US3411435A - Apparatus for recovery of sucrose - Google Patents

Description

Nov. 19, 1968 A..w. FRENCH TAL 3,411,435

APPARATUS FOR RECOVERY OF SUCROSE Filed Oct. 18, 1966 2 Sheets-Sheet 1 DIFFUSION SYSTEM INVENTORS ALFRED W. FRENCH 8 BY FOREST J. STARRETT,JR.

Wail, M931}? ATTORNEYS FIG-2 Nov. 19, 1968 w, FRENCH ET AL 3,411,435

APPARATUS FOR RECOVERY OF SUCROSE Filed Oct. 18, 1966 2 Sheets-Sheet 2 United States Patent 3,411,435 APPARATUS FOR RECOVERY OF SUCROSE Alfred W. French and Forest J. Starrett, Jr., Piqu'a, Ghio, assignors to The French Oil Mill Machinery Company, Piqua, Ohio, a corporation of Ohio Filed Oct. 18, 1966, Ser. No. 587,454 5 Claims. (Cl. 100-43) ABSTRACT OF THE DISCLOSURE A continuously operating mechanical screw press receives bagasse from a diffuser with high moisture content in the order of 85-90% moisture and continuously conveys such material through the press while compressing and continuously working the materal to reduce its volume by passage through several sections of decreasing diameter while subjected to mechanical working, thereby extracting approximately one half of the moisture from the material. This extracted liquid will contain significant amounts of sucrose which can be recovered from the liquid or returned to the diffusion system for use in the diffusion process. A non-rotatable discharge sleeve in the discharge ring is yieldably held against movement out of the press thereby providing for the creation of pressure on the material and automatically avoiding excessive pressure and strain on the press.

In its broadest aspects, the present invention relates to improvements in the apparatus disclosed in U.S. Patents Nos. 3,092,017 and 3,195,446 issued to the assignee of this application. The invention also relates to novel apparatus involving the handling and the removal of surcrose bearing juicies from sugar cane. In a preferred embodiment of the invention, sugar cane is taken in raw out form from the fields, ground or otherwise broken up into relatively small pieces, and passed through a juice extraction system, which may be one or more roller mills, or a diffuser battery where the cane is acted upon by steam or hot water or other hot fluids to soften and break apart the fibrous material and to remove a substantial portion of the sucrose bearing juice from the cane. The output of this diffuser column is most commonly referred to as diffused bagasse, and the output of the mills is known as mill bagasse, and in many instances this bagasse contains a rather large percentage of liquids. These liquids will include some of the fluids with which the cane was treated in the extraction system and/ or some retained juice which has not been removed in the system, but may be present in a dilute state.

The bagasse from a diffuser in many cases has such high moisture content, for example 88% moisture, and is of such a loose nature that it is difficult to form into a blanket which might be passed through a conventional roller mill or the like, and in any event such mills are not satisfactory in removing a substantial amount of the moisture from this diffused bagasse. Furthermore, generally such mills do not operate well on bagasse at temperatures in the range of 140180 F., especially if lime has been added in the diffuser.

Accordingly, the present invention provides a novel mechanical screw press construction, with which bagasse can be reduced in moisture content by a substantial amount, for example, to in the neighborhood of 3545% moisture. The juices so removed can be directed to recovery operations where the sucrose or other chemicals in these juices can be recovered. Additional recovery of a sucrose adds to the overall efiiciency of the operation,

as is common in the sugar cane industry, as a fuel. For

example, the bagasse may be passed into a furnace used to operate a boiler which in turn heats the water or other liquid that is supplied to a diffuser column, and/or to produce stream for other uses in the sucrose extraction process. By removing a substantial amount of the moisture from the bagasse, its fuel value is increased, since there is that much less moisture to be driven off in the combustion process. This results in a further gain in efficiency in the entire operation.

A further object of the invention is to provide a novel mechanical pressing operation which is arranged to receive continuously a supply of moist bagasse, preferably at an elevated temperature in the range of l40180 F., and to subject this bagasse to a compacting, compressing and mechanical working operation which results in extraction of a substantial percentage of the moisture from the bagasse.

An additional object of the invention is to provide a novel mechanical screw press for use in the process of sucrose juice bearing materials, wherein the apparatus is capable of receiving a rather large bulk of the material having a substantially high moisture content, for example, around -90% moisture, and wherein the press is arranged continuously to convey the material through operations of compressing and mechanical working in which the volume of the material is reduced as the moisture is extracted therefrom and collected.

A further object of the invention is to provide such a stationary discharge sleeve construction wherein the sleeve is urged into its normal position within the pressing outlet by a hydraulic cylinder to which hydraulic fluid is supplied at a predetermined pressure, such that the force of the cylinder holding the sleeve in position is available up to a predetermined maximum. force which can be overcome by an excess of pressure within the press, in which event the force of the hydraulic cylinder can be overcome allowing the discharge sleeve to withdraw and thereby prevent excessive pressures on the material within the press.

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

In the drawings- FIG. 1 is a schematic diagram of a sugar processing system incorporating the features of the present invention;

FIG. 2 is a view which is generally a vertical sectional view taken through the press which is shown in the sys- -.tem of FIG. 1;

FIG. 3 is a detail view of portions of an adjustable discharge sleeve incorporated in the press shown in FIG. 2;

FIG. 4 is a detailed partial sectional view showing the general arrangement of the drainage openings provided in the walls of the chamber of the press; and

FIG. 5 is a schematic diagram showing the hydraulic and pneumatic systems used to maintain the discharge sleeve in its normal position within the outlet of the press.

Referring to the drawings, which illustrate preferred embodiments of the invention, in FIG. 1 a system according to the invention is shown schematically. The sugar cane is indicated at 10 flowing into the system on a conveyor 12 which carries the cane to a crusher 15. This may be in the form of cooperating toothed rolls, or similar equipment, which receives the raw sugar cane, or like sucrose bearing fibrous material, and tears the cane (although the cane is not subjected to much pressure at this point) thereby reducing the size of the cane and exposing its fibers, and as a consequence of this action an initial flow of juice from the cane generally occurs. This juice is collected in the tank 16 and piped to the equipment (not shown) which performs the extraction of the sucrose from the juice. In some cases the cane is merely shredded thoroughly without extraction of juice.

In the system shown in FIG. 1 the shredded cane is then fed into a diffusion battery which may be constructed in any one of several different types, as shown in the art. For example, one form of diffusion battery incorporates a number of individual cells, which are roughly in the form of large pressure cookers, and these are charged With the cane in sequence, and are subsequently discharged once the cane has been subjected to hot water or similar liquids which tend to wash and/ or lea-ch the juice from the cane and carry the juice away as a solution of juice and water. In a typical diffusion cell, the amount of juice in the extracted liquid flowing from the cell is a minor portion, but nevertheless significant. A number of these cells are used so that they can be charged and emptied in sequence, thereby producing an essentially constant operation. Other forms of diffusers are known wherein the diffusion process is carried on continuously, the cane being supplied at one end of the apparatus and being discharged after diffusion at another point. The product discharged from the diffusion battery is generally known in the :art as diffused bagasse. In FIG. 1 a conveyor 22 is shown as carrying the diffused bagasse from the battery 20.

This bagasse is conveyed through a collection tank 25 which serves to even out the flow of bagasse, particularly Where a batch type diffusion battery is employed. The diffused bagasse thus is carried from the tank 25 as an essentially continuous stream over the conveyor 27, from which the diffused bagasse is emptied into the inlet hopper or receiving section of the mechanical pressing device, details of which form an important part of the invention. This continuous pressing device is indicated in FIG. 1 by the general reference numeral 30, and it includes a drive motor 31 and drive gear case 32. Further details of the press are shown in FIGS. 2 and 3. The bagasse discharged from the press empties onto a conveyor 35 which in turn can carry the bagasse to the boiler or other power plant in the system, where the bagasse is generally used as a fuel. This power plant is indicated by the general reference numeral 37.

In the system shown in FIG. 1 the diffused bagasse passing over the conveyor 27 to the press 30 may contain substantial moisture, for example in the order of 8590%, and this moisture is in the form of some retained juice as well as liquid absorbed by the bagasse during the diffusion operation, and retained in the fibrous bagasse material as it is carried to the press. The mechanical press can extract a substantial amount of this moisture, for example at least one half of it such that the moisture contents of the bagasse leaving the press is in the range of -45%. The liquid extracted in the mechanical press will contain juice which in turn contains a significant amount of sucrose, and therefore this liquid can be returned to the extraction equipment for recovery of this sucrose, or this liquid can be piped to other recovery equipment. As another alternative, if the sucrose content of the material extracted in the press is not of sufficient amount to warrant passing it to the extraction equipment, it can be returned to the diffusion battery 20 and employed as :a portion of the liquid used in the diffusion process.

Referring to FIG. 2, the screw press 30 has an inlet hopper over the rotating feed worm 42 which picks up the bagasse fibers as they are dropped into the hopper and carries them forward through the hopper, to the right as viewed in FIG. 2, into the first section 45 of the press. It should be noted that the portion of the feed worm 42. extends into this first section, in order to assure that the material is carried into the section past the lip 46 of the inlet hopper. The diameter of the worm 42, at least that portion of it which extends into the section 45, should be sufficiently less than the internal diameter of section 45 where the feed screw revolves within it to provide a substantial clearance between the edge of the feed screw and the walls of the press section or chamber. A clearance in the order of one-half to three-quarters inch, is normally used at this point, and is considered advantageous to assure proper feeding of the stringy tough fibers. The motor 31 drives separate gears which rotate the feed worm 42 at a substantially higher speed than the rotatable shaft 50, which in turn drives the expressing worm means 48. Details of this arrangement are explained in U.S. Patent No. 3,246,597, which is assigned to the assignee of this application.

At the end of the feed worm 42 within the first press section 45 the material is forced past a breaker bar 47 and toward the first of several Working and pressure Worms 48. These worms include a body 48a which is connected to rotate with the internal main drive shaft 50, and a worm flight 4812 which is of such outer diameter that it comes into close relation wtih the walls of the section 45, normally with a clearance of a few thousandths of an inch. In the first section 45, as shown, there may be two or more screw flight portions 48, separated by collar members 49, and spaced outwardly from these collar members there are stationary breaker bars or lugs 47 which tend to resist rotation of the material with the material being carried and urged forward by the preceding screw flight. These lugs preferably are slotted, as of the type disclosed in copending application Serial No. 558,854 filed June 20, 1966, now US. Patent No. 3,366,- 039. This action tends to work the fibrous material and assist in breaking open the cells of the fibers, as Well as exerting mechanical pressure on the material to extract liquid therefrom. The walls of the press section 45 are constructed to have drainage openings for permitting the extracted liquid to flow outwardly and be separated from the fibrous material. A detail of a section of this wall structure is shown in FIG. 4, wherein it will be seen that adjacent bars 51 are separated by small spacers 52, which can be separate pieces or integral projections on the bars, in order to define the drainage openings. These openings are of relatively small cross-section, so that only the finest of the fibers will be liable to pass through the openings, and the fibrous material is thus retained in the press structure, and continually carried through it, while the ex pressed liquid flows through the drainage openings and falls into the pan 55, from whence the liquid can be piped to whatever location is desired.

At the end of the section 45 there is a tapered section which may be formed either as a continuous bushing, or has an assembly of short bars having spaces therebetween for drainage openings. In either event, this bushing (or the equivalent section made up of bars) has an internal surface which tapers inwardly from a diameter corresponding to the internal diameter of the press section 45 to the smaller diameter of the next press section 65. Thus, the mass of the material being carried through the press is compressed and compacted as it passes through the bushing 66, and this in turn provides for a further expression of liquid from the material. It should be noted that the worm flight 68 (which in other respects corresponds in structure to the worm 48) has a correspondingly tapered outer surface so that this worm maintains a close clearance with the internally tapered surface of the bushing 60, or the bars making up the same piece. Thus, the screw flight 68 carries the material through the section of decreasing diameter, and assures that the material continues to move through the press at this point.

It will be noted from FIG. 2 of the drawings that the section is of generally the same configuration as the previous section 45, and terminates in a bushing 70, or equivelent bar assembly as mentioned, in which bars are used having inwardly tapered outer surfaces. Drainage may or may not be provided, as desired.

This bushing opens or discharges into the next press section 75, into which the tapered worm flight carries the materials. Again, the structure of the parts is essentially the same as in the preceding section, but the section has a smaller diameter. At the end of the main shaft, which serves to drive the worm members, there is provided a nut 80 that holds the parts assembled on the shaft. Around this nut is a sleeve or bushing 82 which is pressed against a washer 84. The outer diameter of the sleeve 82 and washer 84 correspond to the diameter of the body of the preceding Worm.

Tapering outwardly toward the discharge end of the press, and fitted around bushing 82, is a discharge sleeve 90 which may have either a solid imperforate surface, or preferably, drainage openings for the purpose of admitting expressed liquid to the interior of the non-rotatable discharge sleeve 90. The final cage bushing 92 surrounds this sleeve at the end of the section 75, and it is held in place in the end frame member 95 next to a discharge ring 96, preferably bolted or otherwise removably secured to the end frame. The inner surface 98 of the bushing 92 tapers first inwardly toward sleeve 90, then outwardly to the inner surface 99 of the ring 96. The material thus experiences a final compression as it is forced between bushing 92 and sleeve 96. Preferably the sleeve is normally positioned with all but approximately one to one and onehalf inches of its length projecting into chamber 75.

The non-rotatable discharge sleeve 90 is mounted for reciprocating movement on a movable rod 160 which is attached to the piston rod 102 of a hydraulic cylinder 103. This cylinder is in turn bolted through supporting structure, such as shown in FIG. 2, to a supporting bracket 105, and this bracket in turn is fastened to arms 106 carried from the end frame member 95. The supply hydraulic actuating fluid to the cylinder 103 is provided through the conduits 107 and 108. The stationary sleeve 90 has its interior opening into a hollow sleeve 110 which is secured to the backside of the member 90, and is therefore movable with it. This sleeve opens into a collector or spout 112 carried on the rear of the sleeve 110 and opening into the drainage tube 114. Therefore, expressed fluids passing through the perforated sleeve 90 will flow through sleeve 110 and spout 112 and through the tube 11 1, regzrdless of changes in the position of the discharge sleeve The pressed bagasse discharges from the ring 96 onto the conveyor 35, where it may be carried to the power plant, or to any other suitable place of disposal. As previously mentioned, the action of the expressing press on the wet bagasse removes a substantial amount of moisture or liquid from the bagasse, and apparatus of this type has been successfully employed to provide bagasse at the discharge, i.e. onto the conveyor 35, with a moisture content of around 45% or less.

The mounting structure for the discharge sleeve, therefore, must be sufliciently rigid to prevent it from rotating, and to maintain it in alignment (assisted by the bearing sleeve 82). This structure is shown in FIG. 3, where the rod 102 of the hydraulic cylinder 103 is threaded, as shown at 120, into the end of the rod or shaft 100. A forward end of this shaft is in turn fastened by bolt 123 to the rear of the cylinder 110, to cause movement of the rod 100 to be directly coupled to the discharge sleeve 90.

The rod 100 has a spline 124, and is slidably mounted in a splined bearing bushing 125 which includes a passage 126 to admit lubricant from the grease fitting 128 into the spline. The sleeve bushing 125 in turn is supported in a larger tube 130 which is welded or otherwise suitably fastened to the mounting bracket. A suitable key (not shown) prevents rotation between the splined bushing 125 andits mounting tube 130.

At the forward end of the cylinder 130 there is a cap 132 which is fastened to the cylinder by a number of bolts, one being shown at 133. Within this cap there is a gland 135 held in place by a washer 137 and one or more bolts 138, and the gland in turn holds suitable packing 140 in place to retain the lubricant.

A suitable circuit for controlling the operation of the hydraulic cylinder 103 is shown schematically in FIG. 5. The pneumatic circuit is illustrated by dash lines, and the hydraulic circuit by solid lines. A regulated source of air pressure is indicated at 150, and this may include conventional pressure regulating valves, etc., of conventional type. This line is connected to the top of a hydraulic reservoir or tank 152 which preferably has an internal diaphragm baflle (not shown) to prevent mixing of the pressure air with the oil while maintaining the hydraulic fluid or oil under enough pressure to insure it is forced into the pumping system. The air source is also connected through a pressure regulator valve 154 to a reciprocable double pilot valve 155. This valve receives pressure air at its central inlet 156 from the regulator 154, and the outlets from the other two ports in the active position are provided with suitable restrictors 158. The pilot chambers 160 of this valve control the shuttling of the valve body, such that the inlet line 156 is connected alternatively to outlet lines 162 and 163, while the central outlet port 164 is connected to one or the other of the restrictors 158.

The lines 162 and 163 extend to opposite sides of a double acting reciprocating booster pump 170, which incorporates a central piston 171 and small hydraulic pistons 172 formed at opposite ends of the rod 173 which moves with the piston 171. It will be seen that when air under pressure is supplied to one side of piston 171, the other side is connected to the exhaust line 164, and the corresponding pilot 160 is likewise connected to tend to move the shuttling valve 155 into the opposite position from which it is then urged. Therefore, the air valve 155 supplies pressure air alternatively to opposite sides of piston 171, causing it to reciprocate and the hydraulic pistons 172 function as hydraulic pumps as follows.

The inlet line to the hydraulic system is through line and filter 181, to check valves 182 which are connected into the chambers at each end of the pump 170 surrounding the piston 172. The outlets of these chambers are through further check valves 184 which are connected to the outlet manifold 185 of the booster pump. Thus, as the piston 171 reciprocates, one of the hydraulic pistons 172 will retract to draw oil through its inlet check valve 182, while the other forces oil out through its check valve 184, and on the return stroke the opposite conditions occur. Therefore, hydraulic fluid or oil under pressure is supplied to hydraulic pressure regulating valve 188.

Fluid in excess of the capacity of this valve is returned through line 189 to the return manifold 190 and from that manifold back to tank 152. The outlet of the pressure regulating valve 188 is connected to the oil supply line 192, which leads to a spring-loaded solenoid operating control vla've 195. Its control solenoid is shown at 196, and the valve itself is shown in the position it occupies when the solenoid is de-energized, and the valve body positioned by the spring 197. In this position of the valve, hydraulic fluid under pressure is admitted to the head end of the hydraulic cylinder 103, and the rod of the end of this cylinder is connected to the return manifold 190. If solenoid 196 is energized it acts against the spring to shift valve 195, and the valvethen blocks the pressure inlet 192 and connects the head end of the cylinder through line 198 to the return manifold 190.

A hydraulic accumulator 200 preferably is connected into line 192, so that if valve 195 is in its de-energized position, and the solenoid 196 is energized, hydraulic fluid under pressure is immediately available from the accumulator in sufficient quantity to advance the hydraulic cylinder 103 immediately, tending to move the discharge sleeve 90 into its restricting position.

By control of the hydraulic pressure regulator valve 188, the force tending to hold the discharge sleeve 90 against the flow of compressed bagasse can be regulated, and the discharge sleeve can fluctuate slightly in response to slight increase or decrease in the flow of material from the press. Thus, this control tends to maintain a constant back pressure within the press and contributes to a uniform expression of liquids from the material. If there is an overload on the press, or if the supply to the press is substantially decreased for some reason, the control system provides for withdrawal of the discharge sleeve 190 to permit the pressure in the press to remain within predetermined limits, and also to avoid clogging of the discharge end of the press.

For this purpose, the solenoid 196 is controlled by conventional meter relays 202 and 2&4, respectively, which sense the amount of electrical current drawn by the press drive motor 31. For example, the relay 292 may be set to close whenever the current drawn by the motor decreases below a predetermined minimum and the relay 204 may be set to close only if the current drawn by the motor exceeds a predetermined maximum. In either event, if the current is outside of the range established by setting these relays, the solenoid 196 will be energized and valve 195 will shift. This equalizes the pressure on opposite sides of the piston, to permit the pressure of material against the discharge sleeve 99 to force it outward of the discharge ring 96.

In the case of the relay 204, it is of course desirable to avoid exceeding a certain predetermined pressure upon a material. If there should be a blockage or unexpected build-up of pressure, this will reflect in an increase in power demand on the motor 31, and the consequent increase in current will cause the relay 2% to trip, whereupon the discharge sleeve 90 can withdraw and the pressure within the press will drop as the restriction at its discharge is increased. Preferably, this relay is set to keep the solenoid 196 energized for a sufficient time to permit the press to reach an equilibrium at a pressure below the maximum corresponding to the setting of relay 294.

If the supply of material to the press should be interrupted for any substantial length of time, the amount of current drawn by the motor will decrease below the minimum to which the relay 202 is set. It has been found that as the press tends to evacuate itself under these conditions, a certain amount of bagasse will remain between the final worm 79 and the discharge sleeve 99, and this bagasse will tend to be worked and heated to the point where it hardens and twists around the discharge sleeve and adjacent structure. To avoid this condition, it is desirable to Withdraw the sleeve under these conditions and thus relieve pressure on the material and permit the material to be expelled from the press.

The operation of the apparatus is such that relatively wet or moisture-laden bagasse, which consequently occupies a rather large volume, is fed into the hopper 4t and carried by the faster rotating feed worm 42 into the first press section 45. As the bagasse is carried through this and subsequent press sections it is subjected to mechanical pressure and working, by reason of the action of the interrupted screw flights and the breaker bars past which the flights move the bagasse. These bars are preferably of the type disclosed, to minimize damage due to foreign material entrained with the bagasse. At the same time, the bagasse is forced into press sections of decreasing cross-sectional area, which contributes to the mechanical compression of the bagasse. Expressed liquid flows outwardly between the screen bars 51, through the spaces provided by the spacer members 52 which occupy only a small amount of the space between the bars, and which may in fact be provided as integral bosses or protrusions from the bars themselves. As the pressed bagasse reaches the final press section '75, it passes the final worm 79, which preferably is decreased in pitch with respect to the preceding worms, and forced around and past the nonrotatable discharge sleeve 90. It is at this location that the mechanical pressure on the bagasse is highest. In order to provide optimum drainage area, both the surrounding walls of the press cage and the walls of the sleeve 90 are capable of conducting away expressed moisture, which may include some vapors as well as liquids.

The cylinder 103 and its associated hydraulic system control the position of the discharge sleeve 90 as to movement in and out of the discharge ring. This also provides a safety feature in that if the pressure exerted against the sleeve 9% increases beyond a desired maximum, the resultant force transmitted through the connecting shaft 100 will overcome the preset force exerted on the piston of the hydraulic cylinder, and the sleeve 90 will move outwardly of the press discharge opening by an amount sufficient to relieve the condition which caused the excess pressure on the bagasse. If pressure in the head end of cylinder 1% exceeds the pressure to which valve 188 is set, there will be reverse flow through this valve and into the tank return line 189 until the pressure in the head end of the cylinder drops to the predetermined value. As soon as this condition is relieved, the sleeve automatically will tend to assume its original position, hence under normal operating conditions equilibrium will exist at the desired pressure.

It should be understood that other controllers responsive to the power demands of the press drive can be employed. For example, when a steam turbine is used to provide driving power, suitable pressure responsive devices can be used to sense the chest pressure in the steam chest at the turbine supply, and the position of the sleeve 9t? will be changed in corresponding fashion, according to the power demands on the turbine reflected as a rise or drop in chest pressure.

It should be understood that while the invention has been described with respect to bagasse which is the product of a difiusion extraction system, the novel apparatus disclosed herein is equally useful in other systems for extracting juice from sugar cane. For example, the press shown in FIG. 2 may receive what is known in the art as mill bagasse, the product of one or more roller type mills or equivalent, where the bagasse fibers are usually longer and stringier, and in most cases do not contain as much moisture when received at the press.

While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms 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. Apparatus for removing liquid from material such as sugar cane bagasse, comprising a pressing machine having a feed cage and at least one expressing cage connected to said feed cage, said feed cage having a larger inner diameter than said expressing cage, a first ring memher mounted between said feed cage and said expressing cage and having a tapered inner surface providing a wall of gradually decreasing diameter to guide material from sad feed cage into said expressing cage, means defining drainage openings for expressed fluids in the walls of said feed cage and said expressing cage, an inlet hopper connected to said feed cage for supply of wet material, a rotatable feed Worm mounted in said feed cage to carry the material toward said expressing cage, a discharge ring defining an outlet on said expressing cage, expressing worm means rotatably mounted in said expressing cage including a worm flight having a tapered periphery corresponding to the tapered inner surface of said first ring member, a discharge sleeve member having a tapered outer surface, means mounting said discharge sleeve for movement between an inner position wherein a major portion of said sleeve is located within said expressing cage and an outer position wherein said sleeve is substantially withdrawn outside said ring, drive means including separate drives for rotating said feed worm at a higher speed and said expressing worm means at a lower speed to force the material through said cages and outward through the space between said ring and said discharge sleeve whereby the material is compressed and fluids are expressed from the material to flow through said drainage openings, and means yieldably urging said discharge sleeve towards its said inner position causing said sleeve to resist the discharge flow of material up to a predetermined pressure and to yield and enlarge the space between said sleeve and said ring when the pressure on the material exceeds said predetermined pressure.

2. Apparatus as defined in claim 1 wherein said expressing cage includes a first expressing cage section and a final expressing cage section at the discharge end of which said discharge ring is mounted, a second ring member having a tapered inner surface and mounted at the entrance to said final expressing section to provide a passage of gradually decreasing diameter thereto, said final cage section having an inner diameter less than said first cage section, and a further tapered worm flight incorporated in said expressing worm means and mounted in closely spaced relation to said second ring member for carrying the material therethrough into said final cage section.

3. Apparatus as defined in claim 2 wherein said expressing worm means comprises a plurality of alternately arranged form members and sleeve members and a drive shaft supporting said members coaxially of said expressing cage, said worm members being connected to rotate with said shaft and having a minimum clearance in the order of a few thousandths of an inch between the periphery thereof and the inner wall surface of the expressing cage, and breaker bars extending inwardly of the walls of said expressing cage toward said sleeve members and terminating a substantial distance from said sleeve members, whereby said breaker bars will resist rotation of the material forced around said sleeve members while leaving a substantial space between the inward ends of the breaker bars and the sleeve members through which foreign material such as rocks or pieces of metal can pass without damaging said breaker bars.

4. Apparatus as defined in claim 1 wherein said yieldable means positioning said discharge sleeve includes a hydraulic cylinder having an output rod connected to said discharge sleeve, a hydraulic pressure fluid supply connected to said cylinder to drive it in a direction advancing said discharge sleeve toward its inner position, and a control establishing a maximum hydraulic fluid pressure within "said cylinder whereby a force on said discharge sleeve in excess of the force exerted by said hydraulic cylinder will automatically move the discharge sleeve toward its said outer position and thereby decrease the resistance to the flow of said material around said discharge sleeve and through said discharge ring.

5. Apparatus as defined in claim 4 wherein automatically operable valve means are provided for interrupting the supply of hydraulic pressure fluid to said cylinder and connecting said cylinder to a lower pressure such that material advancing against said discharge sleeve can readily push said sleeve toward its outer position to relieve the pressure upon the material by said expressing cage to a minimum.

References Cited UNITED STATES PATENTS 1,769,658 7/ 1930 Veenhuyzen -145 1,851,191 3/1932 Lang 100-47 2,178,714 11/1939 Anderson 100-43 2,280,880 4/ 1942 Anderson 100-43 2,340,009 1/ 1944 Meakin 100-148 XR 2,422,895 6/1947 Habenicht 100-127 XR 2,817,287 12/1957 Onarheim et al. 100-147 XR 3,003,412 10/1961 Vincent 100-148 XR 3,062,129 11/1962 Wandel 100-43 3,085,502 4/1963 Hurtig 100-43 3,092,017 6/1963 French et al. 100-93 3,111,082 11/1963 Larsson et al. 100-147 3,140,652 7/1964 Williams 100-43 XR 3,143,956 8/1964 Hurtig 100-43 3,195,446 7/ 1965 French 100-41 XR BILLY J. WILHITE, Primary Examiner.

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