Crossbow Cam Mounting on Stock Assembly
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Solution Overview
Problem
Conventional crossbows with cams mounted on limb tips suffer from inefficiencies in force distribution, leading to less effective bolt firing due to wider axle-to-axle distances and increased lateral force loss when the bowstring is drawn.
Innovation Solution
A crossbow design where cams are mounted to a fixed position on the stock assembly via axles, maintaining a constant axle-to-axle distance and positioning the bowstring forward of the cams, creating a narrower 'V' shape when drawn, which enhances the forward force vector and reduces lateral force loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If cams are mounted on limb tips, then the crossbow structure is simpler, but the axle-to-axle distance increases causing lateral force loss
Solution Approach 1:
The patent introduces a stock assembly as an intermediary structure between the cams and the limbs. The cams are mounted to the stock assembly at fixed points rather than directly to the limb tips, serving as a mediator that maintains optimal axle-to-axle distance while still allowing limb attachment. This resolves the contradiction by decoupling the cam mounting position from the limb tip position.
2Length of moving object
If axle-to-axle distance between cams is increased, then the structure allows greater draw length, but lateral force loss increases reducing bolt speed
Solution Approach 1:
The patent optimizes the axle-to-axle distance parameter by mounting cams at specific fixed points on the stock assembly rather than at extreme positions. This parameter optimization ensures that the distance is sufficient for adequate draw length but not so large as to cause excessive lateral force loss, thereby maintaining bolt speed while achieving sufficient draw length.
3Ease of manufacture
If bowstring is positioned rearward of cams, then the nock point placement is simpler, but the forward force vector is reduced
Solution Approach 1:
The patent creates an asymmetric arrangement where the bowstring nock point is positioned forward of the cam axle positions rather than rearward. This asymmetric placement optimizes the geometry of the bowstring-cam interaction to maximize the forward force vector component while still allowing for practical nock point implementation through the stock assembly structure.
Data Source
AI summary
Certain embodiments of the present disclosure describe a crossbow that includes a stock assembly. Flexible limbs extend laterally from the stock assembly. Cams are rigidly attached directly to the stock assembly or to extensions from the stock assembly, typically within an area defined by the limbs.