Archery bow with axial tensile springs and slope-based CAMS
View Patent ↗An archery bow includes a riser, a cam module rotatably mounted to a fixed pivot supported by the riser, and an energy storage system comprising at least one axial tensile spring operatively coupled to the cam module via a multi-roller shuttle assembly. The cam module includes a cam track with a variable slope profile that governs the draw force curve during rotation. The multi-roller shuttle assembly engages both the cam track and a guide track surface to constrain the shuttle to a defined path, thereby elongating the axial tensile spring as the bow is drawn. The cam module includes parallel string grooves for engaging a single bowstring without synchronization cables. The axial tensile spring may be folded around a turning element to form two tensile legs and housed within the riser. This configuration enables compact, lightweight bows with customizable draw characteristics and reduced lateral torque.
1 . An archery bow comprising:
a riser configured to support a bowstring;
a cam module rotatably mounted to a fixed pivot mounted to or supported by the riser, the cam module including:
a cam track defined by an internal or external surface of the cam module and having a slope that varies along its length to produce a desired draw force curve; and
at least one string groove on an outer periphery of the cam module configured to engage the bowstring;
a multi-roller shuttle constrained to move along a predetermined path by a guide track surface mounted to or formed in the riser as the cam module rotates, the multi-roller shuttle comprising:
at least one cam roller in rolling contact with the cam track;
at least one guide roller in rolling contact with the guide track surface; and
at least one spring attachment feature operatively connected to at least one axial tensile spring;
wherein rotation of the cam module in a draw direction causes the cam track to exert force on the multi-roller shuttle via the cam roller, and the shuttle is constrained by the guide track surface to follow a predetermined path, thereby elongating the at least one axial tensile spring to store energy.
2 . The archery bow of claim 1 , wherein the at least one axial tensile spring comprises two parallel springs, each folded about a turning element such that each spring presents two tensile legs extending in opposite directions.
3 . The archery bow of claim 1 , wherein the at least one axial tensile spring is folded about a turning element to present at least two tensile legs extending in opposite directions.
4 . The archery bow of claim 3 , wherein the turning element is shared with an idler wheel that engages the bowstring.
5 . The archery bow of claim 1 , further comprising an externally threaded spring terminator and nut configured to apply a preload force in the at least one axial tensile spring by tightening the nut against a fixed anchor plate.
6 . The archery bow of claim 1 , wherein the at least one axial tensile spring is disposed symmetrically about a vertical plane of the riser to balance lateral forces.
7 . The archery bow of claim 1 , wherein the riser is configured to enclose the at least one axial tensile spring within a hollow portion in a folded configuration to conserve space while protecting the spring from external elements.
8 . The archery bow of claim 1 , wherein the cam module includes two parallel string grooves configured to simultaneously engage two portions of the bowstring, the grooves being substantially identical or selectively varied to tune vertical nocking point behavior.
9 . The archery bow of claim 1 , wherein the cam track is shaped such that its slope varies along its length to produce a draw force curve that rises steeply during an initial portion of draw, remains substantially flat over a central portion, and includes a region of reduced slope near full draw to produce a let-off effect.
10 . The archery bow of claim 1 , wherein the cam track surface is fully enclosed within the cam module.
11 . The archery bow of claim 1 , wherein the multi-roller shuttle comprises a dual-track roller assembly, including a cam roller engaging the cam track and a pair of flanking guide rollers engaging the guide track surface mounted to or formed in the riser.
12 . The archery bow of claim 1 , further comprising at least one stop feature configured to limit the movement of the multi-roller shuttle along the cam track surface, thereby defining at least one of a brace height position and a full draw position.
13 . The archery bow of claim 1 , wherein the cam module includes replaceable string groove inserts configured for tuning and maintenance.
14 . The archery bow of claim 1 , wherein the cam module comprises a steel core defining the cam track, reinforced with composite plates and wound fiber layers.
15 . The archery bow of claim 11 , wherein the multi-roller shuttle includes thrust bearing elements configured to allow relative rotation between any two adjacent components selected from the cam roller, guide roller, and spring attachment feature.
16 . The archery bow of claim 1 , wherein the multi-roller shuttle includes a carbon fiber axle and shaft collars configured to maintain axial preload without damaging the axle.
17 . The archery bow of claim 1 , wherein the multi-roller shuttle includes at least one roller configured to engage the cam track from below the fixed pivot of the cam module.
18 . The archery bow of claim 1 , wherein the riser comprises at least two parallel tubes connected by cross-members.
19 . The archery bow of claim 1 , wherein the at least one axial tensile spring comprises a composite fiber material selected for high tensile strength and elongation prior to failure.
20 . The archery bow of claim 1 , wherein the riser includes a non-structural removable grip disposed between two parallel tubes.