Compound bow draw position indicating device

A device is mounted to the sighting area of a compound bow for signaling when the bow drawstring has moved to a predetermined position. The device is hollow and serves to maintain the compound cables away from the line of travel of the bowstring. Electrical contacts are mounted within the hollow device and enable a signal when tripped by the movement of the cables.

BACKGROUND OF THE INVENTION 
This invention relates to archery and more particularly to a drawstring 
positioning indicator. 
In archery, it is desirable for the archer to have an illuminated sight. To 
this end, many arrangements have been designed whereby the archer turns on 
a light within the sight by manual manipulation of a switch. This 
arrangement suffers from the basic problem that battery life is limited 
since the light is on for relatively long periods of time. 
It is also a desirable feature to have an audible or visual indication when 
the drawstring has been extended to the proper position. In this regard 
some systems are available whereby a mechanical click is generated when 
the drawstring reaches a certain extension. This arrangement suffers from 
the problem that it must be reset after each click and thus if the string 
is over extended the archer must release the drawstring and start over. 
Thus it is desirable to provide an arrangement which solves these problems 
and which is automatically operated. 
SUMMARY OF THE INVENTION 
I have designed a drawstring position monitoring system in a manner to 
achieve both of the above-discussed problems. My system has the advantage 
that it is easy to adapt to existing compound curve bows and is light in 
weight and fully adjustable. On compound bows the cable wires which reduce 
the draw tension travel away from the bow as the archer pulls back on the 
drawstring. Typically, these cables are held away from the arrow by a 
cable guard. I have modified the cable guard in a manner such that as the 
cables retreat from their quiescent position they trip a switch mounted in 
the cable guide. This switch is adjustable so that it is at a position 
which coincides with the desired bowstring draw. Operation of the switch 
turns on an LED mounted inside the sight. Thus, when the light within the 
sight is illuminated the archer knows that the string is at the proper 
position. Once this position has been attained the archer may track the 
target and if the tension changes, either by pulling the string further or 
by releasing the string slightly, the light will go out. The archer may 
then reposition the drawstring without completely releasing pressure. 
Since the light is only on for a small period of time battery life is 
conserved.

DETAILED DESCRIPTION 
In FIG. 1 there is shown a typical compound bow 10 having handle or riser 
23, upper limb 12, upper nock 20, lower limb 22 and lower nock 21. 
Connected to bow near upper nock 20 and lower nock 21 are cams 19 having 
compound cables 18 connected therebetween. Each cable has one of its ends 
fastened to a cam and stretched around the other cam, the free end then 
being connected to drawstring 33. The purpose of the cams and the cables 
is to control the forces on the arrow (not shown) in a manner so that as 
the drawstring is pulled away from the handle the cams rotate causing the 
tension on the drawstring to be other than linear along its draw length. 
For example, in a typical compound bow when the arrow is drawn to the 
proper distance, as measured from the riser, the bowstring might have a 
force on it of 25 pounds. As the arrow is released and the upper and lower 
limbs straighten, the cams rotate to cause the force of the arrow to 
suddenly increase to, say 50 pounds. 
As the arrow is drawn away from riser 23 the upper and lower limbs flex in 
the direction of the pull on the drawstring. This motion of the bending 
bow causes compound cables 18 to travel backward (to the left in FIG. 2) 
along with the draw of bowstring 33. FIG. 2 shows the drawstring pulled 
back to full draw position and cables 18 moved to the left following the 
bending of bow 10. If nothing more were to be done, the arrow feathers 
would become entangled on the cables. This problem is prevented by 
positioning a rod, such as rod 13, between the bowstring 33 and cables 18. 
Rod 13 is held in position by bracket 11 affixed to handle 23. 
Mounted to handle 23 is bracket 15 to which is attached sight 16. Inside 
sight 16, shown in more detail in FIG. 3, is a light source, such as LED 
34. 
Mounted along rod 13 is a switch 14 positioned at a place such that when 
the bowstring 33 is draw back to the proper draw length, cables 18 will 
come into contact with switch 14 causing the switch to close. The closed 
switch will then turn on LED 34 within sight 16. This situation is shown 
in FIG. 2. 
If bowstring 33 were to be drawn back further cables 18 would pass beyond 
switch 14 causing the switch to again open, turning the LED off. In this 
manner an archer, sighting along line 41 through sight 16 can immediately 
determine when the drawstring has reached the proper draw position by the 
illumination of the LED. If the archer inadvertently draws the arrow back 
further the LED would extinguish and the archer, without taking his eye 
from the sight can reposition the drawstring to the proper predetermined 
position. In this manner the archer will achieve a constant arrow velocity 
with each release of the drawstring. 
As shown in FIG. 3, rod 13 is adjustable by clamp 21 so that switch 14 can 
be positioned any length from the handle. Also mounted to bracket 11 is 
box 43 which contains a battery 40 (FIG. 4), jack switches 35 and 36 and 
variable resistor 37. The resistor is used to control the brilliance of 
the of the LED while the jacks are used to insure that the LED is not 
accidentally turned on. Typically, the sight is removed from the bow 
either for storing or to change sights for different situations and the 
plug allows for such a situation. Thus, this device may be used 
interchangeably with any number of different sights. 
As shown in FIG. 4, when switch 14 is closed current from battery 40 flows 
through resistor 37 to light LED 34. 
In FIG. 5 a cutout view of rod 13 is shown inside which switch 14 is 
fitted. Switch 14 consists of two contacts held apart by insulator 50. 
When cable 18 rides along rod 13 it contacts protrusion 54 of contact 52 
forcing that contact downward against contact 51 thereby closing the 
circuit. 
Of course, the leaf switch may be replaced with any type of switch operable 
by the cable. Also, more than one switch may be mounted to rod 13 so that 
the archer may have more than one indication of drawstring travel. One 
switch could operate the light while the other could sound an electronic 
sounder. There may be more than one LED mounted within the sight or one 
LED can have different colors as an indication of the draw travel. 
It can be seen from the foregoing discussion that the LED is only on for 
the instant of time the archer requires the light giving an indication of 
drawstring travel thereby conserving the battery. Of course, while not 
shown, an audible sounding arrangement may be attached to the circuit to 
give an indication of drawstring length.