Limb tip cam pulley for high energy archery bow

• US 5,040,520 A
• Filed: 02/25/1988
• Issued: 08/20/1991
• Est. Priority Date: 11/01/1982
• Status: Expired due to Term

• Current Assignee: Precision Shooting Equipment Incorporated
• Original Assignee: David J. Nurney
• Inventors: Nurney, David J.
• Primary Examiner(s): Cuomo, Peter M.
• Application Number:
  US07/160,543
• Time in Patent Office: 1,272 Days
• Field of Search: 124/23 R, 124/86, 124/ DIG. 1, 124/24 R, 124/88, 124/25.6, 124/900, 124/23.1, 124/24.1
• US Class Current: 124/25.6
• CPC Class Codes: F41B 5/10 Compound bows compound crossbows F41B5/123
• CPC Class Codes: F41B 5/105 Cams or pulleys for compound bows
• CPC Class Codes: Y10S 124/90 Limb tip rotatable element structure

Abstract

Composite bowstring and take-up string cam pulleys are carried by the tip portions of a compound archery bow limbs extending oppositely substantially symmetrically from a handle with the bowstring connecting the composite cam pulleys and take-up strings extending from each composite pulley to the opposite bow limb. Each composite cam pulley is composed of a generally elliptical bowstring pulley section having a major axis passing through its portions of substantially greatest length and a generally elliptical take-up string pulley section having a major axis passing through its portion of substantially greatest length, which pulley sections are integrated in parallel side by side relationship with planes containing their major axes substantially perpendicularly intersecting. The effective bowstring lever arm of the bowstring pulley section is small and substantially constant during increase of the draw force to at least 90 percent of the maximum draw force while the bowstring nocking point is displaced less than 40 percent of the total displacement during draw and the bowstring lever arm then increases substantially linearly while the draw force remains at a substantially constant maximum value over at least a third of the total bowstring nocking point displacement during draw of the bowstring. The ratio of bowstring draw arm to take-up string draw arm is substantially constant during the draw force increasing phase of the draw.

Claims

1. An archery compound bow composite pulley comprising a generally planar noncircular bowstring cam pulley section and a generally planar noncircular take-up string cam pulley section, substantially the entire peripheral profile of said noncircular take-up string pulley section being of a shape different from the shape of the peripheral profile of said noncircular bowstring cam pulley section, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section in parallel side-by-side relationship for forming a unit with substantially the entire peripheries of said pulley sections being out of registration.

2. An archery compound bow composite pulley comprising a generally planar noncircular bowstring cam pulley section having a major axis extending through substantially its greatest length and lying in a plane which is perpendicular to said generally planar bowstring cam pulley section, a generally planar noncircular take-up string cam pulley section having a major axis extending through substantially its greatest length and lying in a plane which is perpendicular to said generally planar take-up string cam pulley section, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section in parallel side-by-side relationship for forming a unit with the major axes perpendicular planes of said two pulley sections crossing substantially mutually perpendicularly.

3. In the composite pulley defined in claim 2, the integrating means combining the bowstring cam pulley section and the take-up string cam pulley section with the major axis of the take-up string cam pulley section substantially bisecting the major axis of the bowstring cam pulley section.

4. In the composite pulley defined in claim 3, the bowstring cam pulley section having a minor axis, the integrating means combining the bowstring cam pulley section and the take-up string cam pulley section with the minor axis of the bowstring cam pulley section substantially perpendicularly bisecting the major axis of the bowstring cam pulley section and with the major axis of the take-up string cam pulley section being disposed substantially coplanar with the minor axis of the bowstring cam pulley section.

5. In the composite pulley defined in claim 4, the integrating means combining the bowstring cam pulley section and the take-up string cam pulley section with one end of the bowstring cam pulley section minor axis substantially in registration with one end of the take-up string cam pulley section major axis.

6. In the composite pulley defined in claim 2, the take-up string cam pulley section having a minor axis substantially perpendicularly intersecting the major axis of the take-up string cam pulley section, the bowstring cam pulley section and the take-up string cam pulley section being disposed with said minor axis of the take-up string cam pulley section substantially parallel to and spaced from the major axis of the bowstring cam pulley section.

7. An archery compound bow composite pulley comprising a generally planar noncircular bowstring cam pulley section having a major axis extending through substantially its greatest length and lying in a plane which is perpendicular to said generally planar bowstring cam pulley section and a minor axis disposed substantially perpendicular to said major axis, a generally planar noncircular take-up string cam pulley section having a major axis extending through substantially its greatest length and lying in a plane which is perpendicular to said generally planar take-up string cam pulley section and a minor axis disposed substantially perpendicular to said take-up string cam pulley major axis, the minor axis of said take-up string cam pulley section being substantially shorter than the minor axis of said bowstring cam pulley section, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section in parallel side-by-side relationship for forming a unit.

8. In the composite pulley defined in claim 7, the length of the major axis of the take-up string cam pulley section being approximately 80 percent of the length of the major axis of the bowstring cam pulley section.

9. In the composite pulley defined in claim 7, the bowstring cam pulley section minor axis being of a length approximately two-thirds of the length of the major axis of the bowstring cam pulley section.

10. In the composite pulley defined in claim 7, the take-up string cam pulley section minor axis being of a length approximately two-thirds of the length of the major axis of the take-up string cam pulley section.

11. An archery compound bow composite pulley comprising a generally planar generally elliptical bowstring cam pulley section having a major axis extending through substantially its greatest length and lying in a plane which is perpendicular to said generally planar bowstring cam pulley section, a generally planar generally elliptical take-up string cam pulley section having a major axis extending through substantially its greatest length and lying in a plane which is perpendicular to said generally planar take-up string cam pulley section, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section in parallel side-by-side relationship for forming a unit with the major axes perpendicular planes of said two pulley sections crossing substantially mutually perpendicularly, and pivot means defining a turning axis extending transversely of said pulley sections at a location offset substantially equidistantly from both of the pulley section major axes.

12. An archery compound bow composite pulley comprising a generally planar noncircular bowstring cam pulley section, a generally planar noncircular take-up string cam pulley section, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section in parallel side-by-side relationship for forming a unit, said bowstring cam pulley section and said take-up string cam pulley section being constructed for effecting a bowstring lever arm means effective length which increases at least 150 percent, a take-up string lever arm means effective length which decreases at least 40 percent and a ratio of the effective length of the bowstring lever arm means to the effective length of the take-up string lever arm means which increases at least 300 percent while the draw force is at least 90 percent of the maximum draw force during displacement of the bowstring nocking point over a distance of at least one-third of the total displacement of the bowstring nocking point during draw.

13. Two pulley means for an archery compound bow including a handle member, two resilient limbs carried by and projecting oppositely substantially symmetrically from the handle member and mounting the two pulley means on their tip portions, respectively, for turning about an axis relative to the handle member, a bowstring extending between the two pulley means and a take-up string engaged with each pulley means, the improvement comprising each pulley means including a generally planar noncircular bowstring cam pulley section engaged by the bowstring and a generally planar noncircular take-up string cam pulley section engaged by a take-up string, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section of each pulley means in parallel side-by-side relationship for forming a unit, said bowstring cam pulley section and said take-up string cam pulley section of each pulley means being constructed for effecting a bowstring lever arm means effective length which increases at least 150 percent, a take-up string lever arm means effective length which decreases at least 40 percent and a ratio of the effective length of the bowstring lever arm means to the effective length of the take-up string lever arm means which increases at least 300 percent while the draw force is at least 90 percent of the maximum draw force during displacement of the bowstring nocking point during draw.

14. Two pulley means for an archery compound bow including a handle member, two resilient limbs carried by and projecting oppositely substantially symmetrically from the handle member and mounting the two pulley means, respectively, on their tip portions for turning about an axis relative to the handle member, a bowstring extending between the two pulley means and a take-up string engaged with each pulley means, the improvement comprising each pulley means including a generally planar noncircular bowstring cam pulley section engaged by the bowstring and a generally planar noncircular take-up string cam pulley section engaged by a take-up string, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section of each pulley means in parallel side-by-side relationship for forming a unit, said bowstring cam pulley section and said take-up string cam pulley section of each pulley means being constructed for effecting a bowstring lever arm means effective length which increases substantially linearly, a take-up string lever arm means the effective length of which decreases substantially and a ratio of the effective length of said bowstring lever arm means to the effective length of said take-up string lever arm means which increases substantially linearly as the bowstring nocking point is displaced during draw while the draw force is at least 90 percent of the maximum draw force.

15. Two pulley means for an archery compound bow including a handle member, two resilient limbs carried by and projecting oppositely substantially symmetrically from the handle member and mounting the two pulley means, respectively, on their tip portions for turning about an axis relative to the handle member, a bowstring extending between the two pulley means and a take-up string engaged with each pulley means, the improvement comprising each pulley means including a generally planar noncircular bowstring cam pulley section engaged by the bowstring and a generally planar noncircular take-up string cam pulley section engaged by a take-up string, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section of each pulley means in parallel side-by-side relationship for forming a unit, said bowstring cam pulley section and said take-up string cam pulley section of each pulley means being constructed for effecting a bowstring lever arm means effective length which increases substantially and a take-up string lever arm means effective length which decreases substantially as the nocking point is displaced during draw while the draw force is at least 90 percent of the maximum draw force.

16. An archery compound bow composite pulley comprising a generally planar generally elliptical bowstring cam pulley section having a major axis extending through substantially its greatest length and lying in a plane which is perpendicular to said generally planar bowstring cam pulley section, a generally planar generally elliptical take-up string cam pulley section having a major axis extending through substantially its greatest length and lying in a plane which is perpendicular to said generally planar take-up string cam pulley section, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section in parallel side-by-side relationship for forming a unit with said major axis perpendicular plane of said bowstring cam pulley section and said major axis perpendicular plane of said take-up string cam pulley section crossing substantially mutually perpendicularly.

17. In the composite pulley defined in claim 16, the take-up string cam pulley section being sufficiently smaller than the bowstring cam pulley section that the length of the major axis of the take-up string cam pulley section is approximately 80 percent of the length of the major axis of the bowstring cam pulley section.

18. In the composite pulley defined in claim 16, the integrating means combining the cam pulley sections of each pulley means with the major axis perpendicular plane of the take-up string cam pulley section substantially bisecting the major axis of the bowstring cam pulley section.

19. In the composite pulley defined in claim 16, the bowstring cam pulley section having a minor axis perpendicularly bisecting the major axis of the bowstring cam pulley section, and the integrating means combining the cam pulley sections with the major axis of the take-up string cam pulley section substantially coplanar with the minor axis of the bowstring cam pulley section and with one end of the bowstring cam pulley section minor axis being substantially in registration with one end of the take-up string cam pulley section major axis.

20. An archery compound bow composite pulley comprising a generally planar generally elliptical bowstring cam pulley section having a major axis extending through substantially its greatest length and lying in a plane which is perpendicular to said generally planar bowstring cam pulley section and a minor axis disposed substantially perpendicular to said major axis, a generally planar generally elliptical take-up string cam pulley section having a major axis extending through substantially its greatest length and lying in a plane which is perpendicular to said generally planar take-up string cam pulley section and a minor axis disposed substantially perpendicular to said take-up string cam pulley major axis, said take-up string cam pulley section being sufficiently smaller than said bowstring cam pulley section that said minor axis of said take-up string cam pulley section is substantially shorter than said minor axis of said bowstring cam pulley section, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section in parallel side-by-side relationship for forming a unit.

21. An archery compound bow composite pulley comprising a generally planar noncircular bowstring cam pulley section, a generally planar noncircular take-up string cam pulley section, substantially the entire peripheral profile of said noncircular take-up string pulley section being of a shape different from the shape of the peripheral profile of said noncircular bowstring cam pulley section, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section in parallel side-by-side relationship for forming a unit.

22. An archery compound bow composite pulley comprising a generally planar noncircular bowstring cam pulley section, a generally planar noncircular take-up string cam pulley section, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section in parallel side-by-side relationship for forming a unit, said bowstring cam pulley section having bowstring lever arm means and said take-up string cam pulley section having take-up string lever arm means for first increasing the force required to draw the bowstring and subsequently for decreasing the force required to draw the bowstring during draw, the effective length of the bowstring lever arm means acting while the draw force is increasing always being less than 20 percent of the length of the maximum bowstring lever arm means.

23. In the composite pulley defined in claim 22, the bowstring cam pulley section and the take-up string cam pulley section being constructed for effecting a ratio of the effective length of the bowstring lever arm means to the effective length of the take-up string lever arm means during the force-increasing phase of the draw which is always less than 10 percent of the maximum ratio of bowstring lever arm means to take-up string lever arm means during draw of the bow.

24. In the composite pulley means defined in claim 22, the bowstring cam pulley section and the take-up string cam pulley section being constructed for effecting a ratio of the effective length of the bowstring lever arm means to the effective length of the take-up string lever arm means during the force-increasing phase of the draw which is always less than 5 percent of the maximum ratio of bowstring lever arm means to take-up string lever arm means during draw of the bow.

25. In the composite pulley defined in claim 22, the bowstring cam pulley section and the take-up string cam pulley section being constructed for effecting a ratio of the effective length of the bowstring lever arm means to the effective length of the take-up string lever arm means which is within the range of 0.1 to 0.3 during the force-increasing phase of the draw.

26. In the composite pulley defined in claim 22, the bowstring cam pulley section and the take-up string cam pulley section being constructed for effecting a bowstring lever arm means effective length which does not change more than 20 percent and a take-up string lever arm means effective length which does not change more than 20 percent during the force-increasing phase of the draw to a value which is at least 80 percent of the maximum draw force.

27. In the composite pulley defined in claim 22, the bowstring cam pulley section and the take-up string cam pulley section being constructed for effecting a bowstring lever arm means effective length which does not change more than 10 percent and a take-up string lever arm means effective length which does not change more than 10 percent during the force-increasing phase of the draw to a value which is at least 80 percent of the maximum draw force.

28. In the composite pulley defined in claim 27, the bowstring cam pulley section and the take-up string cam pulley section being constructed for effecting a ratio of the effective length of the bowstring lever arm means to the effective length of the take-up string lever arm means which does not change more than 10 percent during increase in the draw force to a value which is at least 80 percent of the maximum draw force.

29. Two pulley means for an archery compound bow including a handle member, two resilient limbs carried by and projecting oppositely substantially symmetrically from the handle member and mounting the two pulley means, respectively, on their tip portions for turning about an axis relative to the handle member, a bowstring extending between the two pulley means and a take-up string engaged with each pulley means, the improvement comprising each pulley means including a generally planar noncircular bowstring cam pulley section engaged by the bowstring and a generally, planar noncircular take-up string cam pulley section engaged by a take-up string, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section of each pulley means in parallel side-by-side relationship for forming a unit, said bowstring cam pulley section and said take-up string cam pulley section of each pulley means being constructed for effecting a draw force of the bow which is increased to at least 90 percent of the maximum draw force of the bow during draw by displacement of the nocking point of the bowstring to an extent less than one-half of the total nocking point displacement during draw of the bow.

30. In the pulley means defined in claim 29, the bowstring cam pulley section and the take-up string cam pulley section of each pulley means being constructed for effecting a draw force of the bow which is increased to at least 90 percent of the maximum draw fore of the bow during draw by displacement of the nocking point of the bowstring to an extent less than 40 percent of the total nocking point displacement during draw of the bow.

31. Two pulley means for an archery compound bow including a handle member, two resilient limbs carried by and projecting oppositely substantially symmetrically from the handle member and mounting the two pulley means, respectively, on their tip portions for turning about an axis relative to the handle member, a bowstring extending between the two pulley means and a take-up string engaged with each pulley means, the improvement comprising each pulley means including a generally planar noncircular bowstring cam pulley section engaged by the bowstring and a generally planar noncircular take-up string cam pulley section engaged by a take-up string, and integrating means directly combining said bowstring cam pulley section and said take-up string cam pulley section of each pulley means in parallel side-by-side relationship for forming a unit, said bowstring cam pulley section and said take-up string cam pulley section of each pulley means being constructed for effecting a draw force of the bow which increases substantially linearly to a value of at least 80 percent of the maximum draw force.

32. In the pulley means defined in claim 31, the bowstring cam pulley section and the take-up string cam pulley section of each pulley means being constructed for effecting a draw force of the bow which increases substantially linearly to a value of at least 95 percent of the maximum draw force.

33. In the pulley means defined in claim 31, the bowstring cam pulley section and the take-up string cam pulley section of each pulley means being constructed for effecting a draw force of the bow which increases substantially linearly to a value of at least 90 percent of the maximum draw force while the nocking point of the bowstring is displaced less than 40 percent of the total nocking point displacement during draw of the bow.