Folding Tray Cart Spring Sheath for Pinch Hazard Control
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Solution Overview
Problem
Folding wheeled tray carts pose a risk of pinching or crushing injuries due to the sudden snap-down movement of their shelves as they transition from a compact storage position to an open operating position, as the extension coil springs exert increasing force, causing a gap that can trap operator's hands.
Innovation Solution
A double open-ended resilient sheath is applied to the extension coil spring to slow down its movement, providing resistance that slows the transition process to a midpoint, requiring additional operator effort to complete the opening or closing, thereby giving more time to remove hands from the closing gap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the extension coil spring is used to facilitate the movement of the folding wheeled tray cart between open and folded positions, then the cart can automatically snap into position, but the sudden snap-down movement creates a pinching hazard that can crush operator's hands
Solution Approach 1:
A safety device is introduced as an intermediary component between the extension coil spring and the split shelf. This safety device includes a safety member that blocks the gap between half-shelves during the snap-down movement, preventing direct contact between the spring's forcing action and the operator's hands. The safety member acts as a mediator that allows the spring to perform its positioning function while simultaneously protecting against the pinching hazard.
2Speed
If the extension coil spring exerts increasing force during the snap-down movement, then the cart reaches its operating position quickly, but the increasing force creates a crushing injury risk in the closing gap
Solution Approach 1:
The safety device converts the harmful increasing force of the extension coil spring into a beneficial protective action. As the spring exerts increasing force during the snap-down movement, the safety member is pushed by this same force to block the gap between half-shelves. The harmful crushing force is redirected to push the safety member into a protective position, transforming the hazard into a safety mechanism that prevents hand insertion while maintaining the quick positioning function.
3Reliability
If the gap between half-shelves is maintained during opening movement, then operator's hands can be trapped, but closing the gap completely eliminates the opening function of the cart
Solution Approach 1:
The safety member is designed to be dynamic rather than static. It moves between different positions based on the cart's state: during normal operation, it allows the gap to open and close freely; during the snap-down movement, it is pushed into a blocking position to prevent hand insertion. This dynamic behavior allows the safety device to protect against pinching hazards while simultaneously preserving the cart's opening and closing functions.
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 reduces the risk of pinching or crushing injuries by slowing the movement of the folding tray cart to a midpoint, necessitating greater operator intervention and control, ensuring hands are out of harm's way during the transition.
Implementation Method 1
The folding wheeled tray cart could further comprise one or more extension (e.g., tension) coil springs that could facilitate the movement of the folding wheeled tray cart between open and folded positions
Implementation Method 2
The sheath could impart resistance to the movement of the extension coil spring in a manner that may slow down the extension coil spring's movement
Data Source
AI summary
The invention is a wheeled folding tray cart and method. The wheeled folding tray cart comprises a collapsible wheeled framework pivotally supporting a set of split shelves, each split shelf comprises a pair of half shelves. The wheeled folding tray cart moves between an open operating position wherein the set of split shelves are held in spaced-apart, stacked, horizontal orientation within the collapsible wheeled framework and a closed storage position wherein the collapsible wheeled framework is collapsed in manner to move each half shelf pair into an accordion-like, inverted “V”-shaped or accordion like configuration. An extension coiled spring attached to the collapsible wheeled framework assists in the movement of the wheeled folding tray cart between open operating position and the closed storage position. A sheath encloses at least a portion of the spring to provide resistance to the spring's movement to limit potential operator exposure to pinch injuries.