Electronic Watch Crown Assembly for Biometric Signal Conduction
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Solution Overview
Problem
Existing electronic devices face challenges in forming a conductive path through intricate crown components while maintaining electrical isolation to prevent interference with biometric sensing, particularly in wearable devices like smart watches.
Innovation Solution
A crown assembly for wearable devices includes a conductive path through a rotatable component and a friction guard, using conductive materials to couple user input to biometric sensing circuitry while isolating it from the device's housing, protected by a polymer-encapsulated conductor and friction guard to prevent grounding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive path is formed through the crown assembly to enable biometric sensing, then biometric signal conduction is improved, but electrical isolation from the housing becomes difficult to maintain
Solution Approach 1:
The crown assembly is divided into multiple components with distinct electrical properties: the crown shaft (conductive) for signal input, the optical encoder component (conductive) for rotation detection, and the friction guard (insulating polymer) for electrical isolation. This segmentation allows the conductive path to be established through specific components while the insulating friction guard prevents unwanted electrical connection to the housing, resolving the contradiction between signal conduction and electrical isolation.
Solution Approach 2:
The friction guard acts as an intermediary component between the conductive crown shaft/optical encoder assembly and the conductive housing. This polymer-friction guard provides mechanical support and friction control while simultaneously serving as an electrical insulator, allowing the conductive path to function properly without creating unwanted electrical connections to the housing, thus maintaining both biometric signal conduction and electrical isolation.
2Adaptability or versatility
If the crown assembly is made rotatable for input operations, then user input capability is improved, but friction and wear on internal components increase
Solution Approach 1:
The friction guard serves as a mediator between the rotatable crown assembly and the stationary switch component. It provides controlled friction to enable reliable rotational input detection while protecting the switch from excessive wear caused by direct contact with the rotating optical encoder component, thus maintaining both input capability and component durability.
Solution Approach 2:
The friction guard is implemented as a polymer-friction component that can deform elastically to accommodate rotational movement. This flexible polymer structure allows the crown assembly to rotate smoothly while distributing mechanical stress, reducing peak friction forces, and protecting internal components from wear, thereby extending the duration of operation.
3Reliability
If the optical encoder component is conductively coupled to the crown shaft, then biometric signal transmission is improved, but electrical interference with the housing increases
Solution Approach 1:
The electrical path is segmented into conductive portions (crown shaft, optical encoder component) for signal transmission and insulating portions (friction guard) for isolation. This segmentation allows the optical encoder component to be conductively coupled to the crown shaft for reliable biometric signal transmission while the friction guard interrupts the electrical path to the housing, preventing electrical interference.
4Volume of moving object
If the switch is positioned close to the crown assembly for compact design, then device size is reduced, but the switch is more susceptible to rotational friction damage
Solution Approach 1:
The friction guard is positioned between the rotatable optical encoder component and the stationary switch, serving as a protective intermediary. It absorbs the rotational friction forces generated during crown rotation, allowing the switch to be positioned close to the crown assembly for compact design while the friction guard shields the switch from direct rotational friction damage, maintaining both compactness and switch durability.
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 solution allows the crown to function as an input member for both rotational and translational inputs while effectively conducting biometric signals, ensuring robust and durable operation of biometric sensors.
Implementation Method 1
an optical encoder component attached to the actuation member and defining a group of optical features. The electronic watch may further include an optical detector configured to detect rotation of the crown assembly by detecting motion of the group of optical features
Implementation Method 2
an electrocardiograph sensor comprising a sensing component. The sensing component may be conductively coupled to the actuation member via a conductive path at least partially defined by the crown shaft
Implementation Method 3
a friction guard having a shear plate positioned between the switch and the optical encoder component. The crown assembly may be rotatable relative to the housing, the crown assembly may rotate against the friction guard when the crown assembly is rotated, and the friction guard may protect the switch from rotational friction from the crown assembly
Data Source
AI summary
An electronic watch may include a housing defining a side wall having a through-hole and a crown assembly including an actuation member. The actuation member may include a crown shaft extending through the through-hole and having an exterior portion defining an input surface and a crown ring coupled to the exterior portion of the crown shaft and electrically isolated from the crown shaft. The crown assembly may further include an optical encoder component attached to the actuation member and defining a group of optical features. The electronic watch may further include an optical detector configured to detect rotation of the crown assembly by detecting motion of the group of optical features and an electrocardiogramansor comprising a sensing component. The sensing component may be conductively coupled to the actuation member via a conductive path at least partially defined by the crown shaft.