Apparatus, system and method for tensioning an emergency brake system

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.

FIELD

This disclosure relates to an apparatus, system and methods associated with the tensioning of an emergency brake system on a vehicle, and more particularly to a tool having an internal tensioning structure that includes a stationary load measuring structure and a movable nut retention assembly, which together act with a nut and cable components and an associated method to tension the brake system to the desired tension level.

BACKGROUND

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 with relatively few moving parts, particularly in the load measurement structure, during brake cable 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 examples of the present disclosure will be recognized from the following description.

SUMMARY

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 example, 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 body, a rotating assembly positioned in the body for engaging the cable end, an engagement member at least partially external to the body and movable between a first position and a second position to secure and release the cable end, the rotating assembly stationarily positioned in the body and forming a load measurement column, wherein insertion of the cable end into rotating assembly and movement of the engagement member from the first position to the second position causes the cable end to be secured in the rotating assembly. Tensioning is performed and tension load measured without substantial axial movement of the load sensor.

In another example, a tensioning tool for use in tensioning an emergency brake cable system for a vehicle is provided, the tool being driven by a rotational driver, and the brake system including a rotatable cable end. The tool includes a body; a first portion rotatably positioned in the body for engaging the cable end, the first portion including a locking mechanism for receiving the cable end, the locking mechanism movable between at least a first locked position and a second unlocked position; and a second portion movably positioned relative to the body and at least partially external to the body and operably engaging the locking mechanism. Upon insertion of a nut into the first portion, movement of the second portion to the second locked position secures the nut in the first portion.

The first portion may be fixed in axial position relative to the body. The first portion may include an input shaft that rotates relative to the body. The first portion may be an elongated shaft having a front portion and a rear portion, the front portion of the shaft including the locking mechanism and defining a recess, the rear portion of the shaft extending through a load cell configured to remain substantially stationary relative to the body and operably bear upon a portion of the body when the shaft is engaged with the cable end. The rear portion of the shaft may extend through a bearing that allows rotation of the shaft relative to the body. The tool may include a gear operably engaged with a source of rotational movement and non-rotatably engaged with the shaft; and a thrust bearing operably engaging the gear and the load cell for allowing rotation of the gear while creating a compressive load on the load cell. The second portion may include an elongated actuator at least partially movable through the body; an engagement actuator operably engaged with the elongated actuator, the engagement actuator operable to actuate the locking mechanism between the locked and unlocked position, the engagement actuator movable relative to the input shaft. The elongated actuator may include an engagement tab that extends through a slot in the body and engages the engagement actuator. The engagement actuator may be a sleeve positioned at least partially interior of the body and at least partially surrounds at least a front portion of the first portion.

In another example, a tensioning tool for use in tensioning an emergency brake cable system for a vehicle is provided, the tool being driven by a rotational driver, and the brake system including a rotatable cable end. The tool includes a front portion having a first axis and a shaft, the front portion configured to selectively secure and release the cable end, the shaft configured to rotate the cable end; a rear portion having a second axis, the rear portion including a gear train for rotating the shaft about a shaft centerline; the front and rear portions positioned offset from one another such that the first axis and the second axis are parallel to and spaced apart from one another, each of the first axis and the second axis are parallel to the shaft centerline.

In another example, a tensioning tool for use in tensioning an emergency brake cable system for a vehicle is provided, the tool being driven by a rotational driver. The tool includes a rotatable shaft, a sleeve at least partially surrounding at least a portion of the shaft and slidable relative to the shaft, and an actuator rod laterally offset from the shaft and movable relative to the shaft, the actuator rod coupled to the sleeve and operable to slide the sleeve relative to the shaft. The tensioning tool may include a first gear meshingly engaged with a portion of the shaft. The tensioning tool may include a second gear operably engaged by the rotational driver, wherein the actuator rod extends laterally between the shaft and the second gear. The actuator rod may extend through an aperture formed in the first gear. A length of the actuator rod may overlap with a length of the shaft. The shaft may define a shoulder, and the tensioning tool may include a load cell at least partially surrounding at least a portion of the shaft axially between the shoulder and the sleeve.

In another example, a method for engaging a tensioning tool with an emergency brake cable system for a vehicle is provided, the brake system including a rotatable cable end movable relative to a cable. The method includes receiving the cable end in the tool; moving an external portion of the tool to a first position to axially secure the cable end in the tool; tensioning the cable system by moving the cable end relative to the cable; and moving the external portion of the tool to a second position to axially release the cable end from the tool.

In another example, a method for tensioning an emergency brake cable system for a vehicle is provided, the brake system including a rotatable cable end movable relative to a cable. The method includes securing the cable end in a recess formed in a tool; rotating a portion of the tool to rotate the cable end relative to the cable; measuring tension in the cable system by a sensor stationarily positioned within the tool; and releasing the cable end from the recess formed in the tool.

In another example, a method for measuring and determining the apparent stiffness of a park brake cable system and adjusting tensioning force applied to the system based upon such determination in real time is provided. The method includes operably engaging a tensioning apparatus with a park brake cable of a park brake cable system, the tensioning apparatus including a housing that contains a load cell and attached to a programmable drive, the brake cable system including an equalizer adapted to balance tensions in at least two lengths of cable, wherein a nut is operably associated with a threaded rod, the nut including a surface for operably engaging the equalizer; securing the nut within the apparatus; positioning the surface of the nut away from the equalizer a specified distance; driving the nut with the tensioning apparatus to tension the park brake cable to a first tension level sufficient to remove voids from the cable system; measuring the first tension level using the load cell; relieving the tension in the park brake cable to a second level approaching zero by driving the tensioning apparatus in reverse; tensioning the cable to a third tension level with the tensioning apparatus, the third tension level being higher than the second tension level; measuring the third tension level with the load cell; tensioning the cable to a fourth tension level with the tensioning apparatus, the fourth tension level being higher than the third tension level; measuring the fourth tension level with the load cell; based on the speed of rotation of the drive and time elapsed, or using total angle of rotation, determining the actual distance traveled by the nut between the third and fourth tension levels; based on the distance traveled, formulating an algorithm that represents the slope of the tension travel relationship or characteristic stiffness of the cable system; based on a desired final residual tension in the cable system, determining the number of reverse revolutions of the nut to achieve the desired final residual tension; driving the nut in reverse the required number of reverse revolutions with the tensioning apparatus; and operably disengaging the tensioning apparatus from the end of the park brake cable, wherein the nut returns to the equalizer and substantially maintains the desired residual tension in the park brake cable system.

In another example, a method of obtaining a desired residual level of tension in a park brake cable system is provided. The method includes determining a tension/travel curve between a lower first tension and a higher second tension by moving a nut along a threaded rod; and using the tension/travel curve to determine a distance to move the nut along the threaded rod to a desired residual level of tension.

While multiple examples are disclosed herein, still other examples will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative examples of the disclosure. As will be realized by those of ordinary skill in the art upon reading the following disclosure, the disclosed examples are capable of modifications in various aspects, all without departing from the spirit and scope of the claimed invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.

This summary of the disclosure is given to aid understanding, and one of skill in the art will understand that each of the various aspects and features of the disclosure may advantageously be used separately in some instances, or in combination with other aspects and features of the disclosure in other instances. Accordingly, while the disclosure is presented in terms of examples, it should be appreciated that individual aspects of any example can be claimed separately or in combination with aspects and features of that example or any other example.

DETAILED DESCRIPTION

The instant disclosure generally provides 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.FIG. 1illustrates a schematic of a system utilizing an example attachment. In particular,FIG. 1illustrates a side pull park brake system100. The park brake system100includes a front cable102, a rear right cable104, and a rear left cable106. The front cable102is attached to a pull handle108at its first end and a connector clip110at its second end. The connector clip110attaches to the front end of the rear right cable104, which extends towards and attaches to the brake assembly112on the rear right wheel. The rear left cable106is attached to the front cable102through a reactive conduit system114as is well-known in the art. The front end of the rear left cable106is attached to one end of an equalizer bracket116, which is in turn attached to and part of the reactive conduit system114. The rear end of the rear left cable106is attached to the rear left brake assembly118. The front cable102and the rear right cable104may be one continuous cable; however, it may be more convenient for the front and rear cables102,104to be separate from one another for ease of manufacturing.

The operation of a reactive conduit side pull park brake system100is well-known. The problem solved by the present disclosure is that the tensioning of the system during assembly is made significantly more convenient by use of a tensioning apparatus in combination with a drive means, which results in an accurately tensioned cable system. In addition, the use of a tensioning apparatus may reduce overall costs of building the park brake system into a vehicle during assembly, improve quality, and reduce labor costs. While described in connection with a side pull park brake system, the tensioning apparatus may be utilized on a center pull park brake system or other brake systems.

The front end of the rear left cable106includes a threaded rod124of 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 bracket116and a nut126is positioned on the free end of the threaded rod124in order to hold the threaded rod in attachment with the equalizer bracket. The tensioning apparatus120and the drive means122are 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 system100functions appropriately during the use of the vehicle, and to lessen slackening or loosening. The particular tensioning apparatus120by itself, or in combination with the drive means122(collectively referred to as the “park brake tensioning system”), may be used together to tension the park brake system.

One of the brake system assembly benefits provided by the park brake tensioning system 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 toFIG. 1, the tensioning apparatus120, including the nut runner122, is interfaced with a control system128to monitor and control the operation of the tensioning apparatus120. The control system128works to measure tension in the system and control the operation of the nut runner122to increase, decrease, or maintain tension. The system in which the tool is utilized includes (in a non-limiting way) the tool120, the nut runner122, and the control system128. The control system128is in operable communication with a load cell (described below), or other load or tension measurement device or component associated with the tensioning apparatus120, to receive and/or send signals there from and thereto. The control system128is also in operable communication with the nut runner122to receive and/or send signals there from and thereto. The control system128may 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 tool120. The control system128may 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 runner122may be controlled manually.

As shown inFIGS. 2,3and4, the tensioning tool120includes a main body130having a barrel132operably associated with a housing134. The tensioning tool120includes a release ring136movable relative to the housing134and the barrel132, and in this embodiment is externally disposed relative to the housing. The release ring136may be internal to or a combination of internal and external to the housing. The release ring136allows the relative motion of internal portions of the barrel132and housing134with respect to the barrel and housing.

The nut126, or cable end, is attached to the threaded rod124as part of the cable assembly in an emergency park brake system. The threaded rod124extends through the equalizer bracket116, with the nut126keeping the rod124(and cable106to which it is attached) from being pulled back through the bracket116by the tension in the cable. The equalizer bracket116, 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 nut126is first threaded on the rod124. The nut126is then positioned into the end effector138in the barrel132of the tensioning tool120. The nut126is then pushed into the end effector138to push the end effector and the nut further into the barrel132. This causes the structure internal to the barrel132to move rearwardly (described in more detail below), freeing the release ring136to move forwardly and lock the nut126in the end effector138and a portion of the internal structure in engagement with the barrel132and the housing134. 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 barrel132resting on the equalizer bracket116, tensioning of the cable system can then begin by actuating the nut runner122, which in turn rotates the end effector138and runs the nut126up the threaded rod124. When the desired tension is reached, the release ring136is manually pulled rearwardly relative to the housing134, which unlocks the internal structure and allows the end effector138and the nut126to move toward the equalizer bracket116and release the nut126from the end effector138.

In general, with reference toFIGS. 5-9, an example tensioning tool and operating method is shown. The housing134is generally cylindrical in shape, with portions having various dimensions, and defining an internal cavity140. A front portion142of the housing134has a reduced external and internal dimension and receives the release ring136, as well as a rear end144of the barrel132. A shoulder148is formed between the rear portion146and the front portion142of the housing134where the internal and external diameters transition. The release ring136is mounted circumferentially around the front portion142, and is axially slidable relative to the housing134. The front portion142of the housing134includes at least one aperture150formed therein. If more than one aperture is formed, they are formed annularly around the front portion142. Each aperture150receives a locking ball152, which moves radially through the aperture based on the relative positioning of the locking ring126and piston assembly154, as is described in more detail below. The rear end144of the barrel132is threadedly engaged with an externally threaded terminal end of the front portion142. An external shoulder156on the front portion142engages an internal shoulder158on the rear end144of the barrel132to seat the two together. The rear portion146of the housing134, as noted above, includes a slot160formed 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 aperture162is also formed to allow the nut runner to be inserted into the housing to actuate the internal components.

Still referring toFIG. 5, the barrel132is shown engaged at its rear end144with the front portion142of the housing134. The barrel132has an elongated cylindrical shape, and includes a front end164opposite its rear end144. The barrel132also defines an internal cavity166extending from one end to the other. The barrel132is 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 length168has a first end170adjacent the front end164of the barrel132, and a second end172adjacent the first end174of the rear collar length176. The first end170of the front collar length168has a first larger interior diameter178, transitioning by a nut-engagement shoulder180or cam surface to a second smaller interior diameter. This internal region formed by the first larger interior diameter178is utilized for grasping the nut126using a series of nut engagement balls182, as described later.

The rear collar length176has a first end174adjacent the second end172of the front collar length168, and a second end184adjacent the threaded engagement between the rear end144of the barrel132and the front portion142of the housing134. The second end184of the rear collar length176has an outwardly extending flange186to allow it to be seated against a shoulder188formed adjacent the rear end144of the barrel132by the terminal end of the front portion142of the housing134when the barrel132and the housing134are engaged together as shown inFIG. 5. The rear terminal end of the barrel132forms a substantially annular axial extending lip190that has a larger internal diameter than the front142of the housing134, and is spaced away there from to form an annular space. The axial lip190extends rearwardly over the front portion142of the housing, and rearwardly from the threaded engagement between the barrel132and the housing134. A washer192may be positioned between the first end170of the front collar length168and the front end164of the barrel132.

Still referring toFIGS. 5-9, the housing134forms 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 shaft194, a piston196, a locking structure198, a tension measurement structure200, and a nut runner engagement portion202. The input shaft194is positioned in the barrel132, inside the sheath, and is rotatable and axially movable relative thereto. The front end204of the input shaft194includes an end effector138, which receives the nut126and threaded rod124(seeFIGS. 6,7,8, and9). The end effector138has at least one aperture206formed therein to receive a corresponding nut engagement ball182and allow the ball to move radially in and out of the aperture in conjunction with the relative position of the input shaft194along the length of the barrel132. The end effector138acts with the nut engagement balls182and the nut engagement cam180to securely trap (both axially and rotationally) the nut in the end effector when desired, and is described in greater detail below.

The input shaft194extends from a front end204adjacent the front end164of the barrel132along the length of the barrel and through the housing134to a rear end208in operable engagement with the nut runner122. The rear end208of the input shaft194is operably associated with the nut runner122, which acts to selectively rotate the input shaft194clockwise or counter clockwise, or to stop rotation, depending on the controls received from the control system128. This rear end208of the input shaft194may move relative to the nut runner122, and may move into and out of operable engagement therewith, or may move relative to the nut runner122and stay in operable engagement therewith through the entirety of the movement.

Along a central section of the input shaft194, near the rear end144of the barrel, prior to entering the front portion142of the housing134, the input shaft194forms a circumferential shoulder210where the outer diameter of the input shaft194is reduced. The input shaft194rotates along its longitudinal axis relative to the housing134and the barrel132, under the control of the nut runner122.

The piston196is received over the input shaft194, and is positioned inside the first142and second146portions of the housing134. The piston196may be fixed in its position relative to the length of the input shaft, but the input shaft194and the piston196may rotate relative to one another. The piston196has a front portion212and a rear portion214. The front portion212is generally coextensive with the front portion142of the housing and also fits closely around the external surface of the input shaft194. The rear portion214is spaced away from the external surface of the input shaft194, and the circumferential piston walls216fit closely with the internal wall of the rear portion146of the housing134, forming an annular space therein. Corresponding internal and external shoulders218are formed where the piston transitions from the front212to the rear214piston portion.

The front end of the front portion212of the piston196engages a spacer sleeve220positioned on the outside of the input shaft194. One end of the spacer sleeve220engages the shoulder210on the outside of the input shaft194, and the other, rear end of the spacer sleeve220abuts the front portion212of the piston196. The front portion212of the piston196, on its external circumference, forms an annular recess222. The rear end of the annular recess forms an annular shoulder224to work in conjunction with the locking balls152to fix the piston196and input shaft194relative to the housing134, as is explained in more detail below.

Referring still toFIGS. 5-10, and particularlyFIG. 6, various components are positioned within the annular space between the walls216of the rear portion of the piston196and the input shaft194, referred to above as the piston assembly154. A load cell200is received on a bearing on the input shaft194in order to allow the input shaft to rotate relative to the load cell, and the load cell abuts on its front side the internal shoulder218of the piston196. The internal shoulder218of the piston196is the surface against which the load cell is compressed to measure the tension in the cable system. In one embodiment the load cell is concentrically positioned around the input shaft194, and because of this annular orientation around the input shaft194, the load cell200measures 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 shaft194is attached.

An assembly of items that generally combine together to apply a load responsive of the cable tension to the load cell200, called the compressive component225, are described hereafter. In one example described herein, an axial collar226abuts the rear surface of the load cell200and extends along the walls216of the second portion214of the piston196. Structure associated with the piston assembly154external to the housing134may be attached to the collar226, such as by a screw228, and extend through the slot160in the housing134. This external structure thus may move along with the piston196. This structure may include the input/output communication cable230for the load cell200, among other items. A radial collar232is positioned about the input shaft194inside the rear end of the axial collar226. The front face of the radial collar232engages a facial bearing234. The radial collar232may rotate with the input shaft194while in engagement with the facial bearing234. The facial bearing234helps isolate the rotation of the radial collar232with the input shaft194from the load cell200. The facial bearing234is supported by a mount236, which may itself be mounted on a bearing on the input shaft194. The front surface237of the mount236may engage the rear surface of the load cell. A retaining collar238is mounted on the input shaft194and is held in axial position against the radial collar232by a retainer240and snap ring washer242. This compressive component225, 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 cell200is derived, in one embodiment, from the cable pulling on the input shaft194as the cable system is tensioned. As the input shaft is pulled to the left (in the orientation ofFIG. 6), the compressive component225applies a load to the load cell200. In more detail of this particular example, the snap ring washer and retainer240apply a force in that direction to the retaining collar238, which in turn applies a load in that direction to the radial collar232, which in turn applies a load in that direction to the facial bearing234and mount236, which in turn apply the load in that direction to the load cell200. The load cell abuts on its front surface the shoulder structure218of the piston196, and is thus compressed between the load applied as described above and the shoulder structure218. The piston196, 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 line230to the control system128for storage, display, analysis and/or possible control of the nut runner and tensioning tool.

Various other structures may be employed to create the compressive component225to apply a load to the load cell200and allow the input shaft194to rotate. For instance, and in a non-limiting manner, the retaining collar238may be circumferentially mounted on the input shaft, similar to the radial collar232. 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 collar232, facial seal234, and/or other components may also not be included. Also, the axial collar226may be axially movable relative to the piston walls and be operably associated with the retaining collar240and snap ring242and 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 mount236, to the load cell200. 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 mount236, facial bearing234and radial collar232mounted 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 cell200. 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 component225may also include, in another example, the radial collar232, mount236and 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 component225in axial position on the input shaft in order to apply the tension load to the load cell. The compressive component225that engage the load cell200may be positioned annularly around the input shaft to engage the load cell200about its annular shape. The portions of the compressive component that are inside the axial collar226may 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 component225associated with the piston assembly and input shaft194may 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 cell200may be positioned in the main body, and operably associated with the main body or piston196in 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 end208of the input shaft194, as mentioned above, is arranged to engage the drive end of the nut runner122, and may axially slide there along as needed when the input shaft194is moved axially, as explained below. The particular engagement arrangement of the nut runner122and the input shaft is not critical to the nature of the invention described herein.

Continuing to refer toFIG. 6, a return spring244is positioned in the second portion146of the housing134to urge the piston196forwardly in the housing134. In this instance the spring244is positioned between a portion of the nut runner122fixed by a snap washer245to the rear of the housing134, and the axial collar226. The return spring244compresses as the input shaft194and piston196are moved axially rearwardly, and continually biases the piston196and input shaft194forwardly. This forward biasing force will be described in more detail hereafter.

Referring still generally toFIGS. 5-8, and particularly toFIG. 7for clarity, the release ring136is positioned around the front portion142of the housing134and moves axially on the along the front portion142. The release ring136includes an annular inner lip246and an annular outer lip248extending forwardly, with a gap250formed there between (SeeFIG. 6). The gap250receives the rear lip190formed on the barrel132. An annular recess252is formed facing rearwardly to receive and seat the front end of the release spring254. The rear end of the release spring254engages the outer shoulder148of the housing134. A rear portion of the release ring136extends over and moves relative to the second portion146of the housing134to help contain the release spring254. The radially inward surface256of the inner lip246acts to retain the locking ball152in the aperture150in the first portion142of the housing134. A cam or shoulder surface258is formed around the base of the inner lip246to encourage the locking ball152to move radially inwardly through the aperture150as the release ring136is moved forward relative to the housing134, as is described below.

The release mechanism, in this instance a release ring136, may move from a forward position to a rearward position along the front portion142of the housing134. The release spring254biases the release ring136towards the forward position. In the forward-most position, the release ring abuts the annular lip190on the barrel132. (SeeFIG. 7). The release ring136may also take the form of a lever or other structure not in the form of a ring or circle.

The input shaft194is operably engaged with the piston196to move the piston rearwardly when the input shaft194moves rearwardly (toward the nut runner122). The input shaft194may be operably engaged with the piston196to move the piston forwardly upon forward movement of the input shaft194.

The operation of the tensioning apparatus120is now described with respect toFIGS. 5-8. After the nut126is threaded onto the end of the threaded rod124as described above, the nut126is positioned in the end effector138and is engaged with the input shaft194to be turned by the input shaft as the input shaft is turned by the nut runner122. Prior to insertion of the nut126, the tensioning apparatus appears in the ready state shown inFIG. 5. In the ready state, the input shaft194is positioned forwardly in the barrel132with the end effector138positioned and ready for insertion of the nut126. In this forward position, the piston196is in its forwardmost position with the outer shoulder218engaging the inner shoulder148of the housing134. The release ring136is in its rearward most position, with the locking balls152moved by the outer surface of the first portion of the piston196to their radially-outermost positions in the respective apertures150in the first portion142of the housing134and bounded by the inner-lip246of the release ring136. The release ring136may not move any more forwardly because of the locking balls152, which engage the cam surface258of the release ring136. Since the locking balls152are held in position by the walls of their respective apertures150, the locking balls152keep the release ring136from moving forward under the force of the release spring254. The return spring244in the housing134is in the extended position. In this embodiment, the rear end of the input shaft194is in engagement with the nut runner122.

FIG. 6shows the tensioning tool120positioned over the nut126, and specifically the nut126being received in the end effector138. This is performed manually, or may be performed automatically with the appropriate automated equipment. In this position the tensioning tool120stays in the ready state. Note that the nut126, in this embodiment, defines a circumferential groove260for receiving the nut engaging balls182in the end effector138. When positioned in the end effector138, the groove260in the nut126is radially aligned with the nut engaging balls182. The arrow262represents the movement of the tensioning tool120towards the bracket116, which may occur at this time.

FIG. 7shows the nut126and the end effector138having been pushed into the barrel132. This movement is performed manually by an operator grasping the threaded rod124and pushing the threaded nut126into the tensioning tool120a certain amount. It may be performed automatically, also, with the appropriate automation device. Moving the nut126further into the tensioning device120has at least two purposes. First, it causes the end effector138to engage the nut126in the input shaft194and retain it there both axially and rotationally (the end effector138has a recess having a complementary shape to the shape of the nut126). Second, the rearward movement of the input shaft194actuates the locking device198to firmly engage the piston196in the retracted position with the barrel132and housing134, forming the rigid structure against which the tension of the system, created by the cable pulling on the input shaft194, is measured during the tensioning step. Also, by moving the nut126away from the equalizer bracket116, the tension load measured is substantially isolated from the normal forces on the face of the nut that would affect that measurement if the nut126was in engagement with the equalizer bracket116.

Referring still toFIG. 7, the nut126is withheld by the end effector138by at least one nut engagement ball182that is held in engagement with a groove260in the nut126. As the nut126is moved rearwardly, the nut engagement ball182moves through the aperture206in the front end of the input shaft194. As the ball182and the input shaft194move rearwardly relative to the barrel132and housing134, the cam surface180on the front collar length168helps urge the ball182radially inwardly through the apertures206and into the groove260in the nut126. The ball182is held in this engaged position with the nut126by the internal surface of the front collar length168of the barrel132. In this way, when the input shaft194is moved rearwardly into the barrel132, the nut126is releasably engaged with the end effector138and the nut126then moves axially and rotationally with the input shaft194. The distance the nut126must be moved into the end effector138to cause engagement is generally the relief distance. The relief distance may be that distance which the nut126must 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 system128may instruct the nut runner to lessen the tension by appropriately rotating the nut along the threaded shaft124.

Still referring toFIG. 7, the rearward movement of the input shaft also causes the piston196(and piston assembly154) to move rearwardly in the tensioning tool120. The input shaft194causes the spacer collar220to move, which in turn causes the piston196to move rearwardly. The piston196moves rearwardly in the housing134, compressing the return spring244. The rearward movement of the piston196also moves the front portion212of the piston196rearwardly relative to the locking ball152held in the release ring136. As the front portion212moves rearwardly, the recess222formed therein moves under the locking ball152(or balls). The locking ball152, while positioned in the recess222and engaging the outer surface of the front portion212of the piston196and the shoulder224of the recess222, moves from engaging the cam258on the release ring136, which was keeping it in its rearward most position. As the locking ball moves radially inwardly, encouraged by the angular force applied by the cam258on the locking ring136, the locking ball152moves through the aperture150into the groove222on the front portion of the piston, and out of interfering engagement with the release ring136. The release spring254then biases the release ring136forwardly on the front portion142of the housing134to the release ring's forward-most position. In this forward-most position, the axial lip190on the rear of the barrel132is received in the annular recess250between the radially inner246and outer lips248at the front end of the release ring136, thus prohibiting the release ring136from any further forward motion. This brings the inner retaining wall270of the release ring136into engagement with the locking ball152, which then holds the locking ball152against the piston196. At this location, the piston196is biased forward, so the shoulder224at the border of the recess222is pushed into engagement with the portion of the locking ball152extending radially inwardly from the aperture150, thus keeping the piston196from moving any further forwardly. The piston196thus may not move any further forwardly relative to the barrel132or housing134, and is fixed axially relative to the input shaft194. The piston walls216, 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 ring245positioned in the inner wall of the housing134at the appropriate location, used to hold a portion of the drive means122in location in the housing134. Note, at this position, if the piston walls216were of shorter length, the input shaft194and piston196may be pushed further into the barrel and housing if desired, but need not be.

The release ring136, forward portion of the housing142, locking balls152and the forward portion212of the piston196combine to create a mechanical locking system198. This mechanical locking system198converts the relative movement between the barrel132and housing134with the piston196into a rigid column. This mechanical locking system198works automatically under the spring bias of the release spring254primarily in operative association with the release ring136. Once the input shaft194and piston196are pushed far enough rearwardly into the barrel132and housing134, the locking mechanism198engages to automatically to form the rigid column between the housing134, barrel132and piston196. 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 arrow272inFIG. 7shows the relative motion of the input shaft194and piston assembly154. The arrow274shows the relative motion of the release ring.

In this locked mechanical column system shown inFIG. 7, the load on the cable system is measured by the load cell200positioned between the now anchored inner shoulder218of the piston196and the compressive component225, including in one embodiment the collar238mounted near the inner end of the input shaft194. As the system is tensioned (as explained below), the cable106pulls the nut126, which pulls the end effector138, which pulls the input shaft194, which pulls the collar238(and the elements of the compressive component225) to effectively compress the load cell200. The compression of the load cell200is communicated to the control system128and translated to a tension load, which data is used by the control system128for display and to control the nut runner122and possibly other equipment.

The cable system, as described above regardingFIG. 7, may now be tensioned with the tensioning tool120. At this position, the control system128may send control signals to the nut runner122, which rotates the input shaft194, and thus rotates the nut126on the threaded rod124. As the input shaft194is rotated, the piston196may not be rotated. In the embodiment described herein, the collar238in engagement with the facial seal rotates with the input shaft194. As the threaded rod124is pulled through the nut126, the tension increases in the brake cable system. As the tension increases, the load cell200senses the load by being compressed by the compressive component and transmits signals to the controls system128to 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 runner122to increase and decrease tension as desired), the nut runner122may be deactivated. During tensioning, the tensioning tool may engage the bracket116, such as at its front end as shown inFIG. 7, against which to react during the tensioning step. The tensioning tool120may be engaged against another fixed or anchor surface whether or not directly in contact with the bracket116.

After tensioning is complete, the tensioning tool120may be released from the nut126. This is shown inFIG. 8. To release the nut126from the tensioning tool120, the release ring136is slid rearwardly (arrow276) on the first portion142of the housing134. This disengages the inner retaining wall270of the release ring136from the locking ball152, and allows the locking ball152to move radially outwardly, being urged radially outwardly by the cam surface224on the forward portion212of the piston. As the locking ball152moves radially outwardly, it disengages from the cam surface224on the piston196, and thus allows the piston196to move further forwardly in the tool120, along with the input shaft194. The piston196moves forwardly far enough to cause the outer shoulder218of the piston196to engage the inner shoulder148of the housing134. This forward movement of the piston196, if not caused by the tension in the cable system pulling the nut126and the input shaft194towards the equalizer116(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 spring244pushing the piston196forwardly in the housing134.

As the piston196moves forwardly in the housing134, it pushes the input shaft194forwardly also. The input shaft194is pushed forwardly far enough to allow the nut engagement balls182to release from engagement with the nut126(by being forced radially outwardly through the apertures206in the forward end of the input shaft194by the cam surface at the border of the groove260on the nut), thus allowing the nut126to be removed from the end effector138. This is shown inFIG. 8. In the position shown inFIG. 8, once the nut126is removed, it is the initialized state as shown inFIG. 5. The tool120is ready to be attached to another brake system for the tensioning operation. The arrow278inFIG. 8shows the relative motion of the piston196, input shaft194, and piston assembly154upon activation of the release ring136, all relative to the housing134and barrel132.

The method in which the tool120is used includes the acts of engaging the nut126in the tool120, causing the nut126to be rotationally engaged with the tool120, causing the tool120to be in an orientation facilitating tensioning the brake cable system with a mechanically rigid structure formed by the tool120(these last two acts may occur simultaneously, as described herein, or may occur non-simultaneously with one occurring before the other); causing the tool120to tension the brake cable system, and causing the tool120to release the nut126from the tool120. The nut126may be positioned manually in the tool or by an automated machine. The release ring136may be operated manually or by an automated machine.

FIGS. 9aand9bare an exploded view of the brake tensioner shown inFIGS. 5-8.FIG. 9a, with reference to the descriptions ofFIGS. 5-8, shows the barrel132, washer192, front collar length168, release ring136, input shaft194, rear collar length176, spacer collar220, release spring254, and housing134.FIG. 9b, as a continuation ofFIG. 9a, shows the piston196, load cell200, radial collar232, axial collar226, return spring244, snap ring245, and nut runner122with components.

FIGS. 10 and 11show another example of the tensioning tool120earlier described, prior to engagement with the nut (FIG. 10) and after the tensioning step, but before disengagement from the nut (FIG. 11). The tool120works in much the same way as that described with respect toFIGS. 5-8above. The barrel132and body134are rigidly attached together, and the input shaft194and piston196, with its accompanying structure (load cell200, washers, etc.) are situated in the barrel132and housing134in order to move relative thereto. The release ring136acts to cause the mechanical locking mechanism198to actuate, and releases the mechanical locking mechanism198similarly to the previous embodiment. The release ring136, in this example however, does not have a forwardly extending lip, nor does the barrel132have a rearwardly extending lip, as the previous embodiment does. Instead, the front edge280of the release ring136is relatively flat and abuts a flange282on the rearward end of the barrel132to denote the forward-most extent of the release ring's movement. The engagement of the nut, formation of the rigid column, tensioning, and disengagement of the nut, are all similarly accomplished in this example.

In other examples, the housing of the tool encloses a tensioning assembly that does not move axially relative to the housing, and instead is axially stationary therein during connection with the cable system, tensioning the cable system, and releasing the cable system. The tensioning assembly moves in a rotational manner about the longitudinal axis of the tool. Two examples of such a tool are described below. The examples of these tools work with the control system as described above as with the previous examples, and may be utilized with a threaded rod, nut, and equalizer structure, also all as described above.

FIGS. 12-22show different aspects of another example of a tensioning tool320.FIGS. 12-13show the tool320having a housing322with a front portion324and a rear portion326. The front portion324encloses a load measuring structure and a nut engagement feature to secure the end of the threaded rod124to the front end of the front portion324. The rear portion326extends downwardly from the rear of the front portion324, and encompasses a gear structure for engagement with the nut runner122to drive the rotational movement of the load measuring structure within the front portion324. An actuator button328on the rear of the rear portion326allows a user to secure and release the threaded rod124from the tool320as explained below.

With specific reference toFIG. 12, the front portion324defines a front aperture330, through which the nut126and an end of the threaded rod124are inserted to be secured in the tool320. A sub-housing332extends down from the front portion324and defines another aperture334. This aperture334receives a fastener398, such as a screw, to secure the sub-housing332with the end of an actuator or push rod397(seeFIGS. 20-22). The other end of the push rod397is attached to the actuator button328. The triangular housing332moves when the push rod397is moved, and causes the engagement and release of the nut126within the aperture330of the front portion324, as described in greater details below. The aperture336shown in the downwardly extending rear portion326may receive a portion of the nut runner122when attached to the tool320.

FIG. 13shows a rear perspective view of the tensioning tool320, which shows a rear aperture338to receive an end of the threaded rod124in the event the nut126is threaded down sufficiently on the rod124to require the free end of the threaded rod124to extend there through. The actuator button328is also shown, which when depressed forwardly (inFIG. 16, into the page in the axial direction of the front portion), the actuator button328moves the triangular sub component332in the same direction.

FIG. 14shows a load cell component340that makes up part of the front housing324and downwardly descending rear housing326. The top portion342of the load cell component340is circular in cross section, and defines a central aperture344for rotatingly receiving an input shaft380(seeFIGS. 20-22) that rotates to turn the nut126on the free end of the threaded rod124. The slot346that extends around a portion of the forwardly-extending cylindrical rim348associated with the top portion342facilitates the axial movement of the triangular sub-housing332as it moves fore and aft. The intermediate aperture344receives the push rod397attached to the actuator button328to move the triangular sub housing332. The lower aperture336is the same aperture336as shown inFIG. 12.

Referring at least toFIG. 14andFIG. 20, the top portion342of the load cell component340includes a central portion or wall347and an annular rim348extending from the perimeter of the central portion347. The central portion347defines the aperture344, and the annular rim348defines a recess350for receiving other components as described below. In this example, the central portion347is configured to integrally include an annular load cell352. In other examples, the central portion347may be hollow or otherwise configured to receive a separate load cell component that would fit into a region of the central portion347.

FIG. 15shows a rear view of the load cell component340. Recesses352a-352care formed in a downwardly-extending leg354of the load cell component340and receive gear assemblies that engage the nut runner tool122and drive the rotational motion of the input shaft380to tension the cables106. The recesses352a-352care substantially vertically aligned with one another in overlapping relationship so that the recesses352a-352care open to one another. In this configuration, when inserted into the recesses352a-352c, the gear assemblies mesh with one another to transfer rotational torque from the nut runner122to the input shaft380, and ultimately to the nut126. A boss or sleeve356may be positioned centrally around the aperture344within the intermediate recess352bto positively locate a gear assembly within the recess352band/or to radially separate the respective gear component from the push rod397(seeFIGS. 20-22). Although not depicted, a boss or sleeve356may be included within the recess352a.FIG. 16shows a side view of the load cell component340of the tool320.

FIG. 17-19are various views of the triangular sub-component332(also referred to as a release fork) of the front portion324. The triangular sub-component332includes a concave outer wall358that generally corresponds in shape to the cylindrical rim348of the load cell component340. A flange360, which may be substantially U-shaped, extends inwardly from the concave wall358. A described in some detail below, the sub-component332(which may be triangular or other suitable shapes) is actuated to move forwardly and rearwardly with the push rod397. The flange360is effectively a key tab, which is received in a slot362in a floating sleeve364(see below). A key tab is a structure that fits into or with a second structure, and may cause the second structure to move under the influence of the key tab. The floating sleeve364is used to engage and disengage the nut126mounted on the free end of the threaded rod124from the tool320. The substantially U-shaped flange360is positioned forwardly of a vertically-extending mid-line, front to back, of the triangular sub-component332.

FIGS. 20-22are cross sectional views of the tool320ofFIGS. 12 and 13. The front housing324includes the top portion342of the load cell component340and a nose portion366having a central aperture368that is fitted to the front of the load cell component340. The nose portion366includes a collar370extending outwardly and around to define the central aperture368, and to form an outer rim372against which the equalizer116is positioned during use. A flange374extends inwardly of the nose portion366to be received inside the outer rim348of the front end of the load cell component340. The flange374and rim348are secured together, such as by being press fit, threaded, glued, welded, or otherwise assembled. Such assembly may be in a manner allowing the nose portion366to be removed if desired. A back cover376is attached to the rear of the front and rear portions to cover the recesses352a-352cin which the gear mechanisms378are positioned to drive the input shaft380. The back cover376includes an aperture382aligned with the central aperture344of the front portion342. The back cover376may be removable.

Referring still toFIG. 20, the input shaft380is rotatably received through the central aperture344of the housing for the load cell384, as well as through the load cell component340. While the load cell component340includes an integrally-formed load cell384for sensing the compression caused by tension in the cable106, as noted above, a separate load cell may be positioned in this central region (shown in dash) and have the same or similar performance. Communication lines386(such as wires) extend from the load cell384through the slot to the control system128for the communication of signals, etc. The input shaft380has a radially extending shoulder386at or near its rear end. The peripheral edge378cof the shoulder386of the input shaft380engages the gear mechanism378a,378bdriven by the nut runner122. The nut runner122thus actuates the gear mechanism378, which in turn actuates the input shaft380to rotate about its longitudinal axis in the central aperture344.

A thrust bearing388is positioned between the shoulder386and the rear surface of the central portion347of the load cell component340, and is loaded against the bearing388in a compressive manner when under tension from the cable system during use. The input shaft380in this example does not move axially inside the housing322, and is instead axially secured to not move appreciably during use, as described below.

Still referring toFIG. 20, the forward end of the input shaft380defines the nut engagement chamber390having the retention ball bearings392as described above, and having faceted internal sidewalls to mate with the sidewalls of the nut126. A generally annular-shaped float sleeve364is positioned around the cylindrical outer circumference of the input shaft380, positioned between a front face of the central portion of the load cell384and the rim of the rear flange374of the nose member366. The float sleeve364defines a circumferential slot362on its outer perimeter. The upwardly-extending, substantially U-shaped flange360on the triangular sub-component332is received in the slot362. A front section of the inner diameter of the float sleeve364has a larger diameter, and the rear section of the inner diameter of the float sleeve has a smaller diameter, with a sloped cam-face394extending between the two diameters. The float sleeve364does not rotate with the input shaft380. The float sleeve364may move axially relative to the input shaft380.

The cam-face394on the float sleeve380is sloped forwardly and outwardly to act as a ramp. When the float sleeve364is moved forwardly in the cavity396between the front face of the central portion347of the load cell component340and the rim of the rear flange374of the nose366, the ramp394pushes the ball bearing engagement structures392inwardly to fit into the groove on the nut126and securely receive the nut126in the end of the input shaft380. This is described below with respect toFIG. 22.

A push rod (release rod)397is received in the aperture344formed in the downwardly extending rear portion354of the tool320. The push rod397, at its rear end, is mounted with an actuator button328that the user may push or pull. The free end of the push rod397is mounted to the triangular sub component332by a fastener398. The push rod397has a length that is sufficient to allow the actuator button328to be pushed forwardly to the second position (generally in the direction of the front portion of the tool) which in turn pushes the triangular sub component332in that direction and for the same distance also. The movement triangular sub component332causes the float sleeve364to move accordingly (due the key tab360engagement in the slot362of the float sleeve364) within the cavity396in the front portion of the tool320. The key tab360extends through a slot346formed in the housing322. This, as explained with respect toFIG. 22, locks the nut126in the input shaft380.

When the push rod397is positioned in the first position, the actuator button328is spaced away from the back cover376of the tool320, and the triangular sub-component332is positioned so that the key tab360has pulled the float sleeve364rearwardly on the input shaft380to release the nut126.

Referring now toFIG. 21, the nut126is received in the end of the input shaft380, and the float sleeve364and push rod397are in the first position with the nut126not secured in the input shaft380. This represents the first step of the method of tensioning the park brake system utilizing this example of the tool320. The nut126, threaded on the end of the threaded rod124with the threaded rod124positioned through the equalizer116, is placed into the end of the tool320and into the nut-receiving chamber390of the input shaft380. This may be done manually by an operator, or automatically. The rim372of the collar370on the nose portion366is then engaged with the equalizer116to bear against the equalizer116as the tensioning steps are performed. The distance between the outer end of the nut126and the equalizer surface116against which the tool320rests is the relief distance399.

FIG. 22shows another step of the method of using the tool320in tightening the cables106of the brake system. The actuator button328is pushed from the first position to the second position, which moves the triangular sub component332forward the same amount, which in turn moves the float sleeve364(by way of the key tab360engagement within the slot362of the float sleeve364). The float sleeve364is moved from a rear position in the cavity396to a forward position in the cavity396, which in turn causes the ramp394to engage the ball bearings392and push the ball bearings392radially inwardly to engage the nut126. The ball bearings392are held in place by the inner radius of the rear portion of the float sleeve364while the actuator button328is in the second position. The nut126is rotationally fixed to the input shaft380due to the mating faceted surfaces of the nut receiving chamber390engaging the corresponding faceted outer surface of the nut126.

As explained in more detail above and below, at this point the control system128operates the nut runner122to perform the tensioning method suitable for appropriately tensioning the brake system cables106. In this tool320example, the load cell384is compressed between the shoulder386of the input shaft380and the rear face of the central portion357of the load cell component340. The load cell component340is a portion of the housing322of the tool320, which through the nose member366, engages the equalizer116to anchor the load bearing system to a fixed position against which to measure. This structure is a solid column against which the load cell384is compressed, and provides superior stability and repeatability in the measurements of the tensioning load applied to the cables106during the tensioning operation. The load cell384is not moved axially during this process, for instance to secure the nut126. Instead just the floating sleeve364is moved relative to the housing322, load cell384, bearings392, nose366, and nut126to lock the nut126into input shaft380. No hydraulics or pneumatics are required to actuate the tool320, simply the manual (or automatic) actuation of the push rod397to engage the nut126, and the control system's128actuation of the nut runner122to perform the tensioning steps.

Another example of a tool420is shown inFIGS. 23 through 35. In this different example, the tool420has a substantially similar structure to the example shown inFIGS. 12 through 22, and operates in a similar manner. As shown inFIGS. 23,24and25, the tool420includes a body or housing422having a front housing or portion424, a rear housing or portion426, and a sub-housing430. The housing422receives the operating parts necessary, as discussed above regarding the previous example, for engaging the threaded rod124and nut126, actuating an engagement structure, and rotating the nut126relative to the rod124to tension the cable system to the desired level.

The rear portion426and the front portion424are generally cylindrical in shape. As shown inFIG. 23-25, the front and rear portions424,426are configured to engage one another adjacent respective ends, and are offset from each other so as to have parallel axes that are spaced apart from one another. The offset of the front portion424relative to the rear portion426is beneficial in reducing the overall length of the tool420(since some parts may be overlapped, such as the gear drive), which enhances maneuverability and the ability to position the tool420in a more direct alignment with the axial extension of the cable end during use. The shape of the tool420(offset front and rear portions424,426) along with the length together are helpful to require less clearance respective of other components during use, and also aids alignment with the cable end.

A release rod428extends through the rear portion426and through the sub-housing430to engage a release tab432. An actuator button434is attached at the opposite end of the release rod428relative to the release tab432to aid in actuating the release rod428and release tab432. The rear portion426receives the nut driver or runner122through an opening or recess436(best seen inFIG. 25) for actuating the input shaft438, which is positioned in the front housing424. The front housing424includes an aperture440at a distal end for receiving the threaded rod124and nut126combination as noted above. A slot442is formed in the front case or casing428adjacent or near the location of the load cell444to accommodate a load cell communication line. A collar446extends through the slot442, and receives or guides the communication lines to and from the load cell444positioned in the front case428as defined below. The slot442has larger dimensions, both axially and radially, than the collar446to facilitate possible movement of the collar446with respect to the front case448.

FIG. 26is a cross section of the tool420of this example, showing the tool420adjacent a portion of an emergency brake cable system, which includes an equalizer116receiving the threaded rod124end of a cable106, and a nut126partially threaded onto the end of the rod124.

Referring still toFIG. 26, the front housing424includes a sleeve or nose portion448attached at its rear end to the front casing430, in turn attached to a back cover450. The rear portion426includes a mounting cylinder452with a mounting cover454positioned at its rear end. The front case430extends away from the front housing424to encompass the front end of the back portion426, and the back cover450of the front housing424extends away from the front housing424and generally coextensive with the front case430to serve as an internal frame structure of the rear portion426. For instance, the back cover450defines an aperture through which the release rod428extends.

With reference toFIGS. 26 and 27, the nut engagement end452of the input shaft438is shown and described, and is also referenced herein as the end effector. The input shaft438is positioned in the nose portion448of the front housing424, and has a front section438ahaving a front end, and a rear section438bhaving a rear end. The front section438adefines a central bore454with a nut receiving engagement cavity456at its terminal front end. The front section438a, adjacent the nut engagement cavity456, is rotatably supported by a bearing458. The nut engagement cavity456is not engaged with the nut126inFIG. 26, and inFIG. 27the nut engagement cavity456has received the nut126, but the nut126is not secured within the cavity456. As shown inFIG. 26, the nose portion448includes a float sleeve460which moves axially under the control of the release rod428and tab432. The float sleeve460, when moved axially towards the front end of the input shaft438causes ball bearings462to move axially inwardly, similar to that described above, to engage the annular groove464formed in the nut126. This locks the nut126in the engagement end452. The nut126has facets formed on its outer perimeter for mating engagement in the engagement end452. Thus, once locked into the engagement end452, the nut126turns with the input shaft438to cause the nut126to move along the threads of the threaded rod124. The input shaft438may be solid, hollow, or a combination, and the outer surface may take the form of a complete cylinder where it is hollow, or a partial cylinder with a discontinuous outer surface (slots, braids, holes, continuous, spiral strips, etc.).

Referring toFIGS. 26 and 28, the input shaft438has a front hollow section438aand a rear solid section438b. The rear section438bforms a solid rod, and has an outer dimension reduced in diameter from the front section438a. A shoulder438cis formed where the front section438atransitions to the rear section438band the outer dimension is reduced in size. The input shaft438is received in the front nose448of the front housing424, and extends through the front housing424. The front wall466of the front case430includes a collar468extending axially there from, coaxial with the input shaft438rotational axis. The collar468forms a cylindrical recess, which receives a rotational bearing470. The rear section438bpasses through the rotational bearing470, and an aperture formed in a front wall466of the front case430, at the center of the base wall of the collar468. The shoulder438cof the input shaft438engages an end of the bearing470, which in turn engages the base wall of the collar468(front face of the front wall466). This forms a solid structure against which the rear section438bof the input shaft438is loaded, as explained in more detail below.

An output gear472is mounted on the rear end of the rear section438bof the input shaft438to engage with the gear drive of the nut runner122. Positioned on the rear section438bof the input shaft438between the rear face of the front wall466and the output gear472are: the load cell444, with a front rim engaging and bearing against the back side of the front wall466of the front case468; a compression washer474, which bears against the back rim of the load cell444; a thrust bearing476positioned between the washer474and the output gear472. The load cell444, compression washer474, thrust bearing476, and output gear472all rotate with the input shaft438. The mounting of the output gear472on the rear end of the rear section438bof the input shaft438may retain the thrust bearing476, compression washer474, and load cell444on the rear portion438bof the input shaft438between the rear face of the front wall466of the front case468and the output gear472. The shoulder438con the input shaft438butts up against the front rim of the shaft bearing470, and provides the anchor against which the fastener478of the output gear472applies a force. As explained in more detail below, when the input shaft438is under load from the tensioning process, the output gear472axially (along the centerline of the input shaft438) compresses the thrust bearing476against the compression washer474, which in turn compresses the load cell444against the rear face of the front wall466, which provides the direct measurement of the tension in the cable106during the tensioning process. The load may be designed to not be axial and along the centerline, but instead may be axial and parallel to but spaced away from the centerline of the input shaft438.

As with some of the previous examples, the load cell444surrounds the input shaft438, and in one example is concentric to the input shaft438. In this way the load cell444is concentric to the axis of the tension load caused by the tensioning of the cable system, and the tension load is axially aligned with the centerline of the input shaft438. As noted elsewhere, the load cell444is stationary relative to the external body or housing422during the tensioning operation. The load cell444may also be axially stationary relative to the input shaft438, which rotates relative to the load cell444.

The rear portion426of the tool420is shown and described with respect toFIGS. 26 and 29. The rear portion426is formed from a portion of the front casing or plate430extending above the front portion424(inFIG. 26andFIG. 29), a portion of the back cover450also extending upwardly from the front portion424and spaced rearwardly from the front casing or plate430to form a cavity there between, a mounting cylinder452extending generally rearwardly from the back cover450and defining a second cavity480for receiving the nut runner122, and a mounting cover454forming the rear wall of the mounting cylinder452.

The release rod428extends through an aperture formed in said rear portion426, which aperture extends through said mounting cover454, back cover450, and front case430. The release rod428defines a rear end having a button434attached thereto, and a front end having a release tab432attached thereto and extending generally radially there from. A pair of grooves or indentations482is formed adjacent the rear end of the release rod428to interact with a spring-loaded ball484to form a detent structure for positioning the release rod428in a forward (actuated) position or a rearward (un-actuated). Each detent structure acts to movably secure the particular axial position of the release rod428in the housing, and indicates that the release rod428, and thus the release tab432, is positioned in either the forward position to actuate the engagement end452of the input shaft438, or the rearward position to de-actuate the engagement end452of the input shaft438. When in actuated or forward position, the release tab432pushes the floating sleeve460towards the nose448, which in turn pushes the ball bearings462radially inwardly to engage the nut126. When in the rearward, or de-actuated, position, the release tab432pulls the float sleeve460rearwardly to disengage from the ball bearings462, and release the nut126. The detent ball484engages the grooves or dents482of the release rod428under the biasing force of a spring486and selectively maintains the release rod428in the particular selected position. The release rod428may be moved from this position by axially loading the release rod428to overcome the spring486bias force holding the ball484in the dent or groove482. Other structures are contemplated for releasably securing the release rod428in the forward position, or in other positions. The floating sleeve460defines an annular groove488adjacent its rear end, the annular groove488receiving the tip of the release tab432(seeFIG. 26). The release tab432, when positioned in the groove488, thus causes the float sleeve460to move, or stay stationary, in conjunction with it. For example, the release tab432moves the float sleeve460forwardly when the release rod428is moved forwardly, and moves the float sleeve460rearwardly when the release rod428is moved rearwardly. The release tab432may be received in a slot489formed in the outer housing490of the front portion424. The edges of the slot489define the maximum extension and retraction of the release rod428, with the detents482described above positioned accordingly at the limits or elsewhere along the extension distance as desired.

Continuing to refer primarily toFIG. 29, as well as others ofFIGS. 26-35, the release rod428, release tab432, and float sleeve460create a manual actuator for the engagement end452of the input shaft438. The manual actuator moves, such as by a human operator pushing or pulling the button434, relative to the tool body or housing422. The manual engagement is effectuated by axial movement of a member (release rod428) in operable engagement (release tab432engaging with the float sleeve460) with the engagement end452of the input shaft438. The movement of the member428relative to the body or housing422causes the engagement end452to secure the nut126for actuation by the input shaft438. The manual engagement is contemplated to be automatically actuated by a solenoid or other switch controlled by an operator or a logic controller. The actuation of the manual actuator moves the float sleeve460to cause retention of the nut126in the input shaft438. During engagement with the nut126, tensioning of the cable system, and disengagement with the nut126, the load cell column, as defined above, is not in this example axially moved relative to the body or housing422, or the input shaft438, and thus remains substantially stationary. The member428allows for external actuation of the input shaft438to engage the nut126, in this example by use of the release rod428. The release rod428, engagement tab432, and float sleeve460move collectively relative to the load cell444. The term “external” as used herein may include by a mechanism not entirely received within the body or housing422.

This structure provides a sound, well anchored, and simplified load cell-based tensioning and measuring system. The load cell444in this and the previous example shown inFIGS. 12-22, is rigidly mounted in a column-like structure, and when under tension load from the cable system, is anchored and compressed against the front case430of the body or housing422, which in turn is abutted against a rigid structure, such as the equalizer116or other such item. This provides a solid foundation for the column structure of the load cell444to be compressed against to register or directly measure the tension in the cable system along the axial line of extension of the cable106. The load cell measurement mechanism described herein need not be assembled into nor disassembled from the cable system itself. Instead it is attached to the end of the cable system, which provides ease of access and accurate measurement, along with a minimal time requirement to tension and measure the brake cable system during assembly, repair or maintenance.

In continuing reference toFIGS. 26 and 29, the cavity480formed between the back cover454and the front case430receives the gear train492. The gear train492includes an input gear493in rotary engagement with an idler gear494, which is in rotary engagement with the output gear472. The output gear472is in rotary engagement with the input shaft438as described above. The input gear493includes a connector structure, such as a receiving aperture495, to receive a nut runner122having a head portion positioned in the second cavity480(seeFIG. 25). The nut runner122is rotated under electric, pneumatic, or hydraulic power to rotate the input gear493, which in turn actuates idler gear494, which in turn rotates the output gear472. The rotation of the output gear472causes the input shaft438to rotate, which in turn rotates the nut126secured in the engagement end452of the input shaft438to rotate relative to the threaded rod124and cable106. More or fewer gears are contemplated for use in the gear train492.

The operation of the tool as described above is now described with reference to the structure and function described above, and with respect to the method steps or acts referred to below, and with respect to FIGS.26and30-35.

The pre-install step includes the threaded rod124as shown inFIG. 26extending through the aperture formed in the equalizer116and secured with the nut126. The nut126is minimally attached to the threaded rod124, engaging with optionally only a few threads to hold it in place on the rod124before or after the vehicle arrives at the tensioning station.

As shown inFIG. 30, in a following step, the nut126and threaded rod124are pushed and/or pulled into the nose448of the end effecter452of the input shaft438. This action positions the nut126inside the engagement end452of the input shaft438, where the nut126is received and oriented in the end effector452to be positioned with groove464of the nut126adjacent to the balls462in the end effector452.

In a following step, shown inFIG. 31, the operator pushes on the engagement button434which moves the release rod428and float sleeve460forward relative to the tool body or housing422. The ramp498in the forward portion of the float sleeve460forces the balls462positioned in the engagement end452radially inward to be positioned in the groove464on the nut126, which locks the nut126in place. The tension in the cable system at this point may be considered a first tension level.

In a following step, show inFIG. 32, the operator insures that the nut runner122is engaged with the tool420, and that the nose end448of the tool420is resting against, or close to resting against, and engaging the equalizer116. Note the relief distance499between the end of the nut126nearest the equalizer116and the equalizer116. This relief distance499is the distance which the nut126moves after being disengaged from the tool420. Moving through the relief distance499reduces the tension in the cable system. The relief distance499may be defined in a fixed value by the extension of the nose end448of the tool420past the end of the nut126. The relief distance499may also be adjustably defined, such as by a selectively movable collar threadedly attached to the nose end448of the tool420. Other adjustable attachment structures are contemplated. The relief distance499may be in the range of 0.00 inches to approximately 1 inch, and is beneficially approximately 0.25 inches. In the examples shown inFIGS. 12-35, the nut126may be moved away from the equalizer116without having to transition or move the load cell444or the input shaft438within the body or housing422. Only the float sleeve460moves, which is intended to simply provide a mechanism to push the ball bearings462into the groove464of the nut126, and retain the ball bearings462therein until it is desired to release the nut126from the end effector452.

Continuing withFIG. 32, the operator actuates the nut runner drive122, which through the gear train492causes the input shaft438to rotate and turn the nut126. The nut126is thereby run up the threaded rod124(moved along the threaded rod124away from its terminal end) to create tension in the cable system. This tension level is referred to as the first higher tension level. In this step as shown inFIG. 32, the rod124is shown in a position to represent the higher tension level, which may be a maximum tension level. The tension in the cable system is measured by the load cell444positioned in the tool420to effectively react against the input shaft438and the fixed body or housing422. The load cell444is in communication with the control system128, and sends signals indicative of the load under which the load cell444is subjected during use. This is the “pre stretch” or higher tension level required to remove voids from the system. Once achieving this level the nut runner122may stop, be inactive for a time period allow the system to relax, and then continue to increase or decrease tension slowly until a stable tension is established or no longer drifts below a specified level. This tension level is referred to as a “stable tension” level. In this position, the nut126may be turned either way by the input shaft438to increase or decrease tension as desired. The nut runner122is controlled by a control system128, such as that shown inFIG. 1and as described above with reference toFIG. 1, and may include a smart phone, tablet, wired or wireless connection to a server or the internet for control, recording, analysis, or maintenance assessment.

Referring toFIG. 33, in a following step, before further tensioning or de-tensioning the cable system and releasing and returning the nut126to the equalizer116, it is often necessary to relieve a specified amount of tension so that when the nut126is fully released the amount of residual or final tension is higher than a determined limit (which for instance, would leave the brakes engaged). It is therefore often necessary to run the nut126in reverse a select number of rotations or angle of rotation to relieve the tension before final release. This may be achieved by slowly running the nut126in reverse to a pre-defined tension lower than the maximum pre stretch level. Any number of tensioning and de-tensioning steps may be performed before releasing the nut126, depending on the desired effect on the cable tensioning system.

Referring toFIG. 34, in a following step, the operator then moves the engagement button434to the disengaged position, causing the release rod428to move rearwardly, in turn causing the float sleeve460to slide rearwardly and release the balls462from the groove464of the nut126. The nut126is released the final relief distance499to contact, engage, and react directly against the equalizer116. A desired final tension is achieved at this point.

Referring toFIG. 35, in a following step, the tensioning tool420may be removed from the system and prepared for use on the next vehicle.

In a typical automotive parking brake system the brake pedal or hand lever is connected to a cable106which passes through an equalizer116. The equalizer116typically divides the tension force so it is evenly distributed between two cables connected to the rear brakes. The cable system typically operates independently of the hydraulic system. The cable106is attached to the braking brake mechanism through an actuator lever attached to parking brake mechanism. Typically in a park brake system there is a return spring which keeps the actuator lever in the fully released position when the brake pedal or hand lever is released.

In many processes used to adjust the parking brake in an automobile, one of the desired outcomes is to achieve a consistent rate of resistance experienced by the driver when the driver actuates the pedal or hand lever for any given model of vehicle. It is additionally desirable to ensure that there is just enough residual tension in the cable system to allow the hand lever or pedal to return fully to the un-actuated position when the brake is released. A significant challenge in this endeavor is to achieve this desired consistency at very low tension levels or at the very beginning of the actuation cycle and, conversely, at the end of the release cycle. At this level, tension in the cable system is caused by compression of a return spring reacting against the actuator lever that is attached to the cable and by compression in the cable conduit thereby causing a small amount of desired residual tension in the overall system and allowing the hand lever or pedal to return fully to the initial position when the driver releases the parking brake.

Adjusting the park brake system so that it is capable of consistently achieving high levels of clamping force when fully actuated is typically a primary goal of the adjustment process. To achieve this high level of tension consistently it may be helpful to utilize a process that mostly or fully stretches the cable and compresses the conduit so that voids in the system are mostly or entirely removed over the long term. It is a further desire, however, to ensure that there is a remaining low level of residual cable tension so that the hand lever or brake pedal returns consistently to its initial position when the system is dis-engaged. This is particularly challenging in that each brake has different initial travel losses due to manufacturing tolerances. This variation in travel losses are compounded with variable ratio levers, variation in return springs, conduit compressibility, and other factors which may result in systems that appear to have different characteristic stiffness. The challenge to tensioning a system with significant apparent stiffness variation is knowing how far to release the system from a high tension level that results in the residual tension being sufficient to return the hand lever or brake pedal to the fully released position without over tensioning the system.

The process or method described herein, whether implemented on the structure described herein or other structure for tensioning an emergency brake cable system, describes how to achieve a final or terminal low level residual tension in the system that addresses and overcomes the inconsistencies associated with the variation in apparent system stiffness. This process could occur supplemental to, integral with, or as a second or final stage of an overall adjustment process.

FIGS. 36 and 37are output graphs that each show tension measurement output of a brake cable system during the tensioning steps, and in particular show the forward tension time between tension levels T3to T4. The time it took the tool to run-up the nut126on the threaded rod124inFIG. 36from tension T3to tension T4was approximately 6 seconds (however it could be longer or shorter).

In the final adjustment of the emergency brake system, the nut126, while held in a position a specified distance (return distance) away from the equalizer116and not reacting against the equalizer116, is slowly run-up the threaded rod124to a predetermined target tension level which is consistent with the brake being applied at a low level T4. During this run-up, the distance traveled can be determined based on the rotational speed of the tool used to rotate the nut126and the time required to go between a low tension level (T3) and a higher target tension level (T4). Based on the speed of the nut runner122, the pitch of the thread on the threaded rod124, and the time interval from tension level T3to tension level T4, the distance traveled may be determined. The distance traveled from tension level T3to tension level T4is used to define the tension/travel relationship. Once the tension/travel relationship is defined for a particular cable system, the desired residual tension may be obtained by translating the nut126(with the nut runner122, for example) toward a free end of the threaded rod124as desired. While there is an assumption in this example that the tension/travel relationship is generally linear in the range of the curve being addressed (low tension region), non-linear characteristics of the curve may be determined by taking more data points along the tension curve between T3and T4, which in turn may be configured into an algorithm used to set the desired residual tension level and to obtain it by reversing the nut126on the threaded rod124.

Additionally or alternately, a servo motor may be used to determine a distance traveled by the nut126along the threaded rod124by counting the total angle needed to go from tension level T3to tension level T4. The servo motor may have a sensor monitoring total angle of rotation, and with the pitch information of the threaded rod124, the distance traveled by the nut126along the threaded rod124corresponding to the tension in the cable system increasing from tension level T3to tension level T4may be determined. With the distance traveled information, the tension/travel curve may be determined, which is used to accurately estimate the distance the nut126needs to be reversed along the threaded rod124toward a free end of the rod124to obtain the desired residual tension level.FIGS. 36 and 37are output graphs that each show an output of a brake cable system during the tensioning steps, and in particular show the forward tension time between tension levels T3to T4. The residual tension level may be greater than, less than, or the same as tension level T3. Other types of measurements may be utilized to determine the distance traveled by the nut126corresponding to the load cell444and thus the cable system tension increasing from tension T3to tension T4, such as by optical sensors, electric eye monitoring, or resistive techniques.

At these low tension levels, the distance traveled and the tension time will often vary from brake to brake. In determining the distance traveled going between tension T3and tension T4, the apparent stiffness of the system (which varies due to variations in the return spring, loss travel, variable ratio levers, conduit compressibility, environmental and other factors) is determined. Based on this apparent system stiffness and target force level (T3), the number of reverse revolutions of the nut126towards a free end of the threaded rod124needed to move the nut126along the threaded rod124a desired or calculated distance and achieve a desired residual tension in the cable system is determined.

This improved method utilizes a performance path whereby tension and travel are adjusted as a result of real time inputs received during the cable adjustment process and adjusts each cable system according to the apparent stiffness of each cable system. Other methods known in the prior art are prescriptive in that they employ a predefined set of travel and tension targets that are applied to each and every cable system. These predefined targets are typically based upon a statistical analysis to define the characteristics of a typical cable system for a particular vehicle.

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'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, joinder 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.