Patent Publication Number: US-4733647-A

Title: Bow having limbs with forks that are fastened to a handle

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a bow having a holding grip arranged in its center and having a cord or bow string. 
     Such bows are used for sports purposes and require repeated actuation. This actuation requires a large amount of physical strength which cannot be reduced or avoided by simple reduction of the tension force since such a measure would adversely affect the path of flight of the arrow. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to modify a bow of the above-mentioned type by giving it such a configuration that the energy stored in the bow is increased or, if no more energy is wanted, the amount of force required to tension the cord is reduced. 
     This increase in energy storage is realized by the present invention in that one limb of the bow emanates to each side of the handle, with a cord being tensioned between one end of each limb and the other end of each limb being shaped into a fork having two line springs. The tines of the fork are separately fastened, each to a frontal face of the handle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 and 2 are side views of two bows of the present invention in their untensioned or undrawn state. 
     FIG. 3 is a side view illustrating the bow of FIG. 1 in its tensioned or drawn state. 
     FIG. 4 is a graph comparing force with respect to draw distance for the bow of FIG. 1 or 2 and for a conventional recurve bow of the same draw weight. 
     FIG. 5 is a graph comparing force with respect to pull-out distance when the cords of the bow of FIG. 1 and a conventional bow are tensioned. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows the bow of the present invention in the untensioned state. The central handle 1 arranged in the center of the bow is supplemented at both sides by means of identical bow limbs 2 and 3 to form the total bow. The bow string or cord 4 is tensioned between the two free ends of bow limbs 2 and 3. Bow limbs 2 and 3 are shaped into forks 5 and 6 whose tines (springs) 7, 8 and 9, 10, respectively, are each fastened (screwed, glued, etc.) to one of frontal faces 11 and 12, respectively of handle 1. Forks 5 and 6 have such a configuration that a free region remains with respect to handle 1 when the bow is in the untensioned state. 
     If cord 4 in the bow of FIG. 1 is tensioned, a state results as shown in FIG. 3. Tines (springs) 8 and 10 of the two forks 5 and 6 rest against surfaces 13 and 14 of handle 1 or against each other and thus are bent over until they are in approximate contact with the corresponding tines 7 and 9. This measure causes the bow to have a non-linear gain in potential energy as shown in FIG. 4 by curve 15 in the force (F) over draw (x in mm) diagram. The force draw curve 16 of the prior art recurved bow is shown for comparison, thus illustrating the energy gain. 
     FIG. 5 shows the force draw curves 15 and 16, but this time with the same energy storage as a related traditional recurve bow. It can be seen clearly that beginning with a certain limit force F G , the bow according to the present invention results in a reduction in the required force, without any loss of energy. 
     In the bow of FIG. 1 the outer frontal faces 11 are preferably either flat or slightly concave and the inner frontal faces 12 are preferably either flat or convex. The surfaces 13 and 14 are preferably concave and merge smoothly with the respective inner frontal face 12. Outer tines 7 and 9 are preferably broadened at the bases of forks 5 and 6, respectively (that is, where tine 7 joins tine 8 and where tine 9 joins tine 10), but tines 8 and 10 preferably have uniform cross-sections from the base of the respective fork 5 or 6 to the respective face 12. When the bow is in its untensioned state, the portions of tines 8 and 10 that are not in contact with surfaces 13 and 4, respectively, are considerably longer than surfaces 13 and 14, respectively, which are in turn approximately as long as the portions of tines 7 and 9 that are not in contact with the respective face 11. 
     In the embodiment shown in FIG. 2, a central handle 1&#39; arranged in the center of the bow is supplemented at both sides by means of identical bow limbs 2&#39; and 3&#39; to form the total bow. The bow string or cord 4&#39; is tensioned between the two free ends of bow limbs 2&#39; and 3&#39;. Bow limbs 2&#39; and 3&#39; are shaped into forks 5&#39; and 6&#39; whose tines (springs) 7&#39;, 8&#39; and 9&#39;, 10&#39;, respectively, are each fastened (screwed, glued, etc.) to frontal faces 12&#39; of handle 1&#39;. 
     In the case of the advanced bow of FIG. 2 the tines (springs) 7&#39;-10&#39; approach each other when the bow is drawn, and tines 8 and 10 do not rest against handle 1. The force-draw curve of this more optimized example (FIG. 2) is similar to that sketched in FIGS. 4, 5. 
     It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.