Piston in bore cutter for severing parachute control lines and sealing cable hole to prevent water leakage into loa

Chandler, J. A.

Grubbs, T. M.

English

NASA Technical Reports Server

REPLY TO 
ATTN OF: GP 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON, D.C. 20546 - 
October 16, 1970 
TO : USI/Scientific & Technical Information Division 
Attention: 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 contained in the Code GP 
to Code US1 memorandum on this subject, dated June 8, 1970, 
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. 3,320,669 
Corporate Source Manned Spacecraft Center 
Supplementary 
Corporate Source 
NASA Patent Case NO,: ms-04072 
Enclosure: 
Copy of Patent 
& 
(NASA CR OR TMX OR AD NUMBER) 
(THRU) 
(CODE) 
/5 
(CATEGORY) N ASA-H Q 
https://ntrs.nasa.gov/search.jsp?R=19700032701 2020-03-17T02:16:04+00:00Z
May 23, 196 J. A. CHANDLER ETAL 3,320,669 
LINE CUTTER 
Filed Sept. 8 ,  1965 2 Sheets-Sheet 1 
5 
J. A, CHANDLER E T A L  3,320,669 
LINE CUTTER 
F i l e d  Sept. b,, 1965 2 Sheets-Sheet 2 
SQ 
/$ (17 39 25 
55 
45 7' I 
atent ce 
3,320,669 
LINE CUTHTER 
Joseuh A. Chandler. Dickinson. and Thomas M. Grubbs. 
buston, Tex., k s i g n ~ r ~  to the United States of 
America as represented by the Administrator of the 
National Aeronautics and Space Administration 
;Filed Sefl. 8, 1945, ser. No. 485,960 
14 Claims. tCl. 30-228) 
'I he invention described herein may be manufactured 
and used by or  for the Government of the United States 
of America for governmental purposes without the pay- 
ment of any royalties thereon or therefor. 
This invention relates to cable cutting tools, and more 
particularly to a device for cutting control lines on para- 
chutes or the like when the b a d  connected thereto is like- 
ly to descend on a body of water. 
In the recovery of certain types of scientific instru- 
ments, spacecnaft, and other loads descending by para- 
chute, a swift retrieval is essential in order to  avoid loss 
or damage thereto by the elements. Due to the unpre- 
dictable nature of winds, the load will oftentimes alight 
on a body of water where, because of the partial inflation 
of the parachute, it will ibe driven in varying directions, 
thereby causing additional delay before recovery. A 
common expedient for precluding this delay is the use 
of automatic cable cutters which sever the parachute con- 
trol lines from the load upon impact with the Iwater. In 
the construction and attachment of these lines to a load 
it is often required to attach them internally of the load 
itself because of their connection to motors controlling 
various guide panels on the parachute. Thus the aper- 
tures in the spacecraft wall through which the lines extend 
become unobstructed holes when the lines ,are severed. 
Upon contact with the water, seepage into the load will 
result, causing damage to the electrical parts, scientific 
equipment, or other components therein. Various de- 
vices such as cutter means in association with a mechani- 
cal type closure for shutting out the w'ater have been de- 
vised to preclude such results, but all are either compli- 
cated in structure or present unsatisfactory results. The 
intstant invention is directed to a device which not only 
obviates the aforementioned problem, but does so with a 
mechanism which is simple in design and completely effec- 
tive in result. It embodies a piston-in-bore type cutter 
in which the piston's dynamic force is utilized to both 
sever the cable and to pressurize 'a viscous grease housed 
in the bore end. The grease, upon impact 'by the piston, 
is forced into sealing relation around the piston adjacent 
the cable hole or eye, thus precluding any leakage into 
the load. Aside from effectively severing the cable and 
insulating the h a d  from seepage, it will be seen that due 
to the simplicity of the structure the chances of malfunc- 
tion are practicalIy nonexistent, and the cost of construc- 
tion is minimal. 
These and numerous other features of the invention 
will 'become apparent to the reader upon examination of 
the following detailed description, claims, ,and drawings 
wherein: 
FIG. 1 shows a half section perspective v i m  of the 
improved cutter of the invention; 
FIG. 2 shows a sectional view along the longitudinal 
axis of the cutter; 
FIG. 3 shows an end view of the improved cutter with 
the rear plate removed therefrom; and 
FIG. 4 shows in plan view the cutter of FIG. 1. 
As shown in FIG. 1, the cutter includes a frame or 
'body housing 3 which is generally rectangular in exterior 
shape and which has a longitudinal bore 5 extending from 
the forward end 7 to the rearward end 9. It should be 
noticed that the bore is of larger diameter at the forward 
end than a t  the rearward, the two ends being joined, how- 
ever, )by the sloping common wall or shoulder 10 at ap- 
proximately the longitudinal center of the housing. At 
the fol;ward end of the housing is forward plate 19 which 
has circular threaded hole I1 therein of smaller radius than 
the bore, but in axial alignment therewith. A squib or 
other explosive cartridge means is threaded into the hole 
11. The forward plate 19 is disposed over a recessed con- 
ventional O-ring 19 and is afltixed to the housing 3 by a 
washer ,and allan-head lock nuts 13. The rearplate-15 
is aflixed to the rear of housing 3 in the same manner 
and completely encloses that end. 
As shown in FIGS. 1 and 2, there is an aperture or eye 
19 at the rear of the housing, extending through the ]bore 
walls perpendicular to the longitudinal axis. The para- 
15 chute cable 20 extends through this aperture with one 
end connected to the control panels of the parachute and 
the other end to the control motor inside the load. The 
eye 19, which as shown in FIGS. 1 and 4 to be elongate 
in form, has both a forwtard 21  and a rearward 23 end, 
20 with the latter serving as the cutting base when severance 
(OCCUTS. The eye is elongated to allow for oscillating 
movement of the cable during payout or retraction. 
A series of apertures extend outwardly from the bore. 
At the forward end is aperture 29 through which extends 
25 ,a shear pin 31 so designed to extend into the piston and 
to withhold movement of it in the bore and retain it ad- 
jacent the squib until the latter is fired. Approximately 
halfway down the axis of the bore's large end, and ex- 
tending radially into the bore, is a first vent 33, the pur- 
30 pose of which is to vent pyrotechnic gases generated on 
explosion of the squib. The venting occurs 'after the 
cable has been severed and is therefore merely to relieve 
internal pressure in the large end of the bore. Disposed 
further down the bore toward the rear end plate, is a 
35 second vent 37 for venting compressed gas in front of the 
piston's sloped wall 39 as it moves down the bore. By 
placing the vents in front and lbehind the piston there is 
little, if any, velocity reduction in the piston's movement 
toward the oable. An annular impact washer 41  made of 
40 soft lead or other equivalent material, is set in the bore 
in abutting relation to the shoulder 10 for absorbing the 
kinetic energy of the moving piston, 
With reference to FIGS. 3 and 4 there is shown a pair 
of bores or metering grooves 43, 45 disposed in axially 
45 parallel relation to the main bore 5 at 120" and 240" to 
the vertical. The grooves, which transfer a viscous 
grease or equivalent substance 44 (see FIG. 2 )  from the 
rear end of the bore to the surface of the piston adjacent 
the eye, are radially disposed near enough to the bore 
50 axis to provide a communicating slot or opening 47 of 
somewhat smaller dimension than the groove itself. The 
metering grooves extend from the rear plate 15 past the 
forward edge 21 of the eye, thus assuring transference 9f 
the grease completely over the piston's surface. 
Extending outwardly from the metering grooves adja- 
cent the forwardmost end thereof are smaller grooves or 
holes 51 for venting the grease after it has traversed the 
metering grooves 43, thus precluding excessive pressure 
buildup in the rear end of the cutter. 
As previously explained, the entire cutter is aflixed to 
the load as by a mounting plate 55, and is in proximate 
relation to  the control motor (schematically shown in 
FIG. 1) which pays out and retracts the cable extending 
to the parachute control panel. Upon impact of the load 
65 with the water, an electrical signal closes a switch and 
fires the squib in the cutter's forward end 7. The pres- 
sure instantaneously overcomes the resisting force of pin 
31, shearing it off and propelling the piston toward the 
cable a t  the rear of the housing. Although initial con- '' tact of the piston and cable may occur at the forward wall 
21 of the eye 19, no shear action occurs until the cable 
is pushed to the rear wall 23, at which time shear occurs 
55 
80 
. . .  
3,320,669 
3 
with the sheared piece of cable 57 being carried down 
the bore into the viscous grease (FIG. 1). Upon impact, 
the grease is forced into the metering grooves 43, 45 
which transmit it to the forward end 21 of eye 19. When 
the grooves 43, 45 are completely filled, the grease, due 5 
to the piston’s continued dynamic force, is pressured fur- 
ther into the bore 5 itself, encircling the piston 25 and 
thus filling any voids or passages in the bore around eye 
19. It is, of course, recognized that the dimensions of 
the piston, bore, and piston travel are such as to allow 
impact of the piston with the grease before there is con- 
tact between the piston wall 39 and the impact washer 
41. After contact, over-pressurization and kick back are 
prevented by the aforementioned small vents 51 which 
allow the viscous grease to escape when under high 15 
pressure. 
It is apparent that various modifications and altera- 
tions to the instant invention may be made. For exam- 
ple, the metering grooves may be disposed in the piston 
itself rather than in the bore, and likewise the piston, 20 
bore, and cutter in general may assume different shapes 
and configurations. While the cuttes is primarily in- 
tended for use in severing lines on parachutes, it is obvi- 
ously useful in other applications where insulation is 
required upon severance of a transverse cable, rope, or 
similar means. Thus it should be recognized that such 
alterations and modifications are within both the spirit 
and scope of the instant disclosure and may be made with- 
out departing from the invention as defined by the ap- 
pended claims. 
That which is claimed is: 
1. In an explosive line cutter: 
a barrel having a pair of holes disposed in the barrel 
bore and forming therewith a transverse eye to re- 
ceive a line: 
a piston in the bore forward of the eye and adapted to 
be impelled rearward by an explosive charge; 
a viscous insulative substance in said bore rearward of 
the eye; and 
an end plate on the rear of the barrel closing the bore 
so that ignition of the explosive charge drives said 
piston into said substance thereby compressing it 
around said piston adjacent said transverse eye. 
2. The explosive line cutter of claim 1 wherein said 
barrel bore has forward and rearward sections, said rear- 
ward section being of smaller cross section than said for- 
ward section and separated therefrom by a common 
shoulder, and said piston likewise has a forward and rear- 
ward section with said rearward section being of smaller 
cross section than said forward section with each said 
piston sections connected by a common wall so that the 
kinetic energy of said piston is absorbed in part by said 
bore common shoulder upon impact by said piston wall. 
3. The explosive line cutter of claim 2 wherein an im- 
pact washer of relatively soft material is disposed in said 
bore against said common shoulder so as to further absorb 
kinetic energy of said moving piston. 
4. In a n  explosive line cutter; 
a barrel having a pair of holes forming with the barrel 
bore a transverse eye to  receive a line; 
a piston in the bore forward of the eye and adapted to 
be impelled rearward to sever the line; 
an explosive element forward of the piston; 
25 
30 
35 
40 
45 
50 
55 
60 
a viscous insulative substance in said bore rearward 
of the eye; and 
an end plate on the rear of the barrel closing said bore 
so that ignition of said explosive element drives said 
piston into said substance, thereby compressing it 
around said piston adjacent said transverse eye. 
5. The explosive line cutter of claim 4 wherein said 
explosive element is a squib fixedly disposed in said for- 
ward end plate. 
6.  The structure of claim 1 wherein said explosive line 
cutter has means therein to facilitate movement of said 
viscous substance along the bore to the eye upon impact 
of the substance by the piston. 
7. The structure of claim 6 wherein said means includes 
a channel proximate said eye and in communicative rela- 
tion with said viscous substance. 
8. The explosive line cutter of claim 4 wherein said 
barrel bore contains channel means therein proximate said 
eye and in communicative relation with said viscous in- 
d a t i v e  substance. 
9. The explosive line cutter of claim 2 wherein said 
barrel bore rearward section has channel means therein 
proximate said eye and in communicative relation with 
said viscous substance. 
10. The structure of claim 8 wherein said channel 
means are disposed parallel to the longitudinal axis of 
said bore. 
11. The explosive line cutter recited in claim 2 wherein 
a first gas vent is disposed in said forward bore rearward 
of said piston; and 
a second gas vent is disposed in said forward bore for- 
12. The explosive line cutter of claim 2 wherein said 
barrel bore rearward section has metering grooves there- 
in forward of said eye for alleviating excessive pressure 
buildup by said viscous substance upon impact by said 
piston. 
13. The explosive line cutter of claim 4 wherein said 
barrel bore has metering grooves proximate said eye but 
forward thereof, for relieving excessive pressure buildup 
by said viscous substance upon impact by said piston. 
14. The structure of claim 13 wherein said explosive 
cutter has channel means therein to facilitate movement 
of said viscous substance along the bore toward the eye 
upon impact of the substance by the piston. 
References Cited by the Examiner 
UNITED STATES PATENTS 
3,003,235 10/1961 Temple et al. _ _ _ _ _ _ _ _ _  30-180 
3,267,573 8/1966 Hill _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  30-228 
References Cited by the Applicant 
UNITED STATES PATENTS 
ward of said piston. 
2,581,645 1/1952 Frieder e t  al. 
2,755,550 7/1956 Benjamin. 
2,924,147 2/1960 Bohl et al. 
2,926,565 3/1960 Thorness. 
WILLIAM FELDMAN, Primary Examiner. 
JIMMY C. PETERS, Assistant Examiner, 


Line cutter Patent

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