Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 Description of the Prior Art
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It is known in the polymer processing field that after
processing polymer by melting, mixing, devolatilizing and the like
5 any processing apparatus used must be capable of generating
pressure in the viscous liquid material sufficient to extrude the
polymer through a shaping die or poulticing plate or merely to
transfer the material to another processing device.
In a screw type processor, a screw running in a bore is
generally provided with channels of reduced cross section such as
caused by channels of diminished depth or by varying the pitch o-f
the screw in order to generate increased pressure. A screw having
reduced depth typically is shown in US. Patent 3023~56. Melting,
mixing devolatilizing and other operations are performed in
relatively wide channels at relatively low pressure. The viscous
liquid polymer, however, is usually pressurized for pumping in
relatively narrow channels which requires considerably greater
expenditure of energy than the other processing channels.
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1 Accordingly, it is an object of the invention to provide a
device for pumping viscous fluid with a significantly less
expenditure of energy and resultant lower costs.
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1 Summary of the Invention
The present invention provides a novel device for pumping
viscous fluids. The pump includes a body member having a central
bearing in which a shaft rotates. The shaft is provided with one
or more radial blades which are received for rotation in one or
more annular channels. At the base of each blade, the shaft is
provided with a groove which extends generally axially along the
shaft from an inlet through which the viscous fluid is supplied to
a recess behind the blade and which also communicates with the
annular channel. As the shaft and blade rotate, the viscous fluid
builds up behind the blade and as the channel fills, the leading
side of the blade engages the bank of material. Since the fixed
walls of the channel apply a drag to the material, pressure is
built up by the advancing blade causing the material to be forced
from the channel through another groove in the shaft leading from
the root of the Front side of the blade to an outlet or to the
backside of a successive blade on the shaft to repeat the
operation and further raise the pressure on the material. To avoid
uneven stresses and deflection of the shaft, the blades may be
arranged equally spaced around the shaft or at diametrically
opposite sides of the shaft. With this arrangement leakage from
the unit can be minimized by a close clearance between the shaft
and a relatively close fitting bearing. To eliminate leakage the
shaft surface can be formed to act as a dynamic seal using the
viscous polymer to fill the clearance. The inlet and outlet
grooves pass through the bearing/sealing areas.
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According to a still further broad aspect of
the present invention, there is provided a pump for
viscous fluid and wherein the pump includes a body
having a central cylindrical bearing and at least
one concentric annular channel open only at the bear-
in. A shaft is rotatable in the bearing closing
the channel and has at least one radial blade complex
Monterey to the cross section of the channel and rotate
ably received in the channel. A first groove is pro-
voided in the shaft and extends axially from the inlet
through the bearing to an area behind the blade con-
ridered in the direction of rotation of the shaft
and blade. A second groove is provided in the shaft
and extends through the bearing from in front of the
blade axially toward an outlet. The fluid enters
behind the blade through the first groove progress
lively filling the channel as the shaft and blade
rotate and the advancing blade engages and forces
the fluid in the channel through the second groove
toward the outlet.
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1 Description of the Drawings
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Fig. 1 it a schematic perspective view of a polymer
processing device embodying the pump of the present invention;
Fig. 2 is a section on line II-II of Fig. 1;
Fig. 3 is a section on line III-III of Fig. l;
Fig. 4 is a longitudinal section through an alternate form of
polymer processing device embodying the invention;
Fig. 5 is a section on line V-V of Fig. 4j
Fig. 6 is an exploded perspective view of parts of the pump
unit of Fig. I;
Fig. 7 is a longitudinal section through an alternate form of
pumping unit;
Fig. 8 is a section on line VIII-VIII of Fig. 7; and
Fig. 9 is a cross section of a pumping unit diagrammatically
illustrating the balancing effect caused by diametrically opposite
blades.
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1 Description of Preferred Embodiments
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Referring to Fig. 1, there is shown a polymer processing unit
10 embodying the pump of the present invention. The unit includes
a body 12 having a central bearing I which receives a shaft 16.
The shaft has fixed thereto one or more radially extending blades
18 which are received in an annular channel 20 in the body 12. At
one end, the body is provided with an inlet 21 which leads to the
surface of a drum 22 on one end of the shaft 16.
As best seen in Fig. 2, solid thermoplastic pellets or liquid
polymer may be fed into inlet 21 and as the drum 22 is rotated by
a source of rotary power (not shown) the liquid polymer or pellets
are fed along a space 19 between the surface of the drum and a
cylindrical surface 23 of the body. To melt the thermoplastic
pellets, the drum and/or the body 12 may be heated in any suitable
manner not shown but which may be by circulation of fluid and/or
electrical band heaters both of which are well known in the art.
The poulticed polymer is progressively melted and fed toward a
collection recess 24 leading to a channel 25. As is well known
in the art a partial dam 26 may extend into the space 19 to spread
the liquid or melted polymer on the surface of the drum forming a
void 27 downstream of the dam. A port 28 extends through the body
12 into the void 27 so that volatile gasses may be drawn therefrom
or additives may be introduced thereto. The melted polymer
collects in the recess I and sufficient pressure is generated to
cause the polymer to flow along the channel 25 (Fig. 1) in the
body 12 and into an annular groove 30 in shalt 16. An axially
extending groove 32 in the shaft leads the liquid polymer into a
recess 34 behind and at the base of the blade 18 (See also Fig.
3). As the shaft rotates and blade 18 sweeps along the annular
channel 20 the polymer continues to be fed into and fill the
channel 20. The stationary walls of the channel apply a drag on
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1 the polymer and the advancing blade causes the pressure in the
polymer to rise and force the polymer into a recess 36 ahead of
the blade and along a groove 38 in the shaft.
As shown in Fig. 1, the pressurized polymer flows along the
groove 38 into a recess 40 at the base of a second blade 41 also
fixed to the shaft 16 and extending radially into an annular
channel 42 similar to channel 20. The already pressurized polymer
fills channel 42 and the advancing blade 41 further pressurizes
the material which is forced into a recess 43 at the base of the
leading side of the blade and along a groove 44 in the shaft and
into an annular groove 45. The pressurized polymer is led from
the groove and the unit through a port 46 into any suitable
apparatus (not shown) for further processing such as extrusion or
molding into shapes or for poulticing Such further apparatus
could include devices for injection molding without departing from
the scope of the invention.
As shown in Fig. 3, the base of the blade 18 may be received
in a recess 50 in the shaft 16 and secured by a bolt 51 which
extends through the shaft. So that the forces acting on the shaft
16 can be balanced to minimize undesirable deflection forces on
the shaft, the blades 18 and 41 can be arranged on opposite sides
of the shaft or could be constructed as seen in Figs. 5 and 8 to
balance forces in each annular channel as shown graphically in
Fig. 9. As illustrated in Fig. 9, the forces which build up
progressively from the inlet grooves 47 to the outlet grooves 49
are balanced by equal and opposite forces.
Referring to Fig. 4, there is shown an alternate form of
polymer processor embodying the invention. The unit includes an
alternate preferred form of pump 60 which could be attached to and
be fed fluid polymer by any one of a number of processors
including a melting screw unit 61 as seen in Fig. I or the drum
type shown in Figs. 1 and 2. As seen in Fig. 4, polymer already
in liquid form or in pellet form is fed through an inlet 62 to the
,
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1 single or multiple flights of a screw 63 which is rotated by a
source of rotary power (not shown). The body 64 and/or the screw
63 may be heated by suitable means (not shown) to melt or
otherwise process the polymer which is fed by the screw toward the
pump unit 50. The liquid polymer is fed from the end of the screw
to a passage 100 formed between a conical recess in an end frame
65 and a conical flange 57 on a shaft 68 fixed to the end of screw
63. The end frame 65 of the pump 60 is secured by bolts 66 to a
flange on the end of unit 61 and in turn is secured by through
bolts 70 to a stepped body 72 and a header 74. A recess between
mating surfaces of the frame 65 and body 72 forms an annular
channel 76 which receives blades 78 extending radially from a hub
80 mounted on shaft 68 and fixed for rotation with the shaft by
keys 81. Two sealing collars 82, 84 and spacer 85 locate the hub
I and blades 78 along the shaft 68 so the blades 78 are received
in the channel 76. The collars 82, 84 are received with a close
sealing but running fit in aligned bores 86 and 88 in the frame 65
and body 72 respectively. An impeller block 93 is mounted on each
blade for relative movement in axial directions via key slots 91,
92 and closely fits the cross sectional area of the channel 76.
This arrangement permits differential axial expansion between the
pump body parts and the rotor parts on the shaft 68 without
interference. The upstream collar 82 is provided with
diametrically opposite helical grooves 94 (see also Fig. 6) which
lead to the channel 76 through recesses 95 at the base of the
trailing sides of the blades 78. The helix angle of the grooves
is adapted to facilitate the flow of the liquid to be pumped.
During the operation of the processor the screw 63 is rotated
by means not shown and feeds liquefied polymer along the screw,
through the passage 100 and in divided streams through grooves 94
and recesses 95 into the annular channel 76 behind the blades 78.
It should be apparent that liquid polymer could be fed to the
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1 passage 100 from any suitable source other than the screw 63
without departing from the scope of the invention. The hub 80 and
blades 78 are rotated with the screw 63 and, when the channel 76
fills, the advancing impeller blocks 93 pressurize the material in
the channel forcing the material through recesses 97 at the base
of the leading side of each blade and through helical grooves 99
in the sealing collar I The liquid polymer then is forced
through an annular passage between the aligned bores 88 and 90 and
a collar 102 and through a passage 104 between a conical nose 105
and a recess in the header 74 to an outlet 106. The outlet can be
used for die extrusion or may lead to other processing devices.
It should be apparent that one or a series of impeller blades
and annular channels could be provided in serial fashion axially
along the shaft 68 to provide additional pumping facilities
without departing from the scope of the invention.
Referring to Figs 7 and 8, a further embodiment of the pump
is shown. As seen a shaft 110 is mounted for rotation in bearings
111 formed in a pair of mating body members 112, 114 which are
secured together by bolts 113. An annular channel 116 is formed
between the members by an appropriate spacer 118. Blades 120
extend from a hub 122 secured to the shaft 110 by a shear pun 115
are rotatable in the channel. Liquid polymer is fed into the
channel through a central bore 123, a passage 124, an annular
groove 125, grooves 126 and recesses 127 at the base of the
trailing side of each blade 120. The pressurized polymer is lead
through recesses 130 at the base of the leading side of each blade
120 and through grooves 131 to an annular groove 132 in a collar
135 on the shaft and then through an outlet 134 to a nozzle 136 or
other suitable processing devices. The assembly on the shaft is
secured by a nut 137 threaded on the shaft.
Experimental tests were run using a pump having a blade
diameter of nine (93 inches running at 100RPM in a channel having
a .25 inch width. The experimental pump successfully pumped
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1 polystyrene, HYPE, LOPE, polypropylene and AS using a 3.5 inch
diameter screw melter similar to that shown in Fig. 4 to feed
liquid polymer to the pump. LOPE was pumped at the rate of 502
lbs/hr at 1200 psi with specific energy use of .033 HP hr/lb. (The
specific energy was based on motor amperage and includes motor and
gear drive losses plus energy consumed by the feed screw which had
a capacity of 500 lbs/hr.) HYPE was pumped with the rotor speed
lowered to reduce the melt temperature at a rate of 153 lbs/hr. at
a pressure of 2400 psi with specific energy use of .06 HP-hr/lb.
In other tests two pumping stages were operated in series
with the channel widths reduced to .20 inch to increase
efficiency. It was found that the pressure generated nearly
doubled with the specific energy used remaining about the same.
Tests analysis indicate that the novel pump is more efficient with
specific energy use of .032 HP-hr/lb. than a comparable screw
extrude at .044 HP-hr/lb.
Little energy savings are expected at such low flow rates.
However, it is indicated that substantial energy savings can be
realized using larger pumps at higher flow rates, and pressures in
excess of 300D psi can be reached with low density polyethylene.
This means that there is a significant potential of replacing
metering sections of conventional feed screws or other processing
units such as shown in Fig. 1 with more efficient pumping sections
as herein described that occupies less space and uses less energy.
It should be apparent that while the pumping/pressurizing
unit has been described with relation to polymer processing
apparatus, the novel unit is equally useful to pump/pressurlze any
fluid including liquids and pastes from any source which have
viscosity high enough so the walls of the annular channels provide
a drag on the material. Obviously, the pumping channels, which
are shown herein as generally rectangular in shape, could have a
variety of shapes including rounded as well as wedge shapes
without departing from the scope of the invention defined by the
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1 appended claims. The various processing units combined with the
pump/pressurizing units have been described by way of illustration
and not for limiting the usefulness of the novel pump/pressurizing
units. The foregoing descriptions have been related to devices
which are shown more or less in a diagrammatic or schematic
manner and various substitutions of parts and combinations could
be made without departing from the scope of the invention.
