Elastomeric Resistance Mechanism for Weight Stack Inertia Compensation
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Solution Overview
Problem
Weight stack exercise machines experience inconsistent resistance due to inertia and friction, limiting exercise speed and form, and offering resistance increments that are too large for certain users and exercises.
Innovation Solution
A supplemental resistance device with pins for insertion at two levels of a weight stack and an elongatable resistance mechanism between these pins to provide consistent resistance throughout the exercise cycle, reducing inertia and friction effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If weights are accelerated quickly during the lift phase, then exercise speed is improved, but resistance becomes inconsistent due to unweighting effects at the top of the lift
Solution Approach 1:
The patent applies counterweight principle by using a spring mechanism that provides opposing force to the weight stack. The spring is pre-loaded to counterbalance the weight stack, creating a system where the combined resistance remains consistent even when the weight stack experiences unweighting effects during acceleration and deceleration phases of the exercise motion.
Solution Approach 2:
The patent changes the physical state of the resistance system by introducing an elastic spring that can dynamically adjust its force output based on displacement. This allows the resistance characteristics to change continuously throughout the range of motion, compensating for the inconsistent gravitational force on the weight stack and maintaining constant total resistance.
2Ease of operation
If friction in cables and pulleys is present, then machine operation is simplified, but resistance feels lighter during the downward phase due to friction losses
Solution Approach 1:
The spring mechanism is pre-loaded during assembly to store potential energy that will be released during the downward phase of exercise. This preliminary action of pre-loading the spring compensates for the friction losses that will occur during cable and pulley operation, ensuring that the total resistance remains consistent regardless of friction in the mechanical components.
3Device complexity
If weight stack increments are increased to 5-10 lbs., then device complexity is reduced, but adaptability for certain users and exercises is limited
Solution Approach 1:
The patent introduces a dynamic spring component that can be adjusted to provide variable resistance increments. Instead of fixed weight plates, the spring system allows for continuous or fine-adjustable resistance changes, enabling users to select smaller resistance increments (e.g., 1-2.5 lbs.) that are more suitable for certain exercises and user needs, while maintaining a relatively simple overall device 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
The device maintains a consistent load on muscles during exercise, allowing for faster and more proper form performance by reducing unweighting effects and friction losses, and enabling customizable resistance increments.
Implementation Method 1
an elongatable resistance component having two ends and being configured to be attached at a first end to the first attachment point and at a second end to the second attachment point
Data Source
AI summary
A supplemental resistance device attachable as an accessory to the weight stacks of weight stack exercise machines to reduce or eliminate the unweighting effects of changes in acceleration at the top of the lift and friction losses during the downward phase of the lift. The supplemental resistance device comprises pins for insertion at two different levels of a weight stack, plus an elongatable resistance mechanism affixed between the pins which supplements the resistance provided by the weight stack as the two different levels of the weight stack are separated from one another. The supplemental resistance device maintains a more consistent load on the muscles during the full cycle of each lift on a weight stack exercise machine.