Patent Publication Number: US-2007095610-A1

Title: Lift ladder

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The invention lies in the field of ladders, especially marine ladders used on swim floats, docks, seawalls, etc. The invention relates to a lift ladder that can be extended and retracted between a maximum extended position and a maximum retracted position and, thus, be adjusted to various heights. More specifically, the invention relates to a lift ladder that can be safely secured in any desired position.  
      Lift ladders for marine application exist in the prior art. Applicant&#39;s U.S. Pat. No. 6,422,340 B1 (Grundler), for example, shows such a lift ladder, which has a catch mechanism for supporting the rungs of the ladder and a stop member for defining the maximum height of the lift ladder.  
      However, the lift ladder as shown in U.S. Pat. No. 6,422,340 has a problem of swinging when the ladder is extended to the maximum extent, which may be caused by the wind or a wake created by a boat, for example. The swaying of the ladder can cause injury to a person swimming toward the ladder or to a person climbing the ladder. When mooring a boat, the swaying of the ladder can also cause damage to the boat.  
      Therefore, there is a need for an improved lift ladder that can be more safely secured in the maximum extended position to prevent injuries to persons or damage to boats.  
     SUMMARY OF THE INVENTION  
      It is accordingly an object of the invention to provide an improved lift ladder that can be more safely secured in the maximum extended position.  
      With the foregoing and other objects in view, there is provided, in accordance with the invention, a lift ladder, comprising: 
          a support frame having two support bars, each of the support bars having: 
            a U-shaped portion; and     a vertical support portion having an end;    
            a transverse bar disposed between the two support bars at the vertical support portion, the transverse bar having a catch;     guide members provided at the end of the vertical support portion of each of the support bars, at least one of the guide members defining a cutout; and     a ladder body movably supported by the support frame, the ladder body having: 
            two vertical support members each slidably guided by a respective one of the guide members;     rungs each releasably engaged with the catch for setting a vertical position of the ladder body with respect to the support frame; and     a locking member formed on at least one of the two vertical support members, the locking member shaped to fit into the cutout for reducing movement of the ladder body with respect to the support frame.    
               

      In accordance with another feature of the invention, each of the guide members defines a cutout; and a locking member is formed on each of the two vertical support members, the locking members each shaped to fit into the cutout.  
      In accordance with a further feature of the invention, the locking member reduces lateral movement of the ladder body with respect to the support frame when disposed in the cutout.  
      In accordance with an added feature of the invention, the support frame has a longitudinal extent; and the locking member reduces movement of the ladder body in a direction orthogonal to the longitudinal extent when disposed in the cutout.  
      In accordance with an additional feature of the invention, the ladder body has an end; and the locking member is disposed on the vertical support member from a second uppermost one of the rungs to the end of the ladder body.  
      In accordance with yet another feature of the invention, the locking member is disposed on the vertical support member substantially at the second uppermost rung.  
      In accordance with yet a further feature of the invention, the ladder body has an end; and the locking members are disposed on a respective one of the vertical support members from a second uppermost one of the rungs to the end of the ladder body.  
      In accordance with yet an added feature of the invention, the locking members are disposed on a respective one of the vertical support members substantially at a location of the second uppermost rung.  
      In accordance with yet an additional feature of the invention, the catch has a L-shape; the rungs have a ceiling and two sides in an upside-down U-shape; and one of the sides operatively connects with the catch to releasably fix the ladder body in a position.  
      In accordance with another feature of the invention, there is provided a cable for connecting a respective one of the vertical support members of the ladder body to a respective one of the support bars.  
      With the foregoing and other objects in view, there is also provided, in accordance with the invention, a lift ladder, comprising: 
          a ladder body having rungs and a locking member;     a support frame slidably supporting the ladder body and having: 
            a guide member for guiding the ladder body between a stowed position and at least one extended position; and     a catch releasably engaging one of the rungs in at least one of the stowed position and the at least one extended position; and    
            the locking member operatively connecting the guide member and locking the ladder body at the at least one extended position.        

      With the foregoing and other objects in view, there is also provided, in accordance with the invention, a lift ladder, comprising: 
          a support frame having: 
            two substantially vertically oriented hand rails having a lower portion; and     a transverse bar fixedly connecting the two hand rails to one another, the transverse bar having a catch;    
            at least one guide member provided at the lower portion of at least one of the hand rails, the at least one guide member defining a cutout; and     a ladder body movably supported by the support frame, the ladder body having: 
            rungs each releasably engaged with the catch for setting a position of the ladder body with respect to the support frame; and     a locking member formed on at least one of the two vertical support members, the locking member shaped to fit into the cutout for reducing movement of the ladder body.    
               

      Other features that are considered as characteristic for the invention are set forth in the appended claims.  
      Although the invention is illustrated and described herein as embodied in a lift ladder, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.  
      Additional advantages of the invention will be set forth in part in the description which follows, and in part will be clear from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an exploded, perspective view of a lift ladder according to the invention secured to a dock;  
       FIG. 2  is a perspective view of the lift ladder of  FIG. 1  in a retracted position;  
       FIG. 3  is a perspective view of the lift ladder of  FIG. 1  in a maximum extended position;  
       FIG. 4  is fragmentary cross-sectional view along section line IV-IV in  FIG. 3 ; and  
       FIG. 5  is fragmentary cross-sectional view along section line V-V in  FIG. 3 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The invention may be understood more readily by reference to the following detailed description of preferred embodiments of the invention.  
      Before the invention is disclosed and described, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise.  
      The invention will now be described in detail with reference to the accompanying drawings.  
      Referring now to the figures of the drawings in detail and first, particularly to  FIG. 1  thereof, there is shown a lift ladder  100  according to the invention having a support frame  110  fixed to a dock  200  and a ladder body  120  that can be slidably supported by the support frame  110 . The support frame  110  includes two support bars  111 , each having a U-shaped portion  112  and a vertical support portion  113 , and a transverse bar  115  with a L-shaped catch member  116  disposed between the two vertical support portions  113  of the support bars  111 . The U-shaped portions  112  of the support bars  111  are each fixed to the dock  200  by a tie-down member  114  or by any other measures. A guide member  117  is provided at an end  113 ′ of a respective vertical support portion  113  of the support bar  111  for guiding the ladder body  120  during the extension and retraction movements. Each guide member  117  has a cutout  118  formed therein. The ladder body  120  has two vertical support members  121  and a plurality of U-shaped rungs  122  adapted to engage with the L-shaped catch member  116  to support the ladder body  120  with the support frame  110 . Each of the vertical support members  121  has at least one locking member  123  projecting outwardly therefrom. In a preferred embodiment, a single locking member  123  is formed between the uppermost rung  122  and the second uppermost rung  122  of the ladder body  120 . The locking member  123  is shaped to fit into the cutout  118  of the guide member  117 . However, each vertical support members  121  may be provided with more than one locking members  123 . For example, another locking member  123  may be provided on the vertical support members  121  at the lowermost rung  122 .  
       FIG. 2  shows the lift ladder  100  in a retracted position. Cables  300  are provided to connect the ladder body  120  to the U-shaped portion  112  of the support bar  111 . The cables  300  can facilitate the extending and retracting movements of the ladder body  120  and more particularly, prevent the ladder body  120  from being lost in the water if it is dropped or knocked loose. As shown in  FIG. 2 , the U-shaped rung  122  second from the bottom of the ladder body  120  is engaged with the L-shaped catch member  116  on the transverse bar  115  of the support frame  110 .  
      In comparison to  FIG. 2 ,  FIG. 3  shows the lift ladder  100  in a maximum extended position, in which the uppermost rung  122  of the ladder body  120  is engaged with the catch member  116  on the transverse bar  115  of the support frame  110 . Each locking member  123  on the ladder body  120  fits into the cutout  118  of the respective guide member  117  to provide the ladder body  120  with additional stability.  
       FIG. 4  even more clearly shows the connection between the catch member  116  and the rung  122 .  FIG. 4  illustrates how the upside-down U-shaped rung  122  of the ladder body  120  is engaged with the L-shaped catch member  116  formed on the transverse bar  115  of the support member  110 . In this view, it can be seen that the transverse bar/support member  115 / 116  connection is a pivot, about which the ladder body  120  can rotate. It is this pivoting motion that the cutout/locking member  118 / 123  prevents.  
       FIG. 5  clearly shows how the locking member  123  fits into the cutout  118  of the guide member  117 . Specifically, the cutout  118  has a diameter  118 ′ that is slightly greater than a diameter  123 ′ of the locking member  123 . Because of this relatively tight fit, the two contact points ( 115 / 116  and  118 / 123 ) are stable and do not present a pivot for movement of the lowermost portion of the ladder body  120  when it is subjected to the moving force of water, or any other force. When a locking member  123  is provided on the vertical support members  121  at the lowermost rung  122 , the two contact points ( 115 / 116  and  118 / 123 ) can also prevent the uppermost portion of the ladder body  120  from swiveling at a stowed position due to the wind.  
      As can be seen from  FIG. 5 , the distance between the two vertical support members  121  of the ladder body  120  is slightly smaller than the distance between the two vertical support portions  113  of the support bars  111  of the support frame  110  to accommodate the ladder body  120  within the guide members  117  on the vertical support portions  113 .  
      It is apparent from the above description that the lift ladder  100  according to the invention has an advantage over the prior art—the ladder body  120  can be secured with additional stability to prevent the ladder body  120  from swaying, thus, preventing injury to a person or damage to a boat.  
      Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only.