Seat Switch Tension Sensing for Operator Presence Detection
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Solution Overview
Problem
Existing operator-presence switches in off-highway vehicles, typically 'pancake' and 'plunger' types, are not effectively integrated with the seat's resilient web to accurately sense an operator's presence, leading to potential unsafe operation of vehicles without a seated operator.
Innovation Solution
A seat design with a resilient web and a switch assembly mounted directly to it, utilizing a tension member and spring to sense the increase in tension indicative of an operator sitting, which is connected to the vehicle's circuit to enable or disable critical systems like the ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional 'pancake' and 'plunger' switches are used under the seat cushion, then the device structure is simple, but the sensing reliability is insufficient to accurately detect operator presence
Solution Approach 1:
A tension member is introduced as an intermediary element that connects the resilient web to the switch actuator. When the operator sits on the seat, the resilient web stretches and pulls the tension member, which in turn actuates the switch. This intermediary mechanism reliably transmits the seating force to the switch, solving the problem of insufficient sensing reliability while maintaining a relatively simple overall structure.
Solution Approach 2:
The patent replaces the direct mechanical compression approach (pancake/plunger switches under the cushion) with a tension-based mechanical system. The resilient web is designed to stretch when the operator sits, creating tension that pulls the tension member to actuate the switch. This substitution improves reliability by using tension rather than compression, as tension transmission is more reliable in this application context.
2Measurement precision
If the switch is not integrated with the resilient web, then the device complexity is low, but the measurement precision of operator presence is insufficient
Solution Approach 1:
The switch assembly is merged with the resilient web through the tension member connection. The resilient web, tension member, and switch actuator form an integrated sensing system where the web's elastic deformation directly actuates the switch. This merging ensures that the switch responds precisely to operator presence by directly coupling the sensing element (web) with the detection element (switch), achieving high measurement precision.
Solution Approach 2:
The resilient web serves dual functions: it provides seat cushioning support and simultaneously acts as the sensing element that triggers the switch. When the operator sits, the web's natural elastic response automatically actuates the switch through the tension member, without requiring additional sensors or complex detection systems. This self-service approach achieves precise operator presence detection while minimizing added complexity.
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
Ensures safe operation by reliably detecting the presence of an operator, preventing vehicle activation when the seat is unoccupied, thereby enhancing safety and operational control.
Implementation Method 1
means for sensing the presence of an operator sitting on the resilient web; wherein at least a portion of the means for sensing is mounted directly to the resilient web... means for sensing an increase in tension in the resilient web indicative of an operator sitting in the seat
Implementation Method 2
a resilient web extending between and connected to the web support portions, and adapted to support an operator of a vehicle... utilizing a tension member and spring to sense the increase in tension
Data Source
AI summary
A seat switch for a seat having a resilient web includes device for sensing the presence of an operator sitting on the resilient web. The seat switch is operably connected to a vehicle circuit which may be for example an ignition system for the engine. The seat switch provides a signal to the vehicle circuit in response to sensing no operator present. The device for sensing may include a switch and a tension member mounted directly to the web. When an operator sits on the seat, the web stretches under the weight of the operator, which results in tension in the tension member. This tension activates the switch to send the operator-present signal to the vehicle circuit. When the operator's weight is removed from the seat, the tension is relieved from the resilient web and the switch discontinues the operator-present signal.