Method for making screen with unlimited fineness of mesh and screen thicknes

Hansen, S.

English

NASA Technical Reports Server

REPLY TO 
ATTN OF: 
FROM : 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASI-IINGTON. D.C. 20546 
October 15, 1970 
~ ~ ~ / ~ c i e n t i f i c  & Technical Information Divis ion 
Attent ion:  M i s s  Winnie M. Morgan 
~ ~ / 0 f f i c e  of A s s i s t a n t  General 
Counsel f o r  P a t e n t  Matters  
SUBJECT: Announcement of NASA-Owned 
U.S. Pa ten t s  i n  STAR 
I n  accordance wi th  t h e  procedures contained i n  t h e  Code GP 
t o  Code US1 memorandum on t h i s  s u b j e c t ,  dated June 8, 1970, 
t h e  a t t ached  NASA-owned U.S. p a t e n t  i s  being forwarded f o r  
a b s t r a c t i n g  and announcement i n  NASA STAR. 
The fol lowing information i s  provided: 
U.S. Patent ,No.  
Corporate Source : Hushes A i r c r a f t  Company 
Supplementary 
Corporate source 
NASA Patent  C a s e  No.: XLE-00953 
P lease  note  t h a t  t h i s  p a t e n t  covers an invent ion  made by an 
employee of a NASA con t rac to r .  Pursuant t o  Sec t ion  305(a) of 
t h e  Nat ional  Aeronautics and Space Act, t h e  name of t h e  
Administrator  of NASA appears  on t h e  f i r s t  page of t h e  p a t e n t ;  
however, t h e  name of t h e  a c t u a l  inventor  (author)  appears a t  
t h e  heading of Column No. 1 of t h e  Spec i f i ca t ion ,  following t h e  
words 'I .  . , with  r e s p e c t  t o  a n  invent ion  o f ,  . . . I 1  
- 
- 
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I 
Gayle Parker n 
(ACF;? I 
Enclosure:  
CODV of Pa tent  2 
(lH2 
E 
2 
u (NASA CR OR TMX OR AD NUMBER) 
Z' (CATEGORY) 
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https://ntrs.nasa.gov/search.jsp?R=19710006491 2020-03-17T02:41:08+00:00Z

1 
March 1, 11966 JAMES E. WEBB 3,23";i,2%3 
ADMINISIRAiOR O F  THE NAT1QNAt AERONAUTICS 
P,ND SPACE ADMlNlSVRAIiOU 
METHOD OF @AXING SCREEN BY CASTING 
Filed Jan. 7, 1964 E SheetsSbeet 8 
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United States Patent 06 ce Patented Mar. 3,239,253 1, 1966
FIG. 6 iifustrates an embodiment %.herein spherical 
3,235,253 particles of iron having an aluminurn coatins appl id 
BTETHOD OF 3tTd4;lXfNG SCREEN BY CbSTmG thereto are u;iIiztrd James E. %"ebb, Adrrcirtistr~tor of fhe Kationd Aeronau- FIG. 7 shows a vat of chemical reagent with a film tics and Space Administrafjon nith respect to an i n v e -  and immeM therein. tion of Sie~+rried Ransen 
Filed Jan. '3,1964, Ser. No. 336,320 Referring now to the drawing, the apparajus iifudratrtd 
5 Claims. (C1. 22-2001 in FIG. 1 is a vacuum evaporator whicb is emploved to 
practice the preseat invention. The vacuum e;,aiorator 
This invention relates to the manlrfacture of mesh includes a bzlljar 4 which is adapted to be mounted on a 
or screen and more particularly it relates to a method 10 base 6. Belijar 4 has a heater element 8 mounted in the 
cf making screen in which the finesness of mesh is es- upper portion thereof and heater element 8 h s  electrical 
sentially unlimited and the screen can be made in m y  connections 10 and 12 connected thereto wtiich extend 
desired thickness regardless of mesh size. outride the &?!jar for connecting the heater element to a 
The' prior art is rc-eplcte with methods of fabricating current s o u r e  (not shown). Base 6 has an aperture 14 
screen, but these methods are complicated and have un- 1.5 formed therein to which a vacullm pump is connected for 
desirable limitations which are eliminated by the presea pmducin_c.a vacuum v;ithin the belljar. A pair of Helm- 
invention. For example, the maximum fineness cf holtz coi!s 16 and 17 are arranged around and closely ad- 
mesh which can b", obtail?ed by conventional methods jacent to the belljar and these coils are supported by s u p  
of making screeo is in the vicinity of five hundred holes port means 18 and 19 mounted to the base. A plate 20 
per linear inch. Further, as the mesh is made finer 20 is supported within the belljar on a pair of supprts  22 
-the screen thickness which can be had are limited and and 23. Plate 20 has a removable rim 24 mounted 
thus, for many applications, even though a screen of thereon and a pluralky of particles 26 are positioned on 
the proper mesh can be made, such screen is too thin the plate ~ylthin the area defined by rim 24. Rim 24 can 
and flimsy. be held in pasition by zny suitable means (not shown). 
There is a need in the field of eledronics, partica- 25 The practice of the present invention requires that par- 
Iarly in electronic tubes and ion devices, for grids on. ticles 26 k stlbstantidlp evenly distributed in a single 
screens having a fine mesh. The prrrent invention pr* layer over the surface of pla:e 20 within the area bounded 
riides a method of making screen which has niore than by rim 21 (wz FIG. 2). The quantity of particles placed 
five hundred holes per linear inch and can be made in on plate 20 is such rhzt there is one particle present for  " 
any desired thickness. This is accomplished, brest:, Do each holz desired in the finished screen. Particle s i x  is 
by positioning a larpe number of particles in 3 single determined b y  the size holes desired in the finished screen 
layer on a plate, the number of particles corresponding in that the holes in the finished screen corespond sub- 
to fhe number of holes per linear inch desired in ths stantially to the sue  of the particles. The paiticles axe 
screen. A film or  coating of a suitzblc materi~l is t h 3  disposed in a sin& Ir.yer %sen they are poured or placed 
applied to the plate and this film partially surrounds ~2 33 on plate 20. The pasides do not occupy all the surface 
particles. The film and par;iclzs are then removed f r o a  area of the plate ~ i t h i n  rim 24 and thrrefore the 
ihe plate and placed in a suitable chemical reagent %*here particles tend to ~ ~ i e 1 3  o u t  in a sin,~!e layer as they are 
zhe particles are dissolved out and only the film, poured on :5s pfate. If necessary, the puticles can be 
perforations v:herr the particles were, remains. The pr* ,9 vibrated, by t igp~ng the 3!a!e, to assure that the particles 
e& invention, in addition to having the advantages men- are seduced to a sh$s layer. Even spacing or distribn- 
tjcned above, also an improved and simpler tion of the p3~icl;-s is achieved, as will be d;s=ussed in 
method of making o d i n a ~  screen ha.zing a ~eJa'jve?f more ds!ct:I hireinafter, by subjecting the particles Eo the 
coarse mesh. magnetic fieid generated by the Helmholtz coil. In 
It  is therefore a principal object of this in\ren;ion to 43 exhibit unifarm magnetic properties. Therefore, the 
provide an improved and simplified process for makkg particles, shown as sp3erisal in FIG. 2, must be uniform 
mesb or screen. 5u:t::hle mi-3e:i: 1natt5aI having sufiicient magnetic 
An additional object of this invention is to prov& ~rmc3bi f i t j .  ti3 be rnagnelized by the magnetic field 
a method t f  making a screen having a very fine mesh- genersted ti hea &$ H?lnrholtz coils are energized. The 
A yet further obyct of this inveniion is to pro+idc quantity and Si-ze of pzr-'dc?es used is determined by the 
a method of making a screen wherein rhe thickness of finefiess of mesh desired in th.e screen being made. 
such screen is not limited or determined by the s:ze of Xeferr5ng @n to FIG. I ,  ~ i l h  the belljar removed 
the holes therein. (not s h o ~ n )  a plurd!ity of par:icles are placed in a sir?& 
Other objects and advantages of the pre*nt in=* 1")" on t k  plate ~ I i h i n  the area defined by the rim, 
tion will bz more filly ur,derrtmd by conridering := 5.7 The HeImhoitz coils are then energi7ed to create a ver- 
following deiajied descrjplion, ia onjunction wi& tically oricn:ed uniform magnetic field in the area oc- 
accompznyk,o Br3wZngs; whexeh: cugicil by :h plate 20. iin 2-1 and panicles ?6. The 
RG, is a side in section, supports for xire We:3bo!tz coiis and plate 20, as  well 
w z h g  vacuum evaporalar appara&s emp?ojcd ~ J J  ca**ng pfafe '' and rim ''- L*e of a n n n m a ~ e ~ i ~  
oirt the invention. rn~tcri31 so 2 5  IO n~1: 23ec1 the magnetic %1d me: presence of Z k  irr:agne?lc Fztfd cauwr each of ifhc pariicks 
TITr. is a plan of plate wiib Ihr. remo"nb'e lo be50rilG r;- b:-,rrizs-J ~ - ; 6  ciji70{e ch2rac~er~-;;ics 
rim mounted thereon 2nd a ~IuraGiy of spher~cal p.4ck.s ii5crcin each r3fliclec acquires a is 
&persed on the plate Ln a uniform army. orien!ed the s z m  as ~d jacen t  prlicles. In other words, 
FIG. 3 is a view of a portion of the plate wi& tf?z the magnegc 6eIJ crtc=es e:ch of the particles to acquire 
sphericat pariiiiclt-5 6Lsp05d lkr2011 and tungsten fifm 6j.5 a ncptive ;md posiiirr fGle and she p!is of ae par- 
deposiled on said pfrre around the pariicles. fictes 2re aliped o r  s r ra~ged  the szniz. As a result of 
FIG. 4 is a view sfrniiar lo FIG. 3 il!us:ra2ing this like pr?jzriurion 3 nurual repulsion js %t up i\stwsen 
use of rod-shaped paflicks rather &an spitericaf particles. the panirlci and t h y  a:%sin an e~G1ibr:~rn eonfiScraiioa 
FIG. 5 is simzlar to RG. 4 except that the rcd-shapd ;O itl wblrh dl the pzrticks are uniformly qaced on & 
. 
Lron particles have a mating of aiilmindm zppfied there- plate. Xf c e c e s ~ y  t5-, arti ides can be vibmted, by 
to; tapping the ~13s for hstxnce, to nld in their d k ~ r s i o n  
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over the plate. The belljar is then replaced, in the posi- b plate 10, A layer of tungstea 33 will be dtsposiied 
?ion shown in FIG. 1, and the inti-rior of thc vacuum on the upper surface cf each of the rod+shaped particles 
evaporator is evacuated by ihe vacuum pump. Heater 34, however, inas~nuch as the tungsten vapor is again 
element 8, contains a quantity of iung5te.n which is deporited downnardly jn a vertical path there aiil tx 
vaporized when the heater elcrnent is encrgiad. The 5 no tungsten deposits on  thc vertical surfaces, indicated 
tungsten vapor descends downwardly in a vertical pS!h by the numeral 35, of the rod-shaped particles hetween 
to f o r n ~  a thin film 29 on the plate. The heating element ihe upper end thereof and the upper surface of tungsten 
8 of  the vacuum evaporator is elevated above plate 20 layer 36. 
sufficiently so that the tungsten vapor will he descend- Ano:her embodiment of  be invention is illustraled in 
ing downwardly toward the plate in  a vertical palh per- 10 FIG. 5. In this embodinert  the iron particles are re- 
pendicillar t o  plate 20 when the vapor readtes the upper placed with particles 38 c o m p o ~ d  of an  iron rod o r  
surface theieof. \%'hen the particles are  spherical i t  is cy5nder 40 having a coating of aluminum 39 applied 
necesszry that the thickness of the film deposited not therelo. The aatilminum coated particles are unifpmly 
exceed one ha!f the diameter of the particles. The rea- d i sp rwd  and a tungsten film a;lplied therearound in the 
son for  this thickness limitation will be more readily 15 same manner as discussed heretofore. However, after 
unders!ood by considering FIG. 3 of the drawings which removal fronl the plate the parlicles and film are heated 
is an  enlarged view of a portion of plate 20 having a raiher than immersed in a chemical reagent. The melt- 
fiim 29 and particles 26 dispowd theieon. Due to the ing point of aluminum is 660 degrees centigrade. Iron 
fact that the lungrten vapor dzbcends down\vardIy in a melts a t  1535 degrees centigrade and tungsten melts at 
vertical path there will be no tungsten deposited o n  the 20 3370 degrees centigrade. Therefore, if the film and 
surface area of the spherical particles indicated by the ~nrticles are &led to a te:nperature in excess of 660 
numeral 28 in FIG. 3. This area extends from the degrees centi~rade, the alumini~m costing will melt and 
center of the sphere, indicated by center line 25, down- the iron pariicles will drop out of the tungsten film 
wardly to  the upper surface of film 29. Also, due to leaving only the tungsten film with holes therein hav- 
the vertical path of the tungsten vapor there will be n o  25 irig a dinmeter equal t o  tbe dian~eter of the composite 
build up of tungsten against the underside of the spheres rod-shaped particles. 
in t h ~ .  area indicated by the numeral 31. Thus, the hales The embodiment shown in FIG. 6 is similar t o  that 
in the screen will be circular and equal to the di,zmeler illu5trated in FIG. 5 except that spherical-shaped p ~ r t i -  
of the sphcrc 26. The tungsten film will, hourever, con- cles 32 having an iron_ co:; 4: and an  aluminum outer 
tact and adhere io the spl~erital particles at  the point 30 conting 36 applied thereto are employed rather lhan rod- 
indicated by the nun~eral 32. When the lungsten film shaped particles. 
has been deposited upon the plate, the He?:nholtz coils, This comp:eies the detailed description of the inven- 
the heater elendent, and vacuum pump are turned off tion, havievcr, it should Se znderstcod tknt many changes 
and the be1lj:ir is removed from base 6 .  Rim 24 is re- and niodifications rhereto, by those skilled in the art lo 
moved from plate 20 and the titng\tcn film and particles 33 which this invention pertains, can be made without de- 
are stripped from plalz 20. Tbe film and partjc!es are  parting from the spirit and scope of the invention a s  
then immersed in a ~uitiible chemical reajient 37, see defined by thc claims appended hereto. 
FIG. 7, which \ r i l l  discolve the particles and leave only What is claimed is: 
a tungsten iilm in the form of a screen. It is  apparent 1. The method of making a screen coinprising tbe 
from FIG. 3 that film 29 is in contact around the sur- 40 stepsof: 
face of sphere 26 only at a point indicated by the nu- ( a )  placing a plurality of magnetically permeable 
rneral 32; thus when the spheres are subjected t o  the sphe1ic.11 panicies on a nonmagnetic plate within 
aclion of the chemical reagent, the particles will either an  area defined by a nonmaznetic rinl nlounled on 
faif out of the film %hen a small an~oun t  of the outer said plate, 
portion of the sphere has k c n  disolved o r  will be dis- (b) subjecting 5aid particles to a vertically oriented 
solved completely if left in .the chemical rqgent  long " magnetic field %hereby said particles will be d i o  
enough. The 1a;er of tung$icn 27 deposited upon the perscd and nssun~e a position wherein said spherical 
spherical panicles during the evaporation process will panicles are substantially evenly spaced in a single 
also fall away when the spherical particles either falls layer on said plate within the area defined by said 
away o r  is dissolved by the chemical reagent rim, 
The particles 26, film 29, and chenlical reagent c3n (c) depositing a film that adheres to said pnrticles, said 
br compozed of any suitable substance -,vithin certain film being deposited on said plate around the parti- 
linlits. Particles 26 must have sufficient nlagnctic per- cles, said film being deposited to a thickness that 
meability so as to be substantially evenly dispersed over is less than one half the diarneter of said particles, 
the surfilce of plate 20 when subjected to a rn,rfnelic 53 (d) removing said fitm and particles from said pla~e, 
field. The composition of  the fi!m material would be and 
determined by the 11t8 for which the screen is intended (t) dissolving said pa;ticies from the film to form a 
and the chemical reagent used must be such that the screen. 
particles anJ not ?he fiirn will Ite dissolved. 2. T i e  rneti~od of making a screen comprising the 
bVhen s,~bericai p~rricles are utilized the thicLness of G:! steps of: 
the screen \:hich c3n be produced, as discussed above, (a), p!acing a plurajity of magnetically permeable, rod- 
is limited la one h d l f  the diameter of the spheres. No%- snaped parlicies o n  a nonmagnetic plaze wrthio an  
ever, if it hr: ili,iicd to produce a screen of greater thick- area defined by a noarnagoefir: rim mounted on 
necs, an arrangement s ~ b  as rhnt shosbn in FIG. 4 can said piate, 
be u-:;lizcd. Ta %is e;rii?m-iimcn? fhe spherical pafiiries bi3 ti31 sukjci t ing =id rod-shqxiii p.rr?icks to a verlia1iy 
have been replaced wit5 rod-rhapci_! o r  cylindrical parti- oriented mape i i c  field wliercby said rud-shayzd 
cles 31 cnrnposed of a suitable magnetic material. A particles uifl be ~ispersed and :issscurne a positiort 
film having a ~hickness sli&rly less than fengh of  wherein s3id rod-shaped particles are mbsiantialty 
the rod can be deposited and, if a thicker film is desired ebcnly spaced in a single :ayer over s ~ i d  pfAe within 
it is onfy necessary t o  employ rods of greater length. io an area dsfincd by said r'm; and, ihe 1nnpi:udinaf 
'When the r d s  are subjected to the magnetic field Fro- axes of said rod-sha,wd panides wjfl be a:igned p r -  
duced by the I?ieimhol% coils they will not only be uni- pendiculat. to said plate, 
Sarnrly spaced. due to  a liked ppofarizarion, as in ihe r a w  fc)  depositing a film that rrdhcres to .;aid pa&liclcs, 
of tie sphericnl psrticles, but they urill asrurne a posi- said film being deposited on said plsle around the 
tion in which \ h i r  longitudinal axes are pcrpendieuJar 75 rod-sh;lped partjcles. =id film being deposited to a 



Method of making screen by casting Patent

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