Note: Descriptions are shown in the official language in which they were submitted.
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I'ANK FOR TRANSPORT AND STORAGE
OF SEMISOLID AND FLUID MATERIALS
Background of_the Invention
This invention relates generally to a system for
transporting or storing semisolid materials, such as grease or
ground or comminuted food products, and fluid materials, such as
oil, in bulk quantities, and more particularly to a tank adapted
for quickly and efficiently unloading semisolid or fluid mate-
rial contained therein.
Coassigned U.S. patent 3,828,988 discloses an earlier
tank for bulk transport and storage of semisolid materials.
This tank has a follower piston with extruded or molded flexible
neoprene seals at each end thereof for sealing the piston rela-
tive to the tank while accommodating changes in internal cross-
section of the tank (variations of as much as 1/4 in. (8 mm) in
diameter), and spring biased nylon rollers for preventing cant-
ing of the piston as it moves within the tank. Although this
tank performs well, and the neoprene seals provide an effective
wiping action of the tank interior, thin smears or patches of
grease sometimes remain on the inside surface of the tank after
evacuation. While this is satisactory for many purposes, it is
not acceptable for all purposes, e.g., where the tank is to be
loaded with a different type of grease after unloading and con-
tamination of the second type of grease with the former type is
not permissable, or where the tank is to be loaded with commi-
nuted food products. Also, the earlier tank follower has numer-
ous parts and is relatively costly to fabricate and somewhat
difficult to assemble and insert into the tank.
Heretofore, ground food products have not commonly
been transported in bulk due to the difficulty or impossibility
of maintaining a high standard of cleanliness and sterility in a
transport tank. In lieu of bulk transport, other, less desir-
able, forms of transport have been used. These methods of
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64725-444
transport typically have been expensive and time consumi~g. For
example, in the processing of chicken, raw backs and wings are
conventionally ground and transpor~ed several hundred miles for
processlng into frankfurters, lunch meat, etc. by packing the
product into 55 gal. drums having plastic liners and transporting
the drums ln refrigerated trucks. Bulk transport of such material
~- has been impractical because it has been too difficult to load and
unload large tanks with the product and to sterilize the tanks,
due, in part, to the excessive time involved in doing so
Bulk transport of transfor~er oil, on the other hand,
has not been uncommon, but because of the sensitivity of the oil
to water and humid alr, it has been very troublesome. Transformer
oil may only be loaded into and unloaded ~rom conventional tank
trucks during condltions of low hu~idity and dryers must be
installed on the truck to permlt ventlng only of dry air. Because
transformer oll must be kept absolutely dry, transformer oil
should be to~ally sealed from ambient air when it is loaded,
~ranspor~ed, and unloaded so that it can be transported regardless
of weather conditions.
Su~mary of the_In~ention
The invention provldes in an elongate tank for transport
or for storage in bulk of semisolid and fluid materials, such as
grease and oil, said tank having an outlet at one end thereof for
the material contained therein, said tank belng of generally
- cylindric internal cross-section; a generally cylindric plston
siæed to slide in the tank and adapted to be moved ln a direction
~oward said outlet thereby to force material in the tank through
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64725-444
the outlet, said piston having a circumferential channel
therearound adjacent one end thereof, said channel carrying an
elas~ic annular seal therein, said seal being hollow and
expandable and having pressuri~ing means for varying the pressure
within the seal between atmospheric pressure and a pressure higher
than atmospheric wherein the seal expands and presses against the
internal surface of ~he tank with the pressure such that when the
piston slides in the tank the seal is maintained in sliding
engagement with the internal surface thereby to ~ipe the material
therefrom and to seal the pis~on relative to the tank, and means
extend~llg radially outwardly beyond the periphery of the piston
for engagement with the internal surface of the tank for holding
the piston against canting in the tank, while permitting said
piston to slide freely in said tank.
The tank is easy to sterilize, thereby to allow food
products to be ~ransported therein. It insures total sealing of
the contents from ambient air, ~hereby permitting the transport o~
materials, such as transformer oil, that must be kept absolutely
dry. The tank is reliahle in operation and relatively simple and
lnexpensive in construction. The pis~on is relatively easy to
assemble and insert lnto the tank.
The means for holdlng the piston against canting in ~he
tank may comprise a plurality of pads fastened to the piston and
extending radially outwardly therefrom beyond the periphery of the
piston for engagement with the internal surface o~ the tank. The
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64725-44
pads are of low fri~tion ma~erial to permit the piston to slide
freely in the tank, and they are spaced axially of the piston from
the seals a distance sufficien~ to prevent canting o~ the piston.
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Brief Description of the Drawings
_
Fig. 1 is a longitudinal cross-section of the end por-
tion of a tank o~ the present invention, showing a piston, par-
tially broken away to illustrate details, movable within the
tank;
Fig. 2 is an enlarged view of the section indicated at
2 in Fig. 1 showing an elastic hollow seal in a channel circum-
ferentially around the piston; and
Fig. 3 is a cross-sectional view on a reduced scale
along 3-3 of Flg. 1 illustrating an arrangement of pads on the
piston.
- Corresponding reference characters indicate corre-
sponding parts throughout the several views of the drawings.
Description of a Preferred Embodiment
Referring to the drawings, an elongate tank of the
present invention is designated in its entirety by the reference
numeral 1. As shown in Fig. 1, the tank has a combination inlet
and outlet port 3 at one end (hereinafter designated the forward
end for convenience only) for filling and emptying the tank with
semisolid material, such as grease, or fluid material, such as
oil
Tank 1 is of generally cylindric internal cross sec-
tion throughout its length. A tank designed to be carried on a
semitrailer, for example, may have an internal diameter of
approximately 68'~ (1730mm) and a length of 42 ft. (12.8m). It
has a generally cylindric piston generally de~signated 5 sized to
slide therein, and which may be moved in a direction toward the
port 3, designated the forward direction (left in Fig. 1), to
force the semisolid or fluid material in the tank through the
port. For example, the piston may be moved by increased air
pressure on its rearward side (right in Fig. 1)~ The piston 5
~L~82~7
may be moved in the rearward direction (riyht in Fig. 1) either
by pumping the material into port 3 or by creating a subatmos-
pheric pressure on the rearward side of piston 5 to draw semi-
solid or fluid material into the tank through the port 3.
The piston 5 has a head 7 at its forward end, which is
preferably configured for complementary engagement with the
interior contour 9 of the forward end of tank 1, so that the
contained material may be efficiently and completely forced
through the outlet (i.e. when the piston head comes into contact
with the forward end, no substantial amount of the material is
left in the tank). For example, the head 7 of the piston may be
convex and the complementary interior contour 9 of the forward
end of the tank 1 may be concave.
Piston 5 has a circumferential channel 11 therearound
adjacent one end thereof in which is carried an elastic annular
seal 13. Channel 11 is formed between retaining walls 15 pro-
jecting from the outer surface 17 of the piston 5. Specif-
ically, two retaining rings (or angles) designated generally as
19 are spaced apart a distance W (e.g., ~ in. (51 mm)) suffi-
cient to receive the seal 13 and mou-nted to the piston (e.g., by
welding, bolts, screws, etc.).
Seal 13 is hollow and expandable, and is formed of
unreinforced synthetic rubber, such as a Buna-N (nitrile) rubber
having a hardness, for example, of approximately 65 durometer
(Shore A scale). ~s shown in Fig. 2, seal 13 is generally
D-shaped in cross-section with the outer surface 20 being gener-
ally arcuate in shape and the inner surface 21 generally linear
in cross-section to contact the outer surface 17 of the cylin-
drical piston 5 across the bottom 23 of the channel 5. The
walls of the seal 13 forming the outer and inner surfaces, 20
and 21, respectively, are sufficiently thick (e.g., 3/8 in.
(lOmm) for a seal having an overall thickness T of 1-5/8 in.
(41mm) when unexpanded) and strong so that when the seal is
pressured it will expand to firmly and completely contact the
interior surface of the tank around its entire periphery.
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Preferably, the depth D of the channel is a substan-
tial portion (e.g., 50-60%) of the thickness T of the seal's
cross-section, thereby preventing the seal from expanding longi-
tudinally of the piston 5 and directing the expansion of the
seal in the radially outward direction so that the seal may be
expanded against the internal surface 25 of the tank. In addi-
tion, the seal 13 should have a thickness T tha~ is sufficiently
greater than the depth D of the channel so that the channel does
not interfere with the ability of the seal to accommodate for
variations in the internal diameter of the tank and imperfec-
tions, such as out of round areas of the tank and dents or
I'dings", etc., in the internal surface 25 of the tank. Of
course, the preferred sizes of the seal 13 and channel 11 change
according to the internal diameter of the tank. In a tank hav-
15 ing a large (50-80 in. (1270-23~0mm)) internal diameterj the
thickness T of the seal 13 may be 1/2 in. (13mm) or more greater
than depth D of the channel (e.g., a depth D of 1 in. (25mm) and
a thickness T of 1-5/8 in. (41mm) for a 68 in. (1730mm) internal
diameter tank).
The seal 13 has pressurizing means 27 for varying the
pressure within the seal between atmospheric pressure and a
pressure higher than atmospheric (e.g., 10-14 psig (69-97 kPa
gage)). As shown in Fig. 3, pressurizing means 27 includes a
normally closed valve 27 openable for pressurizing and depres-
surizing the seal. An opening 28 is provided at the rear end of
the piston 5 for access to the valve 27. When pressurized, the
seal 13 expands and presses against the internal surface 25 of
the tank with the pressure such that when the piston 5 slides in
the tank the seal is maintained in sliding engagement with the
internal surface thereby to wipe the material therefrom and to
seal the piston relative to the tank.
The width SW of the seal 13, when at atmospheric pres-
sure, is substantially that of the width W of the channel so
that the seal is prevented from expanding longitudinally of the
piston and will expand radially outwardly against the internal
surface 25 of the tank when pressurized to higher pressures. In
addition, the width SW of the seal 13 is preferably somewhat
greater than the thickness T of the unexpanded seal and is
D-shaped in cross-section further insuring that it will be
stable in the channel as the piston 5 moves through the tank.
For example, the thickness T of the seal at atmospheric pressure
may be 1-5/8 in~ (41mm) while the width SW of the seal and the
width W of the channel ll may be approximately 2 in. (51mm) for
a tank having an internal diameter of approximately 68"
(173Omm).
Preferably, seal 13 has an unexpanded configuration at
atmospheric pressure wherein the outside diameter of the seal is
slightly less than the internal diameter of the tank to facili-
tate insertion of the piston 5 in the tank. The seal 13 isinflatable, when pressurized, from the unexpanded configuration
to an expanded configuration wherein the seal expands against
the internal surface 25 oE the tank thereby wiping the material
from the internal surface of the tank when the piston 5 slides
within the tank and sealing the piston relative to the tank.
While the seal may be pressurized at pressures of up to 3~ psig
(207 kPa gage) or more, typically the seal is inflated or pres-
surized to 10-12 psig (59-83 kPa gage) to expand it fo~ sealing
the piston 5 relative to the tank.
The outer diameter of the seal 13 when unexpanded may
also be substantially the same as the internal diameter of the
tank, in which case the seal 13 would be collapsible when the
valve 27 is open to facilitate insertion of the piston 5 into
the tank. Seal 13 may then be pressurized so that it presses
against the internal surface 25 of the tank to wipe material
therefrom and to seal the piston 5 relative to the tank.
It will be observed that a significant advantage of
the seal 13, whether it is inflatable from an unexpanded config-
uration to an expanded configuration, or collapsible when the
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valve 27 is open~ or both, is that it allows the piston to be
inserted easily into the tank. Other designs, such as a solid
neoprene or rubber O-ring design conceived and tested during
development of seal 13, do not facilitate inserting a piston
into the tank. Installing the solid rubber O-ring seal involved
a considerable amount of labor, and required come-alongs, bars
and sledge hammers to insert the piston into the tank, none of
which are required to insert the piston 5 having the expandable
seal 13 into the tank.
The piston 5 is held against canting in tank 1 by a
plurality of pads 29, 31 fastened (e.g., by bolts 33 having
recessed heads) to the piston and extending radiall~ outwardly
therefrom beyond the periphery of the piston for engagement with
the internal surface 25 of the tank. The pads are of low fric-
tion material (e.g., nylon), thereby permitting the piston toslide freely in the tank. The pads have a thickness (radially
of piston) somewhat less than one-half of the difference between
the diameter of the piston and the internal diameter of the
tank. For example, if the diameter of the piston is approxi-
mately 64 inches (1630mm) and the internal diameter of the tank
approximately 6~ inches (1730mm), than the thickness of each pad
is approximately 1-1/2 inches (38mm). Also, the pads may be
approximately 3 inches (76mm) long (axially of piston) and 1-1/2
inches (3~mm) wide (circumferentially of piston). The nylon
pads 29, 31 may be trimmed by a file or sand paper to ensure
that the piston moves freely back and forth.
As shown in Fig. 1, pads 29 are spaced axially of the
piston 5 from the seal 13 a distance C sufficient to prevent
canting of the piston (e.g., adjacent the rearward end of the
piston). For example, the pads may be arranged in one circum-
ferential row (i.e. pads 29) around the periphery of the piston,or they may be arranged in two circumferential rows (i.e. pads
29 and 31) around the periphery of the piston wherein the second
row of pads (i.e. pads 31) are generally adjacent seal 13. As
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shown in Fig. 3, each pad may be spaced within its row at
approximately uniform distances from the nearest other pads
(e.g./ at 30 degree intervals around the circumference of the
piston). While two rows of pads are preferred, other arrange~
ments are possible which also prevent canting of the piston 5.
Variations in internal diameter of the tank of 1/4
inch (8mm) or more in a large tank may be accommodated by the
pads 29, 31 and seal 13 of this design without substantially
reducing the wiping and sealing action of the seal. It will be
observed in this regard that the expandable seal 13 is capable
of accommodating significantly greater changes in internal diam
eter of the tank, out-of-roundness of the tank and imperfections
in the internal surface of the tank than the solid rubber O-ring
or molded flexible neoprene seals discussed above. Thus the
unreinforced and pressurized seal 13 will apply substantially
even pressure to the internal surface of a tank even when the
tank is out~-of-round, dinged or when it has a varying internal
diameter.
In operation, air pressure on the rearward side of the
piston may be increased by introducing compressed air, causing
piston 5 to move forward inside the tank, and thereby forcing
semisolid or fluid material through outlet 3. The seal 13 wipes
the semisolid or fluid material ~rom the internal surface 25 of
the tank, thereby causing the tank to be self-cleaning in opera-
tion, and the pads 29, 31 hold the piston against canting,thereby preventing jamming and allowing the piston to move at an
even speed. Semisolid or fluid material is loaded into the tank
by pumping it into port 3 thereby moving the piston rearwardly
(to the right in Fig. 1) and/or by drawing it through outlet 3
by moving the piston 5 rearwardly. Fluid materials, such as
wastewater, and even semisolid materials, such as grease, have
been drawn into the tank by creating a partial vacuum in the
tank rearwardly of the piston 5.
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It will be observed that one particular advantage of
the tank 1 is its ability to handle food products, such as
ground food products (e.g., ground chicken parts). To prepare
the tank 1 for food product, the interior of the tank and the
head 7 of piston 5 are steam cleaned by 800 psig (5,500 kPa
gage) steam while the piston is positioned at the rear end of
the tank (to the right in Fig. 1), thereby sterili~ing the
interior of the tank~ the head 7 of the piston and the seal 13
so that food products may be carried. In addition, the piston 5
is easily removed from the tank for cleaning, when more than
steam cleaning is desired, and then inserted back into the tank
because the seal 13 is collapsible when the valve 27 is open
and/or because the outer diameter of the unexpanded seal is less
than the internal diameter of the tank.
It will be observed from the foregoing that the piston
is easily installed in the tank, self-cleaning, and improved in
performance.
In view of the above, it will be seen that the several
objects of the invention are achieved and other advantageous
2~ results attained.
As various changes could be made in the above con-
structions without departing from the scope of the invention, it
is intended that all matter contained in the above description
or shown in the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
