Patent Publication Number: US-9845640-B2

Title: Extension ladder with cushions

Description:
BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates to an extension ladder and, more particularly, to an extension ladder with cushions. 
     2. Related Prior Art 
     An extension ladder includes several rungs connected to two telescopic rails that are movable between an extended position and a shrunk position. The extension ladder allows a user to reach a high place when the telescopic rails are in the extended position. The extension ladder can easily be carried or stored when the telescopic rails are in a shrunk position. A conventional extension ladder further includes a button operable to allow the telescopic rails to move to the shrunk position from the extended position by the gravity. However, the movement of the telescopic rails to the shrunk position from the extended position is often smooth and fast. Hence, the user could easily get hurt by one of the rungs. Moreover, the telescopic rails could easily be damaged. 
     The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art. 
     SUMMARY OF INVENTION 
     It is the primary objective of the present invention to provide a safe and durable extension ladder. 
     To achieve the foregoing objective, the extension ladder includes sub-ladders and cushions. Each sub-ladder includes a rung s connected to two tubes. The tubes of each sub-ladder are telescopically connected to the tubes of an adjacent sub-ladder. Each cushion includes an air bag and a slow-release unit. The air bag includes an open end with a channel. The air bag of each cushion is inserted in a corresponding tube. The slow-release unit is operable to slowly release air from the air bag and includes a restraint and a membrane. The restraint is connected to the open end of the air bag. The membrane includes an aperture and is movably arranged between the restraint and the open end of the air bag, with the aperture in communication with the channel. 
     Other objectives, advantages and features of the present invention will be apparent from the following description referring to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present invention will be described via detailed illustration of the preferred embodiment referring to the drawings wherein: 
         FIG. 1  is a front and cut-away view of an extension ladder according to the preferred embodiment of the present invention; 
         FIG. 2  is an enlarged view of a portion of the extension ladder marked by “A” shown in  FIG. 1 ; 
         FIG. 3  is an enlarged view of a portion of the extension ladder marked by “B” shown in  FIG. 2 ; and 
         FIG. 4  is a perspective view of a cushion of the extension ladder shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring to  FIGS. 1 through 4 , an extension ladder includes several sub-ladders  1  and several cushions  2  according to the preferred embodiment of the present invention. The sub-ladders  1  are moved from one another as the extension ladder is moved to an extended position. The sub-ladders  1  are moved toward one another as the extension ladder is moved to a shrunk position. Each of the cushions  2  is arranged between two adjacent ones of the sub-ladders  1  so that the cushions  2  are operable to reduce the speed of the movement of the sub-ladders  1  toward one another. Thus, a user is allowed to remove his or her hands from the extension ladder in time, i.e., it is safe for the user to use the extension ladder. Moreover, the sub-ladders  1  would not severely wear against one another, i.e., the extension ladder, which includes the sub-ladders  1 , is durable and lasts for a long period of time. 
     Preferably, each of the sub-ladders  1  includes a rung  11  connected to two tubes  12 . That is, the extension ladder includes two telescopic rails. Each of the telescopic rails includes a group of tubes  12  on a side of the rungs  11 . In each of the groups, the tubes  12  are telescopically connected to one another. Each of the cushions  2  is used between two adjacent ones of the tubes  12 . 
     Preferably, each of the cushions  2  includes an air bag  21  arranged between the two corresponding tubes  12 . Each of the air bags  21  is made with a channel  22  at an end. Air is released from each of the air bags  21  through the channel  22  as the air bag  21  is compressed while the corresponding tubes  12  are moved toward each other, i.e., the extension ladder is moved to the shrunk position. The release of the air from each of the air bags  21  via the channel  22  is slow, and so is the compression of the air bags  21 , and so is the movement of the corresponding tubes  12  toward one another. Air is sucked into the air bags  21  through the apertures  22  as the air bags  21  are expanded while the tubes  12  are moved away from one another, i.e., the extension ladder is moved to the extended position. 
     To control the release of the air from each of the air bags  21 , each of the cushions  2  includes a slow-release unit  3  connected to the open end of the air bag  21  thereof. The slow-release units  3  are operable to slowly release air from the air bags  21  through the apertures  22 , thereby rendering the movement of the sub-ladders  1  toward one another slow. The air bags  21  tend to be compressed faster as they are located lower, for carrying more weight. The slow-release units  3  are operable to cause air to be released from the air bags  21  at a same rate, thereby causing the sub-ladders  1  to be moved towards one another at a same speed. 
     Preferably, each of the slow-release units  3  is a check valve that includes a housing (not numbered) and a membrane  31 . The housing of each of the slow-release units  3  is connected to the open end of the corresponding air bag  21 , over the channel  22 . The membrane  31  of each of the slow-release units  3  includes an aperture  311  in communication with the channel  22  of the corresponding air bag  21 . Air is slowly released from each of the air bags  21  only via the aperture  311  of the membrane  31  of the corresponding slow-release unit  3  while the air bag  21  is compressed. Air is quickly sucked into each of the air bags  21  while the corresponding air bag  21  is expanded. 
     The membrane  31  of each of the slow-release units  3  is an elastic one. Each of the slow-release units  3  further includes a restraint  32  connected to the housing thereof. The membrane  31  of each of the slow-release units  31  is located between the restraint  32  of the same and the channel  22  of the corresponding air bag  21 . The membrane  31  of each of the slow-release units  31  is pressed against the restraint  32  of the same to cause air to be slowly released from the corresponding air bag  21  via the aperture  311  only while the corresponding air bag  21  is compressed. The membrane  31  of each of the slow-release units  3  is removed from the restraint  32  of the same to allow air to be quickly sucked into the corresponding air bag  21  while the corresponding air bag  21  is expanded. 
     Referring to  FIGS. 2 and 4 , to facilitate the sucking of air into the air bags  21  to allow the expansion of the air bags  21 , an end of a rope  33  is tied to a closed end of each of the air bags  21 . Another end of each of the ropes  33  is tied to a corresponding one of the tubes  12  of a lower one of the sub-ladders  1 . Hence, the air bags  21  are smoothly expanded by the sub-ladders  1  via the ropes  33  while the sub-ladders  1  are moved from one another. 
     The present invention has been described via the illustration of the preferred embodiment. Those skilled in the art can derive variations from the preferred embodiment without departing from the scope of the present invention. Therefore, the preferred embodiment shall not limit the scope of the present invention defined in the claims.