Hydraulic drive device translates microinch deviation measurements into precise corrective displacements. The unit is driven by a servomotor activated by the output of an attitude sensing device

Tsutsumi, K.

English

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August 1965	 Brief 65-10230 
NASA TECH BRIEF 
-I& 
NASA Tech Briefs are issued by the Technology Utilization Division to summarize specific 
technical innovations derived from the space program. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia, 22151. 
Hydraulic Device Provides Accurate Displacements to Microinches 
Servomotor 
Input	 .... 
Cylinder	 Cylinder 
The problem: To provide accurate linear displace-
ments on the order of 10- 6 inches. Certain scientific 
instruments such as seismographs, interferometers, 
and autocollimators must be maintained precisely 
level if their outputs are to be valid. Present day atti-
tude sensing devices are capable of detecting devia-
tions on the order of 10- 3 inch. A servo device is
needed to translate these measurements into precise 
corrective displacements. 
The solution: A hydraulic drive that uses a differ-
ential in input-to-output bellows sizes to translate a 
relatively large input to the required microinch output. 
The unit is driven by a servomotor actuated by the 
output of the attitude sensing device. 
-.	
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States Govern-
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes 
any warranty or representation, express or implied, with respect to the 
accuracy, completeness, or usefulness of the information contained in
this document, or that the use of any information, apparatus, method, 
or process disclosed in this document may not infringe privately-owned 
rights; or B. Assumes any liabilities with respect to the use of, or for 
damages resulting from the use of, any information, apparatus, method, 
or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19650000228 2020-03-11T17:19:00+00:00Z
How it's done: The hydraulic drive is composed of 
four interconnecting cylinders, which include a small 
diameter input cylinder, a large diameter output cylin-
der, and two small diameter manual positioning cylin-
ders. Bellows are used in each cylinder. Fluid fills the 
volume of the output cylinder bellows; fluid occupies 
the space outside the bellows of each of the other three 
cylinders. 
A servomotor drives an axle in the input cylinder 
whose endplate has a connecting rod threaded through 
the axle. As the servomotor turns counterclockwise 
the endplate is moved forward, decreasing the fluid 
volume in that cylinder, increasing the fluid volume in 
the output cylinder, and raising the output cap a pro-
portional amount. Output displacement is only a frac-
tion of the input due to the difference in cylinder di-
ameters. Knurled thumbscrews are used to position 
the bellows endplates of the two manual positioning 
cylinders. The use of bellows in place of pistons re-
duces friction drag and thus increases sensitivity in the 
drive movement.
Notes: 
I. This device is capable of raising a load of 18,000 lbs 
with an accuracy of I x 10-6 inch. 
2. By placing these drives with proper inputs at two 
corners of a horizontal triangular platform, a level 
base can be maintained for precision scientific in-
struments. 
3. Inquiries concerning this invention may be directed 
to:
Technology Utilization Officer 
Manned Spacecraft Center 
P. 0. Box 1537 
Houston, Texas, 77001 
Reference: B65-10230 
Patent status: NASA encourages the immediate 
commercial use of this invention. It is owned by 
NASA, and a patent application has been filed. 
Royalty-free nonexclusive licenses for its commercial 
use are available. Inquiries concerning license rights 
should be made to NASA, Code AGP, Washington, 
D.C., 20546.
Source: Kentaro Tsutsumi of
Massachusetts Institute of
Technology under contract to 
Manned Spacecraft Center 
(MSC-1l2) 
Brief 65-10230	 Category No. 05


Hydraulic device provides accurate displacements to microinches

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