Mechanism for controlling the force for tilting a backrest of a chair
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Solution Overview
Problem
Existing mechanisms for controlling the tilt of office chair backrests often compromise between ergonomics, comfort, and ease of use, requiring substantial effort and being structurally complex and costly, while also being unsuitable for various user types.
Innovation Solution
A snap-type command mechanism for the elastic element, featuring a movable stop block and position adjusting means, allows for easy translation of the stop block along a normal direction, enabling adjustable axial positioning of the elastic element without excessive effort, using a box structure with a command rod and abutment element to control the tilt force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If rotation knob or rack-and-pinion systems are used to adjust spring axial load, then the mechanism can provide ergonomic tilt control, but the device complexity increases and manufacturing cost rises
Solution Approach 1:
The patent extracts the essential function of load adjustment from complex rotational mechanisms and implements it through a simple linear translation of a stop block. The stop block directly limits the axial displacement of the elastic element, eliminating the need for rotation knobs, rack-and-pinion systems, and other complex intermediate mechanisms while maintaining ergonomic adjustability.
Solution Approach 2:
Instead of using a rotational motion (knob) to achieve axial displacement adjustment, the patent inverts the approach by using direct linear translation of the stop block along the axial direction. This inversion simplifies the mechanism by eliminating the conversion from rotational to linear motion, reducing structural complexity while preserving the adjustment function.
2Force
If rotation knob is used to transform rotation force to axial thrusting force, then the mechanism can control tilt force, but substantial and prolonged physical effort is required
Solution Approach 1:
The patent removes the force transformation mechanism (rotation knob converting rotational force to axial thrust) and replaces it with a direct linear actuation system. The stop block translates linearly to directly control the elastic element's axial position, eliminating the need for force transformation and significantly reducing the physical effort required from the user.
Solution Approach 2:
The patent replaces the mechanical force transformation system (rotation knob with rack-and-pinion or screw mechanisms) with a simpler linear translation system. The stop block's direct linear movement substitutes for the complex mechanical conversion process, reducing the effort needed while achieving the same force control objective.
3Adaptability or versatility
If complex adjusting systems are used to provide ergonomic comfort, then the mechanism can accommodate different users, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the core adjustment function from complex multi-component systems and implements it through a single translatable stop block. This simplified structure maintains the ability to accommodate different users through adjustable positions while dramatically reducing manufacturing complexity and cost compared to rotation knobs, rack-and-pinion systems, or multiple discrete adjustment 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 mechanism provides ergonomic and comfortable tilt control with reduced effort, offering two selectable force values, is compact, user-friendly, and cost-effective, while maintaining structural simplicity and usability for diverse users.
Implementation Method 1
contrasting an elastic element (10), the backrest... the elastic element being disposed along an axis and being configured to take a first operative position and at least one second operative position
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Mechanism (1) for controlling the force for tilting a backrest (2) of a chair (3) comprising a box structure (5) associated to a seat (4) and to which is articulated, and contrasting an elastic element (10, 20, 21), the backrest (2), the elastic element (10, 20, 21) is disposed along a longitudinal axis (X-X, X'-X') configured to take a first operative position (PI) and at least one second operative position (P2) and a stop device (13) associated to the box structure (5) and provided with a translatingly movable stop block (14), position adjusting means (15) being configured to selectively translate the stop block (14) from a rest position (P3) wherein said stop block (14) is decoupled from said elastic element (10, 20, 21) to at least one abutment position (P4) wherein said stop block (14) abuts against said elastic element (10, 20, 21), by disposing said elastic element (10, 20, 21) in said at least one second operative position (P2).