Abstract:
Embodiments of the invention relate to apparatus and methods for a secondary safety device for use on elevators utilized to move casing, tubing, sucker rods, or other circular tools or members in the oil and gas industry. In one embodiment, a secondary latch lock mechanism for an elevator having a primary safety latch is provided. The secondary latch lock mechanism comprises a base portion that is fixed to a body of the elevator, and a handle movably fixed to the base portion and a first gear device by a biasing member, wherein the handle is movable to a first position proximate to the primary safety latch and a second position that is spaced away from the primary safety latch.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Patent Application Ser. No. 61/553,773, filed Oct. 31, 2011, which is hereby incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the invention generally relate to methods and apparatus for improving safety features of equipment used in the oil and gas industry. More specifically, embodiments of the invention relate to a secondary safety device for use on elevators utilized to move casing, tubing, sucker rods, or other tubular members and/or circular tools, in the oil and gas industry. 
     2. Description of the Related Art 
     An elevator is a device that is used to clamp or grip tubular members or circular tools, such as casing, tubing, drill pipe, or sucker rods, utilized in a drilling operation or rig work-over operation. A conventional elevator includes two arc-shaped members that are hingedly coupled on one end to open and close in a clamshell manner. The members may be closed to define a center hole that receives the circular tool, and opened to allow the circular tool to move into or out of the center hole. In the closed position, a primary safety latch is used to secure the free ends of the two arc-shaped members thereby preventing the two arc-shaped members from opening unexpectedly. 
     Primary safety latches on conventional elevators typically utilize a secondary safety mechanism to prevent the primary safety latch from opening accidently. The secondary safety mechanism may include a pin, such as a rod or a large cotter pin, that may be inserted into a hole or holes that cross the primary safety latch and prevent the primary safety latch from opening. When the elevator is to be opened, the pin is removed from the holes, which allows the primary safety latch to be positioned to allow the arc-shaped members to open. 
     The conventional secondary safety mechanism design has at least the following drawbacks. Use of the secondary safety mechanism typically requires the use of two hands to properly align the holes and install the pin into the holes. The hole/pin alignment and installation process may extend the time needed to properly secure the primary safety latch. Additionally, a hazardous condition is created as the operator has both hands in proximity to pinch points associated with the elevator. Further, the pin must be safely stored when not in use. Some conventional elevators include a storage hole for the pin. However, inserting the pin into the storage hole adds additional operator time. Other conventional elevators utilize a cable or small chain attached to the pin to prevent loss of the pin when not in use. However, the cable or chain may be damaged and the pin may be lost. Additionally, the cable or chain securing the pin may create a hazardous condition by potentially snagging or otherwise injuring an operator. 
     What is needed is an improved secondary safety lock mechanism for safely and efficiently locking a primary safety latch. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention address the issues with conventional secondary safety mechanisms by providing a secondary latch lock mechanism that is integrated onto the elevator. The inventive secondary latch lock mechanism as described herein may be operated with one hand and is coupled to the elevator, which prevents loss of the secondary latch lock mechanism as well as providing additional safety to personnel. 
     In one embodiment, a secondary latch lock mechanism for an elevator having a primary safety latch is provided. The secondary latch lock mechanism comprises a base portion that is fixed to a body of the elevator, and a handle movably fixed to the base portion and a first gear device by a biasing member, wherein the handle is movable to a first position proximate to the primary safety latch and a second position that is spaced away from the primary safety latch. 
     In another embodiment, a secondary latch lock mechanism for an elevator having a primary safety latch is provided. The secondary latch lock mechanism comprises a base portion that is fixed to a body of the elevator, and a handle movably fixed to the base portion, wherein the handle is selectively engaged with a first gear device disposed on a first side of the base portion, and a second gear device disposed on an opposing second side of the base portion. 
     In another embodiment, a method for selectively securing a primary safety latch coupled to an elevator is provided. The method comprises moving the primary safety latch from an open position to a closed position, moving a handle coupled to the elevator to a first position proximate a first surface of the primary safety latch, the first position preventing the primary safety latch from moving to the open position, and moving the handle to a second position that is spaced away from the first surface of the primary safety latch, the second position allowing movement of the primary safety latch to the open position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited aspects of the invention can be understood in detail, a more particular description of embodiments of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is an isometric view of an elevator having a secondary latch lock mechanism according to embodiments of the invention. 
         FIG. 2  is an isometric view of the secondary latch lock mechanism of  FIG. 1 . 
         FIG. 3A  is an isometric view of a primary latch mechanism and the secondary latch lock mechanism of  FIG. 2  in a closed position. 
         FIG. 3B  is a top view of the primary latch mechanism and the secondary latch lock mechanism of  FIG. 3A . 
         FIG. 4A  is an isometric view of the primary latch mechanism in a closed position and the secondary latch lock mechanism of  FIG. 2  in an open position. 
         FIG. 4B  is a top view of the primary latch mechanism and the secondary latch lock mechanism of  FIG. 4A . 
         FIG. 5  is an exploded view of the secondary latch lock mechanism of  FIGS. 2-4B . 
         FIGS. 6A and 6B  are schematic views depicting another embodiment of a secondary latch lock mechanism that may be utilized with the elevator of  FIG. 1 . 
         FIGS. 7A-8B  are various views to describe an opening sequence of the secondary latch lock mechanism of  FIGS. 6A and 6B . 
         FIG. 9  is an isometric view of one embodiment of a striker device that may be used with the secondary latch lock mechanism shown in  FIGS. 6A-8B . 
         FIG. 10  is an isometric view of one embodiment of a housing that may be used with the secondary latch lock mechanism shown in  FIGS. 6A-8B . 
         FIG. 11  is an isometric view of one embodiment of the striker device of  FIG. 9  assembled in the housing of  FIG. 10 . 
         FIG. 12  is an isometric bottom view of the secondary latch lock mechanism of  FIGS. 6A-8B . 
         FIG. 13  is an isometric view of the secondary latch lock mechanism of  FIG. 12  during closing of a latch plate. 
         FIG. 14  is an isometric view of one embodiment of a secondary latch lock assembly that may be used with the elevator of  FIG. 1 . 
         FIGS. 15A-15C  are bottom views of the secondary latch lock assembly of  FIG. 14  depicting a latch opening sequence. 
         FIGS. 15D-15E  are bottom views of the secondary latch lock assembly of  FIG. 14  depicting a latch closing sequence. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is also contemplated that elements and features of one embodiment may be beneficially incorporated on other embodiments without further recitation. 
     DETAILED DESCRIPTION 
       FIG. 1  is an isometric view of an elevator  100  showing one embodiment of the invention. The elevator  100  includes a body  105  having two members  110 A and  1108  that are coupled at one end by a hinge device  112 . The body  105  includes two hooks  114  adapted to receive a bail that is coupled to a travelling block (both are not shown). The member  1108  may be configured as a door  115  that may be closed, as shown in  FIG. 1 , to define a center hole  116  that clamps a tool (not shown), such as casing, tubing, drill pipe, or sucker rods, utilized in a drilling operation or rig work-over operation. The door  115  may be selectively opened to allow passage of the tool into and out of the center hole  116  of the elevator  100 . 
     In the closed position, the door  115  is secured by a primary latch mechanism  120 . The primary latch mechanism  120  comprises a latch plate  125  that is positioned proximate to one or more wedge-shaped latch members  128  in the closed position. The latch members  128  may be formed on the member  1108 . The latch plate  125  is secured to the member  110 A by a hinge device  130 . One or more support members  132  may be used to couple the latch plate  125  to the hinge device  130 . The hinge device  130  allows the latch plate  125  to move in an arc relative to the member  110 A and toward and away from the member  1108 . However, as shown in  FIG. 1 , the latch plate  125  is prevented from moving by a secondary latch lock mechanism  135  coupled to the member  1108 . 
     The secondary latch lock mechanism  135  comprises a handle  140  having a proximal end  142 A and an enlarged distal end  142 B. The enlarged distal end  142 B may comprise a post-like projection extending orthogonally from the handle  140 . The secondary latch lock mechanism  135  also includes an indexer or gear device  144  that selectively locks the handle  140  in a closed position such that the distal end  142 B of the handle  140  is positioned proximate a surface  145  of the latch plate  125  in the closed position. As shown in  FIG. 1 , the secondary latch lock mechanism  135  prevents the latch plate  125  from moving away from the door  115  (or member  110 B) as the distal end  142 B of the handle  140  is in proximity to the surface  145  of the latch plate  125 . As will be explained in greater detail below, the handle  140  is movable from the closed position to an open position (not shown) by lifting the handle  140  upwards (Z direction). Lifting the handle  140  disengages the handle  140  from the gear device  144  and allows rotation of the handle  140 . In operation, personnel may lift the handle  140  with one hand, which disengages the handle from the gear device  144 , and the handle  140  may be rotated away from the latch plate  125 . When the distal end  142 B of the handle  140  is clear of the latch plate  125 , the latch plate  125  may be moved away from the door  115  and the door  115  may be opened. 
       FIG. 2  is an isometric view of the secondary latch lock mechanism  135  of  FIG. 1 . The handle  140  is coupled to a base  200 . The base  200  may be coupled to the door  115  (shown in  FIG. 1 ) by fasteners, such as screws or bolts, welding, or other suitable fastening method. The handle  140  includes a body  205  having an opening formed in the proximal end  142 A that receives a spindle  210 . One or both of the handle and the spindle  210  may be coupled with the gear device  144 . The distal end  142 B also includes a protruded portion  215  that extends from the body  205 . The protruded portion  215  may include a flat face  218  that faces the proximal end  142 A. The flat face  218  may be substantially normal (i.e., about 85 degrees to about 95 degrees) to the longitudinal axis of the body  205 . The body  205  may also include a gripping feature  220 , such as a raised rib or a depressed channel, formed in the body  205  to assist gripping of the handle  140  during opening and/or closing operations. 
       FIG. 3A  is an isometric view of the primary latch mechanism  120  and the secondary latch lock mechanism  135  in a closed position.  FIG. 3B  is a top view of the primary latch mechanism  120  and the secondary latch lock mechanism  135  in the closed position.  FIG. 4A  is an isometric view of the primary latch mechanism  120  in a closed position and the secondary latch lock mechanism  135  in an open position.  FIG. 4B  is a top view of the primary latch mechanism  120  in a closed position and the secondary latch lock mechanism  135  in the open position. As shown in  FIGS. 4A and 4B , the latch plate  125  may be free to move relative to the door  115  when the handle  140  is in the open position. 
       FIG. 5  is an exploded view of the secondary latch lock mechanism  135  of  FIGS. 1-4B . A gear device  144  is shown on the base  200 . The gear device  144  comprises a plurality of teeth that selectively engage with a pin  505  that is disposed in the proximal end  142 A of the handle  140 . An opening  510  formed in the proximal end  142 A of the handle  140  is sized to receive an outer surface  515  of the gear device  144  as well as a spindle, which may comprise a fastener  520 . The fastener  520  includes a first end  550 A and a second end  550 B. The first end  550 A may include an enlarged head portion to prevent the fastener  520  from completely going through the opening  510  in the handle  140 . The fastener  520  includes an outside dimension that fits within an opening  525  of the gear device  144 . The pin  505  is secured to the handle  140  by an opening  530  formed substantially normal to the axis of the opening  510  in the proximal end  142 A of the handle  140 . The pin  505  is also secured to the fastener  520  at a first through-hole  535  formed proximate the first end  550 A substantially normal to a longitudinal axis of the fastener  520 . A region  540  of the pin  505  is received in the first through-hole  535  of the fastener  520  when assembled. Regions of the pin  505  outside of the region  540  are exposed to upper surfaces (i.e., toothed portions) the gear device  144  on opposing sides of the fastener  520  when assembled. A retainer device  545  may be coupled to the second end  550 B of the fastener  520 . A biasing member  555 , such as a spring, may be positioned between the retainer device  545  and the bottom surface of the gear device  144 . The biasing member  555  is utilized to maintain a tensional force on the fastener  520 , and ultimately the handle  140 , to facilitate engagement of the pin  505  and the gear device  144 . The second end  550 B of the fastener  520  may be threaded to facilitate attachment of the retainer device  545  thereon. Alternatively or additionally, a pin  560  may be received in a second through-hole  565  formed proximate the second end  550 B and substantially normal to a longitudinal axis of the fastener  520  in order to secure the retainer device  545  to the fastener  520 . The secondary latch lock mechanism  135  may also include a lubricating port  570 , which may comprise internal fluid distribution channels (not shown) and a grease fitting  575  for facilitating lubrication of the secondary latch lock mechanism  135 . 
     In one aspect, when the secondary latch lock mechanism  135  is assembled, teeth  580  of the gear device  144  engage the regions of the pin  505  to prevent movement of the handle  140  in a first direction A (i.e., a counterclockwise direction) while the handle  140  is biased toward the base  200  by the biasing member  555 . Thus, the force of the biasing member  555  must be overcome by lifting the handle  140  relative to the base  200  (in the Z direction) to move the handle  140  from a closed position as shown in  FIGS. 3A and 3B  to an open position as shown in  FIGS. 4A and 4B . The gear device  144  may also engage the pin  505  to prevent movement of the handle in a second direction B (i.e., a clockwise direction) in a similar manner. However, the gear device  144  may be configured to rotate with minimal lifting force applied to the handle  140  in at least one direction. For example, the teeth  580  of the gear device  144  may be configured to allow the handle  140  to rotate in the second direction B with minimal to no lifting force applied to the handle  140 . In this example, second direction B may be a closed position and the gear device  144  is configured to allow the handle  140  to be easily rotated to the closed position. However, the gear device  144  may be configured to limit movement from the closed position to the open position (i.e., limit movement in the first direction A), requiring the handle to be positively lifted and rotated by personnel before disengagement with the teeth  580  of the gear device  144 . 
       FIGS. 6A and 6B  are schematic views depicting another embodiment of a secondary latch lock mechanism  135 . In this embodiment, an automated safety latch lock mechanism  600  is used in conjunction with the secondary latch lock mechanism  135  described in  FIGS. 1-5 .  FIG. 6A  is a side view of the automated safety latch lock  600  and  FIG. 6B  an isometric bottom view of the automated safety latch lock mechanism  600 . The automated safety latch lock  600  is shown in a closed position in both of  FIGS. 6A and 6B . 
     The automated safety latch lock  600  comprises a sprocket  605  that is coupled to a housing  608  (shown in phantom in  FIG. 6A ) that is coupled to the door  115 . The housing  608  maintains the sprocket  605  in a stable position relative to the door  115  while allowing the sprocket  605  to rotate. The sprocket  605  is coupled to the handle  140  by a lower gear  610  having a pin  612  that selectively engages holes  614 A- 614 D formed in the sprocket  605 . In  FIG. 6B , the pin  612  is disposed in a first hole  614 A. A striker device  615  is coupled to the housing  608  (not shown in  FIG. 6B ) that the sprocket  605  is mounted to. The striker device  615  includes a movable pin  620  that engages teeth of the sprocket  605 .  FIGS. 7A-8B  follow to describe an opening sequence of the secondary latch lock mechanism  135  according to this embodiment. 
       FIG. 7A  is a side view of the secondary latch lock mechanism  135  having the automated safety latch lock  600  shown in  FIGS. 6A and 6B .  FIG. 7B  is an isometric view of the automated safety latch lock  600  of  FIG. 7A . The housing  608  is not shown in these views in order to more clearly show the sprocket  605 . As shown in  FIGS. 7A and 7B , the handle  140  is lifted (in the Z direction), which raises the gear  610  relative to the sprocket  605 . The gear  610  is moved relative to the sprocket  605  to a position that removes the pin  612  from engagement with holes in the sprocket  605 . In particular, the pin  612  is raised out of engagement with hole  614 A of the sprocket  605 . During the raising of the handle  140 , the sprocket  605  is stationary due to a bias against the sprocket  605  provided by the movable pin  620 . When the handle  140  is raised and the pin  612  is disengaged from the hole  614 A, the handle  140 , the lower gear  610 , the pin  612 , and the retainer device  545  may be rotated relative to the sprocket  605  which remains stationary during this process. 
       FIGS. 8A and 8B  show the handle  140  rotated to an open or unlocked position. The handle  140  may be turned in a counterclockwise direction until the pin  612  is aligned with a second hole  614 B on the sprocket  605 . Lifting of the handle  140  during this rotation is not required and the pin  612  remains biased toward a surface of the sprocket  605  by the biasing member  555  (shown in  FIG. 5 ). During the rotation of the handle  140 , and portions coupled thereto, such as the lower gear  610 , the pin  612 , and the retainer device  545 , the sprocket  605  remains stationary. About a 90 degree rotation of the handle  140  allows the pin  612  to be reengaged with the sprocket  605 , but in a second hole  614 B of the sprocket  605 , as shown in  FIG. 8B . 
       FIG. 9  is an isometric view of one embodiment of a striker device  615  that may be used with the secondary latch lock mechanism  135  shown in  FIGS. 6A-8B . The striker device  615  includes an opening  900  for the movable pin  620 . A biasing member  905 , such as a spring, may be disposed in a body  910  of the striker device  615  to bias the movable pin  620  outward of the body  910  (i.e., in the X direction). The striker device  615  also includes one or more indexing features  915  that are configured as a structure facilitating linear movement of the body  910 . The indexing features  915  may be in the form of a protruded shoulder configured to mate with another structure in the housing  608  (not shown) to facilitate linear movement of the striker device  615  relative to the housing  608 . 
       FIG. 10  is an isometric view of one embodiment of a housing  608  that may be used with the secondary latch lock mechanism  135  shown in  FIGS. 6A-8B . The housing  608  includes an axle  1000  having a spindle  1005  that facilitates retention of the sprocket  605  (shown in  FIGS. 6A-8B ). The housing  608  may also include a recess  1010  having one or more channels  1015  that mate with indexing features  915  of the striker device  615  (shown in  FIG. 9 ). A biasing member  1020 , such as a spring, may be coupled to a wall  1025  of the housing  608 . The biasing member  1020  is utilized to bias the body  910  of the striker device  615  (shown in  FIG. 9 ) in the Y direction.  FIG. 11  is an isometric view of one embodiment of the striker device  615  of  FIG. 9  assembled in the housing  608  of  FIG. 10 . 
       FIG. 12  shows the secondary latch lock mechanism  135  in an open position and the latch plate  125  moved a distance away from the door  115 . The striker device  615  is coupled to the housing  608  (not shown for clarity) that allows lateral movement of the striker device  615  relative to the sprocket  605 . In this opened (unlatched) position, the sprocket  605  and handle  140  (not seen in this view) do not move. Movement of the latch plate  125  away from the door  115  allows the striker device  615  to move laterally (in a direction toward the latch plate  125  (in the Y direction)). The movable pin  620  moves past teeth of the sprocket  605  during this lateral movement of the striker device  615  due to the shape of the teeth. The movable pin  620  is coupled to a biasing member  905  (shown in  FIG. 9 ) that biases the movable pin  620  toward the sprocket  605 . In the position shown in  FIG. 12 , the movable pin  620  is fully extended. In this position, the latch plate  125  may be opened and the door  115  may be opened for entry or exit of circular tools. The secondary latch lock mechanism  135  and the striker device  615  (via the housing  608  (not shown)) stays coupled to the door  115  during loading or unloading. The opening process requires only lifting and rotation of the handle  140 , which may be accomplished with one hand. Further, all parts of the secondary latch lock mechanism  135  are securely coupled to the door  115 , requiring no removal of parts which are stored or otherwise bothersome to personnel. Further, the position of the striker device  615  shown in  FIG. 12  is readied for closing which is explained in  FIG. 13 . 
       FIG. 13  is an isometric view of the secondary latch lock mechanism  135  during closing of the latch plate  125 . During closing, an inner surface  1300  of the latch plate  125  contacts a side  1305  of the striker device  615 , which causes the striker device  615  to move laterally away from the latch plate  125  (in the Y direction). This causes the movable pin  620  to engage a tooth of the sprocket  605  and turn the sprocket  605  in a counterclockwise direction. As the sprocket  605  is engaged with the pin  612 , and the pin  612  is coupled to the handle  140  via the lower gear  610  and the retainer device  545 , the handle  140  is caused to rotate in a counterclockwise direction in a position that hinders movement of the latch plate  125 . 
       FIG. 14  is an isometric view of one embodiment of a secondary latch lock assembly  1400  that may be used with the elevator  100  of  FIG. 1 . The assembly  1400  incorporates the housing  608  and the base  200  of the secondary latch lock mechanism  135  as an integral unit that may be coupled to the elevator  100  (not shown) by fasteners (also not shown). 
       FIGS. 15A-15C  are bottom views of the secondary latch lock assembly  1400  depicting a latch opening sequence.  FIGS. 15D-15E  are bottom views of the secondary latch lock assembly  1400  depicting a latch closing sequence. 
       FIG. 15A  shows the latch plate  125  in a locked position. In this position, the handle  140  is engaged with the gear device  144  (shown in  FIGS. 1-5 ) and secures the latch plate  125  to the door (not shown). The movable pin  620  is engaged with a tooth of the sprocket  605 . The movable pin  620  is biased against the sprocket  605  by a biasing member (not shown) disposed in the striker device  615 . The pin  612 , which moves linearly (in the Z direction) as well as rotationally based on movement of the handle  140 , is engaged with the first hole  614 A in the sprocket  605 . 
       FIG. 15B  shows the position of the handle  140  that has been lifted and rotated counterclockwise approximately 90 degrees. This allows the latch plate  125  to move away from the secondary latch lock mechanism  135 . As the latch plate  125  is moved away, the striker device  615  moves in the X direction, which allows the movable pin  620  to slide relative to the sprocket  605  based on the shape of the teeth of the sprocket  605 . Movement of the handle  140  also causes the pin  612  to disengage from the first hole  614 A and engage the second hole  614 B of the sprocket  605 . 
       FIG. 15C  shows the latch plate  125  moved further away from the automated safety latch lock  600 . The striker device  615  is fully extended from the housing  608 . In this position, the striker device  615  may contact a stop (not shown) coupled to the housing  608 , which prevents the striker device  615  from moving too far out of the housing  608 . As shown in  FIG. 15C , the movable pin  620  is fully extended from the body of the striker device  615  and is in position to engage a tooth of the sprocket  605  to facilitate reengagement of the secondary latch lock mechanism  135  during a closing sequence. 
       FIG. 15D  shows the secondary latch lock assembly  1400  in a position to reengage the handle  140  during a closing sequence. As the latch plate  125  is moved in the X direction toward the striker device  615  during a closing sequence, the inner surface  1300  of the latch plate  125  contacts the side  1305  of the striker device  615 . Movement of the latch plate  125  in the X direction causes the striker device  615  to move in the X direction. As the striker device  615  moves in the X direction, the movable pin  620  contacts a tooth of the sprocket  605 . Continued movement of the striker device  615  causes the sprocket  605  to rotate counterclockwise. As the handle  140  is coupled to the sprocket  605  by the pin  612  disposed in the second hole  614 B, the handle  140  will rotate counterclockwise. 
       FIG. 15E  shows the secondary latch lock assembly  1400  in the closed position. In this position, the pin  612  is engaged with the second hole  614 B of the sprocket  605 . During a subsequent opening sequence as described in  FIG. 15B , the pin  612  will disengage with the second hole  614 B of the sprocket  605  and engage with a third hole  614 C of the sprocket  605  based on movement of the handle  140 . 
     Embodiments of the secondary latch lock mechanism  135  described herein provide a secure fastening means for safely locking a latch plate  125  of an elevator. The secondary latch lock mechanism  135  requires one-handed operation which frees the operators other hand to perform other tasks. The secondary latch lock mechanism  135  does not have parts (e.g. pins) that may be lost or require chains or cables as a fastening means to the elevator, which may cause injuries or other accidents. As the handle  140  of the secondary latch lock mechanism  135  as described herein is more clearly seen by the operator in position over the latch plate  125 , the secondary latch lock mechanism  135  also adds value as a positive visual indicator to the operator that the latch plate  125  is locked (e.g., as opposed to pins that may be used in conventional latch locks that may be hard for an operator to see). Embodiments of the secondary latch lock mechanism  135  also include an automated closing feature which further increases the efficient operation of the elevator as well as providing additional safety to personnel. 
     While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.