Abstract:
A retention pin redundancy system and installation method provides a housing having multiple shoulders to encapsulate an installed retention pin and its connecting pin only when the retention pin is fully engaged. Another aspect includes a living hinge. A further aspect provides engagement devices to lock the redundancy clip.

Description:
BACKGROUND  
         [0001]    The invention relates generally to fastening systems and more particularly to a system and process for securing an installation of components joined by a pin and retention element.  
           [0002]    It is well known to secure one or more components by mounting the component(s) onto a pin, where the pin has a through aperture at its distal end for receiving a retention device such as a retention pin. The retention pin is normally deformed such that the deformation prevents removal of the retention pin through the aperture. It is also well known that retention pins (e.g., cotter pins) can be secured to the installation through the use of lock wires and similar devices.  
           [0003]    A pinned connection is conventionally formed by providing a pin of known diameter mounted to a structure or one of a set of items to be joined. The pin is typically provided with a through aperture disposed at a pin distal end such that a retention pin (i.e., a cotter pin or similar device) can be slid into the aperture and deformed thereby preventing removal of the retention pin and therefore removal of the equipment thus secured. The parts to be joined are provided with an aperture sized to slidably mate with the pin diameter. The pin length is normally selected such that the pin extends slightly beyond the total thickness of the parts to be joined exposing the entire diameter of the aperture. This insures that the retention pin can engage the aperture through the pin while preventing excessive clearance between the retention pin and the components to be joined. Excessive clearance can result in loose fit, excessive vibration or motion and damage to the components to be joined or surrounding components. Retention pins known in the art are typically provided of a metal material which is bendable either by hand or with tools such that at least a portion of the retention element is deformed to prevent pin removal from the pin aperture. Retention elements known in the art are provided in standard sizes and diameters to suit the pin aperture and the strength required to connect the parts to be joined. Dimensions for the retention element, including the length, are therefore well known.  
           [0004]    A common form of retention element is the cotter pin. The cotter pin is available in several forms, however, the simplest form is a pin having a loop of material on a first end and two legs distally extending from the loop wherein the legs are initially butted to each other. The legs are slid into a pin aperture and at least one of the legs is deformed such that the diameter of the leg pair increases beyond the pin aperture preventing removal of the cotter pin. Other cotter pin type retention elements are available which include a first leg which is inserted into a pin aperture and a second leg which by spring force deflects above or about the pin such that the second leg retains the cotter pin in the assembly by a spring force. A drawback of retention elements in general and the cotter pin specifically is that an installation of the retention element can be provided wherein insufficient bending or deflection of at least one of the elements of the retention element is performed and subsequent vibration of the component parts and retention element causes the retention element to slip free from the pin aperture. A drawback of the spring type cotter pin is that if insufficient force is used to apply the spring leg over the pin to a fully engaged position, the cotter pin can vibrate loose from the installation.  
           [0005]    It is therefore a common practice to apply additional retention elements to a retention pin installation to ensure that the pin cannot displace from its installed position. Known examples include deformable devices which anchor in the looped end of a cotter pin and provide a male engagement member to engage at least one of the legs of the cotter pin. The disadvantage of deformable devices is the relative ease with which some of the devices either fall off or are displaceable from the retention element. A further known device uses lock-wire which is twisted about the loop end of a cotter pin and around the legs of the cotter pin to insure that the cotter pin stays in place. The ease of failure of the above devices contrasts with the degree of installation difficulty that lock-wire imparts and the degree of difficulty in removing the lock-wire which therefore prevents easy access to the assembled parts. The devices described above do not by their design ensure that the retention element is in a fully engaged position when the device is installed. For example, the spring type cotter pin as discussed above can be installed in an incompletely engaged position and the subsequent installation of a device will not insure that the cotter pin fully engages with the pin aperture.  
         SUMMARY OF THE INVENTION  
         [0006]    In accordance with a preferred embodiment of the present invention, a pin redundancy system provides a multi-part housing which encapsulates a retention element such as a cotter pin as well as the pin end where the retention element is located only when the retention element is in a fully engaged position. In another aspect of the present invention, a retention pin redundancy system includes at least one retention element to prevent displacement of a retention pin. A further aspect of the present invention provides a redundancy clip having hook engagement devices to both close and self lock the redundancy clip. In still another aspect of the present invention, a polymeric retention pin redundancy clip is provided which includes a lever integrally disposed adjacent to a living hinge engaging a lever engagement embossment such that a failure of the living hinge does not result in opening of the redundancy clip. In yet another aspect of the present invention, a process for confirming a correct installation of a retaining pin is provided. In still another aspect of the present invention a method for applying a cotter pin redundancy clip is provided.  
           [0007]    The redundancy clip system and method of the present invention are advantageous over conventional devices in that the present invention provides a positive method/device to ensure that the retention element is in a fully engaged position with the pin prior to engagement of the redundancy clip. The dimensions of the pin and the retention element are known. These dimensions are incorporated within the redundancy clip of the present invention such that individual sections of the redundancy clip enclose distal ends of the pin about a pin clearance aperture provided in the redundancy clip. Features of the redundancy clip including a combination of a predetermined body cavity and integral shoulders prevent the clip from closing about the pin if the retention element is not fully engaged through the pin. The redundancy clip of the present invention is preferably provided in a lightweight moldable material such that installation can be performed manually and the clip can be sized to suit arrangements which are difficult to access.  
           [0008]    A redundancy clip of the present invention also provides a positive locking element which deflects and snaps into engagement with a hook retention element to hold the redundancy clip closed. A living hinge can be operated multiple times to perform maintenance work on the component. Envelope characteristics of the redundancy clip can be easily varied such that a wide variety of pins, retention elements, installation geometries, and access for both removal and replacement of a redundancy clip of the present invention can be provided. Advantages of the redundancy clip of the present invention include: the ability to encapsulate a retention pin to ensure the retention pin is in a fully engaged position; light weight; installation/removal ease using a living hinge; and a removable, self-locking feature. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.  
           [0009]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0011]    [0011]FIG. 1 is a partially exploded, perspective view showing a first preferred embodiment of the redundancy clip of the present invention installed on an automotive brake assembly;  
         [0012]    [0012]FIG. 2 is an exploded and enlarged, perspective view showing the installation of component parts of FIG. 1 with the redundancy clip of the present invention in its open and unlocked position prior to installation over a retention pin;  
         [0013]    [0013]FIG. 3 is a perspective view of a pin mounted device having a retention element in a fully engaged position prior to installation of a redundancy clip of the present invention;  
         [0014]    [0014]FIG. 4 is a perspective view, like that of FIG. 3, further showing the start of an installation phase of a redundancy clip of the present invention;  
         [0015]    [0015]FIG. 5 is a perspective view as seen from 90° from that of FIG. 4, showing rotation of a second section of the redundancy clip about the living hinge during the installation phase of the redundancy clip of the present invention;  
         [0016]    [0016]FIG. 6 is a perspective view, like that shown in FIG. 4, further showing the redundancy clip in its fully engaged and locked position;  
         [0017]    [0017]FIG. 7 is a perspective view, like that of FIG. 4, showing the redundancy clip dimensions and the relationship of the clearance aperture to the pin diameter;  
         [0018]    [0018]FIG. 8 is a perspective view showing a second preferred embodiment of the present invention having a longitudinal living hinge installed between adjacent sides of a redundancy clip;  
         [0019]    [0019]FIG. 9 is a perspective view showing a third preferred embodiment of the present invention having both rigid and flexible shoulders for engagement with a retention element;  
         [0020]    [0020]FIG. 10 is a top perspective view of a fourth preferred embodiment of the present invention for a low profile redundancy clip;  
         [0021]    [0021]FIG. 11 is a perspective view of a fifth preferred embodiment of the present invention for encapsulating a retention pin without integral shoulders; and  
         [0022]    [0022]FIG. 12 is a perspective view of a sixth preferred embodiment of the present invention having a V-shaped deflectable hook.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0024]    [0024]FIGS. 1 and 2 show a first preferred embodiment of a redundancy clip of the present invention. A vehicle sub-system  2  is shown having a brake assembly  4  which mounts to a dashboard structure  6  and subsequently to a brake hydraulic unit  8 . A pin mounted device  10  is shown in its installed position on brake assembly  4 . A redundancy clip  12  of the present invention is shown in its fully engaged and locked position on pin mounted device  10 .  
         [0025]    The pin mounted device  10  is mounted to a plate  14  having a pin  16 . Brake hydraulic unit  8  includes a flange  18  which slidably engages over pin  16  and co-aligns with a pin aperture  20  of pin mounted device  10 . Flange  18  abuts a mounting bracket  22  of pin mounted device  10 . Pin  16  is selectively sized such that a retention pin aperture  24  is exposed at a distal end of pin  16  after installation of both pin mounted device  10  and flange  18 . A retention pin  26  is slidably disposed within retention pin aperture  24  and at least one leg of retention pin  26  is deflected (not shown) to retain retention pin  26  within retention pin aperture  24 .  
         [0026]    Redundancy clip  12  of the present invention is then slidably disposed about pin  16  and under retention pin  26 . Redundancy clip  12  includes features which will be discussed herein to prevent the installation of redundancy clip  12  unless retention pin  26  is in a fully engaged position with pin  16 . Since both the dimensions of pin  16  and retention pin  26  are known, the necessary geometry when selecting redundancy clip  12  for a given installation is predetermined.  
         [0027]    Referring to FIG. 3, the relationship between pin mounted device  10 , pin  16  and retention pin  26  are shown in greater detail. Pin mounted device  10  is shown following engagement with pin  16 . Retention pin  26  is an exemplary application of a retention pin  26  having an engagement portion  28  which ensures full engagement over a pin shoulder  30  of pin  16 . In the fully engaged position shown, engagement portion  28  initially deflects during installation and snaps over pin shoulder  30  to prevent retention pin  26  from vibrating loose from its engaged position.  
         [0028]    Referring to FIG. 4, the first preferred embodiment of a redundancy clip  12  of the present invention is shown in an initial installation step about the configuration shown in FIG. 3. Redundancy clip  12  includes a first section  32  (also herein defined as a female section), and a second section  34  (also herein defined as a male section). First section  32  and second section  34  are connectably and rotatably joined by a living hinge  36 . A pin aperture  38  is disposed in at least one of first section  32  and second section  34 . Pin aperture  38  can also be completely disposed in either of first section  32  or second section  34 . In the application shown in FIG. 4, pin aperture  38  is approximately equally divided between each of first section  32  and second section  34 . Pin aperture  38  is sized to provide a clearance fit about pin  16 .  
         [0029]    Redundancy clip  12  also includes a retention element  40  integrally provided on second section  34  and a retention element  42  integrally provided on first section  32 . The purpose of both retention element  40  and retention element  42  are to slide between shoulder  22  (shown in FIG. 3) and under retention pin  26  such that redundancy clip  12  cannot be removed in a vertical direction as viewed in FIG. 4. As shown, retention element  42  is slidably disposed beneath a retention pin extension  44 . A shoulder  46  adjacent to the looped end of retention pin  26  abuts an engagement shoulder  48  when the two sections of redundancy clip  12  are in the closed and engaged position. Similarly, a shoulder  50  will abut an engagement shoulder  52  when the two sections of redundancy clip  12  are in their fully engaged position. Shoulder  46 , engagement shoulder  48 , shoulder  50 , and engagement shoulder  52  are located based on known geometry of the retention pin  26  engaged. This will be discussed further in reference to FIG. 7 below.  
         [0030]    A deflectable hook element  54  is integrally disposed on the second section  34 . The deflectable hook  54  matingly engages within a cavity  56  against a hook retainer  58  of the first section  32 . A centering boss  60  aligns with the hook retainer  58  to align the second section  34  with the first section  32 . To provide for the event of a failure of the living hinge  36 , an embossment  62  having an aperture  64  is disposed on the first section  32 , and a lever  66  disposed on the second section  34  is aligned to engage within the aperture  64 . Engagement of the lever  66  within the aperture  64  assures that a failure of the living hinge  36  does not permit displacement of the living hinge end of the redundancy clip  12 .  
         [0031]    Referring now to FIG. 5, in the continuing installation phase of redundancy clip  12 , second section  34  is rotated to engage the two clip sections. Second section  34  rotates in a closing direction A about living hinge  36  (not visible in this view) such that lever  66  engages within aperture  65  of embossment  62 . One of a plurality of clearance notches  68  is also shown. The purpose of clearance notches  68  are to receive one of retention element  40  or retention element  42  (shown in FIG. 4). In the partially rotated position shown in FIG. 5, deflectable hook  54  is shown prior to engagement with first section  32 .  
         [0032]    [0032]FIG. 6 shows a fully closed and engaged position of redundancy clip  12 . Deflectable hook  54  is fully engaged and seated within cavity  56 . In the event of a failure of living hinge  36  as discussed above, the curved shape of lever  66  engaged in embossment  62  prevents a displacement of second section  34  in an opening direction B.  
         [0033]    Referring to FIG. 7, the geometrical relationship between pin  16 , retention pin  26  and the first preferred embodiment of the present invention are shown. A clip cavity  70  and a clip cavity  72  are provided to fully enclose fully engaged retention pin  26 . Pin  16  includes a pin centerline  74  and a known pin diameter E. In a fully engaged position, retention pin  26  has a known total length. A span length C is therefore provided within first section  32  and second section  34  between the shoulders previously discussed. Span length C is predetermined such that the known length of retention pin  26  seats fully within each section of the redundancy clip between the shoulders. A pin to shoulder distance D and a cavity height F are provided within the redundancy clip based on the known dimensions of a fully engaged retention pin  26 . Based on the geometry of fully engaged retention pin  26  within pin  16  a redundancy clip  12  having predetermined dimensions is selected. Geometries for the plurality of known retention pins  26  can be accommodated with a plurality of standard sizes of redundancy clips of the present invention.  
         [0034]    As can best be observed in FIG. 8, a longitudinally hinged redundancy clip  116  includes a longitudinal living hinge  136  connectably joining longitudinal edges of longitudinally hinged redundancy clip  116 . A deflectable hook  154  is positioned on an end of longitudinally hinged redundancy clip  116  adjacent to a cavity  156  (similar to cavity  56  shown in FIG. 4). A centering boss  160  is similar to centering boss  60  shown in FIG. 4. Longitudinally hinged redundancy clip  116  closes in a closing direction G as shown. Based on the length of longitudinal living hinge  136 , a lever (not shown) similar to lever  66  shown in FIG. 4 can be installed or eliminated at the option of the designer. The length of longitudinal living hinge  136  provides additional assurance against a failure of longitudinal living hinge  136 .  
         [0035]    As provided in FIG. 9, additional features of a third preferred embodiment of the present invention are detailed. In a redundancy clip  216 , a pair of twist prevention shoulders  218  and a pair of mating twist prevention shoulders  220  are integrally provided. Both twist prevention shoulders  218  and mating twist prevention shoulders  220  have a reduced cross section such that the shoulders deflect when engaging a retention pin (not shown). By providing this deflection capability, additional flexibility in the design of the redundancy clip  216  is possible, such that the redundancy clip  216  can accommodate more than one retention pin design. A pair of rigid shoulders  222  matably align with a pair of mating rigid shoulders  224 . These rigid shoulders are similar to the shoulders previously described herein. The addition of twist prevention shoulders  218  and mating twist prevention shoulders  220  also provide the benefit that redundancy clip  216  is prevented from spinning after redundancy clip  216  is in its closed and fully engaged position. This feature is beneficial in applications where the redundancy clip should not rotate about the pin.  
         [0036]    As detailed in FIG. 10, an open faced, low profile clip  300  is provided. Low profile clip  300  provides an alternate embodiment which permits placement of a redundancy clip in an application where vertical height above the pin is not available to install a redundancy clip similar to those previously discussed. Low profile clip  300  includes a retention pin aperture  302  similar to previous concepts, however, a body pin cavity  304  is provided which allows the overall width of low profile clip  300  to be reduced. A pair of pin retention bosses  306  are provided to matingly engage with the pin (not shown). A clip height H can be reduced in low profile clip  300  providing an open access to the retention pin (not shown) and visible verification that the retention pin is installed. A pair of rigid shoulders  312  and a pair of mating rigid shoulders  314  are shown which serve a similar purpose to shoulders previously discussed. Rigid shoulders  312  and mating rigid shoulders  314  are provided in a horizontal orientation to further reduce clip height H. In the embodiment shown, a single deflectable hook  308  which engages with a single hook retainer  310  is shown. Based on clip height H which is reduced for low profile clip  300 , the single deflectable hook  308  is sufficient to close and fully engage the sections of low profile clip  300 .  
         [0037]    As additionally provided in FIG. 11, a controlled length clip  400  is shown. In applications where the length of the clip is critical, one or more shoulders normally used to engage the retention pin can be eliminated by controlling an overall clip length J such that the ends of the clip engage the retention pin in place of the shoulders. Another preferred embodiment of a single deflectable hook  402  and a single hook retainer  404  are also shown for controlled length clip  400 . Single hook retainer  404  includes a living hinge end rotatably joined to controlled length clip  400  and a free end which engages single deflectable hook  402 .  
         [0038]    As best detailed in FIG. 12, a single hook redundancy clip  500  is detailed. Single hook redundancy clip  500  includes a V-shaped, single deflector hook  502  which provides another preferred embodiment for engagement of a deflector hook. The V-shaped single deflector hook  502  provides a tapered face  506  which deflects V-shaped single deflector hook  502  when engaged with a hook retainer  504 . An end face  508  of V-shaped single deflector hook  502  engages hook retainer  504  in a fully engaged and locked position.  
         [0039]    The various embodiments of redundancy clips provided herein are exemplary in nature. In one preferred embodiment, a redundancy clip of the present invention is provided as an injection molded part having the living hinge integrally joining the two sections. A polymeric material is preferably used for the redundancy clip because of the cost and weight savings from use of a lightweight, yet flexible, polymeric material. The material selected should provide for multiple applications of the redundancy clip without fracture of the living hinge. In a preferred application, nylon is selected for its ability to repeatedly flex in the living hinge. The polymeric material is also selected based on the clip environment. In certain applications, for instance, the redundancy clip of the present invention could contact petroleum based liquids or gasses. A material resistant to petroleum based substances is therefore preferable in some automotive applications of the redundancy clip. Manufacturing processes other than molding are also possible, including casting, machining, cutting, and assembly of individual component parts. Additional materials including metals can be cast or machined for the component parts of the redundancy clip of the present invention if high strength for a detrimental operating environment are foreseen in the use of the redundancy clip.  
         [0040]    While various embodiments have been disclosed it will be appreciated that other configurations may be employed within the spirit and scope of the present invention. For example, the deflectable hook has been described herein as engaging within a cavity. The deflectable hook can also install with an external engagement. The deflectable hook can also have alternate shapes in addition to a common J-shape. The deflectable hook can also be replaced by a friction closing device such that a circumferential deflection within a receiving element occurs during locking of the redundancy clip sections. The hook can also be provided as a female member which extends over and engages with a receiving male member. A lanyard device or an extended retainer can replace the living hinge such that individual sections of the redundancy clip are retained both prior to assembly and following disassembly of the redundancy clip. The body of the redundancy clip is described and shown herein as a two-section body with a living hinge between sections. Multiple/additional sections can also be used, such as a body and two closing members or a three-part body, as well as a design having a main body with a hinged cover. While various materials and dimensions have been disclosed, it should be appreciated that others may be employed.  
         [0041]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.