Backrest Catch Fitting With Compact High-Force Pawl Locking
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Solution Overview
Problem
Conventional locking fittings for adjustable backrests or support parts in furniture are too large, limiting their use in slim furniture due to protruding components and reduced tooth count, which compromises holding force and adjustment range.
Innovation Solution
A locking fitting design with a single stop cam and an engagement surface that interacts with the pawl, eliminating the need for pressure cams, allowing for a larger toothed area and reduced size, where the spring performs a dual function to hold the pawl in both engaged and disengaged positions, and the pawl is crescent-shaped with an asymmetric axis for optimal lever geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional locking fittings with pressure cams and push buttons are used, then the locking mechanism can engage and disengage the pawl, but the overall size of the locking fitting becomes large and protruding components increase
Solution Approach 1:
The patent removes the pressure cam component from the locking mechanism. Instead of using a pressure cam to engage the pawl with the teeth, the design allows the pawl to engage directly with the teeth through its own geometry, eliminating the need for the pressure cam and reducing the overall size of the locking fitting.
Solution Approach 2:
The stop cam and push button are merged into a single integrated component. This combination eliminates the need for separate pressure cam and push button components, reducing the number of parts and the overall volume of the locking fitting while maintaining the engagement and disengagement functionality.
2Adaptability or versatility
If multiple locking settings are provided through additional teeth, then the adjustment range increases, but the area available for toothing is reduced due to protruding components
Solution Approach 1:
By removing the pressure cam, the patent frees up space in the toothed area. This allows for more teeth to be arranged on the locking tab without interference from protruding components, thereby increasing the number of available locking positions and the adjustment range.
3Volume of moving object
If the locking fitting is made compact to fit slim furniture, then the footprint is reduced, but the holding force may be compromised
Solution Approach 1:
The pawl is designed with an asymmetric shape, being wider at the engagement end and narrower at the pivot end. This asymmetric geometry allows the pawl to maintain a large engagement surface area with the teeth for high holding force, while the overall footprint of the locking fitting remains compact due to the tapered shape.
Solution Approach 2:
The engagement surface of the pawl is designed with a curved profile that matches the shape of the teeth. This curved engagement surface maximizes the contact area between the pawl and teeth, distributing the holding force over a larger area and enabling high holding force in a compact design.
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 design results in a compact locking fitting with high holding power and a wide adjustment range, suitable for slim furniture, while maintaining a small footprint and achieving the required holding force of 180 Nm.
Implementation Method 1
a spring (5) acting on the pawl (4) in the engaged position
Implementation Method 2
the spring (5) holds the pawl (4) in the disengaged position
Implementation Method 3
the teeth (8), as the pawl (4) moves in the disengaged position, contact the engaging surface (11) on the pawl (4) and urge it into the engaged position
Data Source
AI summary
The invention relates to a catch fitting (1) of an adjustable back rest or support of a piece of furniture, especially a piece of furniture for sitting or lying down. Said fitting comprises a connection plate (2) and a stop notch plate (3) that is pivotably connected to the connection plate and can be locked in various angular positions. Said stop notch plate comprises a toothing (8) which is concentrically arranged in relation to the axis (6) of the articulation, a locking device (4) which is rotatably mounted on the connection plate (2) engaging with said toothing in the catch position. Said locking device (4) is held by a spring (5) in the released position and is acted upon by the same spring (5) in the engaged position. The aim of the invention is to keep the structural dimensions to a minimum, while ensuring a high holding force and an engagement adjustment region which is as large as possible. To this end, an abutment cam (10) is simply provided on the stop notch plate (3) for releasing the locking device (4) by co-operation with a release lug (12), and the locking device (4) is provided with an engaging surface (11) which co-operates with the toothing (8) for the engagement.