Browse Prior Art Database

Preventing Inadvertent Parameter Changes in Control Knobs

IP.com Disclosure Number: IPCOM000238390D
Publication Date: 2014-Aug-22
Document File: 6 page(s) / 191K

Publishing Venue

The IP.com Prior Art Database

Related People

Scott Covert: INVENTOR [+2]

Abstract

A variety of applications utilize control knobs to allow operator control of functional parameters of a product or system. These knob assemblies are used for a wide range of applications in many design variants. Some of the control knobs have dual function such as rotation of the knob as well as the actuation of a switch by pressing the knob. Such control knobs find application in aircraft for a variety of control parameters. A problem with this type of knob design is that the act of pressing the knob to actuate the switch can create inadvertent rotation of the knob. This presents a functional or safety concern, especially in some implementations where the selected parameter is critical for proper and safe operation. This paper illustrates a method that prevents an unintentional change to a parameter selection due to accidental knob rotation while pressing the switch.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 34% of the total text.

Page 01 of 6

Preventing Inadvertent Parameter Changes in Control Knobs

Scott Covert and Bill Woodruff ABSTRACT

A variety of applications utilize control knobs to allow operator control of functional parameters of a product or system. These knob assemblies are used for a wide range of applications in many design variants. Some of the control knobs have dual function such as rotation of the knob as well as the actuation of a switch by pressing the knob. Such control knobs find application in aircraft for a variety of control parameters. A problem with this type of knob design is that the act of pressing the knob to actuate the switch can create inadvertent rotation of the knob. This presents a functional or safety concern, especially in some implementations where the selected parameter is critical for proper and safe operation. This paper illustrates a method that prevents an unintentional change to a parameter selection due to accidental knob rotation while pressing the switch.


1. Introduction

Control knobs on an aircraft are used by the pilot for selecting different parameters such as heading, altitude, indicated air speed, etc., and are used as navigational aids or by the autopilot.

The rotation of the knob is measured by the rotational sensor assembly in the system. Different rotational sensors such as optical pulsers, potentiometers, variable differential transformers, etc. are used to sense the rotational data. The rotational information measured for these control knobs are typically relational, i.e. the change in knob position is measured for determination of a parameter change. This differs from knob


Page 02 of 6

assemblies where the parameter is determined by the absolute shaft position of the knob assembly.

Some of the control knobs have two functions. The pilot can turn the knob to adjust or set the parameter value, while the same knob also has the ability to be pressed to actuate the switch behind it. The process of pressing the knob, with the intention of actuating the pushbutton switch, can result in an unwanted rotation of the control knob, affecting the value of the controlled parameter.

As an example, current autoflight systems require the pilot to select a value of a flight parameter (e.g. selected altitude) by rotating a control knob. The selected altitude is the flight level at which the aircraft is cleared by air traffic control to fly. The selected altitude knob includes a switch actuated by pressing the knob that performs a related discrete function. When the pilot presses the knob to actuate the switch, the action may inadvertently turn the knob. The inadvertent turn can occur as the knob is being initially pressed before the switch is actuated, while the switch is pressed in, or as the pilot releases the knob to release the switch. This can alter the currently selected parameter (e.g. selected altitude), setting it to a wrong value.

Therefore, a solution is needed that addresses the limitations of dual function control...