Spooled Torsion Spring for HMD Head Strap Adjustment
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Solution Overview
Problem
Head-mounted displays (HMDs) face challenges in securely fitting various head sizes due to the direct pressure exerted by their weight, requiring an adjustable and comfortable strap system to ensure proper fit and wearability.
Innovation Solution
An apparatus featuring a flexible link connected to a head strap with a spool and a driving gear assembly that utilizes a torsion spring to apply a constant biasing torque, adjustable via a biasing torque mechanism, ensuring a secure fit regardless of head size through the winding and unwinding of the flexible link.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a strap system is used to secure the HMD to the user's head, then the HMD can be securely fitted to different head sizes, but the complexity of the strap system increases
Solution Approach 1:
The patent employs a dynamic strap system with a spool mechanism that can wind and unwind the flexible link, allowing continuous adjustment of strap length and tension. This dynamic mechanism enables the strap to adapt to various head sizes while maintaining a relatively simple overall structure through automated tensioning.
Solution Approach 2:
The torsion spring provides self-service by automatically maintaining constant tension on the strap as the spool winds or unwinds. This eliminates the need for complex manual adjustment mechanisms, as the spring self-regulates the force applied to keep the HMD securely fitted regardless of head size variations.
2Force
If a torsion spring is used to apply constant force, then the strap maintains consistent tension, but the device complexity increases due to additional components
Solution Approach 1:
The patent merges the torsion spring with the spool mechanism, where the spring is integrated into the existing structural components rather than being a separate additive element. The spring works in conjunction with the gear assembly and spool, combining multiple functions into a unified mechanism that maintains constant force without proportionally increasing overall device complexity.
Solution Approach 2:
The gear assembly serves multiple functions: it transmits the force from the torsion spring to the spool, provides mechanical advantage for winding the flexible link, and works with the spool to control the strap tension. This multi-functionality reduces the need for separate dedicated components for each function, thereby limiting the increase in device complexity.
3Ease of operation
If the flexible link is wound onto the spool to move the head strap, then the strap position is adjusted, but the mechanism complexity increases
Solution Approach 1:
The spool acts as an intermediary mechanism between the torsion spring and the flexible link. It converts the rotational motion and constant force from the spring into the winding action that adjusts the strap position. This intermediary simplifies the overall operation by providing a single point of interaction (the spool) that mediates between the force source and the strap, rather than requiring direct connection or complex transmission mechanisms.
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 apparatus provides a comfortable and secure fit for HMDs by applying a consistent force to the head, adjustable to accommodate different head sizes, enhancing wearability and usability across various applications.
Implementation Method 1
The apparatus includes a torsion spring connected between a driving gear assembly and a rigid body of the HMD. The driving gear assembly transmits a biasing torque of the torsion spring to the spool.
Data Source
AI summary
An apparatus for adjusting a head strap in a head-mounted display (HMD) includes a rigid body, a flexible link, a spool, a torsion spring, a driving gear assembly a rigid shaft, a rod, and a holder. The driving gear assembly includes a first gear and a second gear. The torsion spring applies a biasing torque onto the driving gear assembly. Based on the biasing torque from the torsion spring, the driving gear assembly rotates. The spool rotates relative to the rigid body to wind the flexible link onto the spool. A biasing torque adjustment mechanism may be provided to adjust the biasing torque applied by the torsion spring.