Zero-Backlash Wedge Brake With Default-to-Lock Rotary Holding
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Solution Overview
Problem
There is a need for motion control apparatus that achieves zero backlash and defaults to lock in rotary systems, particularly in situations of power loss, while applying minimal axial force and ensuring maximum torque with modular and self-centering capabilities.
Innovation Solution
A rotary motion control apparatus featuring a wedge mechanism that moves between positions to engage and disengage a friction surface, utilizing material strength as a spring for return and incorporating radial compliance, with a modular design for various torque amplitudes and sizes, and the ability to be mechanically, pneumatically, or hydraulically engaged.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional brake/locking apparatus is used, then it can provide braking and locking functions, but it produces backlash and does not default to lock in power loss situations
Solution Approach 1:
The brake/locking apparatus inverts the traditional default state by designing the system to default to locked position rather than unlocked. The spring mechanism continuously applies braking force, and only when actuated does the brake release, ensuring that power loss automatically results in locked state, thereby eliminating backlash and improving reliability.
Solution Approach 2:
The apparatus segments the braking and locking functions into distinct operational phases: a default locked state maintained by spring force, and an unlocked state achieved through actuation. This segmentation allows the system to reliably default to lock while providing controlled engagement when needed, resolving the contradiction between reliability and precision.
2Reliability
If a brake mechanism is designed to engage friction surfaces, then it can provide locking function, but it requires significant axial force which increases device complexity
Solution Approach 1:
The apparatus employs pneumatic or hydraulic actuation to generate the necessary forces for engagement and disengagement. The fluid pressure system provides controlled axial force to overcome spring pressure and engage/disengage the friction surfaces, reducing mechanical complexity compared to purely mechanical spring-loaded mechanisms while maintaining reliable locking function.
Solution Approach 2:
The friction surface acts as an intermediary element between the actuating mechanism and the rotational load. By introducing this intermediate friction interface, the system can achieve reliable locking with controlled axial forces, as the friction surface distributes and transforms the actuation force into effective braking and locking action.
3Ease of manufacture
If the cylindrical portion is made from a single material, then manufacturing is simplified, but it must simultaneously provide structural strength and elastic deflection
Solution Approach 1:
The cylindrical portion utilizes parameter changes in material properties through heat treatment or alloy selection to achieve both high strength and adequate elasticity from a single material. By carefully controlling material parameters such as hardness, tensile strength, and yield point through metallurgical processes, the component can be manufactured as a single piece that provides both structural integrity and the necessary deflection for engagement.
Solution Approach 2:
The invention merges multiple functions into a single cylindrical portion made from one material: it serves as the structural support element, the elastic spring element, and the engagement surface. This consolidation simplifies manufacturing by eliminating the need for multiple materials or assembly steps, while the material is engineered to provide both the required strength and elastic properties simultaneously.
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 achieves true zero backlash, self-centers for maximum torque, and defaults to lock in power loss situations with minimal axial force, providing a modular and sealed solution for differing applications.
Implementation Method 1
The disk and the cylindrical portion are formed as a single fixed component from a same material having sufficient material strength and yield to allow deflection of the cylindrical portion to engage the friction surface and face to hold the annular member from rotating relative to the cylindrical portion
Implementation Method 2
Compression springs are sandwiched between the actuator and a bottom housing including the cylindrical portion and the disk
Implementation Method 3
The end of the wedge opposite to the cylindrical portion includes an angled surface which is not parallel to the axial direction and which interfaces with the actuation surface for radially moving the wedge with axial movement of the actuator
Implementation Method 4
A plurality of balls is provided between the angled and actuation surfaces to reduce friction
Data Source
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AI summary
An apparatus (B) controls rotation of an annular member (36) relative to top and bottom housings (12, 10). The bottom housing (10) includes a disk (110) extending radially and terminating in a cylindrical portion (112) having circumferentially spaced slits (212). A wedge (16) abuts with the cylindrical portion (112) and is moved radially between first and second positions by an axially moveable piston (14), with the wedge including an angle surface (340) which interfaces with an angled surface (520) of the piston (14) through a plurality of balls (18). The disk (110) and the cylindrical portion (112) are formed as a single component of material having sufficient material strength and yield to allow engagement and disengagement of the cylindrical portion (112) with the annular member (36). The wedge (16) is slideable between an axial surface (250) of the disk (110) and a guiding flange (450) of the top housing (16).