Special isolator valve prevents malfunction of a closed hydraulic system by converting the initial accumulator-reservoir to a reservoir function only when the system loses oil, or gaseous nitrogen precharge, or has a jammed piston. This permits near-normal operation until the defect is corrected

Walsh, G. D.

English

NASA Technical Reports Server

December 1967	 Brief 67-10528 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Accumulator Isolator Prevents Malfunctioning of Faulty Hydraulic System 
Isolator Valve Control 
Circuit 
Outlet Line (High Pressure) 
II 	 ......._	 L...__....	 I 
Pump l.4  . ..j 
Filter ___.lCheckValvet__J,,,,	
Thj	 I L.J Servo L 
tO11 Load Accumulator Piston 
Motor V Oil Volume	 Typical Hydraulic System 
Bootstrap Piston. 	 Pressurized And Operating 
 
Reservoir Piston	
X Oil Volume	
Normally. 
-	 I 
- 
Return Line )Low Pressure)
Accumulator-Reservoir 
Check	
Servo Valve
Actuator 
Hydraulic System Operating	 - 
With Accumulator-Reservoir 
Bypassed And Convened to 
Reservoir Function Only
__________ Bulkhead 
The problem: 
To prevent malfunction of a closed hydraulic system 
that has oil loss, gaseous nitrogen (GN 2) precharge 
loss, or a jammed piston. These defects degrade system 
operation and cause instability or serious damage to 
system components. Cavitation can result from the 
voids created in system lines and components when 
the accumulator oil volume, stored under operating 
conditions, exceeds the oil available from the
reservoir; or when the accumulator-reservoir does not 
properly function. 
The solution: 
Bypass the normal accumulator reservoir function 
with a special isolator valve. When a closed hydraulic 
system loses oil, or GN 2 precharge, or has a jammed 
piston, the accumulator isolator converts the initial 
accumulator-reservoir to a reservoir function only. 
This greatly extends the life of the system, permitting 
near-normal operation until the defect is corrected. 
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19670000527 2020-03-11T21:00:57+00:00Z
How it's done: 
When a closed hydraulic system becomes defective, 
the isolating valve system must provide positive iso-
lation of the reservoir from the high pressure side, 
return any (pressurized) stored oil from accumulator 
to reservoir, and prevent flow through the reservoir 
during system operation. 
The diagram compares the oil flow in a normal 
operating system with that of a system in which the 
isolator valve has converted the accumulator-reservoir 
to reservoir function. 
The flow of oil from the motor driven pump 
through the high pressure line, filter, and check 
valve are normally fed to the accumulator portion of 
the accumulator-reservoir and then to the servo-
actuator to lift the load. The actuator return oil is fed 
through the reservoir portion of the accumulator-
reservoir and the low pressure return line to the pump.
If the hydraulic system develops an oil leak, loses 
GN 2 precharge, or has a jammed piston, the isolator 
valve feeds the oil directly to the servo-actuator, by-
passing the accumulator-reservoir. 
Notes: 
Inquiries concerning this innovation may be di-
rected to:
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B67-10528 
Patent status: 
No patent action is contemplated by NASA. 
Source: George D. Walsh 
of The Boeing Company 
under contract to 
Marshall Space Flight Center 
(MFS- 1415) 
Brief 67-10528	 Category 05


Accumulator isolator prevents malfunctioning of faulty hydraulic system

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server