Crossbow Plastic Body Metal Frame Screw Fastening
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Solution Overview
Problem
Conventional crossbows face issues with weight and cost due to material choices, as metal components are heavy and expensive, while plastic components are prone to cracking and deformation, leading to accuracy and noise problems.
Innovation Solution
A crossbow device design featuring a plastic body with a metal bow frame and screw-fastened bow string set, which secures the bow string firmly and prevents deformation, maintaining accuracy and reducing noise through a three-point fastening structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the bow rod is made by plastic materials to reduce weight, then the weight of the crossbow is reduced, but the bolt cannot be made by plastic materials because it needs to cooperate with the metal screw, leading to cracking and deformation issues
Solution Approach 1:
The patent employs composite materials by combining plastic for the bow rod (to reduce weight) with metal screws and metal bolts (for strength). The plastic bow rod is designed with integrated screw holes that allow metal screws to be embedded directly into the plastic structure, creating a composite construction that leverages the lightweight property of plastic while incorporating metal components where high strength is required for the bolt connection.
2Ease of manufacture
If the bolt is fastened to the plastic bow rod, then the connection is achieved, but the bow rod cracks easily due to the mismatch between plastic and metal properties
Solution Approach 1:
The patent applies preliminary action by pre-forming screw holes directly into the plastic bow rod structure before assembly. This allows the metal screws to be embedded into the plastic in a controlled manner during manufacturing, creating pre-prepared attachment points that distribute stress more evenly and prevent cracking during subsequent assembly and use.
Solution Approach 2:
The metal screw acts as an intermediary element between the plastic bow rod and the metal bolt. The screw is embedded into the plastic structure and provides a strong mechanical connection point that bridges the material mismatch, allowing the metal bolt to be securely fastened to the plastic bow rod without causing cracks.
3Ease of manufacture
If the slot is made by inert molding to reduce cost, then the manufacturing cost is reduced, but the insert part is easy to be damaged and the slot deforms under long-term use
Solution Approach 1:
The patent uses composite materials in the slot construction by combining plastic with metal reinforcement elements. The slot is designed with metal inserts or reinforcement structures that are integrated into the plastic body, providing the necessary structural integrity to prevent deformation and damage under long-term use while maintaining cost-effectiveness through the use of plastic for the majority of the structure.
4Reliability
If the bow rod is made by metal materials to prevent cracking, then the strength and durability are improved, but the weight increases and the cost becomes very high
Solution Approach 1:
The patent applies composite materials by using plastic for the main bow rod structure (to reduce weight) and incorporating metal components only where high strength is required, such as the bolt and screws. This selective use of metal and plastic creates a composite structure that achieves the necessary strength and durability while minimizing weight and cost compared to a fully metal construction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The crossbow device achieves stable and accurate shooting with reduced noise and lower costs by using a plastic body with a metal bow frame and screw-fastened bow string set, preventing deformation and cracking, and simplifying assembly and disassembly.
Implementation Method 1
a plurality of screw members, each is used for fasten the bow string set to the stock
Implementation Method 2
the projectile (arrow) is shot by the elastic force
Data Source
AI summary
A crossbow device at least comprises a stock with a body portion, a track, and a aiming position member. A lower bow portion is arranged at the front of the body portion which includes a connection portion and a first screw hole is arranged thereinside. A bow frame is fastened in the track and assembled with the aiming position member. A second screw hole is formed at the front of each rod. A bow string set is assembled with the bow frame. Tow positioning blocks are protruded in the limit groove and a third screw hole is arranged at each positioning block and corresponding to the second screw hole. A fourth screw hole is arranged at a hook portion and corresponding to the first screw hole. The screw members are screwed in the third screw hole, the second screw hole, and the fourth screw hole of the hook portion.