Dual-Spring Measuring Tape Retraction Mechanism
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Solution Overview
Problem
Conventional measuring tape devices require a large spring torque to ensure complete retraction of windable materials, which can lead to increased friction and excessive retraction speed, and often occupy more space due to the need for a wider or longer spring to support this torque.
Innovation Solution
The design incorporates a dual-spring system with a first spring having a higher spring constant and a second spring with a lower spring constant, coupled in series, to provide a compact arrangement that stores turns on both springs, allowing for efficient retraction while maintaining a smaller diameter, thus reducing the required torque and space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single spring is used to provide sufficient retraction torque, then complete retraction of windable material is ensured, but the spring occupies more space (wider or longer) than desired
Solution Approach 1:
The patent divides a single spring system into multiple springs (first spring and second spring) connected in series. Each spring contributes to the total retraction torque, allowing the system to achieve the required torque with smaller individual springs that occupy less space collectively.
2Reliability
If a large spring torque is used to ensure complete retraction, then retraction is guaranteed, but friction increases and retraction speed becomes excessive
Solution Approach 1:
The patent modifies the torque characteristics by using multiple springs with different spring constants (k1 and k2). This creates a more controlled torque profile that is sufficient to overcome friction and ensure complete retraction, but not so large as to cause excessive retraction speed or damage to the windable material.
3Device complexity
If a single spring is used, then the structure is simple, but the diameter of the assembly increases
Solution Approach 1:
The patent configures the first and second springs in a nested or compact arrangement where they share space efficiently. The springs are positioned to work together in series, allowing the overall assembly diameter to be reduced compared to a single large spring configuration.
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 configuration facilitates faster initial retraction of the windable material with a slower subsequent retraction, reducing the force on the tape hook and optimizing the retraction process without increasing the assembly's diameter, thereby addressing the issues of space and torque requirements.
Implementation Method 1
a first spring having a first spring constant and a second spring having a second spring constant less than the first spring constant
Data Source
Figure 1
Figure 2~4
Figure 5~6
AI summary
A measuring tape rule device includes a tape rule housing, the housing having a connection portion. The device also includes an axle within the housing, the axle configured to rotate about an axis of rotation. The device also includes a reel within the housing, the reel configured to rotate about the axis of rotation and the axle. The device additionally includes an elongated tape having gradations thereon and wound on the reel. The device further includes a first spring coupled between the axle and the connection portion of the housing, and a second spring coupled between the axle and the reel. Rotation of the reel relative to the housing in a direction tending to tension the second spring transmits rotational movement to the axle through the tensioning of the second spring. Such rotational movement of the axle is applied to the first spring to tension the first spring.