High Let-Off Crossbow

• US 20150233664A1
• Filed: 02/06/2015
• Published: 08/20/2015
• Est. Priority Date: 02/06/2014
• Status: Active Grant

• Current Assignee: MCP IP, LLC
• Original Assignee: MCP IP, LLC
• Inventors: McPherson, Mathew A.
• Granted Patent: US 9,671,189 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F41B 5/123 Compound crossbows

Abstract

In at least one embodiment, a crossbow comprises a stock, a first limb, a first rotatable member, a second limb and a second rotatable member. A bowstring, a first power cable and a second power cable each extend between the first rotatable member and the second rotatable member. The first rotatable member and the second rotatable member are constructed and arranged to provide a left-off during draw of said bowstring in an amount of approximately 70%, 80%, 90% or 95% or more. The drawstring let-off reducing load on a latch assembly and/or a trigger assembly.

Claims

1. A crossbow comprising:

a stock, a first limb, a first rotatable member comprising a cam, a second limb and a second rotatable member;

a bowstring extending between the first rotatable member and the second rotatable member; and

a power cable extending from said cam;

wherein the first rotatable member establishes a draw force left-off for the bowstring of at least 70% during draw of the bowstring from a brace position to a drawn position.

2. The crossbow according to claim 1, said first limb and said second limb each having a length dimension of approximately 12 inches.

3. The crossbow according to claim 1, said first rotatable member supported upon a first axle and said second rotatable member supported upon a second axle.

4. The crossbow according to claim 3, wherein an axle-to-axle separation distance between said first axle and said second axle in said brace position is less than 18 inches.

5. The crossbow according to claim 1, said bowstring applying a first rotational force to said first rotatable member having a bowstring moment arm, said power cable applying a second rotational force to said first rotatable member having a power cable moment arm, wherein said power cable moment arm and said bowstring moment arm change as the crossbow is drawn.

6. The crossbow according to claim 5, wherein a length of said bowstring moment arm in a fully drawn position is at 3 times the minimum length of said bowstring moment arm during draw.

7. The crossbow according to claim 6, wherein a length of said bowstring moment arm in a fully drawn position is at 4 times the minimum length of said bowstring moment arm during draw.

8. The crossbow according to claim 5, wherein a maximum length of said power cable moment arm during draw is equal to or greater than 4 times the length of said power cable moment arm in the fully drawn condition.

9. The crossbow according to claim 6, wherein a maximum length of said power cable moment arm during draw is equal to or greater than 4 times the length of said power cable

10. The crossbow according to claim 1, said first rotatable member comprising a bowstring track, said cam comprising a cable take-up track.

11. The crossbow according to claim 10, wherein said cable take-up track is substantially circular in shape and offset from a rotation axis of said first rotatable member.

12. The crossbow according to claim 11, wherein said bowstring track is substantially elliptical in shape.

13. The crossbow according to claim 5, wherein a ratio of said bowstring moment arm/said power cable moment arm at full draw is equal to or greater than 8.

14. A crossbow comprising:

a stock;

a first limb supporting a first rotatable member, said first rotatable member comprising a bowstring feed-out track, a power cable take-up track and a cable anchor feed-out track;

a second limb supporting a second rotatable member, said second rotatable member comprising a bowstring feed-out track, a power cable take-up track and a cable anchor feed-out track;

a bowstring extending between the first rotatable member and the second rotatable member in communication with said respective bowstring feed-out tracks; and

a first power cable having a first end in communication with said power cable take-up track of said first rotatable member and a second end in communication with said cable anchor feed-out track of said second rotatable member;

a second power cable having a first end in communication with said power cable take-up track of said second rotatable member and a second end in communication with said cable anchor feed-out track of said first rotatable member;

wherein said first power cable applies a rotational force to said second rotatable member at said cable anchor feed-out track, said rotational force having a cable anchor moment arm that changes during draw, said cable anchor moment arm having a maximum value at full draw.

15. The crossbow of claim 14, wherein said bowstring exhibits a draw force let-off of at least 70%.

16. The crossbow of claim 14, wherein said bowstring exhibits a draw force let-off of at least 80%.

17. The crossbow of claim 14, said bowstring applying a bowstring rotational force to said second rotatable member having a bowstring moment arm, said second power cable applying a second power cable rotational force to said second rotatable member having a power cable moment arm, wherein a length of said bowstring moment arm in a fully drawn position is at 3 times a minimum length of said bowstring moment arm during draw.

18. The crossbow of claim 17, wherein a maximum length of said power cable moment arm during draw is equal to or greater than 4 times the length of said power cable moment arm in the fully drawn condition.