Crossbow with bowstring redirection

• US 8,578,918 B1
• Filed: 03/01/2013
• Issued: 11/12/2013
• Est. Priority Date: 03/01/2013
• Status: Expired due to Fees

• Current Assignee: John J. Islas
• Original Assignee: John J. Islas
• Inventors: Islas, John J.
• Primary Examiner(s): RICCI, JOHN A
• Application Number:
  US13/782,446
• Time in Patent Office: 256 Days
• Field of Search: 124/23.1, 124/25, 124/25.6
• US Class Current: 124/25
• CPC Class Codes: F41B 5/123 Compound crossbows

Abstract

A crossbow employs bowstring redirecting wheels, over which the bowstring travels, to keep the bowstring aligned with the main force vectors where the bowstring meets the tips of the crossbow power limbs or spring limbs. The bowstring is anchored to a fixed anchor points, which can be on the pylons on which the redirecting wheels are mounted, or may be at the tips of the spring limbs. In one embodiment the bowstring passes over a pulley wheel at the tip of the spring limb. This crossbow arrangement achieves superior acceleration, and can be constructed of smaller transverse dimension than conventional or compound crossbows.

Claims

1. A crossbow comprising a stock situated at a medial plane of the crossbow and having a proximal end and a distal end, a recurve bow mounted at a distal end of the stock, the bow including pair of spring limbs disposed one at each side of the stock;

wherein a bowstring is anchored at each end to an anchor point on each of the respective limbs and is adapted to accelerate a projectile when released from a full brace position;

at least one strut member extending to right and left sides of the stock and having mounted thereon left and right distal re-directing wheels positioned proximally of the bow and having also mounted thereon left and right proximal re-directing wheels positioned proximally of the aforementioned distal re-directing wheels and distally of the proximal end of the stock;

wherein the distal re-directing wheels are adapted to contact the bowstring between a partial draw and full release position of the crossbow, and the proximal re-directing wheels are adapted to contact the bowstring between a partial draw and full brace position, so that the bowstring achieves an increased transfer of kinetic energy to the projectile.

2. The crossbow of claim 1 wherein the re-directing wheels are positioned to maintain the tension vector of the bowstring to lie along or near bending moments of the respective limbs between the full brace and release positions.

3. The crossbow of claim 1 wherein said at least one strut member includes a left strut and a right strut each projecting back proximally from the bow on left and right sides of the stock, respectfully.

4. The crossbow of claim 3 wherein the respective proximal and distal re-directing wheels are supported one behind the other on said left strut and said right strut, respectively.

5. A crossbow comprising a stock situated at a medial plane of the crossbow and having a proximal end and a distal end, a bow mounted at a distal end of the stock, the bow including a pair of spring limbs disposed one at each side of the stock, wherein a bowstring is secured at each end thereof at a respective anchor point fixed relative to the stock, and wherein the bowstring passes over a pair of pulley wheels disposed respectively at the ends of the spring limbs, the bowstring being adapted to accelerate a projectile when released from a full draw position;

at least one strut member extending to left and right sides of the stock and having mounted thereon left and right distal re-directing wheels positioned proximally of the bow and having also mounted thereon left and right proximal re-directing wheels positioned proximally of the afore-mentioned distal re-directing wheels and distally of the proximal end of the stock;

wherein the distal re-directing wheels are adapted to contact the bowstring between a partial draw and full release position of the crossbow, and the proximal re-directing wheels are adapted to contact the bowstring between a partial draw and full-draw position, so that the bowstring achieves an increased transfer of kinetic energy to the projectile.

6. The crossbow of claim 5 wherein the re-directing wheels are positioned to maintain the tension vector of the bowstring to lie along or near bending moments of the respective spring limbs between the full draw and release positions.

7. The crossbow of claim 5 wherein said at least one strut member includes a left strut and a right strut each projecting back proximally from the bow on left and right sides of the stock, respectfully.

8. The crossbow of claim 7 wherein the respective proximal and distal re-directing wheels are supported one behind the other on said left strut and said right strut, respectively.

9. The crossbow of claim 8 wherein said anchor points at which the ends of the bowstring are secured are located on said left and right struts, respectively, distal of the distal re-directing wheels.

10. The crossbow of claim 8 wherein said bowstring and said pulley wheels achieve a mechanical advantage of substantially 2:

1.