Constant Force Spring Counterbalance for Heavy Test Heads

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Solution Overview

Problem

Automatic test equipment systems face challenges in supporting and moving test heads with weights exceeding 1000 lbs due to high connection and power densities, requiring heavy and cumbersome coaxial cable bundles, which are difficult to manage with existing counterbalancing methods like electric motors, pneumatic rams, and rope and pulley systems.

Innovation Solution

The implementation of a weight compensation device using constant force springs connected between the test head assembly and the supporting structure, which applies a constant supportive force to offset the weight of the test head, allowing for reduced inertia and enabling the use of pulleys for mechanical advantage, thereby reducing the force required to move the test head.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If conventional counterbalancing methods (electric motors, pneumatic rams, rope and pulley systems) are used to support the test head, then the test head can be supported, but the system becomes heavy and cumbersome

Engineering Contradiction:

Improvetest head weightVSAvoidmaneuverability

Core Design Contradiction:

Weight of moving objectVSEase of operation

Solution Approach 1:

The patent applies a constant force spring to provide an upward counterbalancing force that offsets the weight of the test head assembly. This counterweight mechanism reduces the net force required to move the test head, making it easier to maneuver while supporting the full weight of the assembly.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The patent replaces heavy conventional counterbalancing mechanisms (electric motors, pneumatic rams) with a constant force spring system. This substitution uses elastic potential energy storage and release to provide the counterbalancing force, significantly reducing the overall system weight and improving maneuverability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Force

If heavy counterbalancing mechanisms are used to support the test head, then the test head weight is compensated, but the manipulator becomes less mobile

Engineering Contradiction:

Improveweight compensation forceVSAvoidmanipulator weight

Core Design Contradiction:

ForceVSWeight of moving object

Solution Approach 1:

The patent replaces heavy mechanical counterbalancing systems with a constant force spring mechanism. The spring provides the necessary counterbalancing force through elastic deformation, eliminating the need for heavy motors or pneumatic components while maintaining full weight compensation capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical state of the counterbalancing mechanism from rigid mechanical components to an elastic spring system. This parameter change allows the system to provide continuous counterbalancing force without the weight penalty of conventional mechanisms, enabling mobile manipulator design.

Inventive Principle:

Principle #35Parameter changes

3Force

If conventional spring systems are used for weight compensation, then the test head can be supported, but damping issues occur

Engineering Contradiction:

Improvesupportive forceVSAvoiddamping performance

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

The patent replaces conventional damping-prone spring systems with a constant force spring mechanism. This specific type of spring provides consistent counterbalancing force without the oscillatory damping characteristics of traditional springs, improving system reliability and reducing unwanted vibrations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 allows for a lightweight and efficient compensation of the test head's weight, enabling the test head manipulator to be mobile and easily moved between test stations, reducing the mass that needs to be slowed or stopped, and eliminating the damping issues associated with conventional spring systems.

Implementation Method 1

at least one constant force spring connected between a test head assembly of the automated test equipment system and a test head supporting structure. The constant force spring applies a constant supportive force to the test head assembly along a full range of vertical travel

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

The at least one pulley multiplies the force of the constant force spring applied to compensate the weight of the test head

Methodology Applied

Scientific EffectMechanical Advantage: Mechanical Advantage

Data Source

PatentUS7685885B2Manipulator constant force spring counterbalance

Publication Date: 2010.03.30 TERADYNE INC

AI summary

In various embodiments, a test head weight compensation device includes at least one constant force spring connected between a test head assembly of the automated test equipment system and a test head supporting structure to apply a constant supportive force to the test head assembly. The at least one constant force spring is mounted to the test head supporting structure with a distal end of the constant force spring is attached to the test head assembly. Alternately, the constant force spring is mounted to the test head assembly with the distal end of the constant force spring connected to the test head supporting structure. The test weight compensation device may include pulleys attached to the supporting structure or the test head assembly with the constant force spring passed through the pulley to multiply the force of the constant force spring.