Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 12/267,295 filed Nov. 7, 2008, the disclosure of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This patent disclosure relates generally to access systems and, more particularly to systems for accessing operator stations of machines. 
     BACKGROUND 
     Many machines have operator controls located a distance from the ground. For example, large machines, such as large construction machines and large mining machines, often include cabs containing operator controls that are located atop the machines several feet from the ground. In order to access the controls, an operator needs the ability to ascend the distance from the ground to the cab. Many machines include access systems to aid the operator in accessing the controls of the machine. For instance, many machines include ladders, ramps, stair steps, and the like. 
     In many instances, machines must traverse rough terrain during their operation. For instance, wheel tractor scrapers, trucks, excavators, loaders, and other machines often pass over rough, ungroomed or unpaved ground of a construction or mining site. As a result, a large distance, often several feet, between the ground and the machine is desirable to allow the machine to pass over the terrain without hindrance or damage. In addition, large machines must pass vegetation, structures, and other machines while traversing a work site. Therefore, it is desirable that any access system provide adequate clearance to the ground and not project outwardly when the machine is in use, so as to avoid unintended contact with external objects. 
     SUMMARY 
     The disclosure describes, in one aspect, a ladder for access to a structure and egress therefrom, the ladder configurable from a first extended position for providing access to the structure and a second stowage position for storing the ladder when not in use. The ladder comprises an elongate upper member rotatably connected at an upper end to the structure at a connector and at least one upper step extending laterally from the upper member. An elongate lower member is attached to the upper member and configured for translational movement relative to the upper member. At least one lower step extends laterally from the lower member. The ladder includes a link extending between the lower member and the structure such that upward rotation of the upper member from the extended position to the stowage position causes the lower member to move translationally relative to the upper member, thereby moving said at least one upper step towards said at least one lower step. 
     Another aspect of the present disclosure includes a release mechanism for an access ladder. The access ladder including a lever assembly connected to an actuator for rotating the access ladder about an axis between a first extended position for providing access to a structure and a second stowed position. The release mechanism including a first release handle connected to the lever assembly, the first release handle configured to selectively disengage the lever assembly from the access ladder by moving the lever assembly along the axis. 
     Another aspect of the present disclosure includes an access ladder, the access ladder configurable from a first extended position for providing access to a structure and a second stowed position. The ladder including an elongated first member having a first end and a second end and connected to the structure, at least one first step extending laterally from the first member, an elongated second member associated with the first member and configured for translational movement relative to the first member. The second member includes at least one second step extending laterally from the second member, wherein the first member is hollow at the second end and wherein the second member is configured to extend from within the second end. The ladder further including a link pivotally and slidably engaging an elongate channel formed in the elongate second member. The link extends between the second member and the structure through a slot formed in and extending through a surface of the first member, such that rotation of the first member from the extended position to the stowed position moves the second member translationally relative to the first member, thereby moving said at least one second step towards said at least one first step. The ladder further including an actuator for rotating the first member about an axis between the extended position and the stowed position. The actuator including a lever in cooperation with the first member, wherein the lever is biased towards the first member. The ladder further including a release mechanism for mechanically disconnecting the first member from the actuator. The release mechanism including a first release handle positioned remotely from the access ladder configured to cooperate with the lever to selectively disengage the lever from the first member by moving the lever along the axis. 
     Another aspect of the present disclosure includes a vehicle including an access system configurable between a first configuration for providing access to a structure and a second stowed configuration. The access system including a first ladder portion having an elongated first member from which at least one first step extends horizontally, the first ladder portion having a first end and a second end, the first end attached to the structure. The access system further including a second ladder portion having an elongated second member from which at least one second step extends horizontally, the second ladder portion slidably associated to the first ladder portion so as to extend past the second end. The access system further including an actuator connected to the structure and the first ladder portion. The access system further including a link pivotally and slidably engaging an elongate channel formed in the first member, the link extending from the structure to the second ladder portion through a slot extending through a surface of the first member so as to move the second ladder portion to slide relative to the first ladder portion. The access system further including a release mechanism configured to mechanically disconnect the actuator from the first ladder portion. The release mechanism including a first release handle positioned remotely from the access ladder configured to cooperate with the lever to selectively disengage the lever from the first member by moving the lever along the axis, a hinge pin fixed to the lever assembly and disposed coaxially with the ladder axis of rotation, the hinge pin being biased in a first direction, a first feature fixed to the ladder assembly, and a second feature fixed to the lever assembly. The first feature and the second feature are configured to cooperate thereby connecting the ladder assembly and the lever assembly, the bias of the hinge pin engaging the first feature and the second feature, and the first release handle is configured to overcome the bias of the hinge pin thereby selectively disengaging the first feature and the second feature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side perspective view of a machine in accordance with an embodiment; 
         FIG. 2  is a side perspective view of an access system of the machine of  FIG. 1  with the access system in an extended position; 
         FIG. 3  is side a perspective view of the access system of  FIG. 2 ; 
         FIG. 4  is a side perspective view of the access system of  FIG. 2 , shown in greater detail; 
         FIG. 5  is a rear perspective view of the access system of  FIG. 2 ; 
         FIG. 6  is side view of the access system of  FIG. 2 , with the access system in an extended position; 
         FIG. 7  is a side view of the access system of  FIG. 6 , having a ladder portion rotated slightly towards a stowage position; 
         FIG. 8  is a side view of the access system of  FIG. 7 , shown with the ladder rotated further towards the stowage position; 
         FIG. 9  shows a side view of the access system of  FIG. 8 , with the ladder in the stowed position; 
         FIG. 10  is a detailed perspective view of a ladder portion including a portion of a release mechanism according to an embodiment of the present disclosure; 
         FIG. 11  is a detailed perspective view of an actuator lever portion including a portion of a release mechanism configured to cooperate with the ladder portion shown in  FIG. 10 ; 
         FIG. 12  is a perspective view of an embodiment of the release mechanism shown in  FIGS. 10 and 11 ; 
         FIG. 13  is a perspective view of an embodiment of a release mechanism of the present disclosure; 
         FIG. 14  is a detailed view of the embodiment of the release mechanism shown in  FIG. 13 ; 
         FIG. 15  is an elevation view showing an embodiment of the release mechanism of the present disclosure in an engaged position; and 
         FIG. 16  is an elevation view showing the release mechanism shown in  FIG. 15  in a disengaged position. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure relates to powered access systems providing ingress and egress to operator stations of machines. 
     In the following description, various embodiments of the present disclosure will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the present disclosure may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order to focus on the embodiment being described. 
     Referring now to the drawings, in which like reference numerals represent like parts throughout the several views,  FIG. 1  shows a machine  20  in accordance with an embodiment. As shown in the drawings, the machine  20  can be a wheel tractor scraper, which is a machine that scraps dirt, clay, or other material from the ground in order to bring the ground to a desired grade, such as for a road. The machine  20  can be another type of machine, such as an articulated or other truck, a backhoe loader, a cold planer, compactor, feller buncher, forest machine, a forwarder, harvester, excavator, loader, knuckle boom loader, material handler, loader grader, multi-terrain loader, off-highway tractor, off-highway truck, a paving machine, a pipe layer, a road reclaimer, a scraper, a skid-steel loader, a skidder, a telehandler, track loader, track-type tractor, wheeled dozer, wheeled excavator, wheeled loader, or an underground machine, or any other type of machine. The machine  20  can be mobile, but it can also be stationary without the ability to move from one location to another. 
     In the embodiment shown in the drawings, the machine  20  includes a cab portion  22  (also referred to as a tractor portion) and a bed portion  24  (also referred to a hopper, scraper, or bowl portion, the hopper or bowl referring to a receptacle for material scraped into the bed portion  24 ), both of which are supported by a plurality of wheels  26 . The cab portion  22  in an embodiment is configured for operating the machine  20 . In an embodiment, the cab portion  22  includes a cab  28  housing operator controls of the machine  20 . The cab  28  can sit in front of one of a pair of opposing fenders  30 , each fender  30  extending over a wheel  26  on opposing sides of the cab portion  22 . A bumper  32  extends from a front side of each fender  30  around a hood  34  for housing an engine of the machine  20 . In an embodiment, the bumper  32  projects outwardly to form an upper surface of the bumper  32  shared with an upper surface of a ledge  35  extending laterally from a side of the hood  34  in front of the fender  30 . An access system  36  for providing access to and egress from the cab  28  by use of a ladder, as described in more detail below, is connected to the ledge  35 , although the access system  36  can be located at any suitable portion of the machine  20  such as in front of the fender  30  closest to the cab  28 . Access systems such as the access system  36  shown, can be located in multiple locations of the machine  20 . A handrail  38  projecting upwardly from the ledge  35  or other suitable location can be located in close proximity to the access system  36  to provide leverage to an operator utilizing the access system  36  by allowing the operator to grip the handrail  38  for leverage. 
     As shown in  FIG. 2 , the ledge  35  includes two recesses  40  spaced one from the other. As shown in the drawing, the access system  36  includes a left upper member  42  and a right upper member  44 , each rotatably connected to the machine  20  at one of the recesses  40 . In an embodiment, the left upper member  42  is an elongate bar of metal or other suitable material extending to form an “L” shape, the shorter leg of the “L” extending towards the machine  20  at an angle, such as approximately ninety degrees, to the longer leg of the “L.” The right upper member  44  is similarly configured to the left upper member  42  and extends a distance from and parallel to the left upper member  42 . As shown in  FIG. 2 , the access system  36  is in an extended configuration whereby the access system  36  is configured as a ladder, with both the left upper member  42  and right upper member  44  extending downward and away from the ledge  35 . From this position, the access system  36  can be used for accessing the cab  28 , as described more fully below. 
       FIG. 3  shows the access system  36  in a stowage configuration whereby the left upper member  42  and right upper member  44  have been rotated upwardly about a left hinge  46  or other connector located in one of the recesses  40  and right hinge  48  or other connector located in the other recess  40 , respectively, so that the left upper member  42  and right upper member  44  extend upwardly from the left hinge  46  and right hinge  48  respectively. 
       FIG. 4  shows the access system  36  in greater detail. In an embodiment, the left upper member  42  and right upper member  44  extend parallel to one another with a plurality of steps  50  extending parallel and horizontally between them, thereby collectively forming an upper ladder portion. While the drawings show two steps  50  extending between the left upper member  42  and right upper member  44 , only one step  50  or more than two steps  50  can extend between the left upper member  42  and right upper member  44 . For instance, should a longer access system  36  be necessary for a particular machine, a longer left upper member  42  and right upper member  44  can be provided with several steps  50  extending between them. Likewise, should a shorter access system  36  be necessary for a particular machine, a shorter left upper member  42  and right upper member  44  can be provided with only one step  50  extending between them. The steps  50  can be an elongate structure of material, such as metal, able to support the weight of an operator of the machine  20 . 
     In an embodiment, the access system  36  includes a left lower member  52  extending from a lower end of the left upper member  42 . Similarly, the access system  36  includes a right lower member  54  extending from a lower end of the right upper member  44 . In an embodiment, the left lower member  52  is an elongate bar of material configured to fit within the left upper member  42  such that the left lower member  52  can slidably and translationally move along its long dimension relative to the left upper member  42 . In this manner, the left lower member  52  is able to telescope out of an end of the left upper member  42 , the end being the lower end of the left upper member  42  when the access system is in an access position. Nylon plates (not shown) on external faces of the left lower member  52  or other devices for reducing friction between the left upper member  42  and left lower member  52  can be included. Moreover, other configurations for configuring the left upper member  42 , right upper member  44 , left lower member  52 , and right lower member  54  to provide for translational movement between the left upper member  42  and left lower member  52  and between the right upper member  44  and right lower member  54  are possible. For example, the left lower member  52  need not extend into the end of the left upper member  42 , but can be slidably connected to the left upper member  42 , such as by a channel welded to a side of the left upper member  42  that has an inner shape corresponding to the outer shape of the left upper member  42 , so that the left lower member  52  is able to slide adjacent to the left upper member  42 . The right upper member  44  and right lower member  54  can be similarly otherwise configured. The right lower member  54 , in an embodiment, is similarly configured to the left lower member  52 . 
     An extension step  56 , such as a step configured similarly to the steps  50 , can extend between lower ends of the left lower member  52  and right lower member  54 , thereby collectively forming a lower ladder portion. While the drawings show only one extension step  56  extending between the left lower member  52  and right lower member  54 , more than one step can extend parallel between the left lower member  52  and right lower member  54 , for example, to create an access system  36  with greater length. The left upper member  42 , right upper member  44 , left lower member  52 , right lower member  54 , steps  50 , and extension step  56  are collectively referred to as a ladder assembly  57  as, when the access system  36  is in an extended access position, the access system  36  functions as a ladder. 
     As the left lower member  52  and right lower member  54  are connected to the left upper member  42  and right upper member  44 , respectively, the extension step  56  is able to move toward and away from the steps  50  as the left lower member  52  and right lower member  54  slide relative to the left upper member  42  and right upper member  44 , respectively. In this manner, the length between the top most step  50  and the extension step can be varied and, in particular, made shorter when the access system  36  is not in use. 
       FIG. 5  shows the access system  36  from a rear vantage point with the ladder assembly  57  in an access position. In an embodiment, the left hinge  46  and right hinge  48  are attached to the upper surface of a horizontally-extending plate  58  of the machine  20 , which is attached to an interior portion of the bumper  32  so that each hinge is exposed by a respective recess  40 . The left hinge  46  and right hinge  48  can alternatively be attached directly to the bumper  32  or other part of the machine  20  as desired or as warranted by design of the machine  20 . 
     As shown in the drawing, the access system  36  includes a left link  60  extending between the machine  20 , such as at a location of the plate  58  below the left hinge  46 , and an upper end of the left lower member  52 , thereby providing a link between the upper end of the left lower member  52  and the plate  58 . In an embodiment, the left link  60  is rotatably connected to the plate  58  at one end and rotatably connected to the left lower member  52  at an opposite end. Generally, the left link  60  can connect directly to the machine  20 , such as by connecting to connector (also referred to as a link connector) attached to a portion of a frame of the machine  20 , or the left link  60  can connect to the machine  20  indirectly, such as by connecting to a connector located on the plate  58 , as shown in the drawings, or by connecting to another suitable portion of the access system  36 . In an embodiment, the left link  60  is an elongate strip of metal or other rigid material, although it can also be a ribbon of flexible or other material. In an embodiment wherein the left lower member  52  extends into an end of the left upper member  42 , the left upper member  42  includes a left slot  64 , which is a slot extending through a portion of a surface of the length of the left upper member  42 , so as to allow the left link  60  to pass through the left upper member  42  to the left lower member  52 . A right link  62  is configured similarly to the left link  60 , extending from the right hinge  48 , through a right slot  66  extending along a portion of the length of the backside of the right upper member  44 , to an upper end of the right lower member  54 . 
     In an embodiment, one of the upper members, such as right upper member  44 , includes a lever assembly  68  mechanically engaging the right upper member  44  at an upper end of the right upper member  44  in front of the right hinge  48 . The lever assembly  68  is any device, such as a lever rigidly attached to the left upper member  44 , that causes the access system  36  to rotate about the left hinge  46  and right hinge  48  when force is applied to the lever assembly  68 . As shown in the drawing, in an embodiment, the lever assembly  68  comprises two parallel lever plates  70 , each cut so as to form an “L” shape with a leg of the “L” extending upwardly when the access system  36  is in an access position, as shown in  FIG. 5 . The lever plates  70  extend parallel to one another on opposite sides of the upper end of the right upper member  44  and mechanically engage the right upper member  44 , such as with tabs (not shown) extending beneath or into the sides of the right upper member  44 . In an alternate embodiment, the lever assembly  68  and right upper member  44  or left upper member  42  form a unitary component of the access system  36 . A lever bar  72 , which can be an elongate bar of metal, extends between the lever plates  70  above the upper end of the right upper member  44 . 
     In an embodiment, an actuator  74  engages the lever bar  72  and extends from the lever bar  72  toward an interior of the machine  20 , where it is rigidly attached to an appropriate structure of the machine  20 , such as an internal frame component of the machine  20 , as shown more clearly in  FIG. 4 . In an embodiment, the actuator  74  is an electric linear actuator, although it can also be a linear hydraulic cylinder assembly or another type of actuator. Generally, the actuator  74  is any device capable of applying a force to an appropriate component of the access system  36  so as to rotate the left upper member  42  about the left hinge  46  and the right upper member  44  about the right hinge  48 . The actuator  74  need not apply a linear force, but can also utilize rotational or other force according to a particular embodiment. In addition, the actuator  74  can also include a torque limiter or other mechanism for ensuring that the actuator  74  does not apply more force than desired. 
       FIGS. 6 through 9  demonstrate how, in accordance with an embodiment, the access system  36  is moved from an access configuration (also referred to as an access position or extended position), as shown in  FIG. 6 , to a stowage configuration (or stowage position), as shown in  FIG. 9 . 
     Referring specifically to  FIG. 6 , in the access position, the ladder assembly  57  is oriented with the left lower member  52  and right lower member  54  extending downwardly from the left upper member  42  and right upper member  44 , respectively. In an embodiment, the ladder assembly  57  extends downward and slightly away from the machine  20 , when in the access position. The extension step  56  is spaced from the lowermost step  50  enough to allow an operator to place his or her foot atop the extension step  56 , but close enough so that the operator can step from the extension step  56  to the lowermost step  50 . 
     As shown by comparing  FIGS. 6 and 7 , when the actuator  74  contracts, for example after actuation of an electric switch (not shown) by the operator, the actuator  74  pulls the lever assembly  68  towards the machine  20 , thereby causing the ladder assembly  57  to rotate upwardly about the left hinge  46  and right hinge  48 . As the ladder assembly  57  rotates upwardly, the distance between the lower end of the right upper member  44  and the connection of the right link  62  to the machine  20  increases. Consequently, the right link  62  pulls the right lower member  54  further into the right upper member  44 , thereby causing the extension step  56  to approach the steps  50 . As shown by further comparing  FIG. 8 , as the actuator  74  contracts further, the left lower member  52  and right lower member  54  extend further into the left upper member  42  and right upper member  44 , respectively, bringing the extension step  56  closer to the step  50  closest to the extension step  56 . 
     As shown in  FIG. 9 , when the actuator  74  has fully contracted, the ladder assembly  57  has rotated approximately 180 degrees from the access position to the stowage position, wherein the ladder assembly  57  extends upwardly from the ledge  35 , with the ladder assembly  57  oriented with the left lower member  52  and right lower member  54  extending upwardly from the left upper member  42  and right upper member  44 , respectively. In addition, by moving the access system  36  completely to the stowage position, the left link  60  and right link  62  have pulled the left lower member  52  and right lower member  54  nearly completely into the left upper member  42  and right upper member  54 , respectively, so that the extension step  56  is adjacent the closest step  50 , which is the uppermost step  50  shown in  FIG. 9 . Consequently, in the stowage configuration, the access system  36  is more compact than in the access configuration. In addition, the access system  36 , in the stowage configuration, does not have any components extending laterally from the machine  20  or below the machine  20 , thereby reducing any likelihood that the access system  36  may come in contact with the ground or another object or person when the machine  20  is in motion. If a machine contains moving parts, such as a hydraulically-operated boom or rotating cab, moving the access system  36  to the stowage position can also provide for free movement of any moving parts whereas the access system  36  may interfere with movement when in the access position. 
     Operation of the access system  36  from the stowage configuration to the access configuration is achieved similar to operation of the access system  36  from the access configuration to the stowage configuration, with the process proceeding in reverse. In particular, upon activation of a switch or other device, the actuator  74  pushes the lever bar  72 , causing the ladder assembly  57  to rotate downward about the left hinge  46  and right hinge  48 . In an embodiment, while the ladder assembly  57  rotates downward, the left link  60  and right link  62  push the left lower member  52  and right lower member  54 , respectively, out of the lower end of the left upper member  42  and right upper member  44 , respectively, as the distance between the lower ends of the left upper member  42  and right upper member  44  and the connections of the left link  60  and right link  62  to the plate  58  decreases. In an alternate embodiment, the left link  60  and right link  62  are flexible and, consequently, gravity and/or another external force, such as the force of an operator stepping on the extension step  56 , push the left lower member  52  and right lower member  54  out of the lower ends of the left upper member  42  and right upper member  44 , respectively, thereby separating the steps  50  from the extension step  56 . In yet another embodiment, the access system  36  includes only one of the left link  60  and right link  62 , which pushes the corresponding left lower member  52  or right lower member  54  out of the end of the corresponding left upper member  42  or right upper member  44 . 
     Referring back to  FIG. 4 , the access system  36  can include features additional to those listed above. For example, in accordance with an embodiment, the access system  36  can include an emergency release including an emergency release cable  76  and a handle  78 . The emergency release cable  76  releases the ladder assembly  57  from the actuator  74  so that the ladder assembly can be manually placed to the access position should the actuator  74  fail or lack a power source. The handle  78  provides an operator of the machine  20  a mechanism for pulling the emergency release cable  76 , and can be included at a terminal end of the emergency release cable  76  away from ladder assembly  57  and can be mounted on the machine  20  in a convenient location, such as on a portion of the machine  20  that does not frequently move relative to the remainder of the machine  20 , for example, on an external body panel of the machine  20  behind a door of the machine  20 . In an embodiment, the handle  78  pulls the emergency release cable  76 , which releases a mechanical connection between the ladder assembly  57  and the actuator  74 , for example, by pulling one or more components of the lever assembly  68  away from the right upper member  44  so as to mechanically disconnect the lever assembly  68  from the right upper member  44  or from the actuator  74 . Generally, any mechanism for allowing manual movement of the ladder assembly  57  can be used in connection with the emergency release cable  76  or with another mechanism controlling whether the access system  36  is operated manually or by the actuator  74 . 
     Referring to  FIG. 10 , an embodiment of an emergency release  90  may include a collar  92  attached to the ladder assembly  57 , for example at the right upper member  44 , such that the orientation of collar  92  is fixed relative to the upper member. Collar  92  may include one or more protrusions  94 . For example, as shown in  FIG. 10 , collar  92  is shown with two protrusions  94  disposed at  180  degrees relative to each other. Collar  92  may further include an opening  96  configured to align with openings in ladder assembly  57 , and in mounting plate  98 , and configured to receive hinge pin  100  (see  FIG. 11 ). 
     Referring now to  FIG. 11 , lever assembly  68  may include a recess or cut-out  102  disposed in lever arm  104 . Recess or cut-out  102  may be configured to include one or more keyways  106  corresponding to the one or more protrusions  94  on collar  92 . 
     As shown in  FIG. 12 , lever arm  104  may be configured to be positioned towards an inboard side of right upper member  44 . Hinge pin  100  may be disposed through lever arm  104 , right upper member  44 , and mounting plate  98 . A spring  108  may be disposed about an outboard end of hinge pin  100  and secured by a nut  110  and washer  112 . Spring  108  may be configured to exert a force oriented outboard of the right upper member  44 , drawing lever arm  104  and cut-out  102  into engagement with collar  92 . 
     Referring to  FIG. 13 , the emergency release  90  may include a first release handle  78 A located proximate to the cab  28  and a second release handle  78 B located such that the second release handle  78 B is accessible by an operator standing on the ground. A first emergency release cable  76 A and a second emergency release cable  76 B are connected at one end to first and second release handles  78 A and  78 B, respectively. At a second end, first and second emergency release cables  76 A,  76 B are connected to hinge pin  100 . 
     Referring to  FIG. 14 , a cable mounting bracket  114  may be attached to plate  58 . Cable mounting bracket may include a vertical flange  116  oriented substantially perpendicular to the axis of hinge pin  100 . Bushings  118 A,  118 B may be disposed through openings within flange  116  and configured to allow passage of emergency release cables  76 A and  76 B, respectively. 
     The second ends of emergency release cables  76 A,  76 B may be connected to hinge pin  100  by a clevis  120 . Clevis  120  may be configured to rotate about the axis of hinge pin  100 , allowing the ladder assembly  57  to rotate about hinge pin  100  while keeping emergency release cables  76 A,  76 B stationary without twisting. Clips  122 A,  122 B may be disposed on the second ends of emergency release cables  76 A,  76 B for attachment to clevis  120 . In the exemplary embodiment shown in  FIG. 14 , clips  122 A,  122 B may each be disposed about a leg of clevis  120 . Clips  122 A,  122 B and clevis may include openings such that, when aligned, a clevis pin  124  may be placed through the openings and secured with a cotter pin  126 . 
     Referring now to  FIGS. 15 and 16 ,  FIG. 15  shows the emergency release  90  in an engaged position and  FIG. 16  shows the emergency release  90  in a disengaged position. Activation of either handle  78 A or handle  78 B results in a tensile force to cable  76 A or cable  76 B, respectively. The tensile force is transmitted by cable  76 A or  76 B to hinge pin  100 , drawing hinge pin  100  outwardly against the force of spring  108 . Lever assembly  68  moves outwardly with hinge pin  100  until recess is free of collar  92 , thereby disengaging ladder assembly  57  from actuator  74 . 
     Emergency release  90  may further include a sleeve  128  attached to mounting plate  98  and disposed within an interior hollow region of ladder assembly  57 . The sleeve  128  may be fixed to the mounting plate, for example, by welding, interference fit, or other acceptable means known in the art. The sleeve  128  may include a low friction material  130  disposed within an interior surface. The low friction material  130  may be configured to allow the hinge pin  100  to slide freely within sleeve  128  with minimal resistance. Low friction material  130  may be configured as a nylon sleeve bearing. Additionally, emergency release  90  may include bushings  132 ,  134  disposed on either end of the sleeve  128  configured to reduce wear and provide a reduced coefficient of friction. In the exemplary embodiment, bushings  132 ,  134  are shown as top-hat bushings having a bore configured to cooperate with hinge pin  100 . Bushings  132 ,  134  may be constructed from a nylon material having a low coefficient of friction, similar to low friction material  130 . 
     INDUSTRIAL APPLICABILITY 
     When using a machine, an operator must typically ascend to a cab containing controls for operating the machine. For example, an operator of the machine  20  must ascend to the cab  28  of the machine  20  in order to drive the machine  20  around a job site where the machine  20  is being used to haul material in the bed portion  24  from one point to another. 
     To ascend to the cab  28 , the operator climbs the ladder portion  57  as if it were a conventional ladder. In particular, the operator begins by stepping onto the extension step  56  and then systematically ascending successive steps  50  until reaching the ledge  35 . The operator can grip portions of the ladder assembly  57  and the handrails  38 , as necessary, to pull himself or herself up. In the embodiment shown in the drawings, as seen in  FIG. 1 , the operator can climb additional fender steps  80  extending upwardly from in front of the fender  30 , or otherwise suitably located, and ascending the front portion of the fender  30  to access an entrance of the cab  28  or other location on the cab portion  22  of the machine  20 . Other ladders, access systems, or mechanisms can be utilized in connection with the access system  36  in order to ascend a machine. 
     Upon ascending the machine  20 , the operator, in an embodiment, activates an activation switch (not shown) electrically connected to the actuator  74 , causing the actuator  74  to rotate the ladder assembly  57  upward to the stowage position. A safety switch (not shown) and/or alarm may be included for preventing the machine  20  from achieving full operation until the access system  36  is in the stowage configuration or for alerting the operator that the access system  36  is in the extended access configuration while the machine  20  is in use. With the access system  36  in the stowage configuration, the operator operates the machine  20  until work is complete or until the operator otherwise needs to descend from the cab  28 . In order to descend from the cab  28 , the operator activates the activation switch, causing the actuator  74  to rotate the ladder assembly  57  downward until the ladder assembly  57  is in the access configuration. The operator then descends the ladder assembly  57  by systematically stepping on successive steps  50  until reaching the extension step  56  from which he or she makes a small step or jump to the ground. 
     It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated. 
     Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. 
     Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

Technology Category: e