US3721184A

US3721184A - Mechanical screw press

Info

Publication number: US3721184A
Application number: US00161132A
Authority: US
Inventors: A French; F Starrett
Original assignee: French Oil Mill Machinery Co
Current assignee: French Oil Mill Machinery Co
Priority date: 1971-07-09
Filing date: 1971-07-09
Publication date: 1973-03-20
Anticipated expiration: 1990-03-20
Also published as: GB1375497A; AU462946B2; AU4431472A; DE2233875A1

Abstract

A cylindrical cage is lined with spaced screen bars to define drainage slots, a screw extends through the cage and has a plurality of axially spaced worms mounted on a shaft, and axially spaced stationary breaker lugs project inwardly between the flights of the worms. The final discharge worm has a tapered body and two diametrically opposed helical flights each of which extend circumferentially about 170*. The flights are effective to balance lateral forces acting on the discharge end portion of the screw and provide for generally axial flow of material between the flights. The final discharge worm is also adapted to be pulled axially from the shaft without opening the cage, by a fluid cylinder which primarily serves to position a frustoconical drainage sleeve within a surrounding discharge ring to vary the size of the discharge orifice.

Description

United States Patent [191 French et a1.

]March 20, 1973 1 1 MECHANICAL SCREW PRESS [75] Inventors: Alfred W. French; Forest ,1. Starrett,

Jr., both of Piqua, Ohio [73] Assignee: The French Oil Mill Machinery Company, Piqua, Ohio [22] Filed: July 9, 1971 [21] Appl. No.: 161,132

3,003,412 10/1961 Vincent.... ..l00/117 3,285,163 11/1966 Burner 100/117 X 2,090,434 8/1937 Thalmann .....259/l91 3,334,404 8/1967 Torlay ..29/252 Primary Examiner-Peter Feldman Assistant ExaminerPhilip R. Coe Attorney-Jacox & Meckstroth [5 7] ABSTRACT A cylindrical cage is lined with spaced screen bars to define drainage slots, a screw extends through the cage and has a plurality of axially spaced worms mounted on a shaft, and axially spaced stationary breaker lugs project inwardly between the flights of the worms. The final discharge worm has a tapered body and two diametrically opposed helical flights each of which extend circumferentially about 170. The flights are effective to balance lateral forces acting on the discharge end portion of the screw and provide for generally axial flow of material between the flights. The final discharge worm is also adapted to be pulled axially from the shaft without opening the cage, by a fluid cylinder which primarily serves to position a frusto-conical drainage sleeve within a surrounding discharge ring to vary the size of the discharge orifice.

15 Claims, 5 Drawing Figures PATENTEUHARZOIBH 3.721 184 v INVENTORS ALFRED W. FRENCH FOREST J. STARRETT,JR

MECHANICAL SCREW PRESS BACKGROUND OF THE INVENTION In a mechanical screw press such as disclosed in French et al. US. Pat. No. 3,411,435, assigned to the assignee of the present invention, the screw includes a series of axially spaced worms mounted on a shaft, and each worm includes an annular body supporting an integral helical flight which extends circumferentially about 340 around the body. The worms and flights are spaced axially by collars mounted on the shaft, and a series of stationary breaker lugs project inwardly between the helical flights to oppose rotation of the pressed material with, the worms and thereby assure generally axial flow of the material from each worm to the next successive worm.

When a mechanical screw press as shown in the above patent, is used for expressing moisture from an abrasive material, for example, sugar cane bagasse having abrasive foreign particles such as sand, it has been found that the substantial lateral forces acting on the discharge end portion of the screw, cause significant wear on the outer surface of the helical flight on the final discharge worm and also on the surrounding screen bars supported by the discharge end portion of the cage. To minimize this wear, it is common to apply a hard coating on the outer surface of the flight of the discharge worm and to employ particularly hard screen bars. Attempts have also been made to use a support bearing for the discharge end portion of the screw, but this bearing interferes to some extent with the discharge of material from the press.

Thus when pressing sugar cane bagasse which commonly carries sand and other abrasive foreign material, it is occasionally necessary to stop the screw press, open the split cage and replace the final discharge worm on the screw in addition to sometimes'replacing the screen bars adjacent the high pressure discharge end of the press. It is not uncommon for this replacement to require two to four men from 8 to 16 hours. This represents a significant downtime for the screw press.

SUMMARY OF THE INVENTION The present invention is directed to a mechanical screw press incorporating an improved pressing worm which is ideally suited for use at least as the final discharge worm of the press, but which may also be used at other locations on the screw shaft. The improved worm significantly reduces the wear on the worm and the surrounding screen bars and also provides for improved feeding of the material through the press. The mechanical screw press of the invention further provides for conveniently removing and replacing the discharge worm without requiring the cage to be opened. As a result, a screw press constructed in accordance with the present invention may be operated continuously for longer periods of time when handling abrasive material and when it does become necessary to replace the final discharge worm, the replacement of the worm can be accomplished in a significantly shorter period of time.

In accordance with a preferred embodiment of the invention, the final worm adjacent the discharge end of the press, includes a body having an outer surface which tapers outwardly toward the end of the press. A

pair of diametrically opposed helical flights are formed as an integral part of the body, and each flight extends approximately so that there is an approximate 10 gap between adjacent ends of the opposing flights. The two opposed flights are effective to balance the lateral forces acting on the discharge end portion of the screw and thus balance the side thrusts so that deflection of the screw and rubbing of the worm flights against the screen bars are minimized. The opposed flights also cooperate to feed the material up the tapered body of the worm and through the opposed gaps defined between the adjacent ends of the worms.

The body of the discharge worm is provided with two axially extending threaded holes which face the discharge end of the press and are adapted to receive corresponding axially extending bars or rods which extend from the guide member secured to the piston of the hydraulic cylinder. The rods may be adjusted axially relative to the guide member and provide for pulling the final discharge worm from the main screw shaft and onto a shaft extension in response to actuation of the cylinder. The guide member and the hydraulic cylinder are also used during operation of the press for positioning a non-rotating frusto-conical drainage sleeve within a surrounding stationary discharge ring to provide for varying the area of the annular discharge orifice defined between the sleeve and the ring.

Other features and advantages of the invention will be apparent from the following description, the accompanying drawing and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary section of the discharge end portion of a screw press having a final discharge worm constructed and replaceable in accordance with the invention;

FIG. 2 is a somewhat larger fragmentary section taken generally on the line 22 of FIG. 1;

FIG. 3 is an enlarged elevational view of the finaldischarge worm shown in FIGS. 1 and 2;

FIG. 4 is an axial view of the discharge worm shown in FIG. 3; and

FIG. 5 is a view ofa clamping device taken generally on the line 5-5 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the discharge end portion of a screw press which generally includes a cylindrical cage 10 which is constructed in two semi-cylindrical mating cage sections 12 each having a plurality of parallel spaced arcuate ribs (not shown) integrally connected by longitudinally extending cage members. The cage sections 12 are clamped together by a series of tie bolts (not shown) which extend within the holes 14. and the discharge end of the cage is supported by an upright end wall or member 15 of the main frame.

A plurality of axially extending elongated screen bars 16 are mounted on the ribs of each cage section 12 and are circumferentially spaced to define longitudinally extending drainage slots or openings 17 therebetween. The screen bars 16 are secured within each cage section by longitudinally extending retaining bars 18 and cooperate to define a cylindrical pressing chamber 20 having an inlet end (not shown) and a discharge end 22 which abuts the frame member 15.

An elongated screw assembly 25 extends through the pressing chamber 20 and includes a hollow shaft 26 (FIG. 2) which is connected to a suitable drive motor 28. A series of pressure worms, including a discharge worm 29 and a final discharge worm 30, are successively mounted on the shaft 26 within the pressing chamber 20 and are keyed to the shaft. The worm 29 includes a cylindrical body 32 and an integral helical flight 33 which extends circumferentially around the body 32 approximately 340 in a manner as shown in the above patent.

A series of annular collars 36 are mounted on the shaft 26 interspaced between the pressure worms. A series of breaker bars 38 are secured to the retaining bars 18 and include lug portions which project inwardly into the pressing chamber 20 in the areas of the annular collars 36 and between the worm to minimize rotation of the material being pressed with the screw 25. A final breaker bar or lug 39 projects inwardly adjacent the discharge end of the final discharge worm 30.

In accordance with the present invention, the final discharge worm 30 (FIGS. 3 and 4) includes an annular body 42 having an outer frusto-conical surface which tapers outwardly toward the discharge end of the screw assembly 25. A pair of diametrically opposed helical flights 44 are formed as an integral part of the body 42, and each flight passes through a radial reference plane 45 and extends circumferentially approximately halfway around the body 42. Preferably, each of the helical flights 44 extends circumferentially no greater than 200 and at an optimum angle of 170 so that opposing ends of the flights 44 define diametrically opposed axially extending passages or gaps 46. A set of four uniformly spaced axially extended threaded holes 48 (FIG. 4) are formed within the discharge end of the worm 30, and as mentioned above, all of the worms, including the

worms

29 and 30, are secured to the shaft 26 by keys which extend within corresponding keyways 49.

A cylindrical collar 52 is mounted on the shaft 26 adjacent the discharge end of the worm 30 and a pair of diametrically spaced threaded holes 53 are formed axially within the collar 52. A final cylindrical collar 54 is mounted on the end portion of the shaft 26 and has an outer diameter the same as the collar 52. A counterbore 56 (FIG. 2) is formed within the end of the collar 54 and is adapted to receive a circular retaining plate (not shown) which is secured to the end of the shaft 26 by suitable screws and functions to assure that the worms and collars do not shift axially on the shaft 26.

A large diameter counterbore 59 (FIG. 1) is formed within the frame member 15 and receives a hardened discharge ring 60 having a frusto-conical inner surface 61 which continues inwardly onto a smaller adjacent discharge ring 62. The discharge ring 60 is retained by an annular plate 64 which is secured to the frame member 15 by a series of screws 66. A non-rotatable discharge sleeve 70 is mounted on the

discharge collars

52 and 54 of the screw 25 for axial sliding movement and has an outer frusto-conical surface 72 which cooperates with the inner surface 61 of the ring 59 to define an annular discharge orifice 75. An annular array of openings or holes 76 are formed within the surface 72 of the sleeve 70 and provide for an inward escape of expressed fluid which drains from the sleeve 70 through an outlet 77 formed within the lower portion of a circular support or guide member 78 secured to the end of the sleeve 70.

A frame extension member or bracket 80 is rigidly secured to the retaining plate 64 and projects outwardly to support a double acting fluid or hydraulic cylinder 82. The cylinder 82 has a piston rod 84 which is axially aligned with the screw assembly 25 and supports the outer end of the sleeve 70 through the guide member 78. The rod 84 is slidably supported by a bearing 85 mounted on the frame extension member 80 and by a bearing 86 mounted on the outer end of a guide tube 87 rigidly secured to frame extension 80. A grooved collar 88 is secured to the rod 84 and engages a tubular spline 89 confined within the tube 87 to prevent the rod 84 and sleeve from rotating.

As disclosed in the above patent, when a mechanical screw press is operating for continuously expressing fluid from a material such as sugar cane bagasse, the compressed pulp or bulk material is discharged through the annular orifice 75. The discharge sleeve 70 is positioned axially by actuating the fluid cylinder 82 to ad just the area of the orifice 75 according to the back pressure desired in the pressing chamber 20. When the mechanical screw press has been in operation for a substantial period of time and it becomes desirable to replace the final discharge worm 30, the fluid cylinder 82 is actuated, and the discharge sleeve 70 is retracted from the discharge ring 60. The sleeve 70 is then removed from the guide member 78, and the retaining plate is removed from the counterbore 56 within the end portion of the final collar 54.

The guide member 78 is provided with a set of diametrically spaced axially extending holes 91 which receive a corresponding pair of elongated bars or rods 92 each having a threaded forward end portion and a plurality of axially spaced neck portions 94. A spring clamp 95 (FIGS. 2 and 5) is adapted to engage one of the neck portions 94 of each rod 92 and includes a U- shaped fiat spring 96 having end portions secured to a pair of mating block members 98 by a set of screws 99. The block members 98 are urged together by the spring 96 and cooperate to define a cylindrical bore 101 having a diameter approximately the same as the neck por tions 94 on the rods 92. A tapered surface 102 is formed on each block 98, and these surfaces cooperate to provide a lead for pressing each of the spring clamps 95 onto a neck portion 94 of the corresponding rod 92.

After the discharge sleeve 70 is retracted from the screw 25 and removed, a main shaft extension 105 is secured by a set of screws 106 to the end of the screw shaft 26 in place of the retaining plate (not shown). The shaft extension 105 includes a cylindrical portion 108 having an outer diameter slightly less than that of the shaft 26, and a lead portion 110 has a slightly frusto-conical outer surface which tapers from the outer surface of the shaft 26 to the outer surface of the cylindrical portion 108.

As illustrated in FIG. 1, the fluid cylinder 82 primarily functions to position the discharge sleeve 70 and to control the size of the annular discharge orifice 75. In accordance with the present invention, however, the cylinder 82 is also used to aid in removing the

collars

54 and 52 and the final discharge worm 30 from the screw shaft 26 and may be used for removing all members fitted and keyed to the shaft 26. This is accomplished by simply extending the rods 92 through the bores 91 and threading the end portions of the rods into the corresponding axially extending threaded holes 53 within the final collar 54. The piston rod 84 is extended to position the guide member 78 as shown in FIG. 2, and the spring clamps 95 are pressed onto the neck portions 94 of the rods 92 in back of the guide member 78. The piston rod 84 and the guide member 78 are then retracted to pull the end collar 54 from the shaft 26 and onto the shaft extension 105.

After the collar 54 is removed, the pulling operation is repeated again to remove the adjacent collar 52, and again to remove the final discharge worm 30 and again for each worm and collar which is desired to be removed from the shaft 26. However, before the worm 30 is pulled from the shaft 26, the gap 46 between the ends of the helical flights 44, is aligned with the last breaker bar lug 39 by rotating the screw 25. The rods 92, the guide member 78 and the fluid cylinder 82 may also be used for mounting a new final discharge worm 30 on the screw shaft 26 and also for replacing the

final collars

52 and 54. That is, the new final discharge worm 30 is placed on the main shaft extension 105, and the rods 92 are threaded into two of the holes 48 of the worm 30. The spring clamps 95 are then pressed onto neck portions 94 of the rods 92 in front of the retracted guide member 78, and the piston rod 84 is extended so that the worm 30 is pushed or forced back onto the screw shaft 26 and adjacent the collar 36. The plurality of neck portions 94 on each rod 92 enables the pulling operation for removing the worm 30 or the pushing operation for replacing a new worm 30 is to be performed in successive steps simply by resetting the spring clamps 95 to another set of neck portions 94 of the rods 92.

From the drawing and the above description, it is apparent that a mechanical screw press constructed in accordance with the invention provides desirable features and advantages. For example, one important feature is provided by the configuration of the final discharge worm 30. That is, the two diametrically opposed helical flights 44 cooperate to balance lateral acting forces on the discharge end portion of the screw 25, and the gaps 46 between the flights 44 provide for uniform axial flow of the compacted material over the worm 30. As a result, the wear on the outer surface of the flights 44 and on the surrounding screen bars 17, is significantly reduced when the screw press is operating to express moisture from a material containing abrasive particles such as sugar cane bagasse containing sand.

It is to be understood that while only the final discharge worm 30 is shown with the diametrically opposite helical flights 44 because the greatest wear is normally on the final discharge worm and the surrounding screen bars, it is within the scope of the invention to construct the worm 29 and other worms on the shaft 26 in the same manner as the final discharge worm 30. It has also been found that the opposite helical flights 44 on the discharge worm 30, cooperate to feed the material up the tapered outer surface of the body 42 to provide substantial compaction of the material.

Another important feature is provided by adjusting the hydraulic cylinder 82 for both adjusting the axial position of the discharge sleeve 70 during operation of the screw press and for removing the final discharge worm from the main screw shaft 26. That is, the hydraulic cylinder 82, the guide member 78 and the rods 92 provide for conveniently removing and replacing the final discharge worm 30 and any preceeding worm without requiring the cage 10 to be opened. As a result, the downtime of the screw press for replacing a worm, is substantially reduced. As mentioned above, it has previously required two or four men from 8 to 16 hours to open a cage, replace the final discharge worm and close the cage. The present invention provides for replacing the final discharge worm in approximately 1 hour.

The configuration of the discharge worm 30 is also desirable in that one of the gaps 46 between the end surfaces of the helical flights 44, may be aligned with the final breaker bar lug 39 so that the worm 30 can be pulled axially from the screw shaft 26 without opening the cage. Another desirable feature is provided by the bars or rods 92 and the spring clamps 95. That is, the clamps 95 may be conveniently reset to various positions on the rods 92 and thereby enable the removal of a collar or worm in a step-by-step manner when the axial spacing of the worm from the end of the screw is greater than the stroke of the hydraulic cylinder rod 84.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

l. A mechanical screw press for expressing fluid from a material, comprising a cage having means defining an elongated pressing chamber with an inlet end and a discharge end and having means defining fluid discharge openings extending through said cage, a rotatable screw extending through said chamber and including a shaft, a series of axially aligned worms mounted on said shaft and having corresponding bodies and longitudinally spaced helical flights projecting outwardly from said bodies, means for rotating said screw, means for compressing material within said chamber as it moves toward said discharge end in response to rotation of said screw, breaker bar means supported by said cage and including portions projecting into said chamber between said flights as the material is being compressed, at least one of said worms includes a plurality of said flights disposed uniformly around the circumference of the corresponding said body and passing through a common radial reference plane, each of said flights on said one worm extending circumferentially no greater than 200, and means providing for pulling said one worm axially from said shaft.

2. A press as defined in claim 1 wherein each of said flights on said one worm extends circumferentially about 3. A press as defined in claim 1 wherein the body of said one worm has a tapered outer surface increasing in diameter toward said discharge end of said cage, and each of said flights on said one worm extends circumferentially about 170.

4. In a mechanical screw press for expressing fluid from a material and including a cage having means defining an elongated pressing chamber with an inlet end and a discharge end, a rotatable screw extending through said chamber and including a shaft and'a series of axially aligned worms mounted on said shaft, said worms having corresponding bodies and longitudinally spaced helical flights projecting outwardly from said bodies, means for rotating said screw, means for compressing material within said chamber as it moves toward said discharge end in response to rotation of said screw, and breaker bar means supported by said cage and including portions projecting into said chamber between said flights as the material is being compressed, the improvement comprising at least one axially extending pulling member adapted to extend into said discharge end of said cage, means for connecting said pulling member to the final discharge worm on said screw, and means connected to said member for pulling said discharge worm axially from said shaft and through said discharge end of said cage.

5. A press as defined in claim 4 wherein said pulling member comprises an elongated rod, and said pulling means comprises a fluid cylinder.

6. A press as defined in claim 5 including a guide member axially aligned with said screw and movable by said cylinder, means for connecting said rod to said guide member, a discharge sleeve having a tapered outer surface, and means for securing said sleeve to said guide member.

7. A press as defined in claim 5 including means for connecting said cylinder to said rod at longitudinally spaced intervals along said rod.

8. A press as defined in claim 7 wherein said connecting means comprise at least one spring clamp, and means defining a plurality of axially spaced reduced neck portions on said rod for selectively receiving said clamp.

9. A press as defined in claim 4 including a shaft extension member adapted to be mounted on the discharge end of said shaft and having an outer surface smaller in diameter than said shaft for supporting said final discharge worm after being pulled from said shaft.

10, A press as defined in claim 4 wherein one of said breaker bar portions is disposed between said final discharge worm and said discharge end of said pressing chamber, said final discharge worm includes a set of circumferentially spaced said flights, and wherein said flights each extend circumferentially no greater than 180 and cooperate to define a gap for receiving said one breaker bar portion when said discharge worm is pulled from said shaft.

11. In a mechanical screw press for expressing fluid from a material and including a set of mating cage sections having means defining an elongated pressing chamber with an inlet end and a discharge end and having means defining fluid discharge openings extending through said cage, means for releasably securing said cage sections and providing for opening said cage sections, a rotatable screw extending through said chamber and including a series of axially aligned worms having corresponding bodies and longitudinally spaced helical flights projecting outwardly from said bodies, means for rotating said screw, means for compressing material within said chamber as it moves toward said discharge end in response to rotation of said screw, and breaker bar means supported by said cage and including portions projectin into said chamber between said flights as the materra rs being compressed, the rmprovement wherein at least one of the worms comprises a plurality of said flights disposed uniformly around the circumference of the corresponding said body and passing through a common radial reference plane, each of the latter said flights extends circumferentially no greater than and means for pulling said discharge worm axially from said chamber without requiring opening of said cage sections.

12. A press as defined in claim 11 wherein said pulling means comprise a set of axially extending bars, means for connecting said bars to said discharge worm, fluid cylinder means for pulling said bars, and means for connecting said fluid cylinder means to said bars.

13. A press as defined in claim 12 wherein said connecting means comprise a movable guide member having means for engaging said bars, a sleeve positioned adjacent said discharge end of said cage, and means for mounting said sleeve on said guide member to provide for utilizing said fluid cylinder means for adjusting the axial position of said sleeve in addition to removing said discharge worm.

14. A press as defined in claim 1 wherein said means providing for pulling said one worm from said shaft comprise a set of axially extending threaded holes within said one worm.

15. A mechanical screw press for expressing fluid from a'material, comprising a cage having means defining an elongated pressing chamber with an inlet end and a discharge end, means defining fluid drainage openings within said cage, a rotatable screw extending through said chamber and including a shaft, a series of axially aligned worms mounted on said shaft and having corresponding bodies and longitudinally spaced helical flights projecting outwardly from said bodies, drive means for rotating said screw, means for compressing material within said chamber as it moves toward said discharge end in response to rotation of said screw, breaker bar means supported by said cage and including portions projecting into said chamber between said flights, at least one of said worms includes a plurality of said flights disposed uniformly around the circumference of the corresponding said body and passing through a common radial reference plane, and the spacing between adjacent ends of said flights on said one worm being sufficient to define a gap through which said breaker bar means can pass to provide for removing said one worm axially from said shaft.

Claims

1. A mechanical screw press for expressing fluid from a material, comprising a cage having means defininG an elongated pressing chamber with an inlet end and a discharge end and having means defining fluid discharge openings extending through said cage, a rotatable screw extending through said chamber and including a shaft, a series of axially aligned worms mounted on said shaft and having corresponding bodies and longitudinally spaced helical flights projecting outwardly from said bodies, means for rotating said screw, means for compressing material within said chamber as it moves toward said discharge end in response to rotation of said screw, breaker bar means supported by said cage and including portions projecting into said chamber between said flights as the material is being compressed, at least one of said worms includes a plurality of said flights disposed uniformly around the circumference of the corresponding said body and passing through a common radial reference plane, each of said flights on said one worm extending circumferentially no greater than 200*, and means providing for pulling said one worm axially from said shaft.

2. A press as defined in claim 1 wherein each of said flights on said one worm extends circumferentially about 170*.

3. A press as defined in claim 1 wherein the body of said one worm has a tapered outer surface increasing in diameter toward said discharge end of said cage, and each of said flights on said one worm extends circumferentially about 170*.

4. In a mechanical screw press for expressing fluid from a material and including a cage having means defining an elongated pressing chamber with an inlet end and a discharge end, a rotatable screw extending through said chamber and including a shaft and a series of axially aligned worms mounted on said shaft, said worms having corresponding bodies and longitudinally spaced helical flights projecting outwardly from said bodies, means for rotating said screw, means for compressing material within said chamber as it moves toward said discharge end in response to rotation of said screw, and breaker bar means supported by said cage and including portions projecting into said chamber between said flights as the material is being compressed, the improvement comprising at least one axially extending pulling member adapted to extend into said discharge end of said cage, means for connecting said pulling member to the final discharge worm on said screw, and means connected to said member for pulling said discharge worm axially from said shaft and through said discharge end of said cage.

10. A press as defined in claim 4 wherein one of said breaker bar portions is disposed between said final discharge worm and said discharge end of said pressing chamber, said final discharge worm includes a set of circumferentially spaced said flights, and wherein said flights each extend circumferentially no greater than 180* and cooperate to define a gap for receiving said one breaker bar portion when said discharge worm is pulled from said shaft.

11. In a mechanical screw press for expressing fluid from a material and including a set of mating cage sections having means defining an elongated pressing chamber with an inlet end and a discharge end and having means defining fluid discharge openings extending through said cage, means for releasably securing said cage sections and providing for opening said cage sections, a rotatable screw extending through said chamber and including a series of axially aligned worms having corresponding bodies and longitudinally spaced helical flights projecting outwardly from said bodies, means for rotating said screw, means for compressing material within said chamber as it moves toward said discharge end in response to rotation of said screw, and breaker bar means supported by said cage and including portions projecting into said chamber between said flights as the material is being compressed, the improvement wherein at least one of the worms comprises a plurality of said flights disposed uniformly around the circumference of the corresponding said body and passing through a common radial reference plane, each of the latter said flights extends circumferentially no greater than 180*, and means for pulling said discharge worm axially from said chamber without requiring opening of said cage sections.

15. A mechanical screw press for expressing fluid from a material, comprising a cage having means defining an elongated pressing chamber with an inlet end and a discharge end, means defining fluid drainage openings within said cage, a rotatable screw extending through said chamber and including a shaft, a series of axially aligned worms mounted on said shaft and having corresponding bodies and longitudinally spaced helical flights projecting outwardly from said bodies, drive means for rotating said screw, means for compressing material within said chamber as it moves toward said discharge end in response to rotation of said screw, breaker bar means supported by said cage and including portions projecting into said chamber between said flights, at least one of said worms includes a plurality of said flights disposed uniformly around the circumference of the corresponding said body and passing through a common radial reference plane, and the spacing between adjacent ends of said flights on said one worm being sufficient to define a gap through which said breaker bar means can pass to provide for removing said one worm axially from said shaft.