System and method for increased efficiency of screw presses

An improved system and method for increasing the operational efficiency of screw-type presses which express or compress fluids from fibrous material. These improvements generally include improved means for compressing the fibrous material at its interface with both the hollow main shaft and the cylindrical outer housing of the press. Improved split worms having improved attaching means for each worm flight to the main shaft and collar therearound also contribute to improved efficiency. Further included is an improved means for draining the expressed fluids from the compression chamber radially inward into the hollow main shaft and radially outwardly through the outer housing wall of the compression chamber. In addition to improved radially outward drainage, improved wedge-shaped screen bars in the cylindrical outer housing walls eliminate the need for breaker bars which are otherwise necessary to reduce the spiraling effect of this fibrous material during compression. The improved method relates to intermittent compression relaxation of the fibrous material, followed by aeration of the compression chamber and fibrous material with a compressed gas.

BACKGROUND OF THE INVENTION 
This invention relates generally to screw presses for expressing liquids 
from fibrous materials, and more particularly, to high pressure expressing 
presses capable of continuous operation, and to improved operating 
efficiency thereof. 
Dewatering expressing presses are used on a variety of organic products to 
expel liquids from the fibrous solid material. In most cases, any 
remaining liquid must be removed through an evaporative drying process and 
the expenditure of considerable amounts of heat energy thereby. Examples 
requiring a secondary drying process are found in drying brewery spent 
grain, bagasse drying, waste solid concentration, and various vegatable 
oil extractions. 
Screw presses used to express liquids from fibrous materials are well known 
in the industry. As prior art, applicant cites his earlier U.S. Pat. No. 
4,440,076, and further prior art cited therein. Applicant's said prior 
patent was directed to improvements in efficiency derived from improved 
center drainage chamber design and screen bar placement. Other prior art 
known to applicant related to matters of efficiency in these screw presses 
are disclosed in U.S. Pat. No. 3,998,148 to Mainka, et al, and a U.S.S.R. 
Pat. No. 737,446. 
One aspect of applicant's improvements in efficiency is derived from the 
particular construction of split-type worms and worm flights. In this 
regard, applicant further cites prior art in U.S. Pat. No. 3,980,013 to 
Bredeson which relates only generally to split, collared worm flights, and 
to similarly directed prior U.S. Pat. No. 635,868 to Peck. 
The present invention discloses improved structure in the size and shape of 
screen bars in the collar surrounding the hollow main shaft, as well as 
those in the walls of the cylindrical main housing for improved liquid 
discharge from the compression chamber, as well as increased screen bar 
area available in the collar derived from improved split worm flight 
design. An improved method of operation relates to the intermittent 
introduction of compressed gas into the compression chamber during 
intermittent periods of compression relaxation. Further benefits derived 
from the improved screen bar design in the cylindrical outer walls relate 
to the elimination of otherwise necessary breaker bars, consequently 
reducing energy consumption. These improved screen bars are longitudinally 
and radially inwardly disposed from the main housing for eliminating 
spiraling of the fibrous material and for improved efficiency. 
BRIEF DESCRIPTION OF THE INVENTION 
The present invention is directed to an improved system and method for 
increasing the operational efficiency of screw-type presses which express 
or compress fluids from fibrous material. These improvements generally 
include improved means for compressing the fibrous material at its 
interface with both the collar surrounding the hollow main shaft and the 
cylindrical outer housing of the press. Split worm flights having improved 
attaching means for each worm flight and collar therearound to the main 
shaft also contribute to improved efficiency and maintainability. Further 
improvements also include improved means for draining the expressed 
liquids from the compression chamber radially inward into the hollow main 
shaft and radially outwardly through the outer housing wall of the 
compression chamber. In addition to improved radially outward drainage, 
improved wedge-shaped screen bars in the cylindrical outer housing walls 
eliminate the need for breaker bars which are otherwise necessary to 
reduce the spiraling effect of this fibrous material during compression. 
The improved method relates to intermittent compression relaxation of the 
fibrous material, followed by aeration of the compression chamber and 
fibrous material with a compressed gas. 
It is therefore an object of this invention to provide increased efficiency 
in the operation of dewatering mechanical screw presses by the improvement 
in structure of screen bars positioned both in the hollow main shaft and 
in the cylindrical outer housing wall. 
It is another object of this invention to provide improved split worms 
which increase available area on the surface of the main hollow shaft and 
surrounding collar for screen bars and also may provide variable degrees 
of compression during each revolution. 
It is yet another object of this invention to eliminate breaker bars from 
the inner surface of the cylindrical outer housing of the compression 
chamber by the improved tapered design of the screen bars in this area. 
It is yet another object of this invention to provide an improved method of 
operating mechanical screw presses. 
And still another object of this invention is to reduce labor maintenance 
costs and increase the operating life of dewatering mechanical screw 
presses. 
In accordance with these and other objects which will be apparent 
hereafter, the instant invention will now be described with particular 
reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings, and particularly to FIGS. 1-4, improved 
outer cylindrical housing wedge-shaped screen bars are shown generally at 
10. These outer housing screen bars 10 are held radially disposed adjacent 
to conventional screen bars A as shown in FIG. 3 and radially disposed 
around the peripheral tip of the worm flights. Within the screen bars 10 
are provided cavities 12 having openings 16, 18 and 20 which are disposed 
to receive expressed fluids. These fluids are expressed outwardly out of 
the compression chamber through, in addition to the slits formed between 
each screen bar A and 10 by spacer portions 14, also through and out 
discharge portion 12' of cavity 12. 
An important benefit of the wedge shaped screen bar 10 is the tapered lower 
surface 10' which gradually extends radially inward into the compression 
chamber moving in the direction of the expressed fibrous material. In 
conventional screw presses, large breaker bars are placed longitudinally 
on the inside of the compression chamber to prevent or reduce spiraling of 
the fibrous material. This restriction improves the screw press efficiency 
by restricting spiraling of the fibrous material during compression. 
However, these breaker bars include blunt leading ends and extend 
sufficiently into the path of the moving fibrous material which includes 
foreign material therein, such as rocks and stones, that frequent damage 
will occur to the breaker bars, resulting in equipment down time. Further, 
a significant loss of energy occurs in driving the fibrous material 
against the blunt ends of the breaker bars. These improved wedge-shaped 
screen bars 10 eliminate the blunt leading end, and damage thereto, while 
still retaining the anti-spiraling features of conventional breaker bars. 
The tapered lower surface 10' provides gradual increased compression, 
spiraling restriction, and also providing additional fluid exit means 
through openings 16, 18 and 20 at and along an area where the fibrous 
material is more highly compressed. 
Referring now to FIGS. 5, 10 and 13, an improved structure is shown which 
provides both improved fluid extraction from the fibrous material and 
improved exit means for those expressed fluids into the hollow main shaft 
34 of the screw press. The main shaft 34 includes at least one drive key 
74 which interengage to drive collar 38. The main shaft is hollow as shown 
and includes a plurality of apertures 30 through its entire wall 
thickness. The collar 38 includes center drainage screen bars 22 which are 
suitably retained within the collar 38 by tang 40 and other convenient 
means so as to form slots 26. The trailing edges of these screen bars are 
radially extended as compared to the leading edges such that a void is 
created in the area of numeral 24 outwardly adjacent to the inlets for 
slot 26. By this means, as the collar 38 is rotated in the direction of R1 
and against the fibrous material within the screw press chamber, the 
fibrous material is repeatedly compressed slightly or "patted" to extract 
additional fluids, which are then allowed to more easily pass into slits 
26 due to the reduced pressure necessarily created by the void at area 24. 
This novel center drainage screen bar structure also prevents or reduces 
clogging of slots 26. The expressed fluids are then conveyed into the main 
hollow drive shaft 34 through apertures 30, which are in allignment, and 
in fluid communication, with slits 26. An enlarged portion 28 is also 
provided at the interface between apertures 30 and slots 26 to reduce the 
effect of rotational misalignment and enhance fluid flow into the main 
shaft 34 for disposal. 
Referring now to FIGS. 6 and 7, two alternate embodiments of the center 
drainage screen bars are shown generally at 42 and 42' in the form of a 
unitized insert including a plurality of individual screen bars formed 
into a single unit 42 and 42' for easy insertion into the collar 50. These 
screen bar inserts 42 and 42', also having radially extended trailing 
edges in a slightly different end contour, also form slits 44 and 44' 
therebetween which are in fluid communication with passages 52 and 52' for 
delivery of the expressed fluids into passages in the hollow main shaft 
(not shown). Flanges 46 serve to securely retain these screen bar inserts 
42 and 42' within a mating cavity in collar 50. Note that, similar to the 
embodiment shown in FIG. 5, rotation of the collar 50 and screen bar 
insert 42 in the direction of arrow R2 has the same beneficial fluid 
extraction effect produced by the end contour of each individual screen 
bar. 
Another embodiment of the improved center draining screen bars is shown 
generally in FIGS. 8, 9 and 10. In this embodiment, the center drainage 
slots 64 are formed into the collar 56, resulting in a generally 
circumferential outer contour. However, the rearward edge 60 of each 
center drainage slot 64 at 60 is rounded to produce the same negative 
pressure type cavity at 62 which results by rotating the drive shaft 72 
and collar 56 in the direction of arrow R3. The expressed fluids extracted 
from the fibrous material by worm flights 76 more easily enter into the 
main hollow shaft 72 because of the negative pressure created at area 62. 
Center drainage slots 64 and mating apertures 68 in the main drive shaft 
72 are enlarged at their interface to reduce or eliminate the detrimental 
effect of rotational misalignment. 
Referring now to FIGS. 10, 11 and 12, the improved worm includes two mating 
worm flights 76 which are adapted and structured to reduce the amount of 
surface area in the collar in order to maximize the surface area available 
for the improved center drainage screen bars and/or center drainage slots 
previously discussed. As is well known, the worm flight 76, having a 
spiral-type section, serves to compress the fibrous material in screw-type 
fashion as the main shaft 34 is rotated. Traditionally the worm and 
attached or integral worm flights were slid onto and off of the main shaft 
in similar fashion to that of the collar. However, in my previously 
referenced patent, the worm flights were improved in structure and 
function by splitting the worm in half and allowing installation thereof 
without disassembly of the other components on the main shaft. The present 
improvement carries the serviceability one step further, while also 
enhancing the operating efficiency of screw presses. As can be seen, the 
only collar surface area dedicated to each worm flight is substantially 
that necessary for the worm flight 76 itself. As best seen in FIG. 11, the 
worm flight 76 is moved into the collar cavity in the direction of arrows 
B and, thereafter, is rotated in the direction of arrow C such that dogs 
84 and 86 included on worm flight portion 82 interengage and mate with 
dogs 88 and 90 included on the mating wall surface of the collar 38. This 
mating interengagement of dogs 84, 86, 88 and 90 serves, as best shown in 
FIG. 12, to securely lock the worm flight 76 in place during operation. 
One end 82 of the worm flight 76 is tapered as shown so as to slide 
somewhat underneath a mating section of the collar 38 at 96 to abut at 94 
and to further enhance the locking characteristics of this improved worm 
flight 76. A keystone 78 is then bolted into place as shown in FIG. 12. By 
first moving the keystone 78 in the direction of arrow D, contoured 
surface 78' lockingly interengages against the mating surface of the other 
end of the worm flight 76 at 98. Bolt 80 then secures the keystone 78 in 
place during service. 
Referring now to FIGS. 14 and 15, an alternate embodiment of the improved 
center drainage is shown. Worms 100 having worm flights 102 thereon are 
slideably positionable along the hollow main shaft 34' and are shown 
positioned on either side of collar 106, also slideably positionable on 
hollow main shaft 34'. Pins 104 are insertable into mating apertures in 
collar 106 and are sized to protrude slightly from the side surface of the 
collar such that when worms 100 are slid against collar 106 in the 
direction of arrows E, radial and perpendicular slit 110 is created 
therebetween. Slit 110 is in alignment and fluid communication with 
apertures 108 in the hollow main shaft 34'. These apertures 108 are 
slightly enlarged to enhance expressed fluid flow into the main hollow 
shaft, particularly where the fluid is carrying fibrous material in 
suspension. 
As the worms 110 rotate in the direction of R4, the expressed fibrous 
material moves in the direction of arrow F in FIG. 15. To enhance the 
fluid entrance into slit 110 by reducing the fibrous material build-up 
there, the trailing outer edge 112 formed by the collar 106 is rounded to 
produce a low pressure area at the entrance of the slit as previously 
described. 
An alternate embodiment of this form of the improved center drainage is 
formed by slicing collar 106 into a plurality of disc-shaped segments each 
being spaced apart by pins 104 seeded in mating pockets in each disc 
segment. By this means, a plurality of radial and perpendicularly disposed 
center drainage slits are produced. 
Referring to FIG. 16, the outer housing screen bar insert is shown at 116 
having a plurality of elongated longitudinally disposed housing drainage 
slots 114 therethrough. Having a plurality of these housing screen bar 
inserts 116 positioned in the outer housing wall in an end-to-end fashion 
circumferentially provides the necessary housing drainage slots 114 in a 
form which is easily serviceable and replaceable. 
Improved Method of Operation 
During the normal operation of a screw press, the compression is continuous 
by the continuous rotation of the main shaft. The fibrous material is 
loaded intermittently or continuously during this compression process and 
discharges at the opposite end of the press, having been dewatered during 
this process. However, it is well known that substantial amounts of fluid 
remain in the fully compressed discharging fibrous material. In some 
cases, where anhydrous fibrous material is required, further drying by 
heating or other conventional methods is required. However, all of the 
above improvements are intended to provide improved structure and function 
which enhance the dewatering capabilities and efficiency of these 
conventional screw presses. 
The improved method includes the intermittent introduction of a gas under 
pressure into the compression chamber during each scheduled compression 
relaxation cycle. This compression relaxation may be effected by a 
variable pitch in the worm flights or by a variation in chamber size or 
the like. The pressurized gas, preferrably compressed air, may be 
introduced into the compression chamber through the main hollow shaft and 
center drainage slots, through the outer screen bar slots, or through 
either end of the compression chamber. The compressed gas is intended to 
redistribute the fibrous materials so as to provide new surface contact 
within the fibrous material. Thereafter, recompression within the chamber 
will extract greater amounts of fluids due to the relaxation and then 
rearrangement by compressed gas. 
While the instant invention has been shown and described herein and was 
conceived to be the most practical and preferred embodiment, it is 
recognized that departures may be made therefrom within the scope of the 
invention, which is therefore not to be limited to the details disclosed 
herein, but is to be accorded the full scope of the claims so as to 
embrace any and all equivalent apparatus and articles.