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CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 62/349,920, entitled LADDERS, LADDER HINGES AND RELATED METHODS, filed Jun. 14, 2016, the disclosure of which is incorporated by reference herein in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to ladders, ladder systems, ladder components, such as hinges, and related methods. 
       BACKGROUND 
       [0003]    Ladders are conventionally used to provide a user thereof with improved access to locations that might otherwise be inaccessible. Ladders come in many shapes and sizes, such as straight ladders, straight extension ladders, stepladders, and combination step and extension ladders (referred to herein as combination ladders). Combination ladders incorporate, in a single ladder, many of the benefits of other ladder designs as they can be used as an adjustable stepladder, a straight ladder or an extension ladder. 
         [0004]    Combination ladders are particularly useful as they may be adapted for use in a variety of situations. However, the construction of such ladders often requires design elements to enable the ladder may withstand a variety of different loadings and accommodate different relational positions of the ladder components. For example, such a ladder includes locking mechanisms to enable selective adjustment of different rail and rung assemblies, thereby enabling height adjustment of the ladder. Additionally, such a ladder includes hinge mechanisms which enable selective rotational adjustment of one rail assembly relative to another rail assembly. The hinges, thus, may enable the ladder to be placed in a stepladder configuration, an extension ladder configuration, or in a collapsed, stowable state. 
         [0005]    The design of these various components (e.g., the height adjustment mechanism, the hinges, etc.) must take into consideration many factors including strength to withstand loadings while in different positions, the ease of using such mechanisms, the stability of the mechanism while in any of a variety of states or positions, and other safety concerns (e.g., pinching of hands or fingers or the likelihood of being abused in operation by a user). In addition to all of these concerns, the ease and cost of manufacturing such components must also be taken into account in order to bring cost effective solutions to the market 
         [0006]    Considering the desire within the industry to continually improve the safety, functionality, ergonomics and efficiency of ladders, the present disclosure provides a number of embodiments that provide enhanced ease of use, stability and safety in the use of ladders. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    The present disclosure provides various embodiments of ladders, ladder hinges and related methods. In one embodiment, a ladder is provided that comprises a first rail assembly having a first pair of rails and a first plurality of rungs extending between and coupled to the first pair of rails and second rail assembly having a second pair of rails and a second plurality of rungs extending between and coupled to the second pair of rails. The ladder includes a pair of hinge mechanisms coupled between the first rail assembly and the second rail assembly. Each hinge mechanism comprises a first hinge assembly having at least one hinge plate, a second hinge assembly having at least one hinge plate, the first hinge assembly being rotatably coupled to the second hinge assembly, and an adjustment mechanism configured to selectively permit and prohibit relative rotation of the first hinge assembly and the second hinge assembly. The adjustment mechanism comprises a lock plate biased in a first direction along a first axis, the lock plate having a first portion configured to engage at least one recess formed on a periphery of the at least one hinge plate of the second hinge assembly, the lock plate having an opening formed in a surface thereof. A retainer is biased in a second direction along a second axis and toward contact with the lock plate, the retainer having a protrusion configured for selective engagement with the opening in the lock plate. A release structure is located and configured to be displaced along the first axis such that a portion of the release structure becomes interposed between the retainer and the lock plate to displace the retainer opposite the second direction and displacing the protrusion from the opening of the lock plate. 
         [0008]    In one embodiment, the ladder further comprises a biasing member between the release structure and the lock plate, the biasing member biasing the release structure away from the lock plate in the first direction. 
         [0009]    In one embodiment, the at least one recess formed on the periphery of the at least one hinge plate of the second hinge assembly includes at least three recesses formed at spaced circumferential locations on the periphery. 
         [0010]    In one embodiment, the at least one hinge plate of the first hinge assembly includes a first pair of hinge plates and at least one spacer plate disposed between the first pair of hinge plates. 
         [0011]    In one embodiment, the at least one hinge plate of the second hinge assembly includes a second pair of hinge plates and at least one other spacer plate disposed between the second pair of hinge plates. 
         [0012]    In one embodiment, the second pair of hinge plates are disposed laterally inwardly of the first pair of hinge plates along an axis upon which relative rotation of the first hinge assembly and the second hinge assembly is effected. 
         [0013]    In one embodiment, the at least one other spacer includes at least one radial projection configured to engage the release structure upon relative rotation of the first hinge assembly and the second hinge assembly to a predetermined angular position. 
         [0014]    In one embodiment, the at least one radial projection includes at least three radial projections corresponding with three different predetermined angular positions of the first assembly relative to the second assembly. 
         [0015]    In one embodiment, the portion of the lock plate is positioned in a first channel formed in the at least one spacer plate, and wherein at least a portion of the retainer is positioned in a second channel formed in the at least one spacer plate. 
         [0016]    In one embodiment, the release structure includes two spaced apart arms, with one arm positioned on a different side of the lock plate. 
         [0017]    In one embodiment, at least one of the two arms exhibits a tapered geometry for engagement with the retainer. 
         [0018]    In one embodiment, at least one of the two arms includes two spaced apart fingers defining a slot therebetween, the slot being sized to receive a portion of the protrusion. 
         [0019]    In one embodiment, the lock plate includes a main body portion and at least one laterally extending portion. 
         [0020]    In one embodiment, the at least one laterally extending portion extends through a slot formed in the at least one hinge plate of the first hinge assembly. 
         [0021]    In one embodiment, the ladder further comprises a first handle coupled with the at least one laterally extending portion. 
         [0022]    In one embodiment, the lock plate is substantially T-shaped. 
         [0023]    In one embodiment, the first axis and the second axis are substantially orthogonal to one another. 
         [0024]    In one embodiment, the first rail assembly further comprises a third pair of rails and a third plurality of rungs extending between and coupled to the third pair of rails, the third pair of rails being slidably coupled with the first pair of rails. 
         [0025]    In one embodiment, the second rail assembly further comprises a fourth pair of rails and a fourth plurality of rungs extending between and coupled to the fourth pair of rails, the fourth pair of rails being slidably coupled with the second pair of rails. 
         [0026]    In one embodiment, the pair of hinge mechanisms are configured to selectively lock the first rail assembly and the second rail assembly relative to each other in a stored configuration, at least one step ladder configuration and an extension ladder configuration. 
         [0027]    Features, elements and aspects of one described embodiment herein may be combined with features, elements or aspects of other described embodiments without limitation. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0028]    The foregoing and other advantages of the disclosure will become apparent upon reading the following detailed description and upon reference to the drawings in which: 
           [0029]      FIG. 1  is a perspective view of a ladder in accordance with an embodiment of the present disclosure; 
           [0030]      FIG. 2  is a side view of a hinge of the ladder shown in  FIG. 1 ; 
           [0031]      FIG. 3  is a front view of the hinge shown in  FIG. 2 ; 
           [0032]      FIG. 4  is an exploded view of a portion of the hinge shown in  FIG. 2 , 
           [0033]      FIG. 5  shows a portion of the hinge shown in  FIG. 2 ; 
           [0034]      FIGS. 6 and 7  show portions of the hinge shown in  FIG. 2  while the hinge is locked in a stowed state; 
           [0035]      FIGS. 8 and 9  show portions of the hinge of  FIG. 2  while in the ladder is in the stowed state and while a locking component has been actuated; 
           [0036]      FIGS. 10A and 10B  are enlarged detail views of the adjustment/locking mechanism of the hinge shown in  FIG. 2  during different states of operation; 
           [0037]      FIGS. 11 and 12  show portions of the hinge of  FIG. 2  while the ladder is transitioning between a stowed state and a first deployed state; 
           [0038]      FIGS. 13 and 14  show portions of the hinge of  FIG. 2  while the ladder is locked in a first deployed state; and 
           [0039]      FIGS. 15 and 16  show portions of the hinge of  FIG. 2  while in the ladder is locked in a second deployed state. 
       
    
    
     DETAILED DESCRIPTION 
       [0040]    Referring to  FIG. 1 , a combination ladder  100  (also referred to as an articulating ladder) is shown. The combination ladder  100  includes a first rail assembly  102  including an inner assembly  102 A slidably coupled with an outer assembly  102 B. The inner assembly  102 A includes a pair of spaced apart rails  104  coupled with a plurality of rungs  106 . Likewise, the outer assembly  102 B includes a pair of spaced apart rails  108  coupled to a plurality of rungs  110 . The rails  104  of the inner assembly  102 A are slidably coupled with the rails  108  of the outer assembly  102 B. The inner and outer assemblies  102 A and  102 B may be selectively locked relative to each other such that one or more of their respective rungs  106  and  110  are aligned with each other. A locking mechanism  112  may be configured to engage a portion of the inner rail assembly  102 A and the outer rail assembly  102 B so as to selectively lock the two assemblies relative to each other. While only a single locking mechanism  112  is shown due to the perspective of the ladder represented in  FIG. 1 , a second, similar locking mechanism is coupled to the other side of the rail assembly  102 . 
         [0041]    The combination ladder  100  also includes a second rail assembly  114  that includes an inner assembly  114 A slidably coupled with an outer assembly  114 B. The inner assembly  114 A includes a pair of rails  116  coupled with a plurality of rungs  118  and is configured similarly to the inner assembly of the first rail assembly  102 A described hereinabove. Likewise, the outer assembly  114 B includes a pair of rails  120  coupled with a plurality of rungs  122  and is configured similarly to the outer assembly  102 B of the second rail assembly  102  described hereinabove. Locking mechanisms  124  may be associated with inner and outer assemblies  114 A and  114 B to enable selective positioning of the inner assembly  114 A relative to the outer assembly  114 B as described with respect to the first rail assembly  102  hereinabove. 
         [0042]    One exemplary locking mechanism that may be used with the first and second rail assemblies  102  and  114  is described in U.S. Pat. No. 8,186,481, issued May 29, 2012, the disclosure of which is incorporated by reference herein in its entirety. While the locking mechanism described in U.S. Pat. No. 8,186,481 is generally described in conjunction with an embodiment of an adjustable step ladder, such a locking mechanism may by readily used with the presently described combination ladder as well. Another example of a locking mechanism  112  is described in U.S. Patent Application No. 62/303,588, filed on Mar. 4, 2016, entitled ADJUSTMENT MECHANISMS, LADDERS INCORPORATING SAME AND RELATED METHODS, and U.S. patent application Ser. No. 15/448,253, filed on Mar. 2, 2017, the disclosures of which are incorporated by reference herein in their entireties. Additionally, in one embodiment, the rail assemblies  102  and  114  may be configured similar to those which are described in U.S. Pat. No. 4,210,224 to Kummerlin, the disclosure of which is incorporated by reference in its entirety. 
         [0043]    The first rail assembly  102  and second rail assembly  114  are coupled to each other by way of a pair of hinge mechanisms  140 . As will be discussed in further detail below, each hinge mechanism  140  may include a pair of hinge components including a first hinge component (or assembly)  150  coupled with a rail of the first rail assembly&#39;s inner assembly  102 A and a second hinge component (or assembly)  152  coupled with a rail of the second rail assembly&#39;s inner assembly  114 A. The hinge components  150  and  152  of the hinge mechanism  140  rotate about a pivot member such that the first rail assembly  102  and the second rail assembly  114  may pivot relative to each other. Additionally, the hinge mechanisms  140  may be configured to lock their respective hinge components (and, thus, the associated rails to which they are coupled) at desired angles relative to each other. 
         [0044]    The combination ladder  100  is thus constructed so as to assume a variety of states or configurations. For example, using the locking mechanism ( 112  or  124 ) to adjust a rail assembly ( 102  or  114 ) enables the ladder  100  to be adjusted in height. In one example, as the first rail assembly  102  is adjusted, with the outer assembly  102 B being displaced relative to the inner assembly  102 A, the locking mechanism  112  engages the inner and outer assemblies ( 102 A and  102 B) when they are at desired relative positions so that at least some of their respective rungs ( 106  and  110 ) align with each other (such as shown in  FIG. 1 ), or so that the rungs maintain a desired vertical spacing relative to each other. Considering the embodiment shown in  FIG. 1 , this enables the ladder, for example, to be configured as a step ladder with four effective rungs at a desired height (as shown in  FIG. 1 ), or to be configured as a step ladder that is substantially taller having five, six, seven or eight effective rungs, depending on the relative positioning of the inner and outer assemblies. It is noted that the inner and outer rail assemblies may be configured with more or fewer rungs than four. 
         [0045]    It is also noted that the first rail assembly  102  and the second rail assembly  114  do not have to be adjusted to similar heights (i.e., having the same number of effective rungs). Rather, if the ladder is used on an uneven surface (e.g., on stairs), the first rail assembly  102  may be adjusted to one height while the second rail assembly  114  may be adjusted to a different height in order to compensate for the slope of the supporting surface. 
         [0046]    The hinge mechanisms  140  provide for further adjustability of the ladder  100 . For example, the hinge pairs  140  enable the first and second rail assemblies  102  and  114  to be adjusted to a variety of angles relative to each other. As shown in  FIG. 1 , the first and second rail assemblies  102  and  114  may be configured at an acute angle relative to each other such that the ladder may be used as a self-supporting ladder, similar to a step ladder (e.g., the hinge components are positioned such that the ladder assumes a first, deployed state as a step ladder). However, the first and second rail assemblies  102  and  114  may be rotated or pivoted about the hinge mechanisms  140  so that they extend from one another in substantially the same plane (i.e., exhibiting an angle of substantially 180°-placing the ladder in a second, deployed state). When configured in this manner, the ladder may be used as an extension ladder. Moreover, each of the first and second assemblies are still adjustable as to height (i.e., through the relative displacement of their respective inner and outer assemblies). It is additionally noted that the rungs of the various assemblies (i.e., rungs  106 ,  110 ,  118  and  122 ) are configured to have support surfaces on both the tops and the bottoms thereof so as to enable their use in either a step ladder configuration or an extension ladder configuration. 
         [0047]    The hinge mechanisms  140  may also enable the first rail assembly  102  and the second rail assembly  114  to be collapsed adjacent each other so that the ladder  100  is placed in a collapsed or stowed/stowable state. Thus, the ladder  100  is able to be configured in a variety of useable conditions and is further able to be collapsed in a relatively small configuration for transportation and stowing of the ladder. 
         [0048]    Referring to  FIGS. 2 and 3 , a hinge mechanism  140  is shown having an outer hinge assembly  150  (also referred to as a first hinge assembly) pivotally coupled with an inner hinge assembly  152  (also referred to as a second hinge assembly). The “inner” and “outer” designations of the hinge assemblies relate to the fact that hinge plates  154  of the outer hinge assembly  150  are spaced laterally outward of the hinge plates  156  of the inner hinge assembly  152  as best seen in  FIG. 3 . 
         [0049]    The outer and inner hinge assemblies  150  and  152  are coupled together by way of a hinge pin  158  such that the hinge assemblies may rotate relative to each other about an axis extending through the hinge pin  158 . As will be discussed in further detail below, the hinge mechanism  140  may be selectively positioned in a variety of states, including a “fully open” state, a “fully closed” state (such as shown in  FIG. 2 ), and one or more states between the fully open and fully closed states—such states corresponding, for example, with the deployed or stowed conditions of the ladder discussed above. An adjustment mechanism  160 , which includes an actuating handle  162 , enables the selective locking and adjustment of the hinge assemblies  150  and  152  relative to each other. 
         [0050]    Referring to  FIGS. 4 and 5 ,  FIG. 4  shows an exploded view of the outer hinge assembly  150  and  FIG. 5  shows a portion of the outer hinge assembly  150  with various components removed (e.g., one hinge plate  154  and a spacer) to expose various components associated with the adjustment mechanism  160 . As previously noted, the outer hinge assembly  150  includes a pair of spaced apart hinge plates  154 . The hinge plates  154  include a first portion  164  configured for coupling with a ladder rail (e.g., rail  104  of inner rail assembly  102 A or rail  116  of inner rail assembly  114 A as shown in  FIG. 1 ) and a second portion  166  configured for coupling with the inner hinge assembly  152  by way of the hinge pin  158  which is inserted through openings  167  formed in the hinge plates  154  (and through a corresponding opening formed in the hinge plate(s)  156  of the inner hinge assembly  152 ). 
         [0051]    The outer hinge assembly  150  additionally includes a pair of spacer plates  168  disposed between the hinge plates  154 . The spacer plates  168  may each include an abutment shoulder that abuts a portion of the hinge plates  156  of the inner hinge assembly  152  when the hinge mechanism  140  is in a fully opened state. Similarly, the inner hinge assembly  152  may include a pair of spacer members  170  located on the laterally outer sides of the hinge plates  156  with each spacer member  170  also including an abutment shoulder  172  for engagement with the hinge plates  154  of the outer hinge assembly  150  when the hinge mechanism  140  is in a fully opened state. An example of abutment shoulders or surfaces that engage with mating hinge plates are described in U.S. Pat. No. 7,364,017, entitled COMBINATION LADDER, LADDER COMPONENTS AND METHODS OF MANUFACTURING SAME, the disclosure of which is incorporated herein by reference in its entirety. 
         [0052]    In addition to providing a desired spacing of the hinge plates  154  and providing abutment surfaces, the spacer plates  168  may also house a number of components associated with the adjustment mechanism  160 . The adjustment mechanism  160  includes a lock plate  180  and lock plate spring  182  (or other biasing member) positioned within a cavity  224  formed in the spacer plates  168  (see, e.g.,  FIGS. 10A and 10B ), with the lock plate spring  182  biasing the lock plate  180  in a first direction along an axis  184  that extends through the lock plate  180  and associated cavity  224 . The adjustment mechanism  160  additionally includes a lock plate retainer  186  and retainer spring  188  (or other biasing mechanism) positioned within another cavity  226  formed in the spacer plates  168  (see, e.g.,  FIGS. 10A and 10B ), with the retainer spring  188  biasing the lock plate retainer  186  along an axis  190  that extends in a direction toward the locking plate  180  (e.g., in one embodiment, substantially perpendicular with axis  184 ). A retainer release structure  192  is disposed in a common cavity  224  (formed in the spacer plates  168 ) with the lock plate  180  and is configured to slide relative to the lock plate  180 , with a pair of spaced apart arms  194  extending along each side of the lock plate  180 . A pair of spaced apart fingers  196  extend from one of the arms  194  (e.g., the arm located closest to the lock plate retainer  186 ), the fingers  196  being configured to slide between the lock plate  180  and the lock plate retainer  186  as will be discussed in further detail below. A release spring  198  (or other biasing member) is positioned between the lock plate  180  and the release structure  192  and is configured to bias the release structure along the axis  184  away from the lock plate  180 . 
         [0053]    It is noted that the lock plate  180  includes a main body portion  200  and a pair of lateral extensions  202  such that the lock plate generally exhibits a “T” shape. However, other shapes may be utilized as will be appreciated by those of ordinary skill in the art. Each lateral extension  202  passes through an associated slot  204  formed in an adjacent hinge plate  154 . The slots are elongated in a direction that is substantially parallel with the axis  184  associated with the lock plate  180 . Thus, the lock plate  180  may be displaced along the axis  184  and may be limited by the length of the slots  204  formed in the hinge plates  154 , through which the lateral extensions  202  laterally extend and are axially displaced. On the outer side of the hinge plates  154 , caps or handles  162  are coupled with the lateral extensions  202  such as by a mechanical fastener  206  (e.g., a rivet) or other appropriate structure or method. 
         [0054]    It is noted that, as seen in  FIG. 4 , the hinge plates  154  and other components may be assembled and held together by way of various fasteners such as, for example, one or more rivets  208 , one or more compression pins  210  (e.g., pins having an interference fit with the hinge plates  154 ), other fasteners, or a combination of multiple types of fasteners such as shown. 
         [0055]    Referring now to  FIG. 6 , a portion of the inner hinge assembly  152  is shown in relation to the lock plate  180  of the adjustment mechanism  160  for reference in explaining the operation of the adjustment mechanism  160  and, more specifically, the interaction of the lock plate  180  with the inner hinge assembly  152  ( FIGS. 8, 12, 14 and 16 , discussed below, are similar views but with the hinge in different states). The inner hinge assembly  152  includes a spacer plate  212  disposed between the two hinge plates  156  (note that in  FIG. 6 , only a single hinge plate  156  is shown). As with the outer hinge assembly  150 , the hinge plates  156  of the inner hinge assembly  152  include a first portion  214  configured for coupling with a ladder rail (e.g., rail  104  of inner rail assembly  102 A or rail  116  of inner rail assembly  114 A as shown in  FIG. 1 ) and a second portion  216  configured for coupling with the outer hinge assembly  150  by way of the hinge pin  158 . 
         [0056]    A plurality of notches or recesses  218 A- 218 C are formed in the arcuate peripheral edge of the second portion  216  of the hinge plates  156 . These notches  218 A- 218 C are sized and configured to matingly receive a portion of the lock plate  180  such as shown in  FIG. 6 . When the lock plate  180  is positioned such that a portion of it is disposed within any notch or recess  218 A- 218 C, the first hinge assembly  150  and the second hinge assembly  152  are locked relative to one another such that they may not rotate about the hinge pin  158 . Thus, with the first and second hinge assemblies  150  and  152  locked relative to each other, the first and second rail assemblies  102  and  114  of the ladder  100  ( FIG. 1 ) are locked in a given position (e.g., as a step ladder, a straight or extension ladder, or in a stowed condition). 
         [0057]    Referring to  FIGS. 6 and 7 , the hinge mechanism  140  is shown in a collapsed state (e.g., such that the ladder  100  is collapsed, with the first and second rail assemblies  102  and  114  being positioned directly adjacent one another for storage or transportation purposes). In this state, the adjustment mechanism  160  is in a “locked” or engaged state such that a portion of the lock plate  180  extends into the first notch or recess  218 A preventing the first and second hinge assemblies  150  and  152  from rotating relative to each other about the hinge pin  158 . When it is desired to adjust the ladder (e.g., from the stowed state to a step ladder configuration), a user may displace one of the actuating handles  162  of the adjustment mechanism  160  causing the lock plate  180  to be displaced along axis  184 , the lateral extensions  202  thus being displaced within the slots  204  of the hinge plates  154 , such that the locking plate  180  is retracted from and disengages the first notch or recess  218 A as shown in  FIG. 8 . 
         [0058]      FIGS. 8 and 9  show the hinge mechanism  140  still in a collapsed state, but with the lock plate  180  in a retracted or unlocked position. With the lock plate  180  in the retracted or unlocked position, the hinge assemblies  150  and  152  are able to rotate relative to one another about the hinge pin  158  in order to place the ladder  100  in a different state (e.g., a step ladder state). 
         [0059]    Referring to  FIGS. 10A and 10B , when a user retracts the locking plate  180 , via handle  162 , to place it in the position shown in  FIGS. 8 and 9 , the retainer  186  and retainer spring  188  act to maintain the lock plate  180  in the retracted or unlocked position until subsequent action is taken as will be described below. In one embodiment, such as illustrated in  FIGS. 10A and 10B , the lock plate  180  includes an opening or a hole formed therein. In one embodiment, the opening may include a blind opening. In another embodiment, the opening may include a through-bore  220  (shown in dashed lines in  FIGS. 10A and 10B ) extending from one surface of the lock plate  180  to an opposing surface. The opening  220  may exhibit any of a variety of geometries (e.g., round, oval, square, etc.) and is configured for receipt of a protrusion  222  formed on an end of the retainer  186 . As shown in  FIG. 10A , when the lock plate  180  is in a locked or engaged state such that it engages a set of notches or recesses of the hinge plates  154  (e.g., recesses  218 A such as depicted in  FIGS. 7 and 8 ), the protrusion  222  abuts the outer surface of the lock plate  180 . However, when the lock plate  180  is retracted into an unlocked state, the opening  220  aligns with the protrusion  222  and the biasing force of the retainer spring  188  provides a sufficient force to displace the retainer  186  within its slot or cavity  226  in the spacer plate  168  (along axis  190 ), causing the protrusion  222  to engage with the opening  220  of the lock plate  180  thereby retaining the lock plate  180  in the retracted position as shown in  FIG. 10B . 
         [0060]    It is noted that, when the lock plate  180  is displaced within its slot or cavity  224  (along axis  184 ), the lock plate spring  182  is compressed while the release structure spring  198  elongates with the release structure  192  maintaining its original position within its cavity  224  as shown in  FIG. 10A . 
         [0061]    As noted above, with the lock plate  180  in a retracted position (e.g., as shown in  FIGS. 8 and 9 ), the hinge assemblies  150  and  152  may rotate relative to each other about the hinge pin  158  such as shown in  FIGS. 11 and 12 . When the hinge assemblies  150  and  152  rotate relative to each other through a specified angle of rotation, a radial projection (e.g., radial projection  230 B) formed on the spacer plate  212  of the inner assembly  152  engages the release structure  192 . When engaged by the radial projection (e.g.,  230 B), the release structure  192  is displaced along axis  184  within the cavity  224  such that the spaced fingers  196  insert themselves between the lock plate  180  and the retainer  186 . The tapered profile of the fingers  196  provide a ramped surface such that the further the release structure  192  is displaced toward the lock plate  180 , the further the retainer is displaced along axis  190  away from lock plate  180  until the protrusion  222  eventually disengages the opening  220 , resulting in the lock plate  180  being released from the retainer and being displaced along axis  184  towards (but not completely to) a state of engagement. It is noted that in the embodiment shown, the spaced apart fingers  196  are positioned with one finger  196  on each side of the protrusion  222  such that the protrusion fits within a slot or gap formed between the two fingers  196 . It is also noted that a surface of the retainer  186  may be tapered or ramped in addition to, or in the alternative to, the ramped or tapered configuration of the fingers  196 , in order to facilitate the displacement of the retainer  186  along a first axis (e.g.,  190 ) responsive to displacement of the retainer  192  along a second axis (e.g.,  184 ), the two axis being positioned at angles relative to one another (e.g., at right angles relative to one another). 
         [0062]    With the lock plate  180  released from the retainer  186 , it is displaced until an upper surface thereof abuts the peripheral edge of the second portion  216  of the hinge plates  156  (see  FIG. 12 ). The lock plate  180  maintains this position, staying in sliding abutment with the peripheral edge of the hinge plate  156 , while the hinge assemblies  150  and  152  continue relative rotation about the hinge pin  158 . When the hinge assemblies  150  and  152  have rotated relative to one another such that a notch or recess is aligned with the lock plate  180  (e.g., when recess  218 B is aligned with lock plate  180  such as shown in  FIGS. 13 and 14 ), the lock plate  180  engages the recess, due to the biasing force applied by the lock plate spring  182 ) and locks the hinge assemblies  150  and  152  prohibiting further relative rotation. Thus, as shown in  FIGS. 13 and 14 , with the locking plate  180  engaged in recess  218 B, the ladder  100  is in a step ladder configuration such as shown in  FIG. 1 , with the rail assemblies  102  and  114  extending away from each other at an acute angle to provide a self-supporting ladder configuration. 
         [0063]    To adjust the hinge mechanism  140  from the configuration shown in  FIGS. 13 and 14  to another configuration, a user may apply a force to one or both of the handles  162  to actuate the adjustment mechanism  160 , such as discussed above, causing the lock plate  180  to be displaced within its cavity  224  until it is engaged by the retainer  186  and held in a retracted state thereby. The hinge assemblies  150  and  152  may then be rotated relative to one another until a radial projection (e.g., radial projection  230 B or  230 C, depending on the direction of rotation) actuates the release structure  192 , causing the retainer  186  to be retracted from the lock plate  180 , enabling the lock plate  180  to be released from the retracted state and be displaced to the point that it abuts the peripheral edge of the hinge plates  156  as has been previously described. 
         [0064]    As shown in  FIGS. 15 and 16 , the hinge mechanism  140  may be adjusted such that the lock plate  180  engages notch  218 C which places the hinge assemblies  150  and  152  in a configuration such that the first portion of each hinge assembly (the portion configured for coupling with ladder rails) extend away from each other in a straight line or in a common plane, placing the ladder in an extension ladder configuration. 
         [0065]    It is noted that the radial projections  230 A- 230 C of the spacer plate are positioned such that, after the lock plate  180  has been retracted from a recess  218 A- 218 C and retained in a retracted state by the retainer  186 , minimal relative rotation of the hinge assemblies  150  and  152  is required to actuate the release structure  192  in the manner described above, placing the lock member  180  into contact with the peripheral edge of the hinge plate  156  of the inner hinge assembly  152 . Additionally, it is noted that radial projection  230 A is placed such that inward rotation of the hinge assemblies beyond the stored state (i.e., beyond the position shown in  FIGS. 7 and 8 ) will cause the lock plate  180  to be released from the retainer  186 , enabling the lock plate to reengage recess  218 A without having to rotate the hinge assemblies  150  and  152  toward the step ladder configuration. 
         [0066]    The hinge mechanism of the present disclosure provides an adjustable hinge for a ladder that is both light weight and strong. The construction of the hinge provides for simple and efficient manufacture using cost effective techniques and the possibility of using a variety of materials. In one embodiment, the various hinge plates may be formed of a metal (e.g., steel, aluminum, etc.), while the spacers may be formed of a plastic material. Components such as the hinge plates and spacer plates may be formed by molding, stamping, machining, a combination of such techniques or a variety of other techniques. 
         [0067]    While embodiments of the disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.

Summary:
Ladders, ladder components and related methods are provided including embodiments of a hinge that may be used in a combination ladder. In one embodiment, a hinge mechanism includes a first hinge assembly and a second hinge assembly. The first and second hinge assemblies are coupled together for relative rotation about a defined axis. An adjustment mechanism enables the two hinge assemblies to be selectively locked or unlocked to prohibit or permit relative rotation, respectively. In one embodiment, the adjustment mechanism includes a lock plate displaceable along a first axis and a retainer displaceable along a second axis. The retainer is configured to hold the lock plate in a disengaged state until a release structure displaces the retainer away from the lock plate. The release structure may be configured to be actuated and displace the retainer upon relative rotation of the hinge assemblies to (or through) a predetermined angular configuration.