Patent Publication Number: US-7722007-B2

Title: Flip chart easel with improved pivotal strut mechanism

Description:
This patent application relates to a flip chart easel, and in particular to a foldable easel strut assembly providing pivotal movement between a flip chart support structure and a pivotal rear leg. 
     Flip chart easels for use as an aid in making oral or visual presentations usually comprise a support board for holding large display charts, for example, where the board is supported on three or four legs. Two front legs usually extend downward from the support for the display chart, and in some embodiments, the front legs are pivotally attached to the support to allow the front legs to be folded against the support for storage. 
     In some flip chart easel configurations, a rear leg is pivotally attached to a rear portion of the support board, usually at the top. The rear leg is adapted to pivot rearwardly outward from its pivot point on the support board to form a tripod structure in combination with the front legs to maintain the easel in its upright and operative position. For storage purposes, the rear leg pivots to a position against the support board, and in certain embodiments the rear leg comprises two pivotally connected leg portions that also allow the rear leg to be folded on itself for storage purposes. 
     In certain of the tripod embodiments described above, a pivotal strut system extends between the rear of the support board of the easel and the rear leg. The strut system limits the outward movement of the rear leg, and maintains the rear leg in its necessary outward position to form the tripod configuration with the two front legs. It is important that the strut system provide ease of movement of the rear leg from a folded storage position to an extended position forming the tripod structure. It is also important that the strut system automatically limit outward movement of the rear leg when the tripod position is reached. Further, it is important that the strut system be lightweight and inexpensive to manufacture and easy to assemble and operate. 
     SUMMARY OF THE INVENTION 
     The present invention comprises a strut assembly for the legs of a foldable tripod strut support system for a flip chart easel, or other easels. The strut assembly includes a pair of forward struts pivotally attached to a support board of the easel at one end, and pivotally attached at the other end to one end of a pair of rear struts. The opposite ends of the rear struts are pivotally attached to the rear leg of the assembly. The top end of the rear leg is pivotally attached to the easel support board. 
     A portion of the rear struts extend beyond the pivotal connection between the respective front and rear struts. Each of these extensions include a stop flange that extends laterally over an upper edge of the respective forward strut just beyond the pivotal connection. When the rear leg is pivotally moved to its extended or operative position, the forward struts and rear struts move from a folded or storage position to an approximate straight line position when the rear leg is fully extended. In this approximate straight line position, the stop flange on each rear strut engages an upper surface of a respective forward strut, thus preventing further pivotal movement of the strut assembly and maintaining the rear leg in its proper outward position. 
     For added lateral support, a cross beam extends between the two pivotal junctions connecting each front strut to a respective rear strut. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain examples of the present invention are illustrated by the accompanying figures. It should be understood that the figures are not necessarily to scale and that details that are not necessary for an understanding of the invention, or that render other details difficult to perceive, may be omitted. It should be understood, of course, that the invention is not necessarily limited to the particular examples illustrated herein. 
         FIG. 1  is a perspective side elevation view of the pivotal strut assembly for a flip chart easel of the present invention, shown in the extended position; 
         FIG. 2  is a top plan-view of the pivotal strut assembly of  FIG. 1 ; and 
         FIG. 3  is a bottom plan view of the pivotal strut assembly of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
     Referring to  FIG. 1 , U-shaped brackets  10 ,  12  are attached to the rear of easel display or support board  14 . Forward struts  16 ,  18  of strut assembly  15  are pivotally connected to the outer side walls of brackets  10  and  12  at a first end of each forward strut, as shown at pivot points  17  and  19 . Forward legs  21 ,  23  are also pivotally connected to respective brackets  10 ,  12  at pivot points  17 ,  19  respectively, and are adapted to extend downward from between the side walls forming brackets  10 ,  12  when in the supporting or extended position. For storage, forward legs  21 ,  23  are pivoted around pivot points  17 ,  19  to an upward position extending between the sidewalls of the respective channels. 
     Cross beam  20  is pivotally connected to an opposite end of each forward strut  16 ,  18 . Flanges  22 ,  24  are disposed on and extend ninety degrees from either end of cross beam  20 . Rear struts  26 ,  28  are pivotally attached at pivot points  40 ,  42  to forward struts  16 ,  18 , respectively, and to cross beam  20 . The opposite ends of rear struts  26 ,  28  are pivotally attached to a U-shaped bracket  34 . Bracket  34  is pivotally attached to rear leg  36  at pivot point  37 , wherein bracket  34  and rear leg  36  form a rear leg assembly. Rear leg  36  is also pivotally attached at  35  ( FIG. 3 ) to the top of the flip chart easel support board  14 . 
     As seen in  FIGS. 1 ,  2  and  3 , portions of rear struts  26 ,  28  extend beyond pivot points  40 ,  42 . Stop flanges  30 ,  32  are mounted at right angles to the extensions of rear struts  26 ,  28 . Stop flanges  30 ,  32  engage the side surfaces of front struts  16 ,  18  when the easel is fully open, and the stop flanges prevent further over center movement of strut assembly  15  with the legs  21 ,  23  and  36  in the position shown in  FIGS. 1-3 , when the front and rear struts are in a substantially straight line configuration. In this configuration, rear leg  36  is in its full outward position, and is held in that position by rear struts  26 ,  28  and forward struts  16 ,  18 . 
     Upon use of the easel  14 , rear leg  36  is manually pivoted outward from the top of easel  14 . Struts  16 ,  18 ,  26  and  28  pivot until they are in a substantially straight line parallel to the floor, and stop flanges  30 ,  32  engage an edge portion of respective front struts  16 ,  18 . Further pivotal movement of all of the struts relative to cross beam  20  is thus prevented, and rear leg  36  is held in its outermost pivotal position. 
     To fold easel  14  into its storage position, the first step is to manually apply an upward force to cross beam  20 , causing struts  16 ,  18 ,  26  and  28  to pivot at points  40 ,  42 , whereby stop flanges  30 ,  32  become disengaged with their respective edge portions of forward struts  16 ,  18 . Bracket  34  pivots at point  35  toward easel  14  as cross beam  20  is moved upward. At the same time, rear struts  26 ,  28  move towards a parallel relationship with forward struts  16 ,  18 . Also, leg  36  pivots towards a position in the plane of the rear of support board  14  as the strut pairs are moved together. The upward force is continually applied to cross beam  20  until bracket  34  is lodged against easel  14  in its storage position, and forward struts  16  and  18  are substantially parallel to rear struts  26 ,  28 . 
     The length of struts  16 ,  18  is substantially equal to the length of struts  26  and  28 , insuring that when bracket  34  is in its maximum folded position against support board  14 , bracket  34  is closely adjacent to support board  14  and struts  16 ,  18 ,  26  and  28  are in their maximum folded position. Also, the ends of the struts  16 ,  18 ,  26  and  28  are angled to meet in parallel planes with cross beam  20  at pivot points  40 ,  42 , to enable pivoting of the struts and cross beam with minimum friction. 
     After rear bracket  34  is in position against support board  14 , leg  36  is pivoted one hundred eighty degrees around pivot point  37 , until rear leg  36  is lodged in the channel formed by the side walls of U-shaped bracket  34 . In the illustrated embodiment, the lower extent of bracket  34  is approximately at the lower edge  44  of support board  14  when bracket  34  is positioned against support board  14  in the storage position. 
     The next step is to pivot front leg  21  about pivot point  17  over a one hundred eighty degree arc until front leg  21  lies adjacent support board  14 . In similar fashion, front leg  23  is pivoted about pivot point  19  through a one hundred eighty degree arc until front leg  23  is also positioned adjacent support board  14 . With rear leg  36  and both front legs  21 ,  23  positioned adjacent support board  14 , a snap-button strap, or other suitable tying device, may be extended around legs  21 ,  23  and  36 , and around support board  14  to releasably hold the legs in their storage position. 
     The present invention has been described as an embodiment for providing a pivotal, limited movement easy to operate strut assembly for maintaining the rear leg of an easel in a tripod configuration in combination with the front legs of the easel. In addition the present invention provides a strut assembly and pivotal leg combination that allows the front and rear legs of the easel to be individually folded into a storage position when the strut assembly pivots the bracket holding the rear leg to a storage position. It is to be understood that the disclosed strut assembly invention can also be used in support structures other than easels. It is intended that the scope of this invention not be limited by the specification, but be defined by the claims set forth below.