US2249736A - Screw press - Google Patents

Description

July 22, 1941; R. T. ANDERSON SCREW PRESS V Filegl June 24, 1938 4 Shets-Shggt 2 attorneys l l l I I l I IIHHHHHI I I y 22, 1941- R. T. ANDERSON 2,249,736

SCREW PRESS Filed June 24, 1938 4 Sheets-Sheet 3 3nnentor Mun v1.51 6mm 8;; I 4

Gttornegs July 1941. R. 'r. ANDERSON 2,249,736

SCREW PRESS Filed June 24, 1938 4 Sheets-Sheet 4 v o o 95 107 96 6 Znmentor'- Gttomegs Patented July 22, 1941 SCREW PRESS Raymond T. Anderson, Berea, Ohio, assignor to The V. D. Anderson Company, Cleveland, Ohio,

a corporation of Ohio Application June 24, 1938, Serial No. 215,683

8 Claims.

This invention relates to continuous presses and particularly to continuous presses of the type shown in the patent to Anderson No. 829,314, granted August 21, 1906, in which an interrupted screw mounted in a slotted press barrel, containing so-called knife bars to prevent the rotation of the treated material, operates to express oils and similar liquids from various materials. The necessary back pressure is developed upon the material being treated by a choke or discharge orifice at the outgoing end of the press, or by equivalent means within the press barrel.

Presses of this sort are very highly developed and are in successful use with a wide variety of materials. The past practice has been to operate the press at approximately constant speed and with the material fed at an approximately constant rate, the performance of the press being controlled by varying the effective area of the choke. This necessitated frequent adjustment of the choke and the constant attention of an operator, because even different batches of the same material were found to develop markedly different characteristics while passing through the press. The most efiective way heretofore found to stabilize the action of the press was to vary the adjustment of the discharge choke. Smce the results varied with the skill of the operator, or with conditions which could not be detected by mere observation, or in time to permit their correction, it is desirable that the operation of the press be made uniform and be stabilizedin such a way that the extraction rate is ma ntained constant, automatically by instant-to-mstant adjustment of the rate of feed in conformity with changes in the character or condition of the material being fed to the press.

The problem arises from the fact that conditions in a continuous press are not self stabilizing but are inherently unstable. If the resistance starts to build up the result is to cause it to build up further, and hence to change the character of the extraction and of the resulting products.

The present invention is based on the discovery that by measuring the resistance to flow of the material approaching the press, under conditions which develop moderate back pressure, and varying the rate of feed to the press in inverse relation to this resistance to flow, it is possible to stabilize the operation of the press and render adjustment of the choke necessary only when changing from one type of mater al to another of different character. In other words, it is proposed to make the press self regulatmg in its action. Variations in the material being treated through ranges normally encountered in practice are taken care of automatically after initial adjustment has been performed.

In addition to this broad concept, there are several important refinements. In the first place, it has been determined that the best but not the only way to measure the resistance characteristics of the material is to pass the material through a preliminary continuous press in which a part at least, of the moreeasily extracted liquid component is removed, to cause the preliminary press to feed the main press, and then measure the resistance developed by the material in this preliminary press and regulate the speed of the preliminary press, in inverse relation to such resistance. The effect is to vary the rate of feed to the main press and thus stabilize conditions therein. This is possible only because the resistance which the material will develop in the main press is a different function of the resistance which it develops in the preliminary press. The discovery of this fact is the basis of the invention.

The preliminary press may be constructed as an independent unit delivering to the main press, or merely as an independently driven feed screw in the entrance end of the main press.

While many ways of measuring the resistance to flow in the auxiliary or feeding press, and regulating the speed of the auxiliary press accordingly, might be evolved, the simplest and most satisfactory scheme so far discovered is to use a self-regulating electric motor in which the relationship between speed and load is such that the speed falls at the proper rate as the load rises. A very satisfactory motor for this purpose is a slip-ring or wound rotor type of motor hereinafter described. A special shunt wound type of different current motor, or a series direct current motor of special type may also be used. Such motors can be so wound as to give a speed load characteristic which will meet the requirements of the invention as to range and rate of variation.

Consequently, the principle underlying the method and apparatus hereinafter set forth is that the main press is driven at constant speed under a substantially constant load and with a constant discharge choke or orifice or equivalent the speed of which will vary in the proper inverse relation to the feeding resistance developed therein. The possibility of doing this depends on two factors: First, that there is a satisfactory relationship between the resistance developed in the feeding press and the resistance characteristics of the material in the main press where'the extracting pressures are incomparably higher. Second, that simple speed regulation in response to varying load can be had by an electric motor through a sufilcient range and at a satisfactory rate for the purpose in view.

determines its resistance to flow under conditions which resemble conditions inthe press proper, the

feeding, resistance can be used to regulate the rate of feed in such a way as to stabilize the extracting performance of the press, and to maintain constant pressure conditions in the press, particulariydn the vicinity of the discharge end.

While this method of stabilizing the operation of presses is of broad scope and may find numerous applications with various types of apparatus, there are shown herein a few forms of apparatus which may be employed to perform the functions above set forth. The invention will be more fully understood by a reading of the following specification in connection with the accompanying drawings, inwhich- Figure 1 is a diagrammatic view illustrating the principles upon which the method of the present invention is based; I

Fig. 2 is a fragmentary'front view partly in elevation, and partly in section, of one form of press embodying the present invention;

Fig. 3 is a'slde view, partly in elevation and partly in section, of the press feeding mechanism and its drive applied to the machine of Fig. 2;

Fig. 4 is a top plan view of the hopper feeding mechanism, showing the mounting of the feed motor;

Fig. 5 is an enlarged vertical sectional view of the hopper feeding means of Figs. 2, 3 and 4, showing how the driving means are arranged.

Fig. 6 is a side view, partly in section, illustrating a modified form of apparatus suitable for carrying out methods according to the present inventlon;

Fig. 7 is a partial section of the machine of Fig. 6, showing driving mechanism embodying the present invention applied thereto; and

Fig. 8 is a circuit diagram illustrating one manner in which the electrical apparatus shown in Figs. 2 and 7 may be connected.

Fig. 1 of the drawings, in more or less diagrammatic form, illustrates the principles underlying the method of the present invention. In this figure, B represents a continuous press of the interrupted screw type, of which one example is given in the Anderson Patent No. 829,314, referred to above.

This press comprises a frame including end members, only oneof which, designated 8,-is shown, tied together by bars 9. Supported in this frame are two cooperating arcuate barrel bar units which may be secured together to form a barrel of cylindrical cross-section, and made up of individual'bars ll suitably spaced from one another in accordance with the material to be pressed, and held together by a plurality of barrel rings or cross-frames l2. These cross-frames are clamped together by longitudinal bars 13 held by cross-bolts l4.

One example of a barrel arrangement of this particular type is shown in the patent to Ander- In other words, if the material be fed to the press by means which 1 mam son No. 1,321,351, granted November 11, 1919. This barrel contains the usual interrupted screw made up of separate segments fitted on the shaft, and knife bars in the barrel for preventing the materiai'from rotating within the barrel. This interrupted screw is carried on shaft II mounted in suitable bearings and having an adjustable choke Ii at the outlet end where the pressed material is extruded. This choke may take various forms. one of which is described and claimed in the patent to Anderson No. 1,752,054, granted March 25, 1930. The liquid escaping between the barrel bars II is caught in a suitable container such as the trough Ill, from which it is discharged to a point of collection. The press B has an inlet hopper ll into which material to be pressed is fed, the feed screw it being provided to feed the material into the barrel of the press and actuated by a constant speed motor of suitable form designated it, this motor being connected to the shaft it through suitable reduction gearing carried in the housing 21,

In order to obtain a constant rate of extraction in the press-B and to maintain the pressure constant at the outgoing end of the press and for some distance inward from the same, there is associated with the inlet hopper ll of the press 3 an auxiliary pressing unit designated A, having substantially the same structure as that of the main,press B but being of smaller size. The press A contains an interrupted screw of the type used in press B, but has no choke, the outlet end of the press feeding directly into the hopper I! through a suitably reinforced connection 22. The back pressure in the press A is obtained by an accumulation of material in the pipe 22 and the hopper I], it being understood that while the shaft of press A is shown as being horizontal, it may be vertical or it may constitute a part of the screw of press B, so long as it comprises a separate feeding unit which may vary. its speed in accordance with the resistance imposed upon it by the material being fed. The press A has a feed hopper 23 into which the material is placed and passes to the feed screw in the press A, this screw being actuated by a variable speed motor 24 having the characteristic of varying its speed in accordance with the load imposed upon it. The oil or other liquid extracted from the material by the press A may be discharged from a pan 25 and collected at any suitable point.

The back pressure developed in order to cause preliminary press A to function may be caused in several ways, and for the purpose of illustration, only a few of those ways are disclosed herein. It will be obvious that variations in the size of the main worm of press B will vary the back pressure as will clearance conditions-in the main barrel and the relative speeds of the two presses. The press A would normally be designed to deliver more material than press B can handle properly, and hence a back pressure will develop in press A. Variations in the speed of the main press shaft will also affect the back pressure and this offers a convenient means of control. All of these methods are within the scope of my invention where response to back pressure in the preliminary press is relied on to control the operation of the main press.

It will be understood that the purpose of the present invention is to provide means for feeding material to the main barrel B at such a rate as to cause extraction to take place under as nearly uniform pressure conditlons as possible, particularly in the outgoing end of the press and over an area comprising approximately the latter third of the main press barrel. Use of a self-regulating variable speed motor of the type set forth herein brings about this desirable result. The principles of the present invention, however, apply regardless of the type and location of the feeding mechanism, and whether the main barrel of the press be short or long. In other words, the problem is to produce a uniform rate of extraction, and maximum efliciency of extraction, by performing a preliminary adjustment of the choke, and then allowing the press to operate without choke adjustment and without the constant attention of an operator.

Practice of this method not only results in more uniform and more rapid extraction with a larger yield of oil, but the press may be made to operate on widely varying types of materials without the frequent changing of the spacing of the screw segments or the relation of one screw with respect to another, that has been required heretofore. Even a single barrel bar spacing may be employed for different materials provided that those materials have similar fibrous contents. When the fibrous content of one material to be treated differs widely from that of 'a previous material treated, a substitute set of barrel bar units with different spacing may be 'substituted without dismantling the screw or any part of the press other than the barrel bar structure which is on the outside of the press and designed for accessibility.

In prior art devices it was necessary, for ex ample, in changing from one material to another, to remove the barrel bars to reach the worms, and then to dismantle these worms to alter the spacing of the segments. In presses of the type shown in Patent -No. 1,971,632, granted August 28, 1934, it was frequently necessary to alter not only the spacing of the screw segments and of the barrel bars but also the spacing of the vertical screw with respect to the horizontal screw. In all cases it was, of course,

' comes practical to keep pre-assembled barrel bar units ready for substitution when a new type of material is to, be extracted. The range of operation of presses of the present type is illustrated by the fact that one barrel bar spacing can be used for pressing copra, palm kernels, and other materials having similar fibrous content. Another barrel bar spacing would be required for pressing fiaxseed, cottonseed, sesame seed and the like.

While the method of the present invention is a broad concept, certain practical embodiments of mechanism for practicing it have been illustrated by way of example. The preferred form of apparatus is shown in Fig. 2 of the drawings where the parts corresponding to thoseof Fig. 1 are designated by similar reference characters. In this figure, the worm carried by shaft I5 is shown in detail. It has separate screw or worm segments 26 separated by collars 21. Associated with the segments 26 are knife bars 28 provided for the purpose of preventing rotation within the barrel, of the material to be pressed. The knife bars are carried by the barrel.

' into the main barrel of the press.

The presure imposed upon the material passing through the press causes the liquid to be extracted, so that it escapes through'the openings between the bars ll, while the solid material in the form of a dense cake is expelled at the outlet end of the press. Pressure within the press is built up to the desired degree by .a constriction in the form of a choke l6 disposed in the cmtiet from the press orv by equivalent means within the press barrel. One form of choke is that shown in Patent No. 1,752,054, referred to above. The details of this choke are not important in the present invention, since the choke adjustment is not relied on to control the operation of the press, and the frequent adjustments usually characteristic of presses of this type are done away with. It will, therefore, be 'suflicient to state that the, choke may comprise a flared outletof diverging form associated with a cone member 20 carried on the shaft l5 with the worm segments 26, and rotatable with them. Any equivalent choking means may be used.

In accordance with the teachings of the present invention, it is not-contemplated that adjustment of the choke be carried out during the operation of the press, except for preliminary adjustment. In practice it is-desirable to have the choke arranged to permit adjustments when changing from one material to another, where these materials are of widely different characteristics The choke would, under such conditions, be merely subjected to an initial adjustment for each material, and then the control would be exercised by the mechanism for feeding material to the press in accordance with the principles of the present invention.

The choke would also be used to clear the press before shutting it down, thus avoiding the serious consequences of permitting highly compressed material to harden in the press and requiring dismantling of the press for the removal of this material. The choke would be opened and the press allowed to run until'the compressed material was discharged and the barrel filled with at least substantially uncompressed material, leaving the machine ready to be used during a following run.

Associated with the inlet to the press is a vertical barrel 29, preferably having a section 3| made up of spaced bars, substantially as in the main barrel, and capable of subjecting the material to preliminary extraction before its entry In such instances there will be associated with the barrel 29, a worm 32 made up of segments 33 similar to the segments 26 in the main barrel and having knife bars 30.

Material may be fed to the barrel 29 in any suitable manner,'but here shown as comprising a casing 34 wherein the material is tempered, i. e., brought to a proper temperature and moisture content for eflicient extraction, before being fed by means of blades 35 to the inlet opening 36 associated with the barrel 29 and the 'worm therein. The tempering apparatus includes a shaft 31 which may be driven by any suitable mechanism which drives the hopper feeder, and for this purpose will be connected to the gear 38.

Any suitable means may be employed for driving the main shaft l5 of the expeller. For purposes of illustration there is indicated in Fig. 2

- a driving motor I9 which may be of the squirrel event, this motor should be of a constant speed type whether it is driven by alternating or direct current.

The housing 2| may include suitable clutching mechanism for connecting and disconnecting the shaft l from the motor I3 when desired. For emciency of operation it is desirable that the motor l8 operate at substantially constant load,

' for alternating current, or of equivalent type for direct current. In the present illustration, the motor 24 is of the former type and comprises a wound rotor having mounted on its shaft slip-rings 42 which will convey current to an ad- Justable rotor resistance which may be arranged to give the motor the desired starting torque characteristics, and to make it properly responsive to conditions met within a press of the character of that illustrated. While the motor 24 may be variously disposed, it is preferred, in presses of the type shown in Fig. 2, to provide the housing 43 of the hopper feeder with a mounting flange 44, as shown (Fig. 5). A common housing 85 is attached to the casing of the motor 24 as well as to this flange. Hence, the motor and housing 85 are carried by housing 43. The motor shaft 45 carries a. driving pinion 48 meshing with a larger driven gear mounted on a shaft 48 and connected through bevel gears 43 and 5| to shaft 52 which drives the worm 32. The gears 48 and 41 are enclosed by the housing 65 having a cover plate 88. The shaft 48 may in turn carry a sprocket 53 cooperating with a chain 54 to drive the tempering mechanism through sprocket 55 having an idler 56, and thence to convey power to the main shaft 31 of the tempering apparatus through pinion 51 and gear 38.

It is highly desirable that the worm 32 ,inside of barrel 29 be accessible for repair or replacement without dismantling the entire driving apparatus. For this reason, the barrel has an opening 80 normally closed by a cover plate 81 (Fig. 3), held in place by cap screws 38. By removal of these screws it becomes possible after disconnecting the drive shaft from worm 32 to remove the worm through the opening 68.

The driving connection between the worm 32 and the bevel gear 5| comprises, as best shown in Fig. 5 of the drawings, a shaft 89 attached through a, splined coupling I3 to a second shaft 52. The barrel 23 contains an opening Ill behind cover plate I2 through which the coupling I3 is accessible. This coupling connects the shafts 89 and 52 and'holds them in driving relation by means of a clamp I4. After clamp I4 is removed, the coupling I3 can be raised above the shaft 83 to disconnect it from shaft 52. Shaft 69 can then be moved horizontally through the opening left by removal of cover plate 81 and the cover 48 above it, this cover carrying the bearing for shaft 31. Under conditions requiring removal of shaft 89 the barrel 29 would be open from plate I2 (Fig. 3) to the junction between barrel 23 and the frame of the main press. In this way, the worm 32 can be removed from the machine without alteration of the gearing inside of hopper feeder housing 43.

It has been indicated aboveithat the drive to shaft 52 is accomplished through bevel gears 49 and 5|. The shaft 48 to which pinion 43 is keyed is supported in a conical housing |I bolted to the casing 43. This shaft is carried inroller bearings I8 and II. The connection between the cover plate I3 and the shaft 48 is sealed by suitable dust excluding washers I8. The lower end of housing 43 has a flange I31 bolted to a flange I32 on barrel 29 at I33.

The housing 43 is divided into upper and lower compartments by an annular flange 8 I. Housing 43 is ventilated by breather I35. Flange 8| carries a bearing supporting annulus 82 bolted'to it at I34 in which are mounted roller bearings 83 for supporting the bevel gear 5|, this gear being keyed as at 84 to a depending sleeve 85 splined to the upper end of shaft 52 and held in adjusted relation to it by cap screw 90. Associated with the lower end of the sleeve 85 is a bearing race 86 carrying bearings 81 hearing against a raceway inan annulus 88 mounted within the flange 8| and in horizontal alignment with it. The lower end of sleeve 85 also carries a ringlike portion 89 separated from the bearing mount 9| of shaft 52 by roller bearings 32. The roller bearing. 93 carried in support 9| forms an antifriction connection between the shaft 52 and the member 9|. Openings I31 and I38 in the bearing adjusting nut are arranged to receive a bar whereby the taper bearings 83 and 81 may be adjusted. A lubricant fitting I36 is provided in the bottom of housing 43 for supplying grease to bearing 93. All othenworkmg parts within housing 43 are lubricated by an oil bath maintained at a level with pinion 43.

The purpose of this arrangement is to provide an effective driving connection between the hopper feed motor and the worm 32 and, at the same time, to so arrange the parts that they may be accessible for inspection or repair without dismantling the apparatus. The roller bearings in the relations indicated carry the heavy thrusts incident to feeding material to the press. The frictional load is reduced and lubrication is convenient.

Induction motors of the wound rotor type here illustrated are characterized by their ability to start under load when their rotor resistance is suitably adjusted, and to vary their speed according to the load imposed upon them. They also have the desirable characteristic of not running away under no-load conditions, because they can never operate at a speed vabove synchronism no matter what their load conditions may be. Inasmuch as the material being fed to the barrel 29 from tempering apparatus 34 may at times be of a very fluify character such as to impose very little load on the press, and at other times of a very dense character so as to impose a very heavy load on the press, the variations in speed of the motor 24 will vary through a considerable range.

Inasmuch as motors of this type vary their speed in inverse ratio to the load imposed upon them, it will be seen that to produce a constant rate of extraction in the main barrel of the press it will be necessary to vary" the speed of this motor considerably. When the motor is operating under heavy load and at a low speed so as to dissipate a large amount of heat due to resistance losses within itswindings, it will be highly desirable to provide adequate means for keeping the temperature of the motor within satisfactory limits. One convenient method of doing this is to'associate with the endof the shaft 58 of motor I9 a fan 59 which may draw air through the casing of motor I9 to ventilate it and, at the same time, may draw air through inlet 6| and cause it to flow through pipe 52 to an inlet 63 into the casing of motor 24 and thence through a suitable outlet 64 in that casing to atmosphere. In this way, the temperature of motor 24 will be'kept within safe limits and the motor will be able to operate'efliciently under the conditions which it meets.

The mode of operation of the press shown in Fig. 2 is as follows: It will first be assumed that the motor I9 is running to drive the shaft I5 with the associated worm segments 26 thereon; also that motor 24 is running to drive the screw 32 within the barrel 29, and hence to operate the blades 35 inside the tempering apparatus which is filled with material in condition to be run through the expeller and have the liquid content removed therefrom. The blades 35 will feed the materialin condition to be extracted to the expeller through the inlet 36 between the segments of worm 32, and thence down through the barrel 29 into the section 3I, where it is subjected to preliminary expressing and a substantial portion of the liquid content removed.

The fibrous material will then be fed by worm I8 into the first segment'26 and then subjected to pressure within the main barrel of the expeller as it is propelled along, the liquid content being expressed and collected in. suitable mechanism well known in the art, and hence not shown. The cake, substantially free from liquid, will be expelled through the choke I6 and carried away by suitable collecting apparatus.

The choke will be adjusted until the appearance of the cake and analysis of its liquid content are satisfactory; With the choke I6 thus set and the motor I9 operating at substantiallyconstant speed, it is desirable, as pointed out hereinbefore, that the rate of feed of material to the main barrel be so controlled as to stabilize the operation of the press without adjustment of the choke. Accordingly, if the material, such as copra, which enters through the opening 36 should be of greater density than that which has preceded it, more resistance to flow of this material through the barrel 29 would be encountered as the worm 32 drives it through this barrel. Consequently, a heavier load would be imposed upon the motor 24 causing it to'reduce its speed and, hence, to reduce the rate of feed of the material through the preliminary expressing portion of the press, and hence to the main barrel of the press. When the material becomes of less density, that is, more fluffy in character, less load will be imposed upon the worm 32, and hence upon the motor 24, causing the motor to speed up and to feed the material more rapidly, and thus again to stabilize the operation of the main press by maintaining the conditions in the main barrel as nearly constant as possible, and without further adjustment of the choke.

It has been found that by adjusting the rotor resistance connected to the slip-rings 42 of motor 24 in such manner as to cause the motor to maintain between 50 and 70 percent of its full load 7 speed, the press may be made to operate automatically with complete satisfaction with a variety of materials usually treated in presses of the type under consideration. With such an adjustment, the pressure in the main barrel remains faction and without the constant attention of an operator. The operation has been successful even with materials such as corn germs which are subject to wide and frequent variations in character and condition. It is desirable, when working with materials having widely differing fibrous content, to vary the size of the openings in the barrel of the expeller depending upon the fineness of the fibers contained in the material being handled. Such variations can be carried out by substituting anew set of barrel bars as set forth above, and without alteration of the structure of the press worm. The effectiveness of machines of this character is indicated by the fact that whereas machines of the prior art, depending upon manual adjustment of the choke, would express only 300 bushels of flaxseed in 24 hours, the same press, equipped as shown in Fig. 2, would extract500 bushels in 24 hours with 4% of oil remaining in the cake in each case. When operating on copra, previous machines operated on 16 tons of material in 24 hours, leaving an oil content of '7 to 8% in the cake. press, 20 tons of copra were pressed within 24 hours but with only 4 /2 to 5% of oil remaining in the cake.

Whilev the invention has been so far described as applied to presses employing feeding mechanism of the type shown in Anderson Patent No. 1,971,632, it is also applicable to other types of press. In order to make this clear, it has been illustrated as applied to the type shown in Anderson Patent No. 1,694,114, granted December 4, 1928, and illustrated in Figs. 6 and '7 of the drawings.

7 Referring now to Fig. 6, reference character 94 designates the body of a press in which the barrel 95 contains a choke 96, similar to that already described, and worm segments 91 associated with it to express the material and cause a flow of extracted oil or liquid into a collecting means 98. The shaft 99 which carries the worm segments 91 is driven through a gear I M mounted in suitable bearings I02 and I03. Journalled on the shaft 99 adjacent the inlet or hopper I04 to the barrel 95, is a quill shaft I05 rotatable on shaft 99 and carrying a worm I06 for subjecting the material from the hopper I04 to preliminary extraction before it reaches the worm segments 91. Secured to the quill shaft I05 is a driving gear I01 to which mechanism of the present invention will be applied as shown in Fig. '1.

Referring now to Fig. 7, it will be seen that the gear IOI driving the main shaft of the press cooperates with a pinion I08 carried on shaft I09 and is driven from motor III through sprocket chain H2, and suitable sprockets carried by the shaft of the motor III and by the shaft I09. In similar manner, the gear I01 which drives the quill shaft I05 is driven by a pinion I I3 carried on shaft H4 and connected through a chain and sprocket connection II5 to the shaft 6 of a slip-ring or wound rotor induction motor II1 of the type previously described. In order to make With the present the invention more clear. the rotor resistance and the line connections of this motor have been 1 indicated diagrammatically in Fig. 7 and a complete circuit diagram given in Fig. 8.

, It has been assumed that the source of electric current supply is a three phase system having line wires I connected-to the stator of the the problems met when starting and stopping the press make it advisable under most conditions to employ a choke which can be preliminarily adjusted to any particular material and, more esmotor III, the stator windings being designated I I8 and illustrated as of the delta-connected type cooperating with a rotor winding H9 shown as of the star or Y-connected type supplying current through slip-ring l2! to an adjustable rotor resistance I22, While in practice the rotor resistance will be set at some particular value and will remain there, the adjustments have been pose sufiicient load on that motor to prevent it.

from running away if the flow of material to the press ceases entirely or approaches a substantially no-load condition. Although three specific types of motor have been mentioned and the preferred form illustrated, other equivalent types may be used within the scope of the present invention.

The operation of the press shown in Figs. 6 and '7 is similar to that of the press of Fig. 2 already described, and it will be obvious without detailed explanation that as material is fed through the opening I04 to the quill worm Hi6, it will be subjected to preliminary extraction and will be carried into the main barrel 95 of the press associated with the worm segments 81. Variations in the character of the material fed to the quill worm I06 will cause variations in speed of the motor H1 in order to keep the flow of material from the quill worm to the main worm substantially constant, and thus to ensure a uniform rate of extraction of the liquid from the fibrous material and uniform pressure conditions at the discharge end of the press, regardless of variations in the character and condition of the fibrous material, and without attention on the part of an operator.

It is to be understood that while the method pecially, which can be opened to permit discharge of the cake from the press when shutting down after a run. Accordingly it is to be understood that while the choke means in the press is described as being adjustable, it is not adjustable in the usual way, that is, it is not used to controlthe extraction rate of the press except in starting the press as at the beginning of a day, orwhen changing from one material to another.

After the press is put in operation on a particularmaterial, and preliminary adjustment of the choke has been made, the pressure within the press and the rate of extraction are controlled entirely automatically by. the press feeding means and without attention to the choke. It is, therefore, desired that the terminology employed .in this specification be construed in a broad sense commensurate with the radical differences in mechanical structure and operation which characterize the present invention. I What is claimed is:

1. A press comprising a casing having drain-v age openings, a constricted discharge and an expressing worm mounted therein; means for driving said worm at substantially constant speed; means for feeding material from which liquid is to be expressed into operative relation with said worm; and automatic self-regulating means comprising an electric motor for driving said rate of extraction by said press, said motor beof stabilizing the operation of a press according invention is not limited to use with alternating current machinery because, as hereinbefore pointed out, direct current motors having appropriate characteristics may besubstituted for the alternating current motors illustrated. The essence of the invention. regardless of the particular mechanical embodiment utilized to carry it out, consists in maintaining a constant rate of extraction by the press in response to variationsin the resistance to fiow of the material approaching the press, and, hence, to produce constantly uniform operation of the expeller with maximum. efficiency and without the frequent choke adjustment required by prior art apparatus.

While it is possible, according to the present invention, to utilize a fixed choke of appropriate dimensions for a given material, and which can be removed from the barrel of the press when stopping it and inserted when starting up again,

ing independent of the driving means for said worm. 1 v

2. In combination, a press, having a casing having drainage openings, a constricted discharge throat, and interrupted screw means within said casing for subjecting material in said casing to liquid extractingfpressure: means for driving said screw means at a substantially uniform rate; means for feeding material having a liquid content into said casing; and automatic self-regulating means comprising an electric motor having a speed-load characteristic such that its speed decreases as the load increases, said motor being responsive to the load imposed upon said feeding means to cause the material to be fed to said screw means at such a rate as to'produce a uniform rate of extraction by said screw means.

3. An automatic press for extracting liquid from material having a liquid content, said press comprising a main pressing unit having a casing withdrainage openings therein, an inlet, an interrupted screw rotatably mounted in said casing, and a constricted discharge throat:

means comprising an electric motor for driving said screw at a substantially constant speed; an auxiliary pressing unit disposed in series with said main pressing unit so that the discharge from the auxiliary unit enters directly into the inlet of the main unit, said auxiliaryunit comprising a casing having drainage openings therein, an inlet and an interrupted screw rotatable therein; and load responsive driving means for said auxiliary unit, said ,means comprising a self-regulating electric motor having a speed-load characteristic such that its speed falls as the load rises and automatically responds. to variations in the load imposed on said auxiliary unit for feeding material to said main press at such a rate that the main press has a uniform rate of extraction.

4. A press of the interrupted screw type for extracting liquid from material having a liquid content, comprising main and auxiliary pressing units disposed in series relation with the discharge from the auxiliary unit feeding directly into the inlet 01' the main unit; means for operating said main unit at a substantially constant rate; and means comprising. a variable speed self-regulating electric motor automatically re-' sponsive to changes in load on said auxiliary unit for feeding material at a rate which maintains the rate of operation of the main unit constant.

5. A press of the interrupted screw type to extracting liquid from material having a liquid content, comprising a press made up of a casing having drainage openings, an inlet opening, means for applying pressure to material passing through the casing, and a main screw rotatable therein; an auxiliary screw rotatably mounted in said casing in alignment with said first screw adjacent said inlet for cooperation with said casing; a constant speed motor for driving the varies inversely with the resistance imposed upon it by the material being fed.

7. A press of the interrupted screw type comprising a main barrel having drainage openings therein, a restricted outlet, and an interrupted screw rotatably mounted in said barrel; an auxiliary barrel having drainage openings, and an interrupted screw therein, said auxiliary barrel being disposed in angular relation to the main barrel and arranged to feed material to the main barrel; a constant speed induction motor tor driving the main screw; and a variable speed main screw; and a variable speed self-regulating electric motor for driving the auxiliary screw at a speed which varies in response to the resistance imposed upon it by the material being inductionmotor of the slip-ring type" for driving the auxiliary screw at a speed which varies automatically and inversely with the resistance imposed upon it by the material being fed.

8. The combination 'of two presses oi the expeller type arranged in series so that the first feeds the second; means applying a fixed control to'"the discharge from the second press;

press.

RAYMOND T. ANDERSON.

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