A propellant cutting assembly and method of using the assembly to cut samples of solid propellant in a repeatable and consistent manner is disclosed. The cutting assembly utilizes two parallel extension beams which are shorter than the diameter of a central bore of an annular solid propellant grain and can be loaded into the central bore. The assembly is equipped with retaining heads at its respective ends and an adjustment mechanism to position and wedge the assembly within the central bore. One end of the assembly is equipped with a cutting blade apparatus which can be extended beyond the end of the extension beams to cut into the solid propellant

Hoskins, Shawn W.

Payne, Brett D.

Sharp, Roger A.

NASA Technical Reports Server

I 11111 111ll Il1 Il11 III 111l11111 III 11111 1ll1111ll11 
US006378436B3 
(12) United States Patent (io) Patent No.: US 6,378,436 B1 
Sharp et al. (45) Date of Patent: Apr. 30,2002 
PORTABLE PROPELLANT CUTTING 
ASSEMBLY, AND METHOD OF CUTTING 
PROPELLANT WITH ASSEMBLY 
Inventors: Roger A. Sharp, Brigham City; Shawn 
W. Hoskins; Brett D. Payne, both of 
Tremonton, all of UT (US) 
Assignee: Cordant Technologies Inc., Salt Lake 
City, UT (US) 
Subject to any disclaimer, the term of this 
patent is extended or adjusted under 35 
U.S.C. 154(b) by 0 days. 
Notice: 
Appl. No.: 09/506,597 
Filed: Feb. 18, 2000 
Related U.S. Application Data 
Provisional application No. 601125,644, filed on Feb. 22, 
1999. 
Int. C1.7 .................................................. C06D 5/06 
U.S. C1. ....................... 102/287; 1021290; 1021292; 
Field of Search ................................. 1021287, 288, 
1021293; 86120; 86112 
1021289, 290, 291, 292, 293; 86120, 12 
(56) References Cited 
U.S. PATENT DOCUMENTS 
802,347 A * 1011905 Aspinwall ................... 1021292 
930,979 A * 811909 Maxim ....................... 1021292 
3,183,665 A * 511965 Webb ......................... 1021287 
4,148,187 A * 411979 Younkin ................. 1021287 X 
4,552,706 A * 1111985 Ducote ................... 1021290 X 
5,417,161 A * 511995 Sanai et al. ................. 1021290 
5,892,172 A * 411999 Candland et al. ........... 1021292 
* cited by examiner 
Primary Examinerqeter  A. Nelson 
(57) ABSTRACT 
A propellant cutting assembly and method of using the 
assembly to cut samples of solid propellant in a repeatable 
and consistent manner is disclosed. The cutting assembly 
utilizes two parallel extension beams which are shorter than 
the diameter of a central bore of an annular solid propellant 
grain and can be loaded into the central bore. The assembly 
is equipped with retaining heads at its respective ends and an 
adjustment mechanism to position and wedge the assembly 
within the central bore. One end of the assembly is equipped 
with a cutting blade apparatus which can be extended 
beyond the end of the extension beams to cut into the solid 
propellant. 
9 Claims, 3 Drawing Sheets 
c 
https://ntrs.nasa.gov/search.jsp?R=20080005010 2019-08-30T02:49:22+00:00Z
U S .  Patent Apr. 30,2002 Sheet 1 of 3 US 6,378,436 B1 
U.S. Patent Apr. 30,2002 Sheet 2 of 3 
J 
US 6,378,436 B1 
NG. 2 
FIG. 3 
U S .  Patent Apr. 30,2002 Sheet 3 of 3 
FIG. 5 
FIG. 4 
US 6,378,436 B1 
p o o  
US 6,378,436 B3 
2 
retaining head permits relative movement of the distal and 
proximal retaining heads away from and towards each other. 
When the retaining heads are moved towards each other into 
a loading position, the distance between the curvilinear 
s surfaces of the distal and proximal retaining heads is less 
than the diameter of the central bore. As a consequence, the 
assembly may be loaded into the central bore and positioned 
so that the extension beams are oriented as desired. The 
adjustment mechanism can then be actuated to increase the 
i o  distance between the proximal and distal retaining heads so 
that the distance between the curvilinear surfaces of the 
distal and proximal retaining heads is substantially equal, 
but slightly smaller than, the diameter of the central bore. As 
a consequence, the curvilinear surfaces of the heads contact 
is diametrically opposed positions of the inner surface of the 
propellant grain and wedge the assembly into position. A 
cutting blade assembly is provided at the proximal end of the 
extension beams. A driving mechanism is provided to drive 
the cutting blade past the ends of the extension beams and 
20 into the solid propellant. Alevel is also provided to orient the 
blade appropriately for achieving a cut of uniform thickness. 
This invention is also directed to a process of making 
radial cuts in a propellant grain with the above-discussed 
assembly for the purpose of removing samples for testing 
This invention may be used for sampling various types of 
central-perforatedpropellant grains and hybrid fuel grains. 
These and other objects, features, and advantages of the 
present invention will become apparent from the following 
30 detailed description which, when taken in conjunction with 
the accompanying drawings, serve to further describe the 
principles of this invention. 
25 and analysis. 
BRIEF DESCRIPTION OF THE DRAWINGS 
35 The accompanying drawings serve to elucidate the prin- 
ciples of this invention. In such drawings: 
FIG. 1 is a schematic overhead view of a propellant 
cutting assembly in accordance with an embodiment of this 
4o invention, with the assembly being shown loaded into the 
central bore of a propellant grain and in an operative 
position; 
FIG. 2 is an enlarged schematic view of a subassembly of 
the assembly of FIG. 1, showing a cutting blade in coop- 
FIG. 3 is an enlarged schematic view of a subassembly of 
the assembly of FIG. 1, showing an adjustment mechanism 
operatively connecting a distal retaining head to extension 
beams; 
FIG. 4 is a cross-sectional view of a cutting blade; and 
FIG. 5 is an overhead view depicting the relative position 
between the blade and the propellant grain during cutting 
operation. 
DETAILED DESCRIPTION OF THE 
INVENTION 
In the illustrated embodiment, the assembly includes two 
parallel extension beams 10. Preferably, the beams 10 are 
made of a high strength aluminum, although other metals 
60 and alloys may be used, so long as the material has sufficient 
strength to retain its structure and configuration during 
operation. At the distal end of the extension beams 10, a 
traversing bar 12 connects the beams 10 and maintains the 
parallel spacing between the distal ends of the beams 10. A 
65 platform 14 arranged in proximity to the proximal end of the 
extension beams 10 maintains the parallel spacing of the 
beams 10 at the proximate end. 
45 erative association with a load cell; 
50 
55 
1 
PORTABLE PROPELLANT CUTTING 
ASSEMBLY, AND METHOD OF CUTTING 
PROPELLANT WITH ASSEMBLY 
RELATED APPLICATION 
This application claims the benefit of U.S. provisional 
application No. 601125,644, filed Feb. 22, 1999. 
GOVERNMENT LICENSE RIGHTS 
The U.S. Government has a paid-up license in this inven- 
tion and the right in limited circumstances to require the 
patent owner to license others on reasonable terms as 
provided for by the terms of contract NAS8-38100 awarded 
by NASA. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an assembly for cutting samples 
from a center-perforated solid propellant grain for testing 
and evaluation purposes, and to a method of cutting the solid 
propellant grain with the assembly. 
2. Description of the Related Art 
Solid propellant rocket motors contain a solid propellant 
comprised of various ingredients, including binders, for 
example, curing agents and catalysts, fuels, oxidizers, and 
fillers. The presence of each of these ingredients in accept- 
able concentrations and consistencies is essential for ensur- 
ing proper and predictable motor operation upon ignition of 
the solid propellant. 
Therefore, substantial amounts of testing are performed 
on solid propellant grains. These tests usually involve 
removing a sample from the propellant grain after it is cast 
and cured. Removal of the propellant grain sample has 
conventionally involved the use of manual cutting tools, 
such as knives and saws. However, a drawback of manual 
cutting of the propellant grain is production of inconsistent 
shaped samples with insufficiently smooth surfaces to permit 
satisfactory analysis and testing. Another drawback of these 
manual techniques is that the manual cutting of the propel- 
lant grain places the operator at great risk from, for instance, 
an accidental ignition of the propellant. 
SUMMARY OF THE INVENTION 
It is therefore an object of this invention to provide a 
propellant cutting assembly and process that significantly 
improves the repeatability and consistency of the cut sample 
while reducing the risk from accidental ignition. 
In accordance with the principles of this invention, this 
and other objects are attained by the provision of a solid 
propellant cutting assembly suitable for making radial cuts 
into an annular solid propellant grain having a central bore 
of a predetermined diameter. In accordance with an embodi- 
ment of this invention, the assembly comprises one or more 
extension beams extending in length between a proximal 
end and a distal end thereof. The length of the extension 
beams is less than the diameter of the central bore so as to 
permit the assembly to be loaded into the central bore. 
Proximal and distal retaining heads are respectively pro- 
vided at proximal and distal ends of the extension beams. 
Preferably, the retaining heads have respective curvilinear 
surfaces that are complementary to an inner surface of the 
central bore and face away from the extension beams. An 
adjustment mechanism interposed between the extension 
beams and either the distal retaining head or the proximal 
US 6,378,436 B1 
3 4 
The extension beams 10 and platform 14 may be made The cutting blade 18 is extended past the ends of the 
from Aluminum 6061-T6 or 6063-T52. extension beams and into the solid propellant 100 to cut into 
As shown in FIGS. 1 and 3, distal retaining head 16 the propellant 100. The cutting blade 18 is driven and 
includes an outer surface with a curvilinear face having a controlled by the screw jack mechanism 22 and the load 
diameter matching that of the inner surface of the propellant 5 exerted can be monitored by the load cell 24. 
grain 100. During radial cutting of the propellant grain 100, The foregoing detailed description of the preferred 
movement of blade 18 into the propellant 100 imparts a load embodiments of the invention has been provided for the 
in the opposite direction, i.e., towards the distal retaining purposes of illustration and description, It is not intended to head 16. Configuring the curvilinear surface of the distal be exhaustive or to limit the invention to the precise embod.- retaining head 16 to be complementary to the inner surface 
10 ments disclosed. Many modifications and variations will be of the propellant grain 100 optimizes interfacial contact and 
hence, distribution of this load Over a greater portion of thi apparent to practitioners skilled in this art. The embodiments 
propellant grain The retaining heads may include a were chosen and described in order to best explain the 
padding such as rubber, on the surfaces, principles of the invention and its practical application, 
In the illustrated embodiment, an adjusting mechanism 20 thereby enabling others skilled in the art to understand the 
is interposed between the extension beams 10 and the distal 15 invention for various embodiments and with various modi- 
retaining head 16, B~ way of and without fications as are suited to the particular use contemplated. It 
limitation, the adjusting mechanism 20 can have a stud 2oU is intended that the scope of the invention cover various 
engagement with a screw-threaded aperture of the traversing scope of the appended claims. 
bar 12, as is shown in FIG. 3. Reference numerals 20b and 20 
20c designate a nut and bushing, respectively. Rotation of 
the screw-threaded adjusting mechanism in the appropriate 
direction moves the screw away from the traversing bar 12, 
thereby increasing the distance between the distal and proxi- 
mal he ads. 
As shown in FIG. 2, a screw jack 22 is positioned on the 
platform 14 and cooperatively engaged with the blade 18 via 
an optional load cell 24 and bracket 26. Reference numeral 
28 designates set screws for attaching block 30 to the blade 
18, The load cell 24 
18 to monitor for irregularities and permit repeatability of 
the testing. A suitable load cell 24 is an Omegadyne LC402- 
2K with a DP 25-5 meter and PT106F-10-6s connector. The 
screw jack 22 is driven by an air motor, although other 
motors and driving mechanism may be used and would be 35 
apparent to those skilled in the art when considered in 
conjunction with this disclosure. For example, an electric or 
hydraulic motor may be used. A flow control valve may be 
used to provide variable control over the rate at which the 
screw jack 22 is rotated. The motor may be equipped with 40 
a gear reducer to control torque. Design of a suitable gear 
reducer is within the purview of those skilled in the art. As 
is evident from this description, the illustrated embodiment 
permits the operator to control the cutting operation from a 
remote location. 
In a preferred embodiment, the blade 18 is made of 17-4 
PH stainless steel, and has a curvilinear edge, which pref- 
erably is complementary to the bore-defining inner surface 
of the propellant grain 100. As shown in FIG. 4, the blade 
18 preferably has a flat back with a double bevel. Preferably, 50 
the length of the lower bevel (A) is 0.125 inch; angle B is 
8 to 12 degrees, preferably 10 degrees; and angle C is 5 to 
9 degrees, preferably 7 degrees. 
A preferred cutting operation will now be explained with 
reference to FIG. 5. Prior to making a radial cut with the 55 
assembly, longitudinal cuts are made into the propellant 
grain 100 manually, with the longitudinal cuts being spaced 
by a distance no greater than the width of the cutting blade 
18 so as to avoid tearing of the propellant 100. As shown in 
FIG. 5,  the distance Z (i.e., between the non-cutting edge of 60 
the blade 18 and the edge of the propellant 100) was about 
1.55 to 1.60 inches, whereas the distance W (between the 
cutting edge of the blade and the edge of the propellant 100) 
was about 1.25 inches. The length of the blade was about 
9.75 inches. In this manner, a radial cut of substantially 65 
uniform thickness was obtained using as little as 204 lbs. of 
cutting force. 
with a Screw threaded outer surface region in cooperative modifications and equivalents included within the spirit and 
We claim: 
1. A solid propellant cutting assembly suitable for making 
radial cuts into an annular solid propellant grain having a 
central bore of a predetermined diameter, said assembly 
comprising: 
one or more extension beams extending in length between 
a proximal end and a distal end, the length of said 
extension beams being less than the diameter of the 
central bore; 
a distal retaining head provided at said distal end of said 
extension beams, said distal retaining head having a 
curvilinear surface that is complementary to an inner 
surface of the central bore and faces away from said 
extension beams; 
a proximal retaining head provided at said proximal end 
of said extension beams, said proximal retaining head 
having a curvilinear surface that is complementary to 
the inner surface of the central bore and faces away 
from said extension beams; 
an adjustment mechanism cooperatively connecting said 
extension beams to either said distal retaining head or 
said proximal retaining head, said adjustment mecha- 
nism being constructed and arranged to permit relative 
movement of said distal and proximal retaining heads 
towards and away from each other between a loading 
position, in which the distance between said curvilinear 
surfaces of said distal and proximal retaining heads is 
less than the diameter of the central bore to permit 
loading of said assembly into said central bore, and an 
operative Position, in which the distance between said 
curvilinear surfaces of said distal and proximal retain- 
ing heads is approximately equal to the diameter of the 
central bore to permit said support beams and retaining 
heads to be collectively wedged in and supported at 
diametrically opposed Positions of the inner surface of 
the solid propellant grain; 
a planar blade having a cutting edge, said blade being 
movable along at least a portion of the length of said 
extension beams to a position in which said blade 
extends beyond said proximal end of said extension 
beams so that, by placing said assembly in the operative 
position, movement of said cutting edge of said blade 
by a sufficient distance beyond said proximal end 
makes a radial cut into the solid propellant grain; and 
a level constructed and arranged to control the orientation 
of said blade relative to the propellant grain when said 
assembly is in the operative position. 
25 
the force applied to the blade 3o 
45 
US 6,378,436 B3 
5 6 
2. An assembly according to claim 1, further comprising 
a piston for moving said blade relative to said extension 
beams. 
3. An assembly according to claim 2, wherein said piston 
4. An assembly according to claim 2, further comprising 
a motor for driving the piston relative to said extension 
beams. 
5. An assembly according to claim 4, further comprising 
6. An assembly according to claim 1, further comprising 
7. An assembly according to claim 1, wherein said blade 
8. A process for cutting samples from an annular solid IS 
is a screw jack. 5 
a gear reducer for controlling cutting speed. 10 
a load cell for measuring cutting force. 
is remotely operable. 
propellant grain having a central bore of a predetermined 
diameter, said process comprising: 
providing the assembly of claim 1; 
positioning the assembly within the central bore of the 
solid propellant grain; 
orienting the extension beams and blade to permit move- 
ment of said blade along a horizontal direction and 
moving the distal and proximal retaining heads away 
from each other via the adjustment mechanism to 
wedge the assembly between diametrically opposed 
portions of the inner surface of the solid propellant 
grain; 
cutting longitudinal seams into the propellant grain, the 
seams being spaced by a distance no greater than the 
width of the blade; and 
making a radial cut into the propellant grain with the blade 
between the seams to obtain a sample. 
9. Aprocess according to claim 8, wherein the propellant 
grain is cut to a thickness of about 1.25 inches. 
* * * * *  


Portable propellant cutting assembly, and method of cutting propellant with assembly

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server