Spring-Pulley Counterbalance for Freely Rotating Eccentric Loads
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Solution Overview
Problem
Existing load positioning systems face challenges in effectively counterbalancing rotating loads due to the limitations of counterweights, constant-force springs, and pneumatic equilibrators, which often result in increased weight, inertia, and friction, and are difficult to implement for freely rotating shafts.
Innovation Solution
A counterbalance mechanism using a spring and pulley system where a spring is fixed to a frame and coupled to a pulley on a rotating shaft, providing a restoring force through a cable system that allows the shaft to rotate freely, with a configuration that maintains balance throughout the full range of rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a counterweight is used to compensate for gravity, then the counterbalance force is sufficient, but the size, weight, and inertia of the system increase significantly
Solution Approach 1:
The patent uses a spring-based counterbalance mechanism that generates an opposing force to gravity without requiring a physical counterweight. The spring is configured to exert a force equal to the gravitational force on the load, creating a balanced system where the spring force counteracts the weight, thereby eliminating the need for additional mass while maintaining sufficient counterbalance force.
2Weight of moving object
If a constant-force spring is used to counterbalance, then the weight added is reduced, but the spring generates insufficient compensating force and has short dynamic life due to metal fatigue
Solution Approach 1:
The patent modifies the spring configuration by arranging it in a specific geometric arrangement with linkages that transform the spring's linear force into a rotational moment. By changing the parameters of the mechanism (linkage lengths, pivot points, spring mounting positions), the system amplifies the spring's compensating force to match the gravitational force on the load, thereby achieving sufficient force output without increasing spring stress beyond acceptable limits.
3Force
If a pneumatic equilibrator is used to counterbalance, then sufficient compensating force is achieved, but the device becomes long and bulky requiring custom manufacturing
Solution Approach 1:
The patent replaces the pneumatic equilibrator's complex mechanical-hydraulic system with a purely mechanical spring-based system. The spring mechanism uses elastic deformation to store and release energy, substituting the need for pneumatic chambers, seals, and control systems. This substitution achieves the same force compensation function with a more compact, simpler structure that can be manufactured using standard components.
4Ease of operation
If a spring balance system is connected to an unobstructed end of the rotating shaft, then the shaft can rotate freely, but the system cannot be coupled in the middle of the shaft
Solution Approach 1:
The patent segments the counterbalance mechanism into separate functional components: the spring assembly, the cable system, and the pulley mechanism. This segmentation allows the spring and cable to be routed through intermediate positions on the shaft rather than requiring an unobstructed end connection. The cable can be guided along the shaft or through bearings at intermediate locations, enabling coupling at various positions while maintaining free rotation capability.
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 effectively counterbalances rotating loads by providing a consistent restoring force proportional to the load's gravitational force, reducing weight and inertia, and allowing for free rotation of the shaft, thus improving system efficiency and reducing friction.
Implementation Method 1
A spring is fixed at a first end to the frame and has a second end that is coupled to the fourth pulley such that the spring provides a restoring force as the fourth pulley is rotated
Implementation Method 2
A first cable has a first end that is coupled to the fourth pulley and a second end that is coupled to the frame through the third pulley after passing over the first and second pulleys
Data Source
AI summary
A counterbalance mechanism counterbalances an eccentric mass on a rotating shaft supported by a frame. A first pulley is coupled to and concentric with the shaft. An arm is coupled to the shaft to rotatably support a second at a first distance from the first pulley. A third pulley is fixedly coupled to the frame at a second distance from the first pulley. A fourth pulley is rotatably coupled to and concentric with the third pulley. A spring is fixed at a first end to the frame and has a second end that is coupled to the fourth pulley such that the spring provides a restoring force as the fourth pulley is rotated. A first cable has a first end that is coupled to the fourth pulley and a second end that is coupled to the frame through the third pulley after passing over the first and second pulleys.