Flow-rate switch adjusts easily over a wide switching range and operates uniformly over many cycles. It adapts easily to control of various fluids and has the possibility of introducing multi-point switching. Novel design features include the tapered spool, balanced porting, capillary-bypass lubrication, and capillary-restriction damping

Gale, G. P.

English

NASA Technical Reports Server

Entry
P 
• Bypass 
Capillar 
Byp
June 1970	 Rriei 70- l002l 
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech B net program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
High Pressure Flow-Rate Switch 
Ring Magnet 
Adjustable Plug	 Exit Port 
A reliable high pressure flow-rate switch of a new 
design adjusts easily over a wide switching range and 
operates uniformly over many cycles. It should find 
ready acceptance in commercial hydraulic applica-
tions. 
The diagram helps to explain the action of the switch 
Oil enters the switch housing through an entry port. A 
portion of the oil flows through the bypass ports and 
directly to the exit port. An adjustable plug limits or 
controls the amount of oil which can escape by this 
bypass route and, therefore, becomes a coarse range 
adjustment. A small amount of oil flows through the
bypass capillary located in the center of the end of the 
tapered spool, and then around the stem which acts 
both as the guide for the spool and as a housing for the 
magnetic switch. This small flow of oil lubricates the 
guide for the spool and thereby facilitates repeated 
operation of the switch. The bypass capillary creates 
a restricted passage to damp out any surges in oil flow 
rate which could cause erratic switching actions. 
The rest of the oil flows through the annular space 
between the tapered spool and the orifice. The bypass 
ports through the orifice part are arranged symmet-
rically around the spool, so that the oil flow in the 
(continued overkal) 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
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annular space is symmetric with respect to the spool. 
This design eliminates side forces which might cause 
the spool to bind. Increasing the rate of flow forces the 
spool out of the orifice; the distance the spool moves is 
porportional to the rate of flow. A spring resists the 
motion of the spool and returns it to position as the 
flow rate decreases. A ring magnet pressed onto the 
spool actuates a magnetic switch when the spool is 
forced a preset distance out of the orifice. A threaded 
adjustment and a locknut on the housing allow for 
positioning the magnetic switch closer to or farther 
from the magnet on the spool. This position deter-
mines the flow-rate which will actuate the switch. 
Locating several magnetic switches in the housing can 
meet any requirement for multi-point flow-rate switch-
ing. Tapering the spool increases the distance it will 
travel with respect to the rate of flow and improves the 
ability to set precisely the rate of flow at which the 
switching action will take place. 
The orifice part is separate from the main housing 
to provide for easy replacement and for the use of more 
wear-resistant materials for those parts which undergo 
abuse during operation. 0-ring seals are used around 
the removable parts at all points where leaks might 
occur. 
Advantages of the high pressure flow-rate switch 
include ease of adjustment and maintenance, uniform-
ity of operation, wide range of control settings, and
ease of adaptation to the control of various fluids, 
as well as the possibility of introducing multi-point 
switching. These advantages result from the combina-
tion of various novel design features such as: the tá- 
pered spool, balanced porting, capillary-bypass lubri-
cation;and capillary-restriction damping. 
Notes: 
1. This high pressure flow-rate switch was developed 
to replace flow switches currently used on a 210 ft 
advanced antenna system hydrostatic bearing. 
2. No additional documentation is available. Spe-
cific questions, however, may be directed to: 
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: B70-10028 
Patent status: 
This invention is owned by NASA, and a patent

application has been filed. Royalty-free, nonexclu-

sive licenses for its commercial use will be granted by

NASA. Inquiries concerning license rights should be

made to NASA, Code GP, Washington, D.C. 20546.

Source: G. P. Gale of

Caltech/JPL
under contract to

NASA Pasadena Office
(NPO- 10722) 
Brief 70-10028	 Category 07


High pressure flow-rate switch

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