Wiper Arm Sheet Metal Fastener Bolt Attachment
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Solution Overview
Problem
The existing wiper arm designs using sheet metal fasteners face issues with spring degradation over time, leading to reduced contact force and undesirable noise due to burrs and scores during operation.
Innovation Solution
A wiper arm design with internally bent tabs to shorten the bolt length, providing a secure and noise-free attachment using U-shaped or L-shaped recesses and a clamped bolt with a rough surface, and a hardened pin to prevent wear and twisting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a spring hanger made of sheet metal is used, then the wiper arm can be manufactured with sheet metal fasteners, but the spring digs into the sheet metal over time causing loss of contact force
Solution Approach 1:
A bolt is introduced as an intermediary element between the spring and the sheet metal fastener. The bolt absorbs the spring force and prevents direct contact between the spring and sheet metal, eliminating the digging effect while maintaining the sheet metal construction benefits.
Solution Approach 2:
The fastening system is segmented into separate functional components: the sheet metal fastener provides structural attachment, the bolt provides force transmission, and the spring provides tension. This segmentation allows each component to perform its function without interfering with others.
2Reliability
If a long bolt is used to attach the spring, then the spring can be securely attached, but the bolt deflects under spring force reducing bearing force
Solution Approach 1:
The bolt length parameter is optimized to be as short as possible while still achieving secure attachment. The tabs are bent toward the inside of the fastener to reduce the required bolt length, minimizing deflection under spring force and maximizing bearing force transmission.
3Ease of manufacture
If scores and burrs are present on the spring attachment surface, then the spring can be attached to the sheet metal, but undesirable noise develops during operation
Solution Approach 1:
The bolt serves as an intermediary that eliminates direct contact between the spring and the sheet metal surface with scores and burrs. This prevents the generation of noise during operation while maintaining secure spring attachment through the bolt's threaded engagement.
4Device complexity
If the bolt is not clamped, then the structure is simpler, but the bolt twists during operation causing squeaking noises
Solution Approach 1:
The tabs are pre-bent toward the inside of the fastener before bolt installation. This preliminary action creates a clamping effect that secures the bolt in place, preventing twisting and squeaking noises during operation without adding complex clamping mechanisms.
Data Source
Figure 1
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AI summary
The invention relates to a wiper arm of a window wiping device having an attachment part (20) which is manufactured from sheet metal. In the sheet metal attachment parts of the generic type, a spring hook fastening element which is likewise manufactured from sheet metal and into which, however, in the course of time a spring digs is frequently used. This results in a loss of the supporting force of the wiper arm. In order to prevent this in future, the attachment part (20) is provided according to the invention with two clips (21, 22) for receiving a bolt (23).