A method is described for making a structure with a cavity and a thin wall with a precisely shaped slit. An object with a cavity having two openings, one of which is to be closed by a thin wall with a slit, is placed on the surface of a fixture. The fixture surface has a slot conforming to the size and shape of the slit to be formed in the thin wall

Christopher, P. A.

Gross, W. J.

Henley, W. H.

Swirsky, B. D.

English

NASA Technical Reports Server

LCW«/®M
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D.C. 20546
REPLY TO
ATTN OF: GP APR I 0
TO: RSI/Scientific & Technical Information Division
Attn: Miss Winnie M. Morgan
FROM: GP/Office of Assistant General
Counsel for Patent Matters
SUBJECT: Announcement of NASA-Owned U.S. patents in STAR
In accordance with the procedures agreed upon by Code GP
and Code KSI, the attached NASA-owned U.S. patent is being
forwarded for abstracting and announcement in NASA STAR.
The following information is provided:
U.S. Patent No.
Government or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA patent case No.
NOTE - If this patent covers an invention made
employee of a NASA Contractor, the following is
NO
by a corporate
applicable:
Pursuant to Section 305 (a) of the National Aer
Space Act, the name of the Administrator of N
the first page of the patent; however, the nam!
inventor (author) appears at the heading of co
the Specification, following the words "...with
an invention of ..."
*rp.
Bonnie L. Woerner
Enclosure
https://ntrs.nasa.gov/search.jsp?R=19740088523 2020-03-19T19:59:52+00:00Z
United States Patent
Fletcher et al.
[in 3,798,741
[45] Mar. 26, 1974
[54] METHOD OF FABRICATING AN OBJECT
WITH A THIN WALL HAVING A
PRECISELY SHAPED SLIT
[76] Inventors: James C. Fletcher, Administrator of
the National Aeronautics and Space
Administration with respect to an
invention of; P. A. Christopher; W.
J. Gross; W. H. Henley; B. D.
Swirsky
[22] Filed: Mar. 13, 1973
[ 2 1 ] Appl: No.: 340,864
[52] U.S. Cl ....: 29/423
[51 ] Int. Cl .B23p 17/00
[58] Field of Search 29/423, 156.8 H, 557, 558
[56] References Cited
UNITED STATES PATENTS
2.544,934 3/1951 Nase 250/27.5
3,043.147 7/1962 Will, Jr. 74/5
3.461,524 8/1969 Lepselter 29/423 X
3,564,682 2 / 1 9 7 1 ' Carroll, Jr. et al. 29/25.17
Primary Examiner—Charles W. Lanham
Assistant Examiner—V. A; DiPalma
Attorney, Agent, or Firm—John R. Manning; Howard
J. Osborn; Wallace J. Nelson
[57] ABSTRACT
A method of making a structure having a cavity and
having a thin wall with a precisely shaped slit. An ob-
ject having a cavity having two openings, one of which
is to be closed by a thin wall with a slit, is placed on
the surface of a fixture. The fixture surface has a slot
conforming to the size and shape of the slit to be
formed in the thin wall, and a shim member is inserted
into the slot such that it extends into the slot a dis-
tance deeper than the desired thickness of the thin
wall and such that it extends above the surface of the
fixture and into the cavity of the superposed object.
The object and fixture are fixed in position with the
slot properly located in the position of the slit to be
formed, and the cavity is filled with a molten sellable
material from its other end. After the mollen material
has set, the object is separated from the fixture, ihe
shim adhering to the set composition in the cavity of
the object. The surface of the object which was adja-
cent the fixlure is then provided with a plated metal
layer over the opening to be provided with a thin wall .
The plated layer is then machined such that the layer,
in the area covering the cavity opening, has the de-
sired thickness of the thin wall being provided. The
sellable material is then melled out The shim is then
removed by selective etching to produce ihe desired
slruclure.
10 Claims, 6 Drawing Figures
TNASA-Case-LAB-10409-1) METHOD OF
FABRICATING AN OBJECT WITH A THIN WALL
HAVING A PBECISELY SHAPED SLIT Patent
(NASA) 5 p CSCL 13H
N7U-21059>i
Unclas
00/15 33986
PATENTED HAR 2 6 1974 3.798J41
FIG. 1
FIG. 2
FIG. 3
FIG. 4 FIG. 5 FIG. 6
3,798,741
1 2
METHOD OT FABRICATING AN OBJECT WITH A that the portion of the shim extending above the sur-
THIN WALL HAVING A PRECISELY SHAPED SLIT face of the second member extends into the cavity, and
such that the slot is located relative to the cavity in the
The invention described herein was made in the per- desired position of the precision shaped slit, filling the
formance of work under a NASA contract and is sub- 5 cavity with a molten, sellable material composition
ject to the provisions of Section 305 of the National having a melting point lower than that of the first mem-
Aeronautics and Space Act of 1958, Public Law ber, the second member, and the shim member, permit-
85-568 (72 STAT. 435; 42 U.S.C. 2457). ting the molten sellable composition to set to a solid,
BACKGROUND OF THE INVENTION separating the first member from the second member,BACKUKOUINU Oh 1 Hh INVhN 11UN
 remaining with the first member due
This invention relates to a method of fabricating a 'to its adhesion to the solid material set in the cavity,
structure having a cavity closed by a thin wall having plating a metal layer on the second surface of the first
a thin slit extending therethrough. member, the thickness of the plated layer overlying the
The difficulties in machining apertures, particularly cavity being greater than the desired thickness of the
slit apertures, in thin cavity walls having a thickness of 15 thin well, the plated metal having a higher melting
from 0.0005 to 0.05 inches is well known. Such diffi- point than that of the set material in the cavity, machin-
culties are increased where the cavity is of complex . ing the plated layer such that the thickness ihereof
shape such as where access to a large cavity is through overlying the cavity is equal to the desired thickness of
a narrow opening or channel. the thin wall, heating the first member to melt the set
One particular aspect of this problem is to provide a 20 material, the shim member being held in place by adhe-
fluidic element for sensing the position of a gyroscope sion to the plated layer, removing the melted material
rotor. The element includes an enlarged cavity portion from the cavity, and removing the shim member from
closed by a thin wall having a precisely shaped slit. The said cavity to provide the element, the thin wall being
element also includes a small cavity portion opening at formed by the machined, plated, layer, and the pre-
one end to an outer surface of the element and at its 25 cisely shaped slit being formed by the removal of the
inner end to the larger cavity. It is thus difficult to gain shim member from the machined, plated layer.
access to the inner cavity with tools which would be
otherwise useful in providing a slit in the thin wall of DETAILED DESCRIPTION
the enlarged cavity. In use, a surface of a gyroscope There follows a detailed description of a preferred
rotor partially covers the slit, and it is necessary that 30 embodiment of the invention, together with accompa-
the slit is precisely shaped for effective operation. Con- nying drawings. However, it is to be understood that
ventional techniques for cutting the slit, such as ma- the detailed description and accompanying drawngs
chining with a slitting saw or photo etching, are not fea- are provided solely for the purpose of illustrating a pre-
sible for fabricating this element. ferred embodiment and that the invention is capable of
It is an object of the present invention to provide a 35 numerous modifications and variations apparent to
method of forming an element having a cavity closed those skilled in the art without departing from the spirit
by a thin wall having a precision shaped slit there- and scope of the invention.
through. It is a further object to provide such object of FIG. 1 is a diagrammatic sectional perspective view
metal. It is still a further object to provide such metal of a member including a cavity to be closed with a thin
object where the thickness of the thin wall is from 40 wall having a slit therethrough;
0.0005 to 0.05 inches. FIG. 2 is a diagrammatic perspective view of a shim
member used in the method of the present invention;
The foregoing and other objects which will be appar- FIG. 3 is a diagrammatic perspective seclional view
ent to those pf ordinary skill in the aft are achieved ac- 45 of a fixture member used in the method of the present
cording to the present invention by providing a method invention;
of forming an element having a cavity, the cavity hav- FIG. 4 is a diagrammatic perspective sectional view
ing in at least one portion a thin wall with a precision of the elements of FIGS. 1, 2 and 3 assembjed together;
shaped slit therethrough comprising the steps of pro-
viding a first member having a cavity therein, the cavity FIG. 5 is a diagrammatic perspective sectional view
being open at a first surface and at a second surface, of the element of FIG. 1 after being separated from the
the opening at the second surface being the portion of element of FIG. 3 and provided with a metal plated
the cavity which is to be provided with the thin wall layer; and
with the precision shaped slit, providing a second mem- FIG. 6 is a diagrammatic perspective sectional view
ber having a surface for receiving the second surface of of an element having a cavity closed with a thin wall
the first member, the surface of the second member having a slit therethrough according to the present in-
having a slot therein, the cross sectional area of the slot vention.
determining the cross sectional area of the slit to be FIG. 6 shows the final element produced by the pres-
provided in the thin wall of the cavity, the depth of the
 6Q ent invention. The element includes a cavity 10 having
slot being greater than the desired thickness of the thin a thin wall 11 (in this case 0.001 inches) having a preci-
wall, inserting a shim member in the slot, the shim sion shaped slit 12 (in this case 0.002 inches wide). The
member filling the cross sectional area of the slot for a element is made by a process illustrated in FIGS. 1-5
distance greater than the desired thickness of the thin as described below.
wall and extending above the surface of the second
 65 A first metal member 20 (FIG. 1) is provided having
member, positioning the first member on the second a cavity 10 open at a first surface 21 of element 20 and
member such that the second surface of the first mem- open at a second surface 22 of element 20, the opening
ber is adjacent the surface of the second member, such 23 at surface 22 being the portion of cavity 10 which
3,798,741
4
20
is to be provided with thin wall 11 having slit 12. A sec-
ond member 30 is provided having a surface 31 for re-
ceiving surface 22 of member 20. Surface 31 has a slot
36 having a cross sectional area the same as that de-
sired for slit 12 and having a depth greater than the 5
thickness of wall 11.
FIG. 2 shows a metal laminate shim 40 including a
central sheet piece 41 having a cross sectional area the
same as that desired for slit 12, and two outer sheet
pieces 42, 43, each having a thickness of 0.001 inches 10
and forming shoulders 44, 45 with central piece 41.
Central piece 41 extends beyond shoulders 44,45 a dis-
tance greater than the thickness of wall 11 and not
greater than the depth of slot 36.
The lower portion of shim 40 is inserted into slot 36 ''
as shown in FIG. 4 with shoulders 44, 45 abutting sur-
face 31 of member 30. Member 20 is then positioned
on member 30 as shown in FIG. 4 such that surface 22
of member 20 is adjacent surface 31 of member 30 with
the upper portion 46 of shim member 40 extending into
cavity 10, and with slot 36 is located relative to cavity
10 in the desired position of slit 12. Member 30 is con-
veniently provided with means, such as walls 33,34 and
35 to hold member 20 in this position for the next step
of the process.
Cavity 10 is then filled, through opening 13, with a
molten sellable melal material having a relatively low
melting poinl. Surface 31 of member 30 can be pro-
vided wilh a suitable release coating in the event that
 30
the set metal material tends to adhere thereto. After
the material in cavity 10 has set solid, member 30 is re-
moved and the lower (in the sense of FIG. 4) surface
of element 30 is electro plated with a layer 50 of nickel
or other suitable metal thicker than the desired thick- 35
ness of wall 11 as shown in FIG. 5.
The plated layer is then machined such that the
thickness of wall 11 in the area closing cavity 10 is the
desired thickness, in this case 0.001 inch. Since the ex-
tended portion 47 of shim 40 extends further than 40
0.001 inch, the machining operation will cut through
extended portion 47.
The object is now heated to melt out the set metal
composition and it will be apparent that the plated
metal layer 50,.metal shim 40, and metal element 20 all 45
have a higher melting point than that of the set metal
composition.
Shim 40 is removed by selective chemical etching,
the material of shim 40 being different from that of ele-
ment 20 and layer 50 and selectively attacked by the •50
etchant.
The invention has particular application to structures
in which wall 11 is not thicker than 0.05 inches and in
which slit 12 is not wider than 0.05 inches. In general,
wall 11 will be from 0.0005 to 0.05 inches in thickness 55
and slot 12 will be from 0.0005 to 0.05 inches in width.
60
While wall 11 has been shown flat and uniform in
cross section, it will be understood that it can take any
desired shape. For example, the bottom area of shim 40
may be concave and when plated metal layer 50 is ma-
chined, it may be machined concave to provide a con-
cave wall of uniform or varied cross section as desired.
Alternatively, the outer surface of layer 50 could be ,-
machined flat or convex. It will thus be understood that
the cross section of wall 11 in the finished article may
have virtually any desired cross section. Furthermore,
of course, a plurality of slits of desired shape can be
formed in any wall.
What is claimed is: -
1. A method of forming an element having a cavity,
said cavity having in at least one portion a thin wall
with a precision shaped slit therethrough comprising
the steps of:
providing a first member having a cavity therein, said
cavity being open at a first surface and at a second
surface, the opening at said second surface being
the portion of the cavity which is to be provided
with said thin wall with said precision shaped slit;
providing a second member having a surface for re-
ceiving said second surface of said first member,
said surface of said second member having a slot
therein, the cross sectional area of said slot deter-
mining the cross sectional area of the slit to be pro-
vided in said thin wall of said cavity and the depth
of said slot being greater than the desired thickness
of said thin wall;
inserting a shim member in said slot, said shim mem-
ber filling the cross sectional area of said slot for a
distance greater than the desired thickness of said
thin wall and extending above said surface of said
second member;
positioning said first member on said second member
such that said second surface of said first member
is adjacent said surface of said second member,
such that the portion of said shim extending above
said surface of said second member extends into
said cavity, and such that the slot is located relative
to said cavity in the desired position of said preci-
sion shaped slit;
filling said cavity with a molten, sellable material
composition having a melting point lower than that
of said first member, said second member, and said
shim member;
permitting the molten sellable composition to set to
a solid;
separating said fust member from said second mem-
ber, said shim member remaining with said firsl
member due lo ils adhesion to the solid material set
in said cavity;
plating a metal layer on said second surface of said
first member, the thickness of said plated layer
overlying said cavity being greater than the desired
thickness of said thin wall, said plated metal having
a higher melting point than that of said set material
in said cavity;
machining the plated layer such that the thickness
thereof overlying said cavity is equal to the desired
thickness of said thin wall;
heating said first member to melt said set material,
said shim member being held in place by adhesion
to said plated layer;
removing the melted, material from said cavity; and
removing said shim member from said cavity to pro-
vide said element, said thin wall being formed by
the machined, plated layer, and said precisely
shaped slit being formed by the removal of said
shim member from said machined, plated, layer.
2. A method according to claim 1 wherein said shim
member is fabricated of a metal different from said
plated metal and from said first member, and wherein
3,798,741
saidrsh,im is removed by etching with an etchant to
which said plated metal layer is inert.
3. A method according to claim 1 wherein said first
and second members are each metal.
4. A method according to claim 3 wherein said shim
member is metal.
5. A method according to claim 4 wherein said sella-
ble composition is metal.
6. A method according to claim 1 wherein said cavity
comprises a first, narrow, portion and a second, en-
larged portion, said enlarged portion having an opening
at said second surface of said first member provided
wilh said Ihin wall having a precision shaped slit, said
narrow portion exlending from said enlarged portion
10
and having an opening at said first surface of said first
member.
7. A method according to claim 1 wherein said sec-
ond member includes means for holding said first mem-
ber in position Ihereon.
8. A method according to claim 1 wherein said shim
member includes a shoulder abutting the surface of
said second member when inserted in said slot.
9. A method according to claim 1 wherein the struc-
ture is metal and wherein said thin wall has a thickness
of from 0.0005 inches lo 0.05 inches.
10. A method according lo claim 9 wherein the slit
width in said thin wall is from 0.0005 to 0.05 inches.
15
20
25
30
35
40
45
50
55
60
65


Method of fabricating an object with a thin wall having a precisely shaped slit

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server