Bow Saw Frame Torque Limiting Tensioning Mechanism
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Solution Overview
Problem
Existing bow saw frames face the risk of blade tension overload, leading to potential damage or destruction of the mount, as they lack effective mechanisms for precise and safe tensioning of the saw blade.
Innovation Solution
Incorporation of a torque limiting device between the rotary control member and the screw-nut system, featuring asymmetrical toothed crowns with a biasing member, which disengages the control member from the nut system when a torque threshold is reached during tensioning to prevent overload, while remaining coupled during tension release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a screw-nut tensioning system is used to tighten the saw blade, then the blade tension can be increased to improve cutting performance, but the risk of blade tension overload increases which could lead to destruction of the mount
Solution Approach 1:
The patent changes the mechanical parameter of torque transmission by introducing a torque limiting device with asymmetrical teeth. The device allows rotation in the tightening direction while limiting maximum torque, and allows free rotation in the loosening direction. This parameter change enables controlled blade tension increase without exceeding the mount's structural limits, resolving the contradiction between improving blade tension and maintaining mount integrity.
Solution Approach 2:
The torque limiting device acts as an intermediary between the control member and the screw-nut system. It mediates the torque transmission by engaging asymmetrical teeth that permit tightening rotation but disengage when excessive torque is applied, preventing direct transmission of damaging forces to the mount while still allowing effective blade tensioning through controlled torque levels.
2Reliability
If a torque limiting device with asymmetrical teeth is introduced to prevent overload, then the reliability of the mount is improved, but the device complexity increases
Solution Approach 1:
The torque limiting device is merged with the control member to form an integrated sub-assembly. The asymmetrical toothed crowns are combined with the biasing member and control member into a single functional unit that is mounted on the threaded rod. This merging reduces the number of separate components and simplifies assembly while maintaining the torque limiting functionality, thus improving reliability without proportionally increasing device complexity.
3Measurement precision
If the torque limiting device uncouples the control member from the nut system when torque threshold is reached, then blade tension precision is improved, but the ease of operation decreases due to disengagement mechanism
Solution Approach 1:
The torque limiting device operates on a self-service basis through its asymmetrical tooth design. The biased engagement of the asymmetrical teeth automatically causes disengagement when excessive torque is applied in the tightening direction, without requiring external control or complex sensing mechanisms. This self-regulating feature provides precise tension control while maintaining ease of operation, as the user simply needs to rotate the control member without worrying about overload protection.
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
This solution allows for precise and safe tensioning of the saw blade, preventing damage to the frame by limiting excessive torque and ensuring reliable operation.
Implementation Method 1
a biasing member acting to mutually engage said toothed crowns
Implementation Method 2
a screw-nut system wherein the nut system is connected to the rear attachment member
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
The invention relates to a frame comprising a bow that is solidly connected to a rear handle (4), front and rear hook members, and a mechanism for tensioning a saw blade (2) when the blade is hooked to the front and rear hook members. The aforementioned mechanism comprises a rotary control member (34) coupled to a screw-and-nut system (52, 68), and a disengageable rotary device (32) positioned between the control member (34) and the nut-and-screw system (52, 68), said device limiting the torque transmitted from the control member (34) to the nut-and-screw system (52, 68). The invention is suitable for a bow saw.