Rail device

Abstract

A rail device includes an inner rail, a middle rail slidably mounted to the inner rail, and an outer rail slidably mounted to the middle rail. The inner rail forms a first protrusion. The middle rail forms a first locking member and a driving member at a first end. The outer rail forms a second locking member and a pushing member. When the first locking member latches with the first protrusion, and the second locking member latches with the second protrusion, the rail device has a first length. When the first locking member latches with the first protrusion, and the pushing member latches with the driving member, the rail device has a second length.

What is claimed is: 
     
         1 . A rail device, comprising:
 an inner rail forming a first protrusion;   a middle rail slidably mounted to the inner rail, the middle rail comprising a first locking member and a driving member at a first end, and a second protrusion at a second end; and   an outer rail slidably mounted to the middle rail; the outer rail comprising a second locking member and two pushing members at a first end;   wherein when the first locking member is blocked by the first protrusion and the second locking member is blocked by the second protrusion, the rail device is fixed with a first length; when the first locking member is blocked by the first protrusion and the pushing members are latched with the driving member, the rail device is fixed with a second length.   
     
     
         2 . The rail device of  claim 1 , wherein a first fixing portion is formed at a first end of the inner rail, a second fixing portion is formed at a second end of the outer rail. 
     
     
         3 . The rail device of  claim 1 , wherein the inner rail forms two blocks between the first protrusion and a first end of the inner rail, the driving member comprises two arms, each arm expose out of an inner surface and an outer surface of the middle rail, the pushing members protrude from an inner surface of the outer rail and abut against the arms to drive the middle rail to slide together with the outer rail until the arms are deformed away from each other by sliding along sides of the blocks away from each other, to allow the arms to disengage from the pushing members and to stop the middle rail. 
     
     
         4 . The rail device of  claim 3 , wherein the sides of the blocks away from each other are guiding surfaces slantedly extending away from each other and toward the first protrusion, the sides of the pushing member away from each other are guiding surfaces slantedly extending away from each other and toward a second end of the outer rail. 
     
     
         5 . The rail device of  claim 3 , wherein the middle rail defines two receiving slots, each receiving slot comprises a first part and a second part communicating with the first part and less than the first part in width, the driving member further comprises two legs engaged in the first parts, the arms slantedly extend toward each other from the legs and are received in the second parts. 
     
     
         6 . The rail device of  claim 3 , wherein two blocking pieces extend from distal ends of the arms to abut against the pushing members. 
     
     
         7 . The rail device of  claim 6 , wherein two guiding pieces slantedly extend away from each other from distal ends of the blocking pieces to guide the arms to slide along the sides of the blocks away from each other. 
     
     
         8 . The rail device of  claim 1 , wherein the first and the second locking members are resilient pieces, the first locking member is mounted to an outer surface of the middle rail and comprises a first projection exposing out of an inner surface of the middle rail to abut against the first protrusion, the second locking member is mounted to an outer surface of the outer rail and comprises a second projection exposing out of an inner surface of the outer rail to abut against the second protrusion. 
     
     
         9 . The rail device of  claim 8 , wherein each of the first and second locking members forms a guiding surface facing the first end of the middle rail and a stopping surface facing the second end of the middle rail. 
     
     
         10 . The rail device of  claim 1 , wherein the first protrusion and the second protrusion have substantially a same shape, each form a stopping surface facing a first end of the inner rail and a guiding surface slantedly extending toward a second end of the inner rail from a top of the corresponding stopping surface. 
     
     
         11 . The rail device of  claim 10 , wherein the middle rail defines a first opening adjacent to the stopping surface of the second protrusion, the inner rail defines a second opening adjacent to the stopping surface of the first protrusion.