Hydraulic actuator having a microwave antenna

• US 4,901,628 A
• Filed: 10/09/1985
• Issued: 02/20/1990
• Est. Priority Date: 08/11/1983
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Krage, Mark K.
• Primary Examiner(s): Green, Randall L.
• Assistant Examiner(s): Kapsalas, George
• Application Number:
  US06/785,679
• Time in Patent Office: 1,595 Days
• Field of Search: 91/1, 91/8, 91/9, 91/189, 91/191, 91/248, 91/275, 91/361, 91/394, 91/405, 91/407, 91/459, 92/5 R, 342/118, 342/124, 324/58.5 B, 324/58.5 C
• US Class Current: 92/5.00R
• CPC Class Codes: F15B 15/2869 using electromagnetic radiation, e.g. radar or microwaves
• CPC Class Codes: G01R 27/04 in circuits having distributed constants , e.g. having very long conductors or involving high frequencies
• CPC Class Codes: G05D 3/20 using a digital comparing device
• CPC Class Codes: H01P 7/06 Cavity resonators

Abstract

A microwave method and apparatus for detecting the position of a piston of a pneumatic cylinder. While the piston is being moved by fluid pressure a microwave signal is applied to a cavity defined by the piston and interior of the cylinder and the reflected microwave signal is detected. The reflected microwave signal is processed to determine piston position.

Claims

1. A hydraulic actuator having a microwave antenna comprising, a cylinder having an end cap, a piston reciprocable within said cylinder, a rod member extending axially of said piston that moves into an axially extending bore formed in said end cap when the piston has moved to a position engaging a portion of said end cap, passage means connecting the interior of the cylinder and the interior of said bore, an axially extending microwave antenna disposed within said bore and a recess formed in said rod member for receiving said antenna.