Method and apparatus for removing plastic insulation from wire using cryogenic equipmen

Babb, B. D.

English

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REPLY TO 
ATTN OF: GGp 
NATIONAL AERONAUTICS A N D  SPACE ADMINISTRATION 
WASHINGTON, D.C. 20546 
- 
- 
Marshall 
November 6, 1970 
~ ~ I / S c i e n t i f  Fc & Tscknical In:~ormation Division 
. .ztenl;ion: fJl3.a~ W i z n i e  M e  btorgen 
~ ~ / ~ f f i c e  of AssL5Laqt General Coussel for  
Patent  Matters 
SUSJZCT: Announcement of NASA-Owned U. S. Patents  i n  S Z 3  
Xn zccordezce with the ~?::zze&~zes agzeed upon by Coda G? 
and Code UST,  the attached EPSA-o\w.ed U. S .' Patent Fr; 'cc-kzg 
forwarded f o r  zbstract ing and announcement i n  E3SA ST7Z. 
The f o l l a v i n ~  information is provided:: 
U. S. Patent  No. 
Gove~nment o r  
Corgorzte Employee 
Hayes International Corporation 
Huntsville, Alabama 35201 
Supplementary Cosporato 
Source ( i f  applicable) : 
: * . MFS-10340 NASA Patent  Case No. . 
hrOTE - X f  thfs patent covers ;zn invention made by corporate 
employee of a NASA ~oritractor, the following is z9plicale: 
yes so Cr 
Pursuant to Section 305(a) of the Ua-Lional Aero~autics a d  
Space Act, the n&?e of the Adrrrinistr..ztor of N-SA appeaxs on 
the first pzge of the patent; however. the name of the acCual 
inventor (author) appears at the heading of Column Xu. 1 oE 
1 .  
- - t k e  Specification, following khe,wosds a. . . with respect to 
- lizabeth - A, Carter 
. - -  
Z~closure 
Copy of Patent oited abwa 
f 
(AccESsr  NUMBER) 
0 
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(NAG cR QR TMX OR AD NUMBER] 9 
https://ntrs.nasa.gov/search.jsp?R=19710008153 2020-03-17T02:46:15+00:00Z
April 21, 1970 JAMES E. WEBB 3,507,425 
ADMINISTRATOR OF THE NATIONAL A E R O N A U T I C S  
A N D  S P A C E  ADMIRIISTRAliON 
METAOD AND APPARATUS F O R  CRYOGENIC WIRE S T R I P P I N G  
F i l e d  March 26,  1968 2 Sheets-Sheet 1 
INVEM VOR(S1 
BILLY D. B P  ' 
April 21, 1970 JAMES E. WEBB 3,507,425 
ADW11NISTRATOR OF THE NATIONAL AERONAUTICS  
A N D  S P A C E  ADMlNISPRABiQN 
METHOD AND APPARATUS F O R  CRYOGENIC W I R E  S T R I P P I N G  
P i l e d  March 20, 1968 d Sheets-Sheex z 
9Tg. PA 
ATTORNEYS 
United States Patent Offi 3,507,425 ce Pa,,,, ed A,,* 21: ,970 
of cleaning the wire before a good electrical connection 3,507,425 
METHOD Am FOR can be made. Moreover, thermal stripping of some types 
WIRE STRIPPIIVG of plastic insulation may generate noxious fumes. 
James E. Webb, Administrator of the National Aeronau- 
tics and Saace Administration. with respect to an inven- SUMMARY OF THE INVENTION 
tion of Biity D. Babb, ~ a d i s o h ,  Ala. 
- 
r )  
Accordingly, it is an object of this invention to pro- 
Filed Mar. 28,1968, Ser. No. 716,734 
Int. 621. B23p 19/02; B26f 3/00; H02g 1/12 vide an in~proved method and apparatus for stripping 
U.S. CI. 225-1 , Claims wire which neither contaminates, mars, nor damages the wire during the insulation stripping process. 
i n  Still another obiect of this invention is to provide a -- 
ABSTRACT OF THE DISCLOSURE method and apparatus for wire stripping which eliminates 
the need for either thermal treatment of the insulation or 
A method and apparatus for rernovi~g the plastic in- heating elements incorporated into the apparatus. 
sulation from wire by dipping the wire into a cryogenic Yet another object of the invention is to provide a 
liquid so as to freeze the insulation and cause it to 15 method and apparatus for wire stripping which elimi- 
crystallize, breaking the frozen insulation by impacting nates the need for clamping of the wire or the use of 
it with cutters, and then stripping off the fractured in- clamps which physically grip the wire in any way. 
sulation. The apparatus includes a programmer and a These and other objects are acconlplished in the pres- 
fully automatic device for lifting the wire out of the ent invention which includes a method of cryogenic wire 
cryogenic liquid and impacting the wire between fixed 20 stripping. A wire is inserted into the cryogenic liquid 
and movable cutters, thus preparing the wire for strip. SO as to freeze the insulation and cause it to crystallize. 
ping by hand or with a hand tool. The insulation is then impacted with at least one cutter 
at the point where stripping is to be started, in order to 
cut the insulation part way through and fracture the re- 
BACICGROUND OF THE INVENTION 25 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 85-568 30 
(72 Stat. 435; 42 U.S.C. 2457). 
FIELD O F  THE INVENTION 
This invention relates to a method and apparatus for 
wire stripping and more particularly to a method and 35 
apparatus for cryogenic stripping of plastic insulation 
from wire. 
maining thickness -of the insulation. Finally, the insula- 
tion is removed between the impacted point and the 
end. The device for fracturing the insulation of a wire 
to  be stripped comprises a container for a cryogenic 
liquid, a cryogenic liquid in the container for freezing the 
insulation of a wire to be stripped, and means for im- 
pacting the frozen insulation of a wire to be stripped. 
BRIEF DESCRIPTION OF THE DRAWINGS 
The invention will be more fully understood when 
taken together with the accompanying drawings in which: 
FIGURE 1 is a plan view of an enclosed cryogenic 
wire stripping device, made in accordance with this in- 
DESCRIPTION OF THE PRIOR ART vention. FIGURE 2 is a vertical sectional view of the cryogenic 
The stripping of insulation from the ends of electrically wire stripping device of FIGURE 1, taken alone line 
ccmductive wire for purposes of making necessary elec- 2-2 of FIGURE 1. 
tro-mechanical connections is generally achieved by me. 
cl anical means which cut through the insulation of the DESCRIPTION OF THE PREFERRED 
w re beiore removing the same. Such devices frequently ., EMBODIMENT 
result in damage to the wile in the folm of a nick or cut '" With continued reference to the accompanying figures, 
in the wire itself. In many applications, particularly those 2nd with initial attention di~ected to FIGURE 1, there is 
in which the apparatus incorpo~ating the wires is sub- illustrated in plan view a typical embodiment of the 
ject to severe envi~onmental accelerations, failure is often present invention, designated generally by the numela1 
caused by electiical wiles which have been weakened or 16. A base housing 12, shown in the lower portion of 
damaged during the insulation stlipping process. In fact, 50 FIGURE 1, is the primary housing for the device. Top 
it is quite possible that a complex apparatus such as, for 14 is secuiely fastened to base housing 12 by screws 16. 
example, a multi-million dollar misslle may be lost be- Mounted on top of base houstng top 14 is a control hous- 
cause of the failure of a single elect~ical wire connection. ing 18, which contains conttol circuitry for the device, 
Such a fallure may be traced to damage to the wire ;,j '1s will be exp1,iined more fully hereinaftel. Housing 18 
caused dui~ng the st~lpplng of i n s ~ ~ l ~ i i ~ o n  The problenl faiterred to sop I 4  by sclews 20, which ale of the 
of h ~ g h  quality wile stripping is a chclllenging one and s m e  type 2s ?clews 15. At the top of housing 48 1s shown 
r n i ~ ~ h  effoit has been expended la ~ l s  olttt~on. il siait-swltch bution 2% and the bead 2% of a Ilft  solenoid 
One solution to the need fol hrgh yuaiity wire ship- >top bolt, both of vii~icli will be desclibed later. An im- 
ping has been the development of thermal strippers. 60 pact solenord housing 26 1s attached to the side of base 
However, such str~ppels ale complex devices contam- housing 12. Wlre input guide 28 may be seen mounted 
ing heating elements to melt the insulation of the wire. in the base housing top 14. 
In addition, such devices ~asually incorporate clamps which Mounted adjacent to base housing 12 is a cryogenic 
may possibly damage the wire through physical contact liquid reservoir 30, wh~ch is connected to base housing 
with ~ t .  Thermal stripping leaves a residue film on the 12, as will be desciibed later. In the top of reservoir 30 
wire, thus cleating a ~equirernent f o ~  an additional step 13' ib a fill hole and screw-rn fill cap 32 with a vent hole 34. 
3 4 
FIGURE 1, which is T .ic~f::al secrlonal view mkcn the end of a wile to be strip?ed, by dipping it into a 
t h r o u ~ h  base housing 12, conlrof hoasing 18, and impact ciyogenic laquid for a few seconds axd then impacting 
solenoid housirrg 26, sho\rls the detailed constrtlct~on of thc frozen insulation with one or more cuftcrs, the in- 
the invention. & the leal of the device. as viewed in sulation nlay be fraciuied around the entire circumfer- 
FIGURE 2, may be seen the uppei portion of cryogenic ence of the wire w~ti~out  eve1 toucliing the wile itself. 
l iqu~d reservoir 36) and its fill cap 32. As can be seen Moreover, no thermal processing or heating elements 
clearly in FIGURE 2, base housing 12 has an inner wall need be used and the wire need not be gripped by clamps. 
36 which helps enclose an evacuated area 38. Top 14 The apparatus disclosed herein auton~atically prepares a 
of base plate housing 12 has an inner wall 4O which helps wire for stripping, once the wire has been inserted into 
enclose evacuated area 42. Wire guide 44 may be seen the device and the stat-button actuated. The device then 
mounted directly below wire input guide 28. On the right functions automatically to lift the wire out of the cryo- 
side of base housing 12, as viewed in FIGURE 2, may be genic liquid and impact the frozen insulation so as to 
seen screws 27 which fasten impact solenoid housing 26 fracture it and thus prepare it for hand stripping. 
to the base 12. Obviously, nun~erous modifications and variations of 
A cutting assembly, indicated generally by numeral 46, 15 the present invention are possible in the light of the above 
is shown on the right side of FIGURE 2. Stationary cut- teachings. It is therefore to be understood that, within 
ter 48 is securely mounted on the unde~side of top 14, the scope of the attendant claims, the invention may be 
adjacent to wire input guide 28, by a pair of screws 50. practiced otherwise than is specifically prescribed. 
Moveable cutter 52 is fastened to the armature 54 of What is claimed is: 
impact solenoid 56. Solenoid 56 is mounted in inipact 20 1. A method of stripping insulation flom the end of 
solenoid housing 26 by screws 57. Stationary cutter 48 wire comprising the steps of: 
and moveable cutter 5% are positioned opposite each other (a)  inserting the end of the wire into a cryogenc liquid, 
with the cutting edge of their blades in the hoiizontal so as to freeze the insulation and cause it to crystal- 
plane, as viewed in FIGURE 2. lize; 
A wire lift assenrbly, indicated generally by numeral 25 (b) impacting the insulation with at least one cuttei a t  
58, is shown in the center portion of FIGURE 2. Wile the point where stlipping is to be started, in order 
stop platform 60 is attached to armature 62 of wire lift to cut the insulation pait way through and fracture 
solenoid 64. Armature 62 travels through guide bearing the remaining thickness of the insulation; 
66. Upward travel of armature 62 is adjusted by limit (c) relnoving the insulation between the impacted point 
stop bolt 68, which is threaded into nut 70. Nut 70 is 30 and the end. 
welded to the underside of control housing 18. Down- 2. The method of stripping insulation from the end of 
ward travel of platform 60 is limited by stop poltion 72. a wile of claim 1 wherein the icsulation between the im- 
A small concave portion 94 is provided in platform 60 pacted point and the end of the wire is lemoved by hand. 
for ~eceiving the end of a wire to be stripped. 3. The method of stripping insulation from the end of 
A cryogenic liquid fill mechanism, indicated generally 35 a wile of claim 1 wherein the insulation between the im- 
by numeral 76, is shown at the left side of FIGURE 2. pacted point and the end of the wire is removed by hand 
Fill mechanism 76 maintains the proper level of cryo- through the use of a hand tool. 
genic liquid "1 in the container 78 formed by the inner 4. An apparatus for fracturing the insulation of a wire 
wall 36 of the base housing 12. A connecting pipe (not to be stripped, comprising: 
shown) connects cryogenic liquid reservoir 30 with con- 40 (a)  a container fol a c r ~ ~ g e n i c  l quid; 
tainer 78 and terminates at cryogenic liquid inlet $0. Stop (b) a c~yogenic liquid in said container, for freezing 
valve 82 mounted on armature 84 of fill solenoid 86 con- the insulation of a wile to be stripped; 
trols the flow of ciyogenic liquid from inlet 80. Arma- (c) means for impacting the frozen insulation of a wire 
ture 84 travels through guide bearing $7. Fill solenoid to be stripped, said impacting means comprising: 
86 is controlled by microswitch 88 and liquid level float $5 ( 1 )  a movable cutter, arranged and positioned so 
90 in a manner well known to those who are skilled in as to move in a dilection normal to the axis of 
the art. the wire to he stripped; 
The control circuit for the device includes start-switch (2) a stationa~y cutter mounted opposite said 
button 22 and programmer-sequence timer 92, which is moveable cutter, and 
known in the art, and is not per se considered patentably 50 ( 3 )  an impact solenoid connected to said moveable 
distinct. cutter. 
One cycle of operation of the device is as follows: The 5. The apparatus for fracturing the insulation of a wire 
end of a wire to be stripped of insulation is inserted into to be stripped of claim 4 including a wire lifting mecha- 
wire input guide 28 and pushed down through wire guide nism, said mechanism complising: 
44 until the end of the wire protrudes into cryogenic 55 (a)  a wile lift solenoid mounted above said container, 
liquid 77 and contacts concave portion 74 of wire stop said solenoid including an elongated armatuie which 
platform 60. After a time delay of the order of fifteen extends down into said container; 
seconds pre-set into programmer 92, which allows the (b)  a wile stop platform attached to said armature and 
end of the wile to freeze and the insulation of the wire extending under said cutting mechanism, for stopping 
to crystallize, the programmer 82 actuates lift solenoid the downward travel of a wire in said CI yogenic liquid 
64. This raises platform 60, thus l~fting the frozen por- and then lifting the frozen portion of the wire into 
tion of the wire to be stripped to a posltion opposlte the position between said cuttels, said platform having 
cutters 48 and 52. Programrnel 9% then actuates lmpact 
a lower liniit stop portlon extending do~vnward to 
solenoid 56, causing the wire to be impacted by move- 
able cutter 52 and stattonay cutre1 48. T h ~ s  cuts the 's touch the bottom of said containel; and 
surface of the froiea rnsulation on fnlo  ides to a cleplir ( c )  an adjrrstabfe stop for sard armature ntot~nted ahove 
of about one-third of the th~cliness of ihe tnsrllalion and said solenoid. 
causes the remaining portion of the in~ulation to frac- 6 The apparatus for fractu~lng the insulat~on of a wlre 
Lure. ~l~~ wire is t:len removed from the device and the to be stripped of c!aim 5 including a ciyogenic liquid fill 
insulation between the point of f~acture and the end of 70 mzchanism, comprising: 
the wire is easily removed by hand or with a hand tool. (a)  a cryogenzc liquid reservoir mounted beside and 
Fiom the foregoing it may be seen that applicant has connected to said cor~tainer; 
invented both a novel method of stlipping insulation (b) a cryogenic liquid level float; 
f ~ o m  the end of a wile and a novel apparatus for car- (c)  a n~icioswitch connected to said float: 
rying out the method. By first freezing the insulation on 75 (d) a fill solenoid connected to said microswitch, said 
3,507,425 
5 6 
solenoid including a n  elongateii arrnnit~i-c 1.vhich es- References Cited 
ierrtls cEomn iit!o s ~ , i i i  con tairier; ;rnd 
( t . )  a stop \~:ilv? connccted to said fill solenoid arma- UNITED STATES PATENTS 
ture, for controlling the fiow of cryogenic liquid 2,849,005 3/1959 larvis ------_-_--- 241-65 X 
fro111 said reservoir to said container. 2,956,717 10/1960 Scharf ----------- 81-9.51 X 
4. The apparatus for f~acturiitg the insulation of a \.?,ire 2,919,862 1/1960 Beike et al. -_---- 241-65 X 
to be stripped of claim 4 including a control circuit corn- 3,101,757 8/1963 Ilanson ---------- 81-9.51 X 
prising: 
(a) a programmer connected to said wire lift solenoid JAMES M. MEISTER, Primary Examiner 
and said impact solenoid, for controlling the opera- 
tion of said solenoids in sequence; and U.S. C1. X.R. 
(b)  means for starting said programmer. 29-427; 81-9.51; 225-103 


Method and apparatus for cryogenic wire stripping Patent

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