U.S. patent number 3,708,993 [Application Number 04/871,277] was granted by the patent office on 1973-01-09 for solidified gas pellets and apparatus for manufacturing.
This patent grant is currently assigned to Chemetron Corporation. Invention is credited to Robert C. Hardt, Edward Kozlow.
United States Patent |
3,708,993 |
Hardt , et al. |
January 9, 1973 |
SOLIDIFIED GAS PELLETS AND APPARATUS FOR MANUFACTURING
Abstract
Carbon dioxide pellets of a high density formed in a manner to
break easily into minute pieces yet not agglomerate during
shipment, together with a head member for a pellet machine to form
pellets of this kind.
Inventors: |
Hardt; Robert C. (Chicago
Heights, IL), Kozlow; Edward (Homewood, IL) |
Assignee: |
Chemetron Corporation (Chicago,
IL)
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Family
ID: |
25357095 |
Appl.
No.: |
04/871,277 |
Filed: |
November 12, 1969 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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660790 |
Aug 15, 1967 |
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Current U.S.
Class: |
62/605 |
Current CPC
Class: |
C01B
32/55 (20170801) |
Current International
Class: |
C01B
31/22 (20060101); C01B 31/00 (20060101); F25j
001/00 (); F25j 003/00 () |
Field of
Search: |
;62/10,35
;18/12A,12P |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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484,570 |
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Oct 1929 |
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DD |
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805,534 |
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Apr 1936 |
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FR |
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1,172,242 |
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Jun 1964 |
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DT |
|
Primary Examiner: Yudkoff; Norman
Assistant Examiner: Purcell; A. F.
Parent Case Text
This application is a division of application Ser. No. 660,790
filed Aug. 15, 1967 and now abandoned.
Claims
We claim:
1. The method of forming pellets of solid carbon dioxide comprising
the steps of providing a quantity of carbon dioxide snow in a
compression cylinder having an extrusion head, compacting the snow
into a plug against said head, maintaining said plug against said
head while extruding successive portions of said plug through a
passage in said head, said passage having a length to diameter
ratio of about 1:1 and a frusto-conical section with an included
angle not exceeding 15.degree. and its larger diameter at its
discharge end.
2. The method of claim 1 wherein successive portions of the solid
carbon dioxide plug are first passed through a straight wall
section of said passage.
3. The method of claim 1 wherein successive portions of the solid
carbon dioxide are first passed through a converging wall section
of said passage.
4. The method of claim 3 wherein said passage has a length to
diameter ratio of about 1:1.
5. An apparatus for making rod-like carbon dioxide pellets,
comprising a closed chamber, means for flashing liquefied carbon
dioxide into said chamber to form carbon dioxide snow, an extrusion
head at one end of said chamber, said head having a compression
side and a discharge side and at least one passage having a length
about equal to its diameter and a frusto-conical section with an
included angle not exceeding 15.degree. communicating with said
sides of said head, said passage having its widest dimension
proximate to said discharge side of said head, a ram reciprocable
in said chamber toward and away from said head, the end of said ram
at the end of its compression stroke terminating short of said
compression side a distance sufficient to provide a plug of
compacted snow across said passage.
6. The apparatus as defined in claim 5 wherein each said passage is
about one-half inch long and further includes a converging wall
portion with the widest dimension in direct communication with the
compression side of said head, the diameter of said passage being
from three-eights to five-eights of an inch.
7. The apparatus as defined in claim 5 wherein each said passage
further includes an annular straight wall section in direct
communication with the compression side of said head at one end and
said conical section at the other end.
8. The apparatus as defined in claim 6 wherein said converging wall
and said conical section are contiguous in said head at their
narrowest dimensions.
9. The apparatus as defined in claim 8 wherein a plurality of said
passages are disposed in a circular manner in said head with an
additional passage disposed in the center of said circular
arrangement.
10. The apparatus as defined in claim 6 wherein said conical
section has a narrower taper than said converging wall.
Description
This invention relates in general to pellet machines and to pellets
produced by pellet machines of the reciprocating plunger type. More
particularly, this invention is concerned with pellet machines for
manufacturing frangible pellets from liquefied gas and to the
pellets so formed.
The customary practice of furnishing finely shaved or crushed solid
carbon dioxide presents problems to the user because of its
tendency to cake. The prior art as described in U.S. Pat. Nos.
1,919,698; 2,200,577 and 3,077,081 illustrates carbon dioxide
pellets in the form of rods which are cut or otherwise severed into
smaller pellets. In copending application Ser. No. 500,426 rods of
carbon dioxide formed with random transverse fracture lines which
can be broken into pellets are described. However, carbon dioxide
pellets manufactured by prior methods do not have the desired
configuration and density to make them separate or shatter into
small pieces for better heat transfer purposes when they are, for
example, ground into food or other materials during a grinding
stage and yet be capable of non-agglomeration during shipment thus
affording free flow at time of use. It has now been discovered in
operating the apparatus therein disclosed in U.S. Pat. No.
3,576,112, application for which was copending herewith filed Oct.
21, 1965 with a specially designed head or die that a novel
configuration of a carbon dioxide pellet which promotes breaking up
of the pellet into minute pieces could be produced.
It is accordingly an object of the present invention to provide a
novel rod-like pellet formed from a liquefied gas. Another object
of this invention is to provide an apparatus for producing laminar
type pellets of a unique configuration. Still another object of
this invention is to provide a novel carbon dioxide pellet having a
high density and ability to break into minute pieces. It is yet
another object to provide an apparatus for producing the unique
carbon dioxide pellets at a rapid rate.
These, and other objects of this invention, will be readily
appreciated by reference to the following detailed description when
considered in conjunction with the accompanying drawing
wherein:
FIG. 1 is a vertical sectional view of a pellet machine for making
the novel pellets of this invention.
FIG. 2 is a view in horizontal section taken along line 2--2 of
FIG. 1.
FIG. 3 is a view in vertical section taken along line 3--3 of FIG.
2.
FIG. 4 is a fragmentary view of the head member of the pellet
machine shown in FIG. 1 illustrating pellets being ejected
therefrom.
FIG. 5 is a view in vertical section of an alternative head member
for a pellet machine such as shown in FIG. 1 for making the present
novel pellets.
FIG. 6 is a perspective view of the novel pellet of this
invention.
FIG. 7 is a view in horizontal section taken along line 7--7 of
FIG. 6.
FIG. 8 is a view in vertical section taken along line 8--8 of FIG.
6.
Briefly stated the novel carbon dioxide pellets are formed in a
pellet machine having a reciprocating piston wherein liquid carbon
dioxide is sprayed into a chamber, expanded into snow and then
compressed and extruded through openings in a head member which is
counterbored from each side of the head to present either: (a) a
converging-diverging wall surface or (b) an annular straight wall
contiguous with a diverging wall. The pellets produced in such a
head member are formed with a solid core and have integral,
uniformly spaced, radiating projections extending from the core
formed with oblique lines of fracture substantially completely
around the core. The relatively uniformly spaced projections are
somewhat concavo-convex with the convex side in the direction of
flow as it is extruded from the pellet machine. The core of the
pellets forms about 10 to 25 percent of the cross-sectional area
through the concavo-convex radiating projections and the pellets
have a specific density in the range of 60 pounds per cubic foot to
about 95 pounds per cubic foot.
Referring now to the drawings there is shown an apparatus generally
indicated at 10 for making pellets, for example pellets 32 of solid
carbon dioxide. The apparatus 10 in its overall operation is
generally similar to that described in the previously referred to
copending patent application Ser. No. 500,426 filed Oct. 21, 1965.
Any suitable drive mechanism can be used such as the one
illustrated in the copending patent application having the usual
crank shaft and a connecting rod attached to a guide 16 which is
mounted for reciprocation in a bore 18 in block 19. As guide 16 is
reciprocated in bore 18, ram 17 rigidly bolted to the upper surface
of guide 16 by bolt 15 is in turn reciprocated.
A cylindrical member or casing 20 is secured to block 19 by a
tubular flanged connector 21. The cylindrical member 20 receives a
porous separator or filter 22 which is preferably composed of
sintered stainless steel or reinforced sintered bronze and is
supported in the enlarged upper portion 23 of casing 20 by a porous
filter support 24. Clearance is provided between ram 17 and the
inner surface of separator 22.
A plug 28 of solid carbon dioxide snow is partly formed in bore 27
of casing 20 and partly in bore 29 of head 30. The head 30 has a
plurality of small bores or openings 31 of the converging-diverging
type which communicate with the bore 29.
A conduit 33 communicates with a standard insulated carbon dioxide
storage tank 36 and a valve assembly 34 of the electrical type. A
cooling coil, compressor, pressure regulator, and liquid and vapor
separator for supplying carbon dioxide liquid through conduit 33
are standard and are described in U.S. Pat. No. 3,576,112,
application for which was copending herewith.
The stroke of the ram 17 extends from the upper position shown in
broken lines at the lower end of plug 28 to the lower end of bore
27 as shown in solid lines. The upper end of the ram 17 has a
recess 54 which terminates in a sharp peripheral edge 55. A bearing
56 is disposed between a washer 57, on internal shoulder 59 and an
upper shoulder 58 formed along bore 27. The bearing 56 is
preferably composed of polytetrafluoroethylene known commercually
as "Teflon." A seal ring 60 is disposed between the adjacent
surfaces of casing 20 and connector 21. Encircling ram 17 is a
U-cup seal 61 composed, for example, of leather into which a ring
62 fits. A compression spring 63 acts against an internal shoulder
64 of the connector 21 and against the ring 62. The seal 61 is
urged against the upper portion 65 of T-shaped connector 66 which
is secured to block 19 by bolts 67 and nuts 68.
Referring to the head member 30 as particularly shown in FIGS. 2, 3
and 4 it will be seen that a plurality of double frusto-conical
passages 31 are arranged in a circular pattern with one such
passage disposed centrally of the circular pattern. Each passage 31
is formed with a converging wall portion 70 which communicates with
the compression side of head portion 30 and with its widest
dimension proximate to the compression side. In direct extension
from each converging wall portion 70 is a diverging wall section
71, the converging and diverging wall sections 70 and 71,
respectively, being joined at their narrowest dimensions with the
diverging wall section 71 of greatest divergence proximate to the
discharge side of head 30.
FIG. 5 illustrates an alternative embodiment of a head member 80
wherein a plurality of passages 81 are formed each having a
straight wall portion 82 proximate to the compression side of head
member 80 and a frusto-conical section having a diverging wall
portion 83 with its narrowest dimension in communication with
straight wall section 82 and disposed with the wall portion 83 of
greatest divergence proximate to the discharge side of head member
80.
The novel rod-like pellet generally 32 is particularly illustrated
in FIGS. 6-8 and comprises a generally overall cylindrical
configuration with a substantially solid cylindrical core portion
90 and radiating projections 92 integral with said core and spaced
substantially uniformly along the core. The spaced projections 92
are formed in a generally concavo-convex configuration with the
circumferential ends being substantially flat, thus providing
together with the core a generally circular cross-section. The
density of rod-like pellet 32 is in the range of about 45-95 pounds
per cubic foot when the solidified gas is carbon dioxide. The core
member 90 comprises about 10-25 percent of the cross-sectional area
of the rod-like pellet member.
In operation, a suitable drive mechanism will continuously
reciprocate ram 17 by means of guide 16, the drive mechanism and
valve mechanism 34 being in synchronism so that liquid carbon
dioxide from conduit 33 is flashed into chamber 27 when the head of
ram 17 passes on its downward stroke the entrance of conduit 35
into chamber 27 and ceases the flashing of liquid carbon dioxide
when the head of ram 17 begins its upward stroke. The operation of
the valve 34 and the drive mechanism is substantially the same as
that disclosed in copending application Ser. No. 500,426. The snow
accumulates in the chamber designated by the letter "C" and carbon
dioxide vapor or gas can pass from the chamber through porous
filter 22 into outlet conduit 39 and subsequently to a storage
chamber for reuse. When the ram 17 moves upwardly, the snow in
chamber "C" is moved toward head 30 and is progressively
compressed. Some of the solid carbon dioxide which constitutes the
plug 28 is forced through the openings or bores 31, some of the
solid carbon dioxide remaining in the bores and newly compressed
snow constituting the plug 28 as the stroke cycle of ram 17 is
repeated. It is apparent that with each stroke of the ram 17 toward
the head 30 some solid carbon dioxide is forced through the
openings 31 and rod-like pellets 32 are intermittantly made.
Although not definitely known, it is postulated that with each
stroke cycle of ram 17 one radiating projection 92 and an adjacent
core section are formed.
The formation of the novel rod-like pellets 32 is effected by
extrusion through either a straight wall section 82 followed by a
diverging wall 83 or a converging wall 70 with subsequent passage
through a diverging wall 71 although the use of the converging wall
70 to effect initial stresses is preferred as it produces more
clearly defined radial projections 92. It is theorized that as the
compacted carbon dioxide snow passes beyond the narrowest dimension
of the diverging wall section a release of pressure occurs and thus
the formation of the spaces between the circumferentially extending
projections 92 around core 90 and the novel configuration of pellet
32. However, this release of pressure must not be too rapid lest
the pellet will break or be ejected in piecemeal fashion. Under
normal operating conditions with ram 17 in its retracting stroke an
internal pressure of 45 p.s.i.g. remains. For this reason it will
be noted that diverging wall sections 71 and 83 have only a slight
taper not exceeding an included angle of 15.degree.. This preferred
range provides expansion with simultaneous retention or frictional
drag between the edges 93 of projections 92 and the surface of
diverging walls 71 and 83. This frictional drag effects the convex
and concave sides of projections 92 and in effect pre-weakens
pellet 32 so that upon application of force on pellet 32 breaks
will occur across core 90 between the projections 92 forming
wafer-like objects which in turn then break into small pieces.
A head member which is approximately one-half inch in thickness is
preferred with a converging wall countersunk at an angle of
30.degree. for an included angle of 60.degree. to a depth of
approximately three-sixteenths of an inch. The outside diameter of
opening 70 is five-eights inch and the narrowest diameter is
three-eights of an inch. The diverging wall 71 contiguous therewith
completing the passage 31 through head 30 is countersunk at a taper
of 1.degree. 30 minutes for an included angle of 3.degree. and a
depth of five-sixteenths of an inch. While converging wall 70 has a
preferred angle of 30.degree. any angle of taper between 45.degree.
and 30.degree. works well.
Pellets formed by pellet machine 10 can be formed with varying
diameters and lengths, although it has been found that pellets
having diameters of one-fourth to three-eights of an inch are
preferred. When employing head members 31 and 81, pellets will
attain a length in a range about equal to their diameter or twice
their diameter before self-severance occurs.
Although the invention has been described as being practiced with
carbon dioxide to make solid carbon dioxide pellets, it will be
understood that any liquefied gas which will flash to both a solid
and vapor below its triple point can be formed into pellets such as
32 when employing the head members 30 and 81 in a piston or ram
type pellet machine.
The pellet 32 is unique in that it has a very high density and yet
possesses laminations or uniform pre-weakened fracture lines which
makes the pellet highly frangible into minute pieces upon forced
contact with any solid object. The density of pellet 32 provides
for a free flowing pellet which, although severed into suitable
lengths will not agglomerate. Thus, a novel rod-like pellet member
formed from a liquefied gas is provided which can be rapidly formed
and readily shipped without the pellets agglomerating. Moreover, in
use, the pellets can be shattered into minute particles thus
affording greater heat transfer efficiency than any herebefore
known carbon dioxide pellet.
Others may practice the invention in any of the numerous ways which
will be suggested by this disclosure to those skilled in the art by
employing one or more of the novel features disclosed or
equivalents thereof. All such practice of the invention is intended
to be within the scope of the appended claims.
* * * * *