Passive Gripper With Deflectable Elements For Fragile Objects
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Solution Overview
Problem
Existing grippers for fragile or irregularly shaped objects often cause damage due to stress concentration and inadequate force distribution, particularly in low-gravity and 0G environments where traditional grippers are not designed to handle fragile materials.
Innovation Solution
A passive gripper assembly with a series of deflectable elements that distribute clamping pressure across the object's surface, minimizing stress concentration and accommodating irregular geometries, while an actuator provides a load to close the gripper fingers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a rigid non-conforming surface is used to apply gripping force, then the gripping force is sufficient to secure the object, but stress concentration occurs on the object surface causing damage
Solution Approach 1:
The contact surface is segmented into multiple independent conforming elements (such as spherical segments or curved surfaces) that can individually adapt to the object's surface geometry. This segmentation allows the gripping force to be distributed across multiple contact points rather than concentrated at a single rigid contact point, reducing stress concentration while maintaining sufficient total gripping force.
Solution Approach 2:
The gripping surface incorporates elements with locally adapted geometry (curved surfaces, spherical segments) that match the local curvature of the object being gripped. This local conformity ensures that each contact point distributes pressure appropriately to the local surface properties, preventing stress concentration on brittle or sensitive surfaces while maintaining effective gripping force.
2Stress or pressure
If a monolithic pad is used to conform to the object surface, then the pressure is distributed, but stress concentration still occurs due to the monolithic nature making it hard to control local applied pressure
Solution Approach 1:
The monolithic pad is divided into multiple independent conforming elements that can individually control their contact pressure. Each element acts as an independent pressure control unit, allowing the system to distribute total gripping force while preventing localized stress concentration by adjusting individual element pressures based on local surface requirements.
Solution Approach 2:
The gripping elements are designed to dynamically adapt their contact pressure based on the object's surface geometry and material properties. This dynamic adjustment allows the system to maintain optimal pressure distribution across the entire contact surface, preventing stress concentration on sensitive areas while ensuring sufficient grip on more robust areas.
3Force
If active controls with sensors and processors are used to limit forces, then the force applied to objects can be controlled, but the system becomes expensive, complex, and life-limiting
Solution Approach 1:
The gripping system uses passive mechanical elements (spring-loaded conforming elements, elastic materials) that automatically regulate their own contact pressure based on the object's surface properties. The system self-adjusts to distribute force appropriately without requiring external sensors, processors, or active control systems, thereby reducing complexity while maintaining effective force control.
Solution Approach 2:
The system changes the physical parameters of the gripping elements (using elastic materials, spring constants, curved surface geometries) to inherently limit and control the maximum force applied. These parameter choices in the mechanical design replace the need for electronic control systems, achieving force limitation through passive mechanical properties rather than active sensing and control.
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 solution effectively secures fragile objects without causing damage by distributing pressure evenly and conforming to irregular surfaces, making it suitable for low-gravity and 0G environments.
Implementation Method 1
a plurality of deflectable elements configured to deflect upon contacting the contact surface of the object to distribute a gross clamping pressure
Data Source
AI summary
An apparatus for gripping fragile or irregularly shaped objects is provided. The apparatus includes a passive gripper assembly including an actuator for providing load to the passive gripper assembly. The passive gripper assembly further includes fingers to transmit the load to the object. Each finger includes a mechanical linkage to direct the load to the object, having a first end connected to the actuator and a second, free end. Each finger further includes a contact assembly disposed at the free end of the mechanical linkage that acts as a gripping interface. At least one of the contact assemblies is passive including deflectable elements configured to deflect upon contacting the object to distribute a gross clamping pressure. The load causes the fingers of the passive gripper assembly to close around the object such that the contact assemblies contact and apply the gross clamping pressure to the object.