Parallel Mechanical Adjustment Unit for Spring Prestress Control
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Solution Overview
Problem
Existing systems for body weight-supported treadmill training, used for rehabilitation of paraparetic and hemiparetic patients, face challenges with inertia-induced large forces during movement and difficulty in adjusting the unloading force, especially when a large mass is suspended, and require complex control devices for precise force control.
Innovation Solution
A mechanical adjustment unit connected in parallel to the elastic means, such as springs, compensates for force changes by adding an adjustment force when deviations occur, allowing for a nearly constant spring force and precise control of the relief force through two separate cable length adjustment mechanisms, one for height and one for force, eliminating the need for a winch and complex control devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a large mass is attached on the other side of the rope to achieve large unloading force, then the relief force is sufficient, but the inertia of the mass causes large forces during up and down acceleration
Solution Approach 1:
The patent replaces the conventional mechanical counterweight system with an elastic means (spring) that provides the relief force through elastic deformation rather than gravitational force on a mass. This substitution eliminates the inertia problems associated with large masses while maintaining the ability to provide sufficient relief force for patient suspension during treadmill therapy.
2Ease of manufacture
If a conventional counterweight system is used to achieve unloading, then the structure is simple, but it is not easy to change the amount of unloading during training
Solution Approach 1:
The patent employs a dynamic adjustment mechanism that allows the unloading force to be easily modified during therapy sessions. The system includes adjustment means that can change the prestress of the elastic means or the position of the connection, enabling therapists to adapt the relief force to different patient needs and training phases without complex reconfiguration.
3Measurement precision
If electronic control devices are used to adjust spring prestress, then precise force control is achieved, but the device complexity and cost increase
Solution Approach 1:
The patent implements a self-adjusting mechanism where the elastic means automatically maintains appropriate prestress levels through its inherent elastic properties. The system uses mechanical feedback through the connection between the elastic means and the moving portion, allowing the device to self-regulate the relief force without requiring complex electronic sensors or control algorithms, thus reducing cost and complexity while maintaining precision.
4Ease of manufacture
If the prestress of the elastic means is not adjusted, then the structure is simple, but the spring force changes with position causing unpredictable force variations
Solution Approach 1:
The patent applies preliminary prestress to the elastic means during assembly or before use, establishing a predetermined initial tension or compression state. This preliminary action ensures that the spring operates from a known starting point, and combined with the adjustment mechanism, maintains consistent and predictable force characteristics throughout the range of motion, improving reliability without significantly complicating the structure.
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
This solution provides a simpler, more precise method for adjusting the prestress of springs, allowing for predictable force changes and improved control of the relief force during locomotion therapy, reducing variations in support and enhancing the therapy experience by maintaining a nearly constant force over a range of motion.
Implementation Method 1
the functions of the spring adjustment has preferably to be achieved through mechanical means... use of a spring means... spring force changes with position
Implementation Method 2
a force exerting means being attached at said movable portion... the force exerting means adds an adjustment force upon deviation
Data Source
AI summary
A device for adjusting the prestress of an elastic means around a predetermined tension or position can especially be used to adjust the height of and the relief force acting on a weight. A mechanic adjustment unit is connected in parallel to the elastic means to preadjust the value of the predetermined tension comprising a movable portion engaging the connection portion between elastic means and adjustment unit and a force exerting element being attached at said movable portion. The mechanic adjustment unit is in an unstable equilibrium position at said predetermined tension or position, the movement of the movable portion being such that the force exerting element adds an adjustment or compensation force upon deviation of the predetermined tension or position of the elastic means.