Abstract:
A brake tensioning system and method are described herein for use on vehicles. The system includes a tool, and the method includes the use of the tool to effectuate tensioning of a brake system conveniently, accurately, and repeatably.

Description:
RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 60/953,185, filed Jul. 31, 2007, and entitled “System and Method for Tensioning a Brake System,” which is incorporated by reference as if fully disclosed herein. This application also incorporates by reference U.S. patent application Ser. No. 10/369,989, filed Feb. 18, 2003, and entitled “Method and Apparatus for Tensioning an Emergency Brake System on a Vehicle,” now U.S. Pat. No. 7,331,255; and U.S. patent application Ser. No. 10/254,050, filed Sep. 23, 2002, and entitled “Method and Apparatus for Tensioning an Emergency Brake System on a Vehicle,” now U.S. Pat. No. 7,331,254, both of which are incorporated by reference as if fully disclosed herein. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to apparatus and methods associated with the tensioning of an emergency brake system on a vehicle, and more particularly to an end effector that receives a nut and cable assembly and acts in conjunction with a tool and associated method to tension the brake system to the desired tension level. 
     BACKGROUND OF THE INVENTION 
     Conventional apparatus used in the assembly of emergency brake cable systems often require more than one person and more than one station on an assembly line for adequate installation and tensioning. Once the emergency brake cable system is initially installed, one assembly worker typically first tensions the system to the desired level, at which the voids are removed from the cable and the conduits through which the cable runs. At a second assembly position, a second assembly worker then typically reduces the tension in the system in a variety of ways so that the emergency brake cable system is not causing the brakes to be engaged. The existing systems require more than one assembly worker and more than one station, and thus are a relatively expensive endeavor. 
     A further limitation of the existing brake cable system installation technology is that the tension in the cable system is typically measured by indirect methods, such as strain gauges and other types of transducers. This means that the actual tension in the brake cable system, which is important to the proper functioning of the emergency brake, is at best characterized and not directly known during the assembly process. This indirect tension measurement has limited measurement accuracy, and thus causes there to be a relatively wide variation in the ultimate tension at which the emergency brake cable system is assembled in a vehicle. This creates unwanted variations in the emergency brake cable system operation on the finished vehicle. 
     Some other emergency brake tensioning systems have reduced the human element involved in the process by use of automated mechanisms. However, these systems use hydraulics or pneumatics as part of the process, which may lead to maintenance problems, cleanliness issues, tension measurement inaccuracies, and generally to a more complicated and inconvenient system. 
     What is needed is an emergency brake cable tensioning method and apparatus that overcomes the above issues, and allows fewer resources to be used in tensioning the cable system, thus saving money in the assembly process and ultimately allowing automobiles to be manufactured more efficiently. In addition, what is needed is an emergency brake cable tensioning method and apparatus that allows the direct measurement of the tension of the brake cable system during assembly to allow the accurate tensioning of the emergency brake cable system for proper performance in the finished vehicle. These and other advantages provided by embodiments of the present invention will be recognized from the following descriptions of embodiments of the invention. 
     SUMMARY OF THE INVENTION 
     In overcoming the shortcomings noted above, an inventive tensioning tool and associated method are described herein that, among other things, selectively create a mechanical column coupling to allow for the accurate measurement of the tension developed in an emergency brake tensioning system. 
     In one aspect of the invention, a tensioning tool for use in tensioning an emergency brake cable system for a vehicle is provided, the apparatus being driven by a rotational driver, and the brake system including a rotatable cable end. The apparatus includes a main body, a first portion movably positioned in the main body for engaging the cable end, the first portion movable between a first position and a second position, a second portion movably positioned in the main body and operably engaging the first portion, a locking mechanism associated with the main body and the second portion, the locking mechanism selectively actuable between a locked and unlocked engagement with the second portion, a release mechanism associated with the main body, the release mechanism actuable to unlock the locking mechanism from the second portion, wherein insertion of the cable end into the first portion and movement of the first portion to the second position causes the second portion to move to the second position and actuate the locking mechanism. 
     In a continuing aspect of the invention noted above, the main body includes a barrel portion, the first portion includes an input shaft positioned inside the barrel portion and that is movable relative thereto between the first position and the second position, the second portion including a piston assembly positioned inside the main body and being operably associated with the input shaft, and being movable relative to the main body between the first position and the second position, the locking mechanism mounted on the body and being operably engageable with the piston assembly to hold the piston assembly in the second position when actuated, and to allow the piston assembly to return to the first position upon deactuation, a release mechanism mounted on the main body and movable relative thereto and being operably associated with the locking mechanism to selectively de-actuate the locking mechanism, and wherein insertion of the cable end into the input shaft and movement of the input shaft into the barrel to the second position moves the piston assembly into the second position and actuates the locking mechanism to hold the piston assembly in an axial position relative to the barrel, and actuation of the release mechanism deactuates the locking mechanism and allows the input shaft and the piston assembly to return to the first position. The main body and the piston assembly may become a rigid mechanical column upon actuation of the locking mechanism in the second position. 
     In another aspect of the invention described herein, an apparatus for use in tensioning an emergency brake cable system for a vehicle is disclosed, the apparatus being driven by a rotational driver, and the brake system including a rotatable cable end, the apparatus including a main body having a rotatable portion rotatably movable and axially movable relative to the main body and adapted to receive the cable end, a tension measuring device, such as a load cell or other similar device, operably associated with the rotatable portion, and a first moving portion and a second moving portion, each of the first and second moving portions moving axially relative to the main body. The first and second moving portions having a first position wherein the cable end is movable relative to the rotatable portion, and a second position wherein the cable end is rotationally fixed relative to the rotatable portion, and wherein movement of the first movable portion from the second position to the first position causes the second movable portion to move to the first position and release the cable end. Further to this example, the first moving portion is positioned substantially external to the main body, and the second moving portion is a slider positioned substantially internal to the main body. 
     A method of practicing the invention is described herein and includes tensioning a brake system on a vehicle comprising the acts of inserting a cable end into a tool, manually actuating a locking mechanism to engage the cable end to establish a tensioning condition, tensioning the cable, and manually deactuating the locking mechanism to disengage the cable from the tool. Further to this method, the manually actuating step creates a rigid mechanical column against which to measure tension in the cable. 
     While multiple embodiments of the present invention are disclosed herein, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. As will be realized, by those of ordinary skill in the art upon reading the following disclosure, the invention is capable of modifications in various aspects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a diagram of an exemplary emergency brake cable system to be tensioned by the inventive tensioning tool and associated method as described herein. 
         FIG. 2  is a perspective view of the tensioning tool of the present invention, prior to mounting the nut in the end effector. 
         FIG. 3  is a side view of the tensioning tool of  FIG. 2 . 
         FIG. 4  is an end view of the tensioning tool of  FIG. 3 . 
         FIG. 5  is a section view taken along line  5 - 5  of  FIG. 4 , showing the tensioning tool of the present invention prior to receiving a nut in the end effector, and with the input shaft and piston assembly in their forward-most position. 
         FIG. 6  is a section view similar to that of  FIG. 5 , but after the nut has been inserted into the end effector, and prior to moving the input shaft and piston assembly rearwardly relative to the barrel and housing. 
         FIG. 7  is a section view similar to that of  FIG. 6 , but after the input shaft and piston assembly have been moved rearwardly into the barrel and housing, causing the release ring to move forward and actuate the locking mechanism to form a rigid mechanical column structure. 
         FIG. 8  is a section view similar to that of  FIG. 7 , but after the nut runner has been actuated to rotate the input shaft to turn the nut up the threaded rod and tension the associated cable system. 
         FIGS. 9   a  and  9   b  are an exploded view of the inventive tensioning tool showing the components associated therewith as described with respect various figures listed above. 
         FIG. 10  shows a section view similar to that of  FIG. 5 , for an alternative embodiment of the invention, where the release ring has a different structure for engaging the barrel in its forward-most position. 
         FIG. 11  shows a section view similar to that of  FIG. 8 , for the alternative embodiment of the invention shown in  FIG. 10 , with the nut positioned in the end effector and having been run up the threaded rod to tension the associated emergency brake cable system. 
     
    
    
     DETAILED DESCRIPTION 
     The instant invention is embodied in a tensioning apparatus attachment to a drive tool, such as a ratchet, nut runner, or other type of wrench, used for tensioning the park brake cable system of an automobile during assembly. A schematic of one embodiment of the present invention and the system in which it works is shown in  FIG. 1 .  FIG. 1  illustrates a side pull park brake system  100 . In the park brake system  100  in which this invention is described, there is a front cable  102 , a rear right cable  104  and a rear left cable  106 . The front cable  102  is attached to a pull handle  108  at its first end and at its second end it is attached to a connector clip  110 , which in turn attaches to the front end of the rear right cable  104 . The rear right cable extends towards and attaches to the brake assembly  112  on the rear right wheel. The front cable  102  and the rear right cable  104  could be one continuous cable, however, it has been found more convenient to have them be separate cables for ease of manufacturing. The rear left cable  106  is attached to the front cable  102  through a reactive conduit system  114  as is well-known in the art. In the instant embodiment, the front end of the rear left cable  106  is attached to one end of an equalizer bracket  116 , which is in turn attached to and part of the reactive conduit system  114 . The rear end of the rear left cable  106  is attached to the rear left brake assembly  118 . 
     The operation of a reactive conduit side pull park brake system  100  is well-known. The problem solved by the present invention is that the tensioning of the system during assembly is made significantly more convenient by use of a tensioning apparatus  120  conforming to the present invention in combination with a drive means  122 , which results in an accurately tensioned cable system. In addition, the use of a tensioning apparatus  120  can reduce overall costs of building the park brake system into a vehicle during assembly, it can improve quality, and its use can reduce labor costs. 
     The front end of the rear left cable  106  includes a threaded rod  124  of approximately one-half inch to four inches long. The free end of the threaded rod is positioned through an aperture in the end of the equalizer bracket  116  and a nut  126  is positioned on the free end of the threaded rod  124  in order to hold the threaded rod in attachment with the equalizer bracket. The tensioning apparatus  120  and the drive means  122  are used to tension the entire park brake cable system to remove voids and stretch from the various park brake cables so that the park brake cable system  100  functions appropriately during the use of the vehicle, and to lessen slackening or loosening. The particular tensioning apparatus  120  by itself, or in combination with the drive means  122  (collectively referred to as the “park brake tensioning system”), which are used together to tension the park brake system, incorporate the present invention. 
     One of the brake system assembly benefits provided by the park brake tensioning system of the present invention involves the utilization of a relief distance. The relief distance is the distance that the end of the cable being used to tension the system is allowed to relax after the tensioning of the system has been performed. Relaxation of the tension releases the engaged brakes from the drums, or the calipers from the disk (for disk brakes), just enough to allow the wheel to turn freely while keeping a sufficient level of tension in the park brake system in order to easily engage the parking brake. 
     Note that the tensioning method and apparatus of the present invention can be implemented at any place in a park brake cable system where there is an action/reaction point, such as where the park brake handle attaches to the front cable, where the rear cable is attached to the brake assemblies, where the front cable and rear right cable attach together, or other locations. 
     Referring still to  FIG. 1 , the tensioning apparatus  120 , including the nut runner  122 , is interfaced with a control system  128  to monitor and control the operation of the tensioning apparatus  120 . The control system  128  works to measure tension in the system and control the operation of the nut runner  122  to increase, decrease or maintain tension. The system in which the tool is utilized includes (in a non-limiting way) the tool  120 , the nut runner  122 , and the control system  128 . The control system  128  is in operable communication with a load cell (described below), or other load or tension measurement device or component associated with the tensioning apparatus  120 , to receive and/or send signals therefrom and thereto. The control system  128  is also in operable communication with the nut runner  122  to receive and/or send signals therefrom and thereto. The control system  128  may include software, CPU, memory, inputs and outputs, digital or analog components, displays and data outputs, and programmable logic units to facilitate controlling and feedback instructions and data collection and analysis from the system for operation of the tensioning tool  120 . The control system  128  may include the ability to receive from and output to a data and/or display signal and/or to a wired or wireless network for observing and operating of the control system. Alternatively, the nut runner  122  may be controlled manually. 
     As shown in  FIGS. 2 ,  3  and  4 , the tensioning tool  120  includes a main body  130  having a barrel  132  operably associated with a housing  134 . The tensioning tool  120  includes a release ring  136  movable relative to the housing  134  and the barrel  132 , and in this embodiment is externally disposed relative to the housing. The release ring  136  may be internal to or a combination of internal and external to the housing. The release ring  136  allows the relative motion of internal portions of the barrel  132  and housing  134  with respect to the barrel and housing. 
     The nut  126 , or cable end, is attached to the threaded rod  124  as part of the cable assembly in an emergency park brake system. The threaded rod  124  extends through the equalizer bracket  116 , with the nut  126  keeping the rod  124  (and cable  106  to which it is attached) from being pulled back through the bracket  116  by the tension in the cable. The equalizer bracket  116 , as explained above, is attached to the reactive conduit of the emergency brake system, or it may be attached directly to the frame of a vehicle, depending on the design of the emergency braking system. 
     In general, the nut  126  is first threaded on the rod  124 . The nut  126  is then positioned into the end effector  138  in the barrel  132  of the tensioning tool  120 . The nut  126  is then pushed into the end effector  138  to push the end effector and the nut further into the barrel  132 . This causes the structure internal to the barrel  132  to move rearwardly (described in more detail below), freeing the release ring  136  to move forwardly and lock the nut  126  in the end effector  138  and a portion of the internal structure in engagement with the barrel  132  and the housing  134 . This locking mechanism causes the internal structure, housing and barrel to form a rigid, mechanical structure or column against which to tension the emergency brake system. This mechanical structure is effectively a column oriented along the length of the cable, which will provide a very incompressible system against which to measure the tension. Because generally in this example the system does not rely on any pneumatic or hydraulic components to maintain its incompressibility, it may be simpler, more reliable, and have less associated support equipment and related maintenance than those that do. 
     With the end of the barrel  132  resting on the equalizer bracket  116 , tensioning of the cable system can then begin by actuating the nut runner  122 , which in turn rotates the end effector  138  and runs the nut  126  up the threaded rod  124 . When the desired tension is reached, the release ring  136  is manually pulled rearwardly relative to the housing  134 , which unlocks the internal structure and allows the end effector  138  and the nut  126  to move toward the equalizer bracket  116  and release the nut  126  from the end effector  138 . 
     In general, with reference to  FIGS. 5-9 , an example of, and the operating method, of the present invention is shown. The housing  134  is generally cylindrical in shape, with portions having various dimensions, and defining an internal cavity  140 . A front portion  142  of the housing  134  has a reduced external and internal dimension and receives the release ring  136 , as well as a rear end  144  of the barrel  132 . A shoulder  148  is formed between the rear portion  146  and the front portion  142  of the housing  134  where the internal and external diameters transition. The release ring  136  is mounted circumferentially around the front portion  142 , and is axially slidable relative to the housing  134 . The front portion  142  of the housing  134  includes at least one aperture  150  formed therein. If more than one aperture is formed, they are formed annularly around the front portion  142 . Each aperture  150  receives a locking ball  152 , which moves radially through the aperture based on the relative positioning of the locking ring  126  and piston assembly  154 , as is described in more detail below. The rear end  144  of the barrel  132  is threadedly engaged with an externally threaded terminal end of the front portion  142 . An external shoulder  156  on the front portion  142  engages an internal shoulder  158  on the rear end  144  of the barrel  132  to seat the two together. The rear portion  146  of the housing  134 , as noted above, includes a slot  160  formed in its sidewall for allowing axial motion of certain components that are positioned in the housing and extend through the slot to outside the housing. An aperture  162  is also formed to allow the nut runner to be inserted into the housing to actuate the internal components. 
     Still referring to  FIG. 5 , the barrel  132  is shown engaged at its rear end  144  with the front portion  142  of the housing  134 . The barrel  132  has an elongated cylindrical shape, and includes a front end  164  opposite its rear end  144 . The barrel  132  also defines an internal cavity  166  extending from one end to the other. The barrel  132  is lined by a sheath including two collar lengths positioned end to end. Each collar length has a first end and a second end. The front collar length  168  has a first end  170  adjacent the front end  164  of the barrel  132 , and a second end  172  adjacent the first end  174  of the rear collar length  176 . The first end  170  of the front collar length  168  has a first larger interior diameter  178 , transitioning by a nut-engagement shoulder  180  or cam surface to a second smaller interior diameter. This internal region formed by the first larger interior diameter  178  is utilized for grasping the nut  126  using a series of nut engagement balls  182 , as described later. 
     The rear collar length  176  has a first end  174  adjacent the second end  172  of the front collar length  168 , and a second end  184  adjacent the threaded engagement between the rear end  144  of the barrel  132  and the front portion  142  of the housing  134 . The second end  184  of the rear collar length  176  has an outwardly extending flange  186  to allow it to be seated against a shoulder  188  formed adjacent the rear end  144  of the barrel  132  by the terminal end of the front portion  142  of the housing  134  when the barrel  132  and the housing  134  are engaged together as shown in  FIG. 5 . The rear terminal end of the barrel  132  forms a substantially annular axial extending lip  190  that has a larger internal diameter than the front  142  of the housing  134 , and is spaced away therefrom to form an annular space. The axial lip  190  extends rearwardly over the front portion  142  of the housing, and rearwardly from the threaded engagement between the barrel  132  and the housing  134 . A washer  192  may be positioned between the first end  170  of the front collar length  168  and the front end  164  of the barrel  132 . 
     Still referring to  FIGS. 5-9 , the housing  134  forms an anchor structure relative to which some of the internal components move in one condition, and to which some of the internal components are locked in another condition. The internal components include an input shaft  194 , a piston  196 , a locking structure  198 , a tension measurement structure  200 , and a nut runner engagement portion  202 . The input shaft  194  is positioned in the barrel  132 , inside the sheath, and is rotatable and axially movable relative thereto. The front end  204  of the input shaft  194  includes an end effector  138 , which receives the nut  126  and threaded rod  124  (see  FIGS. 6 ,  7 ,  8 , and  9 ). The end effector  138  has at least one aperture  206  formed therein to receive a corresponding nut engagement ball  182  and allow the ball to move radially in and out of the aperture in conjunction with the relative position of the input shaft  194  along the length of the barrel  132 . The end effector  138  acts with the nut engagement balls  182  and the nut engagement cam  180  to securely trap (both axially and rotationally) the nut in the end effector when desired, and is described in greater detail below. 
     The input shaft  194  extends from a front end  204  adjacent the front end  164  of the barrel  132  along the length of the barrel and through the housing  134  to a rear end  208  in operable engagement with the nut runner  122 . The rear end  208  of the input shaft  194  is operably associated with the nut runner  122 , which acts to selectively rotate the input shaft  194  clockwise or counter clockwise, or to stop rotation, depending on the controls received from the control system  128 . This rear end  208  of the input shaft  194  may move relative to the nut runner  122 , and may move into and out of operable engagement therewith, or may move relative to the nut runner  122  and stay in operable engagement therewith through the entirety of the movement. 
     Along a central section of the input shaft  194 , near the rear end  144  of the barrel, prior to entering the front portion  142  of the housing  134 , the input shaft  194  forms a circumferential shoulder  210  where the outer diameter of the input shaft  194  is reduced. The input shaft  194  rotates along its longitudinal axis relative to the housing  134  and the barrel  132 , under the control of the nut runner  122 . 
     The piston  196  is received over the input shaft  194 , and is positioned inside the first  142  and second  146  portions of the housing  134 . The piston  196  may be fixed in its position relative to the length of the input shaft, but the input shaft  194  and the piston  196  may rotate relative to one another. The piston  196  has a front portion  212  and a rear portion  214 . The front portion  212  is generally coextensive with the front portion  142  of the housing and also fits closely around the external surface of the input shaft  194 . The rear portion  214  is spaced away from the external surface of the input shaft  194 , and the circumferential piston walls  216  fit closely with the internal wall of the rear portion  146  of the housing  134 , forming an annular space therein. Corresponding internal and external shoulders  218  are formed where the piston transitions from the front  212  to the rear  214  piston portion. 
     The front end of the front portion  212  of the piston  196  engages a spacer sleeve  220  positioned on the outside of the input shaft  194 . One end of the spacer sleeve  220  engages the shoulder  210  on the outside of the input shaft  194 , and the other, rear end of the spacer sleeve  220  abuts the front portion  212  of the piston  196 . The front portion  212  of the piston  196 , on its external circumference, forms an annular recess  222 . The rear end of the annular recess forms an annular shoulder  224  to work in conjunction with the locking balls  152  to fix the piston  196  and input shaft  194  relative to the housing  134 , as is explained in more detail below. 
     Referring still to  FIGS. 5-10 , and particularly  FIG. 6 , various components are positioned within the annular space between the walls  216  of the rear portion of the piston  196  and the input shaft  194 , referred to above as the piston assembly  154 . A load cell  200  is received on a bearing on the input shaft  194  in order to allow the input shaft to rotate relative to the load cell, and the load cell abuts on its front side the internal shoulder  218  of the piston  196 . The internal shoulder  218  of the piston  196  is the surface against which the load cell is compressed to measure the tension is the cable system. In one embodiment the load cell is concentrically positioned around the input shaft  194 , and because of this annular orientation around the input shaft  194 , the load cell  200  measures the load in-line with the application of the load by the input shaft, and generally in-line with the terminal end of the cable system to which the input shaft  194  is attached. 
     An assembly of items that generally combine together to apply a load responsive of the cable tension to the load cell  200 , called the compressive component  225 , are described hereafter. In one example described herein, an axial collar  226  abuts the rear surface of the load cell  200  and extends along the walls  216  of the second portion  214  of the piston  196 . Structure associated with the piston assembly  154  external to the housing  134  may be attached to the collar  226 , such as by a screw  228 , and extend through the slot  160  in the housing  134 . This external structure thus may move along with the piston  196 . This structure may include the input/output communication cable  230  for the load cell  200 , among other items. A radial collar  232  is positioned about the input shaft  194  inside the rear end of the axial collar  226 . The front face of the radial collar  232  engages a facial bearing  234 . The radial collar  232  may rotate with the input shaft  194  while in engagement with the facial bearing  234 . The facial bearing  234  helps isolate the rotation of the radial collar  232  with the input shaft  194  from the load cell  200 . The facial bearing  234  is supported by a mount  236 , which may itself be mounted on a bearing on the input shaft  194 . The front surface  237  of the mount  236  may engage the rear surface of the load cell. A retaining collar  238  is mounted on the input shaft  194  and is held in axial position against the radial collar  232  by a retainer  240  and snap ring washer  242 . This compressive component  225 , made up of elements described herein that apply a load to the load cell, acts to transmit the load applied to the input shaft to the load cell. 
     The compression applied to the load cell  200  is derived, in one embodiment, from the cable pulling on the input shaft  194  as the cable system is tensioned. As the input shaft is pulled to the left (in the orientation of  FIG. 6 ), the compressive component  225  applies a load to the load cell  200 . In more detail of this particular example of the invention, the snap ring washer and retainer  240  apply a force in that direction to the retaining collar  238 , which in turn applies a load in that direction to the radial collar  232 , which in turn applies a load in that direction to the facial bearing  234  and mount  236 , which in turn apply the load in that direction to the load cell  200 . The load cell abuts on its front surface the shoulder structure  218  of the piston  196 , and is thus compressed between the load applied as described above and the shoulder structure  218 . The piston  196 , being locked to the housing by the structure described herein, provides a solid base against which the load cell may be compressed. The load cell creates a signal indicative of the load (cable tension) and transmits that signal along line  230  to the control system  128  for storage, display, analysis and/or possible control of the nut runner and tensioning tool. 
     Various other structures may be employed to create the compressive component  225  to apply a load to the load cell  200  and allow the input shaft  194  to rotate. For instance, and in a non-limiting manner, the retaining collar  238  may be circumferentially mounted on the input shaft, similar to the radial collar  232 . It may turn with the input shaft or be rotationally independent of the input shaft. It may extend all or partially through the input shaft, as shown, acting in part as a pin, as a manner of mounting on the input shaft. The radial collar  232 , facial seal  234 , and/or other components may also not be included. Also, the axial collar  226  may be axially movable relative to the piston walls and be operably associated with the retaining collar  240  and snap ring  242  and be loaded thereby (ultimately by the tension load on the input shaft as described above) and in turn apply a load, along with or separate from the mount  236 , to the load cell  200 . The axial collar may also be cup-shaped and rotatably mounted on the input shaft, and axially movable with respect to the piston walls, with the mount  236 , facial bearing  234  and radial collar  232  mounted relatively within the cup. When the load is applied through the retaining collar to the radial collar, the facial bearing and to the cup-shaped axial collar, the bottom of the cup-shaped axial collar may apply the compressive load to the load cell  200 . Further, all of the structure described above may not be required to create the resulting load on the load cell. Additionally, other structure may be added if desired. 
     The compressive component  225  may also include, in another example, the radial collar  232 , mount  236  and any additional structure retained on the input shaft in an axial location by a pin positioned through the input shaft. When the tension is applied to the input shaft, the pin holds the compressive component  225  in axial position on the input shaft in order to apply the tension load to the load cell. The compressive component  225  that engage the load cell  200  may be positioned annularly around the input shaft to engage the load cell  200  about its annular shape. The portions of the compressive component that are inside the axial collar  226  may rotate with the input shaft, or may not rotate with the input shaft. 
     As can be appreciated from the above description, the structure of the compressive component  225  associated with the piston assembly and input shaft  194  may have many forms different than that described above to perform the same or similar function of allowing the input shaft to rotate relative to the piston, and apply a load to a load cell for measuring the tension in the cable system during the tensioning process. Further, the load cell  200  may be positioned in the main body, and operably associated with the main body or piston  196  in other orientations to measure the load. The load cell may also be replaced with another type of load sensor that works to measure load in either compression, tension, lateral deflection or the like. 
     The rear end  208  of the input shaft  194 , as mentioned above, is arranged to engage the drive end of the nut runner  122 , and may axially slide therealong as needed when the input shaft  194  is moved axially, as explained below. The particular engagement arrangement of the nut runner  122  and the input shaft is not critical to the nature of the invention described herein. 
     Continuing to refer to  FIG. 6 , a return spring  244  is positioned in the second portion  146  of the housing  134  to urge the piston  196  forwardly in the housing  134 . In this instance the spring  244  is positioned between a portion of the nut runner  122  fixed by a snap washer  245  to the rear of the housing  134 , and the axial collar  226 . The return spring  244  compresses as the input shaft  194  and piston  196  are moved axially rearwardly, and continually biases the piston  196  and input shaft  194  forwardly. This forward biasing force will be described in more detail hereafter. 
     Referring still generally to  FIGS. 5-8 , and particularly to  FIG. 7  for clarity, the release ring  136  is positioned around the front portion  142  of the housing  134  and moves axially on the along the front portion  142 . The release ring  136  includes an annular inner lip  246  and an annular outer lip  248  extending forwardly, with a gap  250  formed therebetween (See  FIG. 6 ). The gap  250  receives the rear lip  190  formed on the barrel  132 . An annular recess  252  is formed facing rearwardly to receive and seat the front end of the release spring  254 . The rear end of the release spring  254  engages the outer shoulder  148  of the housing  134 . A rear portion of the release ring  136  extends over and moves relative to the second portion  146  of the housing  134  to help contain the release spring  254 . The radially inward surface  256  of the inner lip  246  acts to retain the locking ball  152  in the aperture  150  in the first portion  142  of the housing  134 . A cam or shoulder surface  258  is formed a the base of the inner lip  246  to encourage the locking ball  152  to move radially inwardly through the aperture  150  as the release ring  136  is moved forward relative to the housing  134 , as is described below. 
     The release mechanism, in this instance a release ring  136 , may move from a forward position to a rearward position along the front portion  142  of the housing  134 . The release spring  254  biases the release ring  136  towards the forward position. In the forward-most position, the release ring abuts the annular lip  190  on the barrel  132 . (see  FIG. 7 ). The release ring  136  may also take the form of a lever or other structure not in the form of a ring or circle. 
     The input shaft  194  is operably engaged with the piston  196  to move the piston rearwardly when the input shaft  194  moves rearwardly (toward the nut runner  122 ). The input shaft  194  may be operably engaged with the piston  196  to move the piston forwardly upon forward movement of the input shaft  194 , but is not necessarily so engaged. 
     The operation of the tensioning apparatus  120  of the present invention is now described with respect to  FIGS. 5-8 . After the nut  126  is threaded onto the end of the threaded rod  124  as described above, the nut  126  is positioned in the end effector  138  and is engaged with the input shaft  194  to be turned by the input shaft as the input shaft is turned by the nut runner  122 . Prior to insertion of the nut  126 , the tensioning apparatus appears in the ready state shown in  FIG. 5 . In the ready state, the input shaft  194  is positioned forwardly in the barrel  132  with the end effector  138  positioned and ready for insertion of the nut  126 . In this forward position, the piston  196  is in its forwardmost position with the outer shoulder  218  engaging the inner shoulder  148  of the housing  134 . The release ring  136  is in its rearward most position, with the locking balls  152  moved by the outer surface of the first portion of the piston  196  to their radially-outermost positions in the respective apertures  150  in the first portion  142  of the housing  134  and bounded by the inner-lip  246  of the release ring  136 . The release ring  136  may not move any more forwardly because of the locking balls  152 , which engage the cam surface  258  of the release ring  136 . Since the locking balls  152  are held in position by the walls of their respective apertures  150 , the locking balls  152  keep the release ring  136  from moving forward under the force of the release spring  254 . The return spring  244  in the housing  134  is in the extended position. In this embodiment, the rear end of the input shaft  194  is in engagement with the nut runner  122 . 
       FIG. 6  shows the tensioning tool  120  positioned over the nut  126 , and specifically the nut  126  being received in the end effector  138 . This is performed manually, or may be performed automatically with the appropriate automated equipment. In this position the tensioning tool  120  stays in the ready state. Note that the nut  126 , in this embodiment, defines a circumferential groove  260  for receiving the nut engaging balls  182  in the end effector  138 . When positioned in the end effector  138 , the groove  260  in the nut  126  is radially aligned with the nut engaging balls  182 . The arrow  262  represents the movement of the tensioning tool  120  towards the bracket  116 , which may occur at this time. 
       FIG. 7  shows the nut  126  and the end effector  138  having been pushed into the barrel  132 . This movement is performed manually by an operator grasping the threaded rod  124  and pushing the threaded nut  126  into the tensioning tool  120  a certain amount. It may be performed automatically, also, with the appropriate automation device. Moving the nut  126  further into the tensioning device  120  has at least two purposes. First, it causes the end effector  138  to engage the nut  126  in the input shaft  194  and retain it there both axially and rotationally (the end effector  138  has a recess having a complementary shape to the shape of the nut  126 ). Second, the rearward movement of the input shaft  194  actuates the locking device  198  to firmly engage the piston  196  in the retracted position with the barrel  132  and housing  134 , forming the rigid structure against which the tension of the system, created by the cable pulling on the input shaft  194 , is measured during the tensioning step. Also, by moving the nut  126  away from the equalizer bracket  116 , the tension load measured is substantially isolated from the normal forces on the face of the nut that would affect that measurement if the nut  126  was in engagement with the equalizer bracket  116 . 
     Referring still to  FIG. 7 , the nut  126  is withheld by the end effector  138  by at least one nut engagement ball  182  that is held in engagement with a groove  260  in the nut  126 . As the nut  126  is moved rearwardly, the nut engagement ball  182  moves through the aperture  206  in the front end of the input shaft  194 . As the ball  182  and the input shaft  194  move rearwardly relative to the barrel  132  and housing  134 , the cam surface  180  on the front collar length  168  helps urge the ball  182  radially inwardly through the apertures  206  and into the groove  260  in the nut  126 . The ball  182  is held in this engaged position with the nut  126  by the internal surface of the front collar length  168  of the barrel  132 . In this way, when the input shaft  194  is moved rearwardly into the barrel  132 , the nut  126  is releasably engaged with the end effector  138  and the nut  126  then moves axially and rotationally with the input shaft  194 . The distance the nut  126  must be moved into the end effector  138  to cause engagement is generally the relief distance. The relief distance may be that distance which the nut  126  must travel, after the brake system has been tensioned, in order for the brakes shoes or calipers to release from the drums or discs (respectively) to allow the wheels to turn freely. Alternatively, the control system  128  may instruct the nut runner to lessen the tension by appropriately rotating the nut along the threaded shaft  124 . 
     Still referring to  FIG. 7 , the rearward movement of the input shaft also causes the piston  196  (and piston assembly  154 ) to move rearwardly in the tensioning tool  120 . The input shaft  194  causes the spacer collar  220  to move, which in turn causes the piston  196  to move rearwardly. The piston  196  moves rearwardly in the housing  134 , compressing the return spring  244 . The rearward movement of the piston  196  also moves the front portion  212  of the piston  196  rearwardly relative to the locking ball  152  held in the release ring  136 . As the front portion  212  moves rearwardly, the recess  222  formed therein moves under the locking ball  152  (or balls). The locking ball  152 , while positioned in the recess  222  and engaging the outer surface of the front portion  212  of the piston  196  and the shoulder  224  of the recess  222 , moves from engaging the cam  258  on the release ring  136 , which was keeping it in its rearward most position. As the locking ball moves radially inwardly, encouraged by the angular force applied by the cam  258  on the locking ring  136 , the locking ball  152  moves through the aperture  150  into the groove  222  on the front portion of the piston, and out of interfering engagement with the release ring  136 . The release spring  254  then biases the release ring  136  forwardly on the front portion  142  of the housing  134  to the release ring&#39;s forward-most position. In this forward-most position, the axial lip  190  on the rear of the barrel  132  is received in the annular recess  250  between the radially inner  246  and outer lips  248  at the front end of the release ring  136 , thus prohibiting the release ring  136  from any further forward motion. This brings the inner retaining wall  270  of the release ring  136  into engagement with the locking ball  152 , which then holds the locking ball  152  against the piston  196 . At this location, the piston  196  is biased forward, so the shoulder  224  at the border of the recess  222  is pushed into engagement with the portion of the locking ball  152  extending radially inwardly from the aperture  150 , thus keeping the piston  196  from moving any further forwardly. The piston  196  thus may not move any further forwardly relative to the barrel  132  or housing  134 , and is fixed axially relative to the input shaft  194 . The piston walls  216 , at this position, are sized to engage in physical interference at or near the end of the housing, but may not be required to. In this embodiment, the interference is caused by a snap ring  245  positioned in the inner wall of the housing  134  at the appropriate location, used to hold a portion of the drive means  122  in location in the housing  134 . Note, at this position, if the piston walls  216  were of shorter length, the input shaft  194  and piston  196  may be pushed further into the barrel and housing if desired, but need not be. 
     The release ring  136 , forward portion of the housing  142 , locking balls  152  and the forward portion  212  of the piston  196  combine to create a mechanical locking system  198 . This mechanical locking system  198  converts the relative movement between the barrel  132  and housing  134  with the piston  196  into a rigid column. This mechanical locking system  198  works automatically under the spring bias of the release spring  254  primarily in operative association with the release ring  136 . Once the input shaft  194  and piston  196  are pushed far enough rearwardly into the barrel  132  and housing  134 , the locking mechanism  198  engages to automatically to form the rigid column between the housing  134 , barrel  132  and piston  196 . The rigid column allows the tension of the cable system to be measured directly through a rigid mechanical structure by the load cell with no reliance on an incompressible fluid system, such as hydraulics, or high-pressure pneumatics, and the associated support equipment and maintenance. The arrow  272  in  FIG. 7  shows the relative motion of the input shaft  194  and piston assembly  154 . The arrow  274  shows the relative motion of the release ring. 
     In this locked mechanical column system shown in  FIG. 7 , the load on the cable system is measured by the load cell  200  positioned between the now anchored inner shoulder  218  of the piston  196  and the compressive component  225 , including in one embodiment the collar  238  mounted near the inner end of the input shaft  194 . As the system is tensioned (as explained below), the cable  106  pulls the nut  126 , which pulls the end effector  138 , which pulls the input shaft  194 , which pulls the collar  238  (and the elements of the compressive component  225 ) to effectively compress the load cell  200 . The compression of the load cell  200  is communicated to the control system  128  and translated to a tension load, which data is used by the control system  128  for display and to control the nut runner  122  and possibly other equipment. 
     The cable system, as described above regarding  FIG. 7 , may now be tensioned with the tensioning tool  120 . At this position, the control system  128  may send control signals to the nut runner  122 , which rotates the input shaft  194 , and thus rotates the nut  126  on the threaded rod  124 . As the input shaft  194  is rotated, the piston  196  may not be rotated. In the embodiment described herein, the collar  238  in engagement with the facial seal rotates with the input shaft  194 . As the threaded rod  124  is pulled through the nut  126 , the tension increases in the brake cable system. As the tension increases, the load cell  200  senses the load by being compressed by the compressive component and transmits signals to the controls system  128  to monitor the load (tension) in the brake cable system. Once the appropriate tension load is achieved, and the tensioning act is completed (more than one series of tensioning can be accomplished at this stage by controlling the nut runner  122  to increase and decrease tension as desired), the nut runner  122  may be deactivated. During tensioning, the tensioning tool may engage the bracket  116 , such as at its front end as shown in  FIG. 7 , against which to react during the tensioning step. The tensioning tool  120  may be engaged against another fixed or anchor surface whether or not directly in contact with the bracket  116 . 
     After tensioning is complete, the tensioning tool  120  may be released from the nut  126 . This is shown in  FIG. 8 . To release the nut  126  from the tensioning tool  120 , the release ring  136  is slid rearwardly (arrow  276 ) on the first portion  142  of the housing  134 . This disengages the inner retaining wall  270  of the release ring  136  from the locking ball  152 , and allows the locking ball  152  to move radially outwardly, being urged radially outwardly by the cam surface  224  on the forward portion  212  of the piston. As the locking ball  152  moves radially outwardly, it disengages from the cam surface  224  on the piston  196 , and thus allows the piston  196  to move further forwardly in the tool  120 , along with the input shaft  194 . The piston  196  moves forwardly far enough to cause the outer shoulder  218  of the piston  196  to engage the inner shoulder  148  of the housing  134 . This forward movement of the piston  196 , if not caused by the tension in the cable system pulling the nut  126  and the input shaft  194  towards the equalizer  116  (typically the tensioning step is performed with the end of the barrel of the tool in engagement with the equalizer), is effected by the return spring  244  pushing the piston  196  forwardly in the housing  134 . 
     As the piston  196  moves forwardly in the housing  134 , it pushes the input shaft  194  forwardly also. The input shaft  194  is pushed forwardly far enough to allow the nut engagement balls  182  to release from engagement with the nut  126  (by being forced radially outwardly through the apertures  206  in the forward end of the input shaft  194  by the cam surface at the border of the groove  260  on the nut), thus allowing the nut  126  to be removed from the end effector  138 . This is shown in  FIG. 8 . In the position shown in  FIG. 8 , once the nut  126  is removed, it is the initialized state as shown in  FIG. 5 . The tool  120  is ready to be attached to another brake system for the tensioning operation. The arrow  278  in  FIG. 8  shows the relative motion of the piston  196 , input shaft  194 , and piston assembly  154  upon activation of the release ring  136 , all relative to the housing  134  and barrel  132 . 
     The method in which the tool  120  is used includes the acts of engaging the nut  126  in the tool  120 , causing the nut  126  to be rotationally engaged with the tool  120 , causing the tool  120  to be in an orientation facilitating tensioning the brake cable system with a mechanically rigid structure formed by the tool  120  (these last two acts may occur simultaneously, as described herein, or may occur non-simultaneously with one occurring before the other); causing the tool  120  to tension the brake cable system, and causing the tool  120  to release the nut  126  from the tool  120 . The nut  126  may be positioned manually in the tool or by an automated machine. The release ring  136  may be operated manually or by an automated machine. 
       FIGS. 9   a  and  9   b  are an exploded view of the brake tensioner shown in  FIGS. 5-8 .  FIG. 9   a , with reference to the descriptions of  FIGS. 5-8 , shows the barrel  132 , washer  192 , front collar length  168 , release ring  136 , input shaft  194 , rear collar length  176 , spacer collar  220 , release spring  254 , and housing  134 .  FIG. 9   b , as a continuation of  FIG. 9   a , shows the piston  196 , load cell  200 , radial collar  232 , axial collar  226 , return spring  244 , snap ring  245 , and nut runner  122  with components. 
       FIGS. 10 and 11  show an alternative embodiment of the tensioning tool  120  earlier described, prior to engagement with the nut ( FIG. 10 ) and after the tensioning step, but before disengagement from the nut ( FIG. 11 ). The tool  120  works in much the same way as that described with respect to  FIGS. 5-8  above. The barrel  132  and body  134  are rigidly attached together, and the input shaft  194  and piston  196 , with its accompanying structure (load cell  200 , washers, etc.) are situated in the barrel  132  and housing  134  in order to move relative thereto. The release ring  136  acts to cause the mechanical locking mechanism  198  to actuate, and releases the mechanical locking mechanism  198  similarly to the previous embodiment. The release ring  136 , in this example however, does not have a forwardly extending lip, nor does the barrel  132  have a rearwardly extending lip, as the previous embodiment does. Instead, the front edge  280  of the release ring  136  is relatively flat and abuts a flange  282  on the rearward end of the barrel  132  to denote the forward-most extent of the release ring&#39;s movement. The engagement of the nut, formation of the rigid column, tensioning, and disengagement of the nut, are all similarly accomplished in this embodiment. 
     All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader&#39;s understanding of the examples of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention unless specifically set forth in the claims. Joinder references (e.g., attached, coupled, connected, joined, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joined references do not necessarily infer that two elements are directly connected and in fixed relation to each other. 
     In some instances, components are described with reference to “ends” having a particular characteristic and/or being connected with another part. However, those skilled in the art will recognize that the present invention is not limited to components which terminate immediately beyond their points of connection with other parts. Thus, the term “end” should be interpreted broadly, in a manner that includes areas adjacent, rearward, forward of, or otherwise near the terminus of a particular element, link, component, part, member or the like. In methodologies directly or indirectly set forth herein, various steps and operations are described in one possible order of operation, but those skilled in the art will recognize that steps and operations may be rearranged, replaced, or eliminated without necessarily departing from the spirit and scope of the present invention. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims. Accordingly the matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting.