Patent Publication Number: US-9422768-B2

Title: Multifunctional ladder

Description:
CROSS REFERENCE 
     The application claims priority on Korean Patent Application No. 20-2013-0006274, filed on Jul. 26, 2013, and the disclosure of which is incorporated by reference into this application as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     Generally, a stepladder or a work platform is used to perform a work at an elevated location above reach. 
     A stepladder is used for a relatively simple work within a limited work area and work platform, which is made to have extended length in transverse direction and allows moving along the platform during work, is used for relatively complicated work. 
     However, it is inconvenient and uneconomical to prepare and store the both of stepladder and work platform. 
     SUMMARY OF THE INVENTION 
     The present invention contrives to solve the disadvantages as described above. 
     The object of the invention is to provide a combined stepladder and work platform assembly which is easy to convert between its functions. From the folded position, the assembly can be opened to be the stepladder position or work platform position, according to the purpose of use. 
     To achieve the above-described object, the present invention provides a work platform assembly that comprises a top frame having two side rails and footplate that is fixed between the side rails, a back frame pivotally attached to back side of the top frame and having two side rails, each of which having an upper end and pivotally attached to the side rail of the top frame at the back end, a front frame pivotally attached to the front side of the top frame and having two side rails, each of which having an upper end and pivotally attached to the side rail of the top frame at the front end, a plurality of steps, each end of which are pivotally attached to the side rails of the front frame and a pair of link bars at the same intervals so that the steps are substantially horizontal, a pair of braces, each of which having an upper end pivotally attached to the side rail of the top frame and a lower end pivotally attached to the side rail of back frame so that it secures the back frame with the top frame at a certain angle and another pair of braces, each of which having an upper end pivotally attached to the side rail of the top frame and a lower end pivotally attached to the side rail of the front frame so that it secures the front frame with the top frame at a certain angle. 
     The assembly includes an elastic foot attached at the lower end of each of the side rails of the front frame and an L shape elastic foot attached at the lower end of each of the side rails of the back frame and another pair of elastic feet attached at the backside of upper portion of the side rails of the back frame. 
     The brace above mentioned further includes a shorter arm and a longer arm pivotally connected by a pin to allow pivoting of front frame and back frame. 
     A support bracket bar is pivotally attached to the inside of side rails of top frame, supporting the overhung end portion of the above-described step so that the steps are substantially horizontal in the step ladder position. 
     The advantages of the present invention are numerous in that: (1) only easy and simple operations are required to convert the assembly between folded, stepladder, and work platform positions; (2) the assembly is sturdy and stable when it is used in any positions according to the purpose of use; (3) the assembly is convenient to store and carry since the front frame and back frame are folded flat. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects and advantages of the present invention will become better understood with reference to the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of the assembly in the work platform position. 
         FIG. 2  is a front elevation view of the assembly in the work platform position. 
         FIG. 3  is a perspective view of the assembly in the stepladder position. 
         FIG. 4  is a front elevation view of the assembly in the stepladder position 
         FIG. 5  is a perspective view of the assembly in the folded position. 
         FIG. 6  is a front elevation view of the assembly in the folded position. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 and 2  show a combined stepladder and work platform assembly of the present invention in its work platform position. The assembly has a top frame ( 100 ) having a footplate ( 120 ), that is fixed between the side rails ( 110 ), covering only the rear part of the top frame ( 100 ), a back frame ( 200 ) pivotally attached to the backside of the top frame ( 100 ) by a hinge axis bar ( 800 ) and having two side rails ( 210 ), each of which having an upper end and pivotally attached to the side rail ( 110 ) of the top frame ( 100 ) at the back end, a front frame ( 300 ) pivotally attached to the front side of the top frame ( 100 ) by a hinge axis bar ( 800 ) and having two side rails ( 310 ), each of which having an upper end and pivotally attached to the side rail ( 110 ) of the top frame ( 100 ) at the front end, a plurality of steps ( 500 ), each end of which is pivotally attached to the side rails ( 310 ) of the front frame ( 300 ) and a pair of link bars ( 400 ) at the same intervals so that the steps ( 500 ) are substantially horizontal, a pair of braces ( 600 ), each of which having an upper end pivotally attached to the side rail ( 110 ) of the top frame ( 100 ) and a lower end pivotally attached to the side rail ( 210 ) of back frame ( 200 ) so that it secures the back frame ( 200 ) with the top frame ( 100 ) at a certain angle and another pair of braces ( 600 ), each of which having an upper end pivotally attached to the side rail ( 110 ) of the top frame ( 100 ) and a lower end pivotally attached to the side rail ( 310 ) of the front frame ( 300 ) so that it secures the front frame ( 300 ) with the top frame ( 100 ) at a certain angle. 
     The assembly includes an elastic foot ( 710 ) attached at the lower end of each of the side rails ( 310 ) of the front frame ( 300 ), an L shape elastic foot ( 720 ) attached at the lower end of each of the side rails ( 210 ) of the back frame ( 200 ) and another pair of elastic feet ( 730 ) attached at the backside of upper portion of the side rails ( 210 ) of the back frame ( 200 ). 
     The brace ( 600 ) above mentioned further includes a shorter arm ( 610 ) and a longer arm ( 630 ) pivotally connected by a pin ( 620 ) to allow pivoting of front frame ( 300 ) and back frame ( 200 ). 
     As described above, the assembly of the present invention in its work platform position includes a back frame ( 200 ), the upper end of which is pivotally attached to the back end of the top frame ( 100 ) by a hinge axis bar ( 800 ) and a front frame ( 300 ), the upper end of which is pivotally attached to the front end of the top frame ( 100 ) by a hinge axis bar ( 800 ). In its work platform position, the bottom surfaces of the L shape elastic feet ( 720 ) attached at the lower ends of side rails ( 210 ) of the back frame ( 200 ) make contact with floor and at the same time the elastic feet ( 710 ) attached at the lower ends of side rails ( 310 ) of the front frame ( 300 ) make contact with floor. However, the upper elastic feet ( 730 ) attached at the backside of upper portion of the side rails ( 210 ) of the back frame ( 200 ) remain attached at the upper portion of the side rails ( 210 ). 
     One ends of a plurality of steps ( 500 ) are pivotally attached to the side rails ( 310 ) of the front frame ( 300 ) at regular intervals, and the other ends of the steps ( 500 ) are pivotally attached to the link bars ( 400 ) at the same intervals. 
     The overhung end portion ( 510 ) of the uppermost step ( 500 ) is supported by the recessed end portion ( 130 ) of the foot plate ( 120 ) which blocks downward rotation of the steps ( 500 ) to maintain the steps ( 500 ) horizontal. As a result, the upper surface of the footplate ( 120 ) and the uppermost step ( 500 ) cover the top frame ( 100 ) jointly to form the top surface of the work platform. 
     The upper ends of two pair of braces ( 600 ) are pivotally attached to the side rails ( 110 ) of the top frame ( 100 ) and the lower ends of each pair of braces ( 600 ) are pivotally attached to the side rails ( 210 ,  310 ) of back frame ( 200 ) and front frame ( 300 ). 
     In case that the assembly of the present invention is desired to be used as work platform for the work such as painting or papering wall, from the folded position shown in  FIGS. 5 and 6 , the back frame ( 200 ) is rotated outward on the hinge axis bar ( 800 ) until the braces ( 600 ) are fully unfolded so that the back frame ( 200 ) makes a certain angle with the top frame ( 100 ). Then, the front frame ( 300 ) is rotated outward until the braces ( 600 ) are fully unfolded so that front frame ( 300 ) makes a certain angle with the top frame ( 100 ), and the link bars ( 400 ) are unfolded so that the steps ( 500 ) are substantially horizontal. 
     At this time, the overhung end portion ( 510 ) of the uppermost step ( 500 ) rests on the recessed end portion ( 130 ) of the foot plate ( 120 ) so that the steps ( 500 ) maintain substantially horizontal. 
       FIGS. 3 and 4  show a combined stepladder and work platform assembly of the present invention in its stepladder position. 
     In case that the assembly is used as stepladder for a simple work such as replacing a light bulb, this stepladder position can be made easily from the folded position shown in  FIGS. 5 and 6 , or the work platform position shown in  FIGS. 1 and 2 . 
     If the stepladder position is made from the work platform position, the back frame ( 200 ) is rotated inward on the hinge axis bar ( 800 ) until the back frame ( 200 ) is parallel to the floor so that the upper elastic feet ( 730 ) and L shape elastic feet ( 720 ) make contact with floor. 
     Accordingly, the top frame ( 100 ) which is attached to the back frame ( 200 ), is also rotated on the hinge axis bar ( 800 ) so that the top frame ( 100 ) makes the acute angle with the front frame ( 300 ). 
     By connecting the lower end of the front frame ( 300 ) to the lower end of the back frame ( 200 ) as shown in  FIG. 3 , the front frame ( 300 ), the top frame ( 100 ) and the back frame ( 200 ) make a triangular shape. 
     When the triangular shape is made, the steps ( 500 ) are lifted up until the overhung end portion ( 130 ) of the second step ( 500 ) from the top rests on the support bar ( 900 ) which is pivotally attached to the inside of side rails ( 110 ) of the top frame ( 100 ) so that the steps ( 500 ) are maintained substantially horizontal. 
     In this stepladder position, the back frame ( 200 ) maintains a certain distance from the floor by the same thickness of the L shape elastic feet ( 720 ) and the upper elastic feet ( 730 ). 
     Although the invention has been described in considerable detail, other versions are possible by converting the aforementioned construction. Therefore, the scope of the invention shall not be limited by the specification specified above and the appended claims.