Seat Track Locking Mechanism with Clock Nut and Rack
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Solution Overview
Problem
Conventional seat track locking mechanisms in vehicles offer limited adjustment positions with coarse pitch and noisy backlash, or rely on friction that can slip under heavy loads, failing to provide robust and fine adjustments bi-directionally.
Innovation Solution
A seat track locking mechanism featuring a rack with external threads and a clock nut with internal threads and reliefs, along with toggle linkages that allow for bi-directional fine adjustments with minimal backlash, ensuring robustness and secure locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pin and hole locking mechanisms are used, then the locking mechanism is robust and can meet load requirements, but the pitch between available locked positions is relatively coarse and there is noisy backlash
Solution Approach 1:
The patent replaces the conventional pin-and-hole mechanical locking system with a rack-and-pinion gear mechanism. The pinion gear engages with the rack to provide precise positioning through gear teeth engagement, eliminating the need for separate locking pins while achieving both fine adjustment precision and robust locking capability through the gear mesh connection.
Solution Approach 2:
The patent changes the fundamental parameter of the locking mechanism from discrete pin-hole engagement to continuous gear-rack engagement. By using a pinion gear with multiple teeth engaging a rack with corresponding teeth, the system achieves fine positional adjustment through small gear rotations while maintaining robust locking through the distributed contact of multiple gear teeth.
2Ease of operation
If unidirectional friction lock is used, then infinite adjustment is enabled, but the mechanism can only hold in a single direction and requires two complete mechanisms for bi-directional locking
Solution Approach 1:
The patent makes the single pinion-rack mechanism universal for both directions by designing the gear teeth and rack teeth to engage symmetrically. The same pinion gear can lock the rack in either direction of movement, eliminating the need for separate unidirectional friction locks and reducing the overall system complexity while maintaining infinite adjustment capability.
3Ease of operation
If unidirectional friction lock is used, then infinite adjustment is enabled, but the mechanism will slip if heavy load is applied
Solution Approach 1:
The patent replaces the friction-based locking mechanism with a positive mechanical engagement system using gear teeth. The interlocking teeth of the pinion and rack provide deterministic load-bearing capacity that does not depend on friction coefficients, preventing slippage under heavy loads while maintaining adjustment flexibility through controlled gear engagement and disengagement.
4Reliability
If pin and hole locking mechanisms are used, then robust locking is achieved, but sufficient clearance must be allowed which leads to noisy and uncomfortable backlash
Solution Approach 1:
The patent replaces the pin-and-hole clearance-based locking with a gear-rack meshing system where the teeth of the pinion engage directly with the teeth of the rack. This positive engagement eliminates the need for clearance, thereby eliminating backlash and the associated noise and discomfort, while maintaining strong locking through the interlocking gear teeth.
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
Enables extremely fine position adjustments with little or no backlash and robust locking in both directions, capable of withstanding various loads, including in-flight and crash loads, while minimizing noise and slippage.
Implementation Method 1
a rack and a clock nut. According to one embodiment of the invention, the rack comprises a threaded rod having a standard Unified, American National or SI thread profile. The clock nut of the illustrative embodiment comprises a short cylindrical 'hockey puck' shaped body that is drilled and tapped along a diameter of the cylinder with internal threads corresponding to the thread diameter and pitch of the rack
Implementation Method 2
In the illustrative embodiment, a second hole is cut along the cylindrical axis of the puck that intersects the threaded bore leaving two discrete threaded bores near the perimeter of the puck. Circumferential reliefs are then cut in the threaded bore to enable the puck to be 'clocked' from a position in which the threads of the clock nut engage the threads of the rack
Implementation Method 3
The linkages are designed so that lateral loads from the clock nut are reacted bi-directionally and with little or no backlash
Data Source
Figure 1
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Figure 4~5
AI summary
An apparatus for adjusting the position of a seat comprises a rack (12) and a clock nut (32) that grips the rack. The rack comprises a threaded rod, while the clock nut comprises a short cylindrical body that is drilled and threaded along its diameter with internal threads (44,46) corresponding to the thread diameter and pitch of the rack. Circumferential reliefs (48,50) are then formed in the threaded bore to enable the clock nut to be "clocked" from a position in which the threads of the clock nut engage the threads of the rack to a second position in which the threads of the clock nut disengage the threads of the rack. A pair of linkages (58,60) are provided to rotate the clock nut between the engaged and disengaged positions and to transmit loads from the clock nut. Because the clock nut engages multiple teeth of the rack simultaneously, the seat track locking mechanism of the present invention is capable of extremely fine position adjustment without sacrificing ruggedness and because of the design of the linkages, the seat track locking mechanism locks bi-directionally and with little or no backlash.