Static friction free altimeter

#This invention relates to a vibratory apparatus for attenuating static friction in an altimeter having an indicator driven by a low power sensor.

#Since such low power sensors are responsive to the changes in pressure associated with changes in altitude, it is necessary that each increment of torgue developed by these sensors be transmitted to an output pointer without modification to assure that indicated altitude is the actual altitude.

#Initially, it was thought that the vibrations produced within an aircraft would be sufficient to prevent static friction. However, from observation it was observed that the indicator pointer movement was erratic, especially when the aircraft was operating on a smooth glide path.

#The single FIGURE in the drawing schematically illustrates an altimeter and associated piezoelectrical transducer made according to the principles of this invention.

#The altimeter 10 shown in the drawing is similar to the altimeter disclosed in U.S. Pat. No. 3,916,185. The altimeter has a pressure responsive sensor with a first aneroid 12 and a second aneroid 13 located in a chamber 14 of a housing 16. The first aneroid 12 is connected to a shaft 18 through an arm 20. Ends 22 and 24 of shaft 18 are journalled in jeweled bearings 26 and 28 which are pressed into openings in housing 16.

#A sector gear 30, which is fixed to shaft 18, engages gear 32 on the aneroid output shaft 34. The second aneroid 13 is similarly connected to a shaft 19 which retains sector gear 36. The output shaft 34 is carried through opening 38 in wall 40 of housing 16. A driver gear 44, which is fixed to the end of the output shaft 34, positions a barometric input gear 42 adjacent wall 40. The driver gear 44 is connected to output shaft 46 through reduction gears 48, 50 and 52. A pointer 54 attached to the end of shaft 46 is located over dial 56 to provide an operator with an indication of the altitude as measured by the aneroids 12 and 13.

#A piezoelectrical transducer apparatus 58 which is attached to the housing 16 provides a controlled built-in vibration to compensate for static friction which can occur between the gears in the drive train of the altimeter 10.