Patent Publication Number: US-2010116260-A1

Title: Titlting limb system for bows and crossbows and equipment formed therewith

Description:
The present invention relates to a tilting limb system for bows and crossbows and equipment formed therewith. 
     At firing, the energy stored by a bow or crossbow is known to be released through the arrow via the bowstring and onto the central support for bidirectional connection with the limbs. 
     While energy is required to be released onto the arrow, it should not be released onto the central support, because it generates strong vibration, disturbing the shooter and damaging with time the attitude and mechanical balance of the archery device. 
     Manufacturers recommend to avoid firing without an arrow, which could cause the limbs to break, because energy would be entirely released onto the point of attachment of the limbs to the support thereby creating a mechanical stress peak which causes them to break. 
     At present, certain limbs installed on bows and crossbows, of either recurve or compound type, are allowed some adjustment but all are rigidly secured to the central support and remain integral therewith at firing. 
     This problem may be obviated by using heavier arrows but, in spite of the high energy they release, these arrows have a slow flight with excessive parabolas, which is exactly the opposite of what is currently desired: fast flight and straight trajectory. 
     The object of the present invention is to obviate the above drawbacks by providing a novel limb fixation system for an archery device, such as a bow or a crossbow, in which the limbs can tilt, with a unidirectional connection to the central support, to ensure self-absorption of the released energy, and protect the central support from such effect. 
     The present limb fixation system achieves the following advantages:
         no vibration for the shooter,   long-lasting reliable mechanical attitude of the archery device,   no limb failure in case of dry fire,   possibility of using arrows of any weight,   improved performance with limbs having the same geometry and power.       

     These objects and advantages are achieved by the coupling system for limbs of archery devices such as bows and crossbows according to this invention, which is characterized by the annexed claims. 
    
    
     
       This and other features will be more apparent from the following description of a few embodiments, which are shown by way of example and without limitation in the accompanying drawings, in which: 
         FIG. 1  is a general view of a crossbow having the limb coupling system of the invention, 
         FIG. 2  is an exploded perspective view of the limb elements and their support, 
         FIG. 3  is a sectional view proximate the support/limb coupling point, 
         FIG. 4  is a second sectional view proximate the support/limb coupling point, 
         FIG. 5  is a sectional view of three limb arrangements at firing, 
         FIG. 6  is a top view of the central area of the weapon as shown in  FIG. 1 . 
     
    
    
     Referring to  FIG. 1 , numeral  1  generally designates an archery device, namely a crossbow, having a limb disengagement system of the present invention. 
     Hence, the crossbow  1  has a pair of limbs  3  mounted, as described below, to a support  2 , which is in turn integral with the crossbow body; a bowstring  4  connects the ends of the limbs  3  and allows energy to be released onto the arrow. 
     Referring now to  FIGS. 2 ,  3  and  4 , these show in detail the limb/support coupling system adapted to improve the performance of the device  1  by self-absorption of the released energy and protection of the central support  2  from such effect. 
     As shown in the figures, the limbs  3 , and particularly the hinges  7  for attachment of their ends, are coupled to the front of the support  2  by appropriate means, such as screws  8 . 
     Therefore, each hinge  7  is integral with the end of its respective limb and is coupled to the support  2  by means of a pin  5 , which allows it to pivot about the axis A 1  of the pin for the limb to tilt relative to the pin  5 ; each pin  5  (and hence the axis A 1 ) is obviously perpendicular to the plane that passes through the limbs  3  and the bowstring  4 . 
     Accordingly, by such coupling arrangement, the limbs are allowed to pivot open through a few degrees forward, in the direction of arrow F 1 , as the bowstring  4  is released and then move back (in their return stroke) towards the support  2 , in the direction of arrow F 2 . 
     The above clearly shows that the support  2  acts as an abutment for the limbs  3 , to prevent them from excessively bending towards the center of the device  1  when the bowstring  4  is drawn: thus, the limbs  3  may flex at firing and be also retained by the support  2  as if they were interlocked therewith whereas, upon release (F 1 ) they may pivot forwards through a certain angle and accompany the arrow for a certain length of its trajectory. 
     One or more pad means  6  with the ability of absorbing part of the stored energy, are provided to prevent impacts against the support  2  during the return stroke. 
     Referring now to  FIGS. 5 and 6 , these show three different arrangements C 0 , C 1 , C 2  of the limbs  3  during the device loading step (C 1 ), the pushing and releasing step (C 2 ) and the rest or repositioning step (C 0 ) 
     As shown from  FIG. 5 , the limb system as described above, as compared with a bow of identical power and geometry, allows the stroke to be increased by an amount C, which provides increased thrust: the longer the stroke the faster the arrow. 
     The center-to-center A of the limbs  3  can decrease but not increase, because it is limited by the maximum length of the bowstring  4 .