Abstract:
A failsafe mechanism for a lanyard comprising a backing plate, a pawl rotatably mounted on the backing plate and having an engagement portion and a cam portion, and a sperrad mounted on the backing plate in proximity to the pawl. The sperrad has engagement and cam portions and rotates relative to the pawl to define an engagement zone where the pawl and sperrad engage. The sperrad and pawl engagement portions engage when the pawl engagement portion is within the engagement zone and the sperrad engagement portion rotates into engagement. The pawl is configured to rotate only between a first arc in which the engagement portion remains at least partially within the engagement zone and a second arc in which the pawl halts the sperrad rotation should the pawl be held within the second arc.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application derives and claims priority from U.S. provisional application 61/738,981 filed Dec. 18, 2012, and U.S. provisional application 61/732,400 filed Dec. 2, 2012, both applications which are incorporated herein by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    This invention relates generally to retractable lanyards, and more particularly to a mechanism for a retractable lanyard that is configured to ensure that the lanyard will not unwind should the lanyard components become fouled or frozen in place. 
         [0004]    Lanyards are safety devices that are designed to allow an individual to operate safely at what would otherwise be dangerous or deadly heights without risk of harm. Each lanyard comprises a cable, known as a lifeline, that is held in the lanyard on a reel. When the lifeline is pulled from the lanyard at a relatively slow rate, such as when the user is moving about but not falling, the lanyard allows the reel unwind and the lifeline to extend from the lanyard. However, when the lifeline is pulled from the lanyard at a very rapid rate such as when a user is falling, a clutch or shock absorber or other similar mechanism in or associated with the lanyard will automatically engage and slow and/or stop the reel from unwinding. This halts the individual&#39;s fall after only a very brief interval. 
         [0005]    One such lanyard has an internal clutch system in which a pawl plate has a stack of friction discs on each side of mounted with Bellville springs that apply up to approximately 3000 pounds per square inch of compressive force to each side of the plate. This creates normal forces on friction pads that softly stop the release of the lifeline. 
         [0006]    In many circumstances, lanyards are used in conditions that can result in the lanyard mechanism becoming fouled with debris or ice such that the components do not operate properly and freeze in place. This results in a very dangerous situation in that the lanyard components may become frozen in a release position that allows the lifeline to freely discharge from the lanyard without stopping. Should a user be attached to a lanyard in this condition and fall, relying upon the lanyard to stop the fall, the lifeline will instead continue to discharge to its full length and can thereby cause serious injury or even death to the user. 
         [0007]    It would therefore be desirable to have a lanyard that comprises a mechanism that allows for the proper operation of the lanyard but that is configured to operate to stop a fall even if the mechanism is subjected to conditions that foul or freeze the components. 
         [0008]    As will become evident in this disclosure, the present invention provides benefits over the existing art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The illustrative embodiments of the present invention are shown in the following drawings which form a part of the specification: 
           [0010]      FIG. 1  is a plan view of a traditional lanyard pawl and sperrad mechanism positioned on a backing plate and oriented at maximum rotational travel of the pawl along its cam interface with the sperrad; 
           [0011]      FIG. 2  is another plan view of the traditional lanyard pawl and sperrad mechanism of  FIG. 1  oriented at minimum rotational travel of the pawl along its cam interface with the sperrad; 
           [0012]      FIG. 3  is a plan view of a lanyard pawl and sperrad mechanism incorporating one embodiment of the present invention positioned on a backing plate and oriented at maximum rotational travel of the pawl along its cam interface with the sperrad; 
           [0013]      FIG. 4  is another plan view of the lanyard pawl and sperrad mechanism of  FIG. 3  oriented at minimum rotational travel of the pawl along its cam interface with the sperrad; 
           [0014]      FIG. 5  is a perspective view of the lanyard pawl and sperrad mechanism of  FIG. 1  positioned on a backing plate and oriented at maximum rotational travel of the pawl along its cam interface with the sperrad; 
           [0015]      FIG. 6  is a perspective view of the lanyard pawl and sperrad mechanism of  FIG. 3  positioned on a backing plate and oriented at maximum rotational travel of the pawl along its cam interface with the sperrad; 
           [0016]      FIG. 7  is a plan view of the lanyard pawl components of  FIG. 3  positioned on a backing plate and attached to springs; 
           [0017]      FIG. 8  is a plan view of the lanyard sperrad of  FIG. 3 ; 
           [0018]      FIG. 9  is cross-sectional view A-A of the lanyard sperrad of  FIG. 8 ; 
           [0019]      FIG. 10  is cross-sectional view B-B of the lanyard sperrad of  FIG. 8 ; 
           [0020]      FIG. 11  is a plan view of the obverse of the lanyard sperrad of  FIG. 3 ; 
           [0021]      FIG. 12  is a plan view of a lanyard pawl and sperrad mechanism incorporating another embodiment of the present invention positioned on a backing plate and oriented at maximum rotational travel of the pawl along its cam interface with the sperrad; 
           [0022]      FIG. 13  is another plan view of the lanyard pawl and sperrad mechanism of  FIG. 12  oriented near the minimum rotational travel of the pawl along its cam interface with the sperrad; 
       
    
    
       [0023]    Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0024]    While the invention will be described and disclosed here in connection with certain preferred embodiments, the description is not intended to limit the invention to the specific embodiments shown and described here, but rather the invention is intended to cover all alternative embodiments and modifications that fall within the spirit and scope of the invention as defined by the claims included herein as well as any equivalents of the disclosed and claimed invention. 
         [0025]    In referring to the drawings, for comparative purposes a traditional internal clutch lanyard pawl and sperrad mechanism lacking the present failsafe configurations of the present invention is shown generally at  10 ′ in  FIGS. 1-2  and  5 . As can be seen, the lanyard mechanism  10 ′ includes three pawls  12 ′ rotatably mounted on a circular pawl backing plate  14 ′ by capped pawl pins  16 ′. The backing plate  14 ′ has various mounting holes  17 ′ for attachment to other lanyard components. The pawls  12 ′ are mounted equidistant from one another along a radius near the outer edge of the backing plate  14 ′. A substantially flat and hexagonal sperrad  18 ′ is rotatably mounted in the center of the backing plate  14 ′, where the sperrad  18 ′ is able to rotate about its central axis X′ (see  FIG. 5 ) in a counterclockwise rotational direction A. The sperrad  18 ′ has a set of six teeth  20 ′ that extend at uniform intervals outward from each side of the sperrad  18 ′ near the hexagonal peaks of the sperrad. Each of the teeth  20 ′ are of uniform shape and size and are all uniformly oriented in the same rotational direction, similar to a circular saw blade. 
         [0026]    Each of the pawls  12 ′ has an engagement end  22 ′ and an opposing cam end  24 ′. A hook  26 ′ is positioned on the cam end  24 ′ for attachment to a tension spring that is attached to the backing plate  14 ′ (not shown). The engagement end  22 ′ has an engagement tip  28 ′ that extends downward towards the sperrad  18 ′ and is oriented to face and at times interact with the teeth  20 ′ as they rotate in the direction A. Similarly, the cam end  24 ′ has a cam face  30 ′ that extends downward towards the sperrad  18 ′ and is oriented to face and interact with the hexagonal perimeter of the sperrad  18 ′ as it rotates about its central axis in the backing plate  14 ′. 
         [0027]    In referring to  FIG. 5  it can be seen that the pawls  12 ′ and the sperrad  18 ′ share complementary layered dimensions. That is, the teeth  20 ′ and the engagement tips  28 ′ of each pawl  12 ′ are all positioned at a planar level or layer closest to the backing plate  14 ′, while the cam faces  30 ′ of each pawl  12 ′ are all positioned at a planar level or layer distanced from the backing plate  14 ′. As can be appreciated, this configuration allows the teeth  20  engage the engagement tips  28 ′ while at the same time preventing the teeth  20 ′ from engaging the cam faces  30 ′ as the sperrad  18 ′ rotates about its central axis within the backing plate  14 ′. 
         [0028]    As can be appreciated, the pawl  12 ′, the sperrad  18 ′ and the backing plate  14 ′ are configured such that when the sperrad  18 ′ rotates about its axis X′ within the backing plate  14 ′, the cam ends  30 ′ of each pawl  12 ′ will ride along the hexagonal perimeter of the sperrad  18 ′. The movement of the cam ends  30 ′ on the sperrad  18 ′ in turn define the opposing movement of the engagement ends  28 ′ as the pawls  12 ′ rotate about the pins  16 ′. Hence, when the cam ends  30 ′ engage the corners of the hexagonal perimeter of the sperrad  18 ′, the engagement ends  22 ′ of the pawls  12 ′ reach their minimum engagement position relative to the teeth  20 ′. Contrastingly, when the cam ends  30 ′ engage the center of the sides of the hexagonal perimeter of the sperrad  18 ′, the engagement ends  22 ′ of the pawls  12 ′ reach their maximum engagement position relative to the teeth  20 ′. The area in which the cam ends  30 ′ engage the sperrad  18 ′ is known as the engagement zone, which has a maximum radius or engagement zone limit when the pawls  12 ′ reach their maximum engagement positions, as depicted by the broken line at  40 ′. 
         [0029]    Under normal operating conditions, and in particular when the pawl and sperrad mechanism is clean, the pawl  12 ′ can rotate sufficiently for the engagement tip  28 ′ to travel into the engagement zone below the engagement zone limit  40 ′ to engage the teeth  20 ′. Unfortunately, it has been learned that when debris, such as grit or ice, lodges in the components having a mechanism such as in  FIGS. 1 ,  2  and  5 , the pawl  12 ′ can become immobile at or near the position depicted in  FIG. 1 . When this happens, the engagement ends  28 ′ cannot engage the teeth  20 ′ to stop the rotation of the sperrad  18 ′, which is then free to spin about its axis X′ and fully release the entire lifeline. 
         [0030]    In contrast to a traditional internal clutch lanyard pawl and sperrad mechanism such as  10 ′, an embodiment of the failsafe retractable lanyard mechanism is shown generally at  10  in  FIGS. 3-4  and  6 , where the present invention is depicted by way of example. As can be seen, the novel failsafe lanyard mechanism  10  includes three pawls  12  rotatably mounted on a circular pawl backing plate  14  by capped pawl pins  16  (see also  FIG. 7 ). The backing plate  14  has various mounting holes  17  for attachment to other lanyard components. The pawls  12  are mounted equidistant from one another along a radius near the outer edge of the backing plate  14 . A substantially flat and hexagonal sperrad  18  (see  FIGS. 8-11 ) is rotatably mounted in the center of the backing plate  14 , where the sperrad  18  is able to rotate about its central axis X (see  FIG. 6 ) in a counterclockwise rotational direction A. The sperrad  18  has a set of six teeth  20  that extend at uniform intervals outward from each side of the sperrad  18  near the hexagonal peaks of the sperrad. Each of the teeth  20  are of uniform shape and size and are all uniformly oriented in the same rotational direction, similar to a circular saw blade. 
         [0031]    Each of the pawls  12  has an engagement end  22  and an opposing cam end  24 . A hook  26  is positioned on the cam end  24  for attachment to one end of a tension spring  50  that is in turn attached at its other end to the backing plate  14  (see  FIG. 7 ). The spring  50  urges the pawl  12  to rotate about the pawl pin  16  such that the pawl engagement end  30  maintains contact with the hexagonal perimeter of the sperrad  18 . The engagement end  22  has an engagement tip  28  that extends downward towards the sperrad  18  and is oriented to face and at times interact with the teeth  20  as they rotate in the direction A. However, in contrast to the engagement ends  28 ′ of the traditional mechanism  10 ′, the engagement ends  28  have extended downwardly directed tips. Similarly, like the cam ends  24 ′ of the traditional mechanism  10 ′, the cam ends  24  have each have a cam face  30  that extends downward towards the sperrad  18  that is oriented to face and interact with the hexagonal perimeter of the sperrad  18  as it rotates about its central axis in the backing plate  14 . However, in contrast to the cam ends  24 ′ of the traditional mechanism  10 ′, the cam faces  30  of each end  24  are also modified to extend downward further than the traditional cam faces  30 ′. 
         [0032]    In referring to  FIG. 6  it can be seen that the pawls  12  and the sperrad  18  share complementary layered dimensions. That is, the teeth  20  and the engagement tips  28  of each pawl  12  are all positioned at a planar level or layer closest to the backing plate  14 , while the cam faces  30  of each pawl  12  are all positioned at a planar level or layer distanced from the backing plate  14 . As can be appreciated, this configuration allows the teeth  20  engage the engagement tips  28  while at the same time preventing the teeth  20  from engaging the cam faces  30  as the sperrad  18  rotates about its central axis within the backing plate  14 . 
         [0033]    As in the traditional mechanism  10 ′, for the novel mechanism  10  the pawl  12 , the sperrad  18  and the backing plate  14  are configured such that when the sperrad  18  rotates about its axis X within the backing plate  14 , the cam ends  30  of each pawl  12  will ride along the hexagonal perimeter of the sperrad  18 . The movement of the cam ends  30  on the sperrad  18  in turn define the opposing movement of the engagement ends  28  as the pawls  12  rotate about the pins  16 . Hence, when the cam ends  30  engage the corners of the hexagonal perimeter of the sperrad  18 , the engagement ends  22  of the pawls  12  reach their minimum engagement position relative to the teeth  20 . Contrastingly, when the cam ends  30  engage the center of the sides of the hexagonal perimeter of the sperrad  18 , the engagement ends  22  of the pawls  12  reach their maximum engagement position relative to the teeth  20 . The maximum radius or engagement zone limit of the novel failsafe lanyard mechanism for the configuration  10  is depicted by the broken line at  40 . 
         [0034]    As can be seen, when operating the mechanism  10 , the pawl  12  can rotate sufficiently for the engagement tip  28  to travel into the engagement zone below the engagement zone limit  40  to engage the teeth  20 . However, unlike the traditional mechanism  10 ′, because of the extension to the cam faces  30  as compared to the cam faces  30 ′, and the extended engagement tips  28  as compared to the engagement tips  28 ′, the pawls  12  cannot rest or become locked in a position, such as the mechanism  10 ′ seen in  FIG. 1 . Rather, the even if the pawls  12  were to lock in the position as shown in  FIG. 4  with the engagement tips  28  outside the engagement zone, the contact between the cam end  24  and the sperrad  18  will either force the sperrad  18  to cease rotation or alternatively the rotation of the sperrad  18  in the direction A will force the sperrad  18  to rotate the engagement tips  28  into the engagement zone where they will engage the teeth  20 . In either case, there is no position or dead zone for the pawl  12  to rest at which the pawl  12  will allow the sperrad  18  to rotate freely without stopping the rotation of the sperrad  18 . 
         [0035]    Referring now to  FIGS. 12 and 13 , an alternate embodiment of the failsafe retractable lanyard mechanism is disclosed and shown generally at  100 . As can be seen, this embodiment of the novel failsafe lanyard mechanism  100  includes a set of cantilevered pawls  102 , though only one is shown by way of example in  FIGS. 12 and 13 . Each of the pawls  102  is fixedly mounted at one end to a frame (not shown) by pawl pins  106 . The pawls  102  are mounted equidistant from one another along a radius near the outer edge of a circular backing plate  104 . Each of the pawls  102  has an inward facing rounded cam surface  108  and an elongated engagement tip  110  pointed away from the pawl pin  106 . 
         [0036]    A substantially flat and hexagonal sperrad cam  112  is rotatably mounted in the center of the backing plate  104 , where the sperrad cam  112  is able to rotate about its central axis X, perpendicular to the plane of the mechanism  100  as shown in  FIGS. 12 and 13 . A set of springs (not shown) apply constant force to each of the pawls  102  to urge the pawls  102  to rotate about the pawl pins  106  toward, and maintain contact with, the hexagonal perimeter of the sperrad cam  112 . 
         [0037]    A generally flat rotatable sperrad ring  114  is generally coplanar with and encircles the pawls  102 . The sperrad ring  114  has a set of tooth-shaped and angled grooves  116  that face generally inward toward the pawl engagement tips  110 . The grooves  116  are positioned at regular and uniform intervals along the inner edge of the sperrad ring  114 . Each of the grooves  116  are all uniformly oriented in the same rotational direction and of uniform shape and size to complement and releasably receive the pawl engagement tips  110 . The sperrad cam  112  and the sperrad ring  114  are both rigidly mounted to the backing plate  104  and slidingly mounted to a drum housing (not shown), and accordingly rotate in unison about the axis X in a clockwise direction B. In this way, when the sperrad cam  112  and the sperrad ring  114  rotate in the direction B, the pawl cam surface  108  rides along the hexagonal perimeter of the sperrad cam  112  and the pawl  102  rotates up and down about the pawl pin  106  in response. The mechanism  100  is attached to a rotatable clasp  120  for securing or clasping of the mechanism  100  to another object. 
         [0038]    As can be seen in  FIGS. 12 and 13 , the minimum radius or engagement zone limit of the novel failsafe lanyard mechanism for the configuration  100  is depicted by the broken line at  118 . For the embodiment  100 , the position of the pawl pin  106  relative to the sperrad cam  112  and the sperrad ring  114 , the distance between the pawl  102  and the sperrad cam  112 , the distance between the pawl  102  and the sperrad ring  112 , the distance between the engagement tip  110  and the pawl pin  106 , the thickness of the pawl  102 , and the shape of the pawl cam surface  108  are all configured such that engagement tips  110  do not normally engage the sperrad ring  114 . Rather, when the cam surfaces  108  engage the corners of the hexagonal perimeter of the sperrad cam  112 , the engagement tips  110  of the pawls  102  reach their maximum engagement position relative to the grooves  116 . Contrastingly, when the cam surfaces  108  engage the center of the sides of the hexagonal perimeter of the sperrad cam  112 , the engagement tips  110  of the pawls  102  reach their minimum engagement position relative to the grooves  116 . 
         [0039]    Accordingly, and as can be appreciated, when operating the mechanism  100 , the pawl  102  can rotate sufficiently for the engagement tips  110  to travel into the engagement zone above the engagement zone minimum limit  118  to engage the grooves  116 . However, because the cam surfaces  108  force the pawls  102  to rotate about the pawl pins  106  to such an extent that engagement tips  110  engage the grooves  116  as the pawl cam surfaces  108  ride atop the corners of the hexagonal perimeter of the sperrad cam  112 , the pawls  102  cannot rest or become locked in a position in which the pawls  102  will not engage the grooves  116 . Rather, the even if the pawls  102  were to lock in the position as shown in  FIG. 13  with the engagement tips  28  outside the grooves  116 , the contact between the pawl cam surfaces  108  and the sperrad cam  112  will either force the sperrad cam  112  to cease rotation or alternatively the rotation of the sperrad cam  108  in the direction B will force the sperrad cam  108  to rotate the engagement tips  110  into the engagement zone where they will engage the teeth  116 . In either case, there is no position or dead zone for the pawl  102  to rest at which the pawl  102  will allow the sperrad  108  to rotate freely without stopping the rotation of the sperrad  108 . 
         [0040]    While I have described in the detailed description several configurations that may be encompassed within the disclosed embodiments of this invention, numerous other alternative configurations, that would now be apparent to one of ordinary skill in the art, may be designed and constructed within the bounds of my invention as set forth in the claims. Moreover, the above-described novel mechanisms of the present invention, shown by way of example at  10  and  100 , can be arranged in a number of other and related varieties of configurations without departing from or expanding beyond the scope of my invention as set forth in the claims. 
         [0041]    For example, the sperrad  18  need not be hexagonal, but may be a variety of other shapes, such as for example octagonal or heptagonal, as long as the sperrad  18  is configured to interact properly with the other components of the mechanism  10  to achieve the novel results as described herein. Similarly, by way of example, the teeth  20  need not be shaped as shown, but may be any variety of differing shapes so long as they properly interact with the engagement tips  28 . Still further, the mechanism  10  need not have exactly three pawls  12 , but may have as few as a single pawl  12  or many more than three, again, so long as the pawls  12  enable the mechanism  10  to operate as described herein. 
         [0042]    Also, the sperrad  18  is not restricted to having a set of exactly six teeth  20  at uniform intervals, nor that the teeth  20  must all be of uniform shape and size and uniformly oriented in the same rotational direction. Rather, there may be more or less than six teeth  20  on the sperrad  18 , and the teeth  20  may be of varying sizes and shapes, so long as they properly operate as part of the failsafe mechanism as outlined in this disclosure. 
         [0043]    Additional variations or modifications to the configuration of the novel mechanism of the present invention, shown by way of example at  10  and  100 , may occur to those skilled in the art upon reviewing the subject matter of this invention. Such variations, if within the spirit of this disclosure, are intended to be encompassed within the scope of this invention. The description of the embodiments as set forth herein, and as shown in the drawings, is provided for illustrative purposes only and, unless otherwise expressly set forth, is not intended to limit the scope of the claims, which set forth the metes and bounds of my invention.