Delayed vent valve system in a mechanical backing pump in a vacuum system allows the pneumatic foreline valve to seal before the pump vent opens. The system is designed to be fail-safe and operate even though there is loss of electrical power

Dameron, C. E.

English

NASA Technical Reports Server

To Foreline
'
Air 
Supply 
(75 to 125 
PSIG) 
August 1966	 Brief 66-10369 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Automatic Protective Vent Has Fail-Safe Feature 
Needle Bleed Valve
Solenoid Valve 
Slave Valve 
Pilot Timer Valve - - 
Dry Air Or Nitrogen 
The problem: 
When a mechanical backing pump in a vacuum sys-
tem is cut off for any reason, the vent valve opens 
before the larger pneumatic foreline valve is able to 
seal, even though the two valves are energized at the 
same time. Under this condition, a burst of air will 
enter the vacuum chamber and diffusion pump. 
The solution: 
A delayed vent valve system that allows the foreline 
valve to seal before the pump vent opens. The system 
is designed to be fail-safe and operate even though 
there is a loss of electrical power.
(continued overleal) 
How it's done: 
The removal or loss of power to the solenoid oper-
ated control valve shuts off the supply of service air to 
the pilot timer valve. The pressurized air in the pilot 
chamber bleeds off through an adjustable needle 
valve, allowing the spring loaded diaphragm to actu-
ate a slave valve under the pilot chamber. This slave 
valve opens to admit service air to the normally closed 
pneumatic vacuum valve, thus providing a delayed 
venting of the mechanical pump foreline. The time 
delay is controlled by the needle valve on the pilot 
chamber. 
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=19660000368 2020-03-11T17:40:47+00:00Z
Note: 
Inquiries concerning this innovation may be di-
rected to:
Technology Utilization Officer 
Langley Research Center 
Langley Station 
Hampton, Virginia 23365 
Reference: B66-10369 
Patent status: 
No patent action is contemplated by NASA. 
Source: C. E. Dam eron 
(Langley-218) 
Brief 66-10369
Category 05


Automatic protective vent has fail-safe feature

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