncoiling the cable from the coiling device and advancing it through the looped guide duct; and    pushing and/or blowing the second length of cable into the second trajectory duct.    
     
     
         32 . An improved cable coiling apparatus of the type including a frame, a coiling basket mounted on the frame, a fixed guide arm mounted on the frame, a spinning guide arm mounted for rotation on the frame and multiple pairs of guide wheels mounted on the fixed guide arm and on the spinning guide arm for engaging a length of cable and guiding the cable during cable coiling and uncoiling operations, characterized by apparatus forming a guide loop of about one turn disposed adjacent the frame, wherein the guide loop apparatus comprises a tubular duct having a first open end and a second open end through which the cable is fed during coiling operation and through which the cable is advanced during an uncoiling operation.