Leaf Spring Cam Biasing for Balanced Articulated Seating
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Solution Overview
Problem
Conventional office chairs lack individual adjustability of the seat and backrest, leading to inadequate support and comfort for users of varying sizes and postures, with tilting mechanisms that do not provide a balanced ride throughout the range of motion.
Innovation Solution
A seating structure with an articulated seat and backrest, featuring a linkage assembly that allows the rear portion of the seat to pivot independently, an adjustable seat depth mechanism, and a biasing system with a leaf spring and cam surfaces to provide balanced torque and visual adjustment of the return force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the seat is formed as a rigid, fixed component, then the seat structure is simple and stable, but the user cannot be easily adjusted or customized to accommodate different sizes and postures
Solution Approach 1:
The seat is divided into a front portion and a rear portion that can articulate independently relative to each other. The backrest is segmented into upper and lower portions that can move independently. This segmentation allows each portion to be adjusted for different user needs without requiring complex mechanisms throughout the entire seat structure.
Solution Approach 2:
The seat transitions from a rigid, fixed structure to a dynamic structure where the front and rear portions can articulate relative to each other during tilting. This dynamic capability allows the seat to adapt to user posture changes while maintaining structural simplicity through the use of straightforward hinge connections.
2Ease of operation
If the seat depth is adjusted by moving the entire rigid seat fore-aft, then the seat depth is adjustable, but an unsightly gap forms at the rear of the seat and a pinch point is created
Solution Approach 1:
By dividing the seat into front and rear portions connected by an articulation hinge, the rear portion can remain stationary while the front portion moves forward or backward for depth adjustment. This eliminates the need to move the entire seat, preventing gap formation at the rear and avoiding pinch points that would occur with whole-seat movement.
3Reliability
If compression and/or tension springs, torsion springs and/or torsion bars, or leaf springs are used to bias the seat and back, then the seat and back are biased upwardly and rearward tilting is counterbalanced, but the mechanisms are complicated and require multiple, excessive rotations of a knob to obtain the desired setting
Solution Approach 1:
The spring mechanism is designed with an adjustable fulcrum position that changes the mechanical advantage and thus the biasing force. By simply moving the fulcrum to different positions along the lever arm, the return force can be adjusted without requiring complex multi-position knobs or excessive rotations, simplifying the control mechanism while maintaining reliable counterbalancing.
4Reliability
If the spring load is adjusted to match user weight, then a balanced ride can be achieved, but the chairs lack any indicia for the user to determine the setting of the return force before the user sits
Solution Approach 1:
Visual indicia such as colored markers, numbered scales, or position indicators are provided on the adjustment mechanism to show the fulcrum position and corresponding spring load settings. This allows users to see and select the appropriate setting before sitting down, ensuring a balanced ride without requiring trial and error or complex adjustments.
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 ensures comfortable support for users by reducing hip drop, allowing customizable fit, and providing a balanced ride and easy adjustment, eliminating the need for additional support members and complex spring mechanisms.
Implementation Method 1
Tilt chairs normally employ compression and/or tension springs, torsion springs and/or torsion bars, or leaf springs to bias the seat and back upwardly and to counterbalance the rearward tilting of the user.
Implementation Method 2
A biasing mechanism includes a leaf spring, a fulcrum, and a cam. The cam provides a visual indication of a setting of the return force of the spring.
Data Source
AI summary
A seating structure includes a leaf spring and a body support structure biased by the leaf spring. One of the leaf spring and the body support structure has a cam with a concave cam surface, while the other of the leaf spring and body support structure has a cam follower with a convex cam surface. The cam follower engages the cam.