Ball-Lock Tool Changer Coupling With Cross-Contact Recesses

Solution Overview

Problem

Robotic tool changers experience torsional freeplay due to diametral clearance in ball-lock configurations, leading to positional repeatability issues and premature failure, especially in large end-of-arm tools.

Innovation Solution

The implementation of cross-contact recesses in the bearing race and master assembly bores, which contact rolling members at two separate angles, preventing side-to-side movement and substantially eliminating torsional freeplay.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If diametral clearance is provided between alignment pin and alignment bushing to prevent binding, then ease of operation is improved, but torsional rigidity deteriorates causing rotational freeplay

Engineering Contradiction:

Improveease of operationVSAvoidtorsional rigidity

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The contact interface is segmented into multiple discrete contact points (first contact point on alignment pin, second contact point on alignment bushing, third contact point on alignment bushing) rather than a continuous surface contact. This segmentation allows the clearance to be distributed and controlled, preventing binding while maintaining rigidity through the geometric arrangement of contact points.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solution moves from considering only radial clearance (one dimension) to incorporating angular positioning of multiple contact points (adding rotational dimension). By strategically positioning contact points at specific angles around the clearance, the system achieves both ease of operation and torsional rigidity through spatial arrangement rather than relying solely on clearance magnitude.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Strength

If smaller clearance is used between alignment pin and alignment bushing, then torsional rigidity is improved, but binding occurs reducing ease of operation

Engineering Contradiction:

Improvetorsional rigidityVSAvoidease of operation

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The contact interface is segmented into multiple discrete contact points (first contact point on alignment pin, second contact point on alignment bushing, third contact point on alignment bushing) rather than a continuous surface contact. This segmentation allows the clearance to be distributed and controlled, preventing binding while maintaining rigidity through the geometric arrangement of contact points.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solution moves from considering only radial clearance (one dimension) to incorporating angular positioning of multiple contact points (adding rotational dimension). By strategically positioning contact points at specific angles around the clearance, the system achieves both ease of operation and torsional rigidity through spatial arrangement rather than relying solely on clearance magnitude.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Ease of operation

If rolling members are allowed to rock back-and-forth within scallops, then ease of operation is improved, but positional precision deteriorates due to torsional freeplay

Engineering Contradiction:

Improveease of operationVSAvoidpositional repeatability

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The contact interface is segmented into multiple discrete contact points (first contact point on alignment pin, second contact point on alignment bushing, third contact point on alignment bushing) rather than a continuous surface contact. This segmentation allows the clearance to be distributed and controlled, preventing binding while maintaining rigidity through the geometric arrangement of contact points.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solution moves from considering only radial clearance (one dimension) to incorporating angular positioning of multiple contact points (adding rotational dimension). By strategically positioning contact points at specific angles around the clearance, the system achieves both ease of operation and torsional rigidity through spatial arrangement rather than relying solely on clearance magnitude.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS11850733B2Robotic tool changer coupling mechanism with increased torsional rigidity and reduced freeplay

Publication Date: 2023.12.26 ATI IND AUTOMATION INC

AI summary

To substantially eliminate torsional freeplay in a robotic tool changer having a ball-lock coupling mechanism, scallop-like features in the form of cross-contact recesses are formed in at least one of, and preferably both of, a bearing race in a tool assembly at the points of contact of rolling members, and in the opposing inner surfaces of bores containing the rolling members in a master assembly. The cross-contact recesses are sized and shaped to receive a rolling member, but have a central void, or channel, perpendicular to the rolling member's motion in torsional freeplay, which does not contact the rolling member. The cross-contact recess contacts the rolling member at contact areas on either side of the central void. These contact areas impart two separate contact forces on the rolling member, both angled toward the center of the rolling member and hence operative to prevent side-to-side movement, or rocking, of the rolling member within the cross-contact recess, and hence substantially eliminating torsional freeplay of the robotic tool changer.