US3892173A

US3892173A - Horizontal screw press

Info

Publication number: US3892173A
Application number: US406475A
Authority: US
Inventors: Howard W Hall; William A Avilla
Original assignee: Rietz Manufacturing Co
Current assignee: Bepex International LLC; Rietz Manufacturing Co
Priority date: 1973-10-15
Filing date: 1973-10-15
Publication date: 1975-07-01
Anticipated expiration: 1992-07-01

Abstract

A screw conveyor type dewatering press having means for obtaining better forward material pressure and relatively uniform discharge of dewatered material. Employs means near the trailing edges of screw flights, preferably in the form of radially extending bead bars, which act upon the material as it is being urged forwardly to the discharge end of the press.

Description

United States Patent 1 Hall et a1.

1 1 HORIZONTAL SCREW PRESS [751 inventors: Howard W. Hall; William A. Avilla,

both of Santa Rosa, Calif.

[73] Assignee: Rietz Manufacturing Co., Santa Rosa, Calif.

[22] Filed: Oct. 15, 1973 [21] Appl. No.: 406,475

[52] US. Cl. 100/117; 100/148; 100/150 [51] Int. Cl B30b 9/12; B30b 15/00; B30b 3/02 [58] Field of Search 100/117, 145, 146, 147,

156] References Cited UNITED STATES PATENTS 7/1887 Gray 100/145 UX 6/1922 Meakin 1. 100/117 10/1961 Vincent 100/117 [451 July 1,1975

3,126,818 3/1964 Koelsch 100/117 3.144.818 8/1964 Sullivan 100/117 X FOREIGN PATENTS OR APPLICATIONS 74,207 11/1948 Norway 1. 100/150 Primary Examiner-Peter Feldman Attorney, Agent, or Firm-Flehr, Hohbach, Test, Albritton & Herbert 1 5 7 1 ABSTRACT A screw conveyor type dewatering press having means for obtaining better forward material pressure and relatively uniform discharge of dewatered material. Empioys means near the trailing edges of screw flights. preferably in the form of radially extending bead bars which act upon the material as it is being urged forwardly to the discharge end of the press.

7 Claims, 11 Drawing Figures 1 HORIZONTAL SCREW PRESS BACKGROUND OF THE INVENTION This invention relates generally to dewatering presses of the type making use of screw conveyor means for expressing water or other liquids from various materials.

Prior apparatus of the above type makes use of a screen assembly which surrounds the screw conveyor means. The flights of the screw conveyor means are carried by a rotatable shaft, and generally are disconnected, or in other words, they are disposed in flight sections or sets. The housing is constructed to provide a hopper at the feed end of the screw, into which material is supplied. At the discharge end of the screen it is customary to provide an obdurator, which generally is in the form of a cone assembly which is yieldably urged against the discharging material to develop extraction pressure. The screen assembly is provided with socalled interrupter bars or ridges, which tend to prevent cylindering, or in other words rotation of the material about the axis of the screw shaft, without proper forward movement and pressure.

In the handling of certain materials that tend to be slippery, as for example crushed grapes, it has been found that such presses do not always operate satisfactorily. The press may operate satisfactorily for a short period of time, with discharge of dewatered cake past the cone, and then the discharging material becomes insufficiently dewatered to force the cone to a proper normal operating position, with the result that the cake is not permitted to discharge from the press. After several minutes of operation the press may return to normal operation, only thereafter to repeat the cycle. Ac cording to applicant's observations, these difficulties are due to improper continued forward movement of the material towards the discharge end of the screen assembly, and inability to develop and maintain pressures upon the material to express a sufficient amount of juice to provide a cake of proper consistency for final uniform discharge.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a dewatering press of the screw conveyor type which is capable of effective dewatering of various materials without the difficulties previously mentioned.

Another object is to provide a dewatering apparatus of the screw conveyor type which is relatively efficient in dewatering materials which tend to be slippery.

Another object is to provide relatively simple means for attaining the foregoing objects, which can be incorporated in existing designs of dewatering presses.

In general the present invention involves the incorporation of special means on the faces of the conveyor flights of a screw press. This means is disposed near the trailing edges of the flights, and upon that side which acts upon the material being advanced through the screen assembly. In its preferred form this means consists of one or more so-called bead bars which are secured to flights near their trailing edges.

Additional objects and features of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a side elevational view partly in section illustrating a dewatering press incorporating the invention.

FIG. 2 is a cross-sectional detail taken along the line 22 of FIG. 1.

FIG. 3 is a cross-sectional detail taken along the line 3-3 of FIG. 1.

FIG. 4 is an end view looking toward the right hand end of FIG. 1.

FIG. 5 is a side elevational view showing screw conveyor means as incorporated in FIG. 1.

FIG. 6 is a cross-sectional detail taken along the line 6-6 of FIG. 5.

FIG. 7 is a cross-sectional detail taken along the line 7-7 of FIG. 5.

FIG. 8 is a side elevational view showing a shaft section provided with one set of interrupted flights.

FIG. 9 is a sectional view taken along the line 9-9 of FIG. 8.

FIG. 10 is a detail showing the trailing edge of the flight illustrated in FIG. 9, as it appears in plan.

FIG. 11 is a detail showing a typical bead bar.

DESCRIPTION OF THE PREFERRED EMBODIMENT The press illustrated in FIGS. 1 4 consists of a suitable housing IO having a feed hopper 11 at one end. A rotatable shaft 12 extends longitudinally through the housing, and is carried at its ends by the

bearings

13 and 14. The shaft is provided with conveyor flights as will be presently explained.

A screen assembly 16 forms the bottom of the hopper II and surrounds the lower side of the feed end of the shaft 12. This assembly can consist of the semicyclindrical screen 17 supported by the arcuate grid structures 18.

Referring to FIG. 3 a cylindrical screen assembly 21 surrounds the shaft 12 and shaft flights, and as shown in FIG. 1, this assembly extends between and is supported by the

spaced walls

22 and 23 of the housing. The assembly includes the semicylindrical screen sections 24, supported by the semicylindrical gridlike structures 26. The supporting grid structures 26 are secured to the bars 27 which likewise extend between the

walls

22 and 23. Resistor bars 28 are disposed between the bars 27, and these parts are secured together by suitable means such as bolts. The bars 28 are provided with portions 29 which are disposed at spaced intervals along the length of the shaft 12, as shown in FIG. I. The screen assembly may also include the arcuate bars 31 (FIG. 3) which surround the grid structures 26 and are secured to the plates 27. It is a function of portions 29 to act upon the material in such a fashion that it does not freely rotate as a mass (i.e., cylinder) about the axis of the shaft 12.

As shown in FIG. 1, the conveyor flights carried by the shaft I2 are discontinuous, rather than a continuous helix. The helicoidal flight 32 extends from the lower portion of the hopper 11 into the entrant end portion of the screen assembly. Additional spaced

zones

33, 34, 35, 36 and 37, which are distributed along the length of the shaft 12, are separated by the resistor bar portions 29. The shaft carries a set of flights 38 operating within the zone 33. It also carries additional sets of

flights

39, 40, 41 and 42, arranged to operate within the

zones

34, 35, 36 and 37. The arrangement of the disconnected flights on the shaft 12 is more clearly shown in FIG. 5.

The discharge end of the screen assembly is flared or divergent as illustrated. and is attached to wall 23 about the edge of the wall opening 43.

The cone assembly 44 at the discharge end of the housing consist of a cylindrical shell 46. together with a frustoconical end wall 47 which is a screen or perforated sheet metal. These parts are carried by sleeve 48 which is journalled upon the adjacent portion of the shaft 12. The diameter of the shell 46 is somewhat greater than the diameter of the opening 43. The other end of the cone assembly is rotatably carried by a thrust frame 49, the wall 51 of which has an opening to accommodate the adjacent end of the cone assembly. A thrust bearing ring 52 is secured to wall 51, and is also retained upon the shell 46 of the cone assembly. The cone assembly also carries a sprocket 53 which can engage a driving chain, and a bearing ring 54 is shown interposed between the sprocket and the ring 52.

The bearing 14 is carried by the supporting frame portion 56 and the corresponding end of the shaft 12 is coupled by the clevis S7 to the piston rod of the piston-cylinder assembly 58. The cylinder of this assembly is mounted upon the thrust frame 49.

The thrust frame 49 is also supported by guide bars 59 which track between rollers 61 that are carried by the vertical members 62 of the frame portion 56.

The cylinder of the piston-cylinder assembly 58 is normally connected to a source of air under pressure that can be controlled to apply a predetermined amount of yieldable force to the cone assembly 44. thereby permitting the cone assembly to move relative to the wall 23 for the discharge of presscake. During normal operation the cone assembly can be permitted to turn with the shaft or it can be driven at a desired speed by motive means including a chain engaging the sprocket 53.

Liquid expressed from the material being treated can be removed through drainage means at the lower part of the housing. Thus the drain pan 66 is provided for the feed hopper 11, pan 67 for that part of the housing occupied by the main screen assembly, and pan 68 for receiving liquid expressed through the screen 47 of the cone assembly 44.

The arrangement of flights shown in FIG. 1 is shown more clearly in FIG. 5. The feed flight 32 is a single helix, whereas the sets of

flights

38, 39, 40, 41 and 42 conform generally to double helixes. Also the flights 39 are oriented 90 with respect to flights 38, flights 40 oriented 90 with respect to the flights 39, flights 41 oriented 90 with respect to flights 40. and flights 42 oriented 90 with respect to flights 41.

At least some of the flights are provided with means which act upon the material being advanced through the main screen assembly. A preferred construction of this means can be best understood by referring to FIGS. 8 to 11. Here a set of flights 71 are shown fixed to the shaft 120, and the pitch is exaggerated for clarity of illustration. For the direction of rotation illustrated, the product flow is to the right. Each flight has a leading edge 72 and a trailing edge 73, with these edges extending generally radially of the shaft 12a. One face 74 of each flight acts upon the material and urges it towards the discharge end of the screen assembly. As shown in FIGS. 9 and it is desirable for the trailing edge portion to be machined to provide a surface 76 which is substantially coincident with a plane perpendicular to the shaft axis. Secured to and protruding from the face 74 of each flight there is at least one and preferably two members 77 which extend generally radially in the manner shown in FIG. 9. These members can be bars of square cross-section as shown in FIG. 11, with outer end portions bent as shown in this Figure. in a direction opposite to the direction of rotation. These members can be secured to the flight as by welding. They are spaced angularly and are located near the trailing edge 53. Also it is desirable for their outer ends to be spaced somewhat from the perimeter of the flights. The leading faces or edges 79 of these bars form shoulders or ledges which act upon the material as the flight rotates.

In a typical instance. where the diameter of the conveyor flights is about 16 inches, the bead bars may project from the face 74 by about 3/16 inch, the length of the straight portion of the bead bar may be about 3 inches and the bent portion 80 may be on a radius of about 1% inches. Also the portion 80 may be spaced from the perimeter of the flight by about inches. The end of bent portion 80 may be disposed about inches from the trailing edge 53. Assuming that two such bead bars are used, they may be set apart by an angle of about 30.

Referring to FIGS. 6 and 7, it will be seen that the

flights

41 and 42 have such bead bars near their trailing edges. Although in this particular embodiment the remaining disconnected flights are not equipped with the bead bars. it should be understood that certain or all of the other flights may be so equipped, depending on the operating conditions and the material being handled.

Operation of the press is as follows. It is assumed that the material to be dewatered is crushed grapes. This material is fed continuously into the hopper 11 and is carried by the flight 32 into the entrant portion of the main screen assembly. Some juice drained from the material is removed by way of the pan 66. Air pressure at a predetermined regulated value is applied to the cylinder assembly 58. This serves to apply a predetermined amount offorce opposing movement of the cone assembly away from the opening 43 in the wall 23. As the shaft 12 rotates the material is progressively advanced through the

flight zones

33, 34. 35, 36 and 37, with progressive dewatering. The material presented to the cone assembly should be of such consistency that it maintains a relatively uniform pressure upon the as sembly whereby the assembly is moved against the force of the cylinder 58 a sufficient distance to permit substantially uniform and continuous discharge of the.

press cake.

As previously explained when the flights are all of conventional construction, the operation tends to be erratic. Although the resister bar portions 29 tend to prevent or minimize cylindering, after a short period of operation the material presented to the cone assembly is insufficiently dewatered to move the cone for discharge of the cake, thus temporarily interrupting or reducing the amount of discharging material. After several minutes of operation the material near the cone again becomes sufficiently dewatered to move the cone and permit some cake to be discharged. This cycle tends to be repetitive. thus greatly reducing the capac' ity of the equipment.

When the sets of

flights

41 and 42 are equipped with bead bars applied as shown in FIGS. 6 and 7, the difficulty just described is completely overcome. The material presented to the cone is sufficiently dewatered to force back the cone and maintain a continuous discharge of press cake.

While the effect of the bead bars is not completely understood, it appears that they cooperate with the resistor bar portions 29 to obtain more effective dewatering action. The action of the bead bars upon the material tends to produce localized cylindering. However, as the bead bars approach an adjacent interruptor bar portion 29, the cylindering" is resisted in such a manner as to develop pressure within the product, thus causing liquid to be extracted through the screen. In this connection it has been noted that the beads appear to be most effective when mounted near the trailing edges of the flights, thus indicating that there is an interaction between the resistor bar portions and the bead bars. Thus instead of promoting cylindering such as would impair dewatering action, the bead bars actually promote dewatering while the resistor bar portions continue to prevent cylindering.

By use of the present invention it has been found that higher pneumatic cylinder pressures can be applied, because of the more efficient dewatering action before the material reaches the cone assembly. Better dewatering results in a material of such consistency that the action of the flights produces greater pressures for more effective dewatering. A lower moisture content of the material also tends to cause a scouring effect on the screen surfaces, and this tends to prevent the screens perforations from becoming blocked or plugged.

We claim:

1. In a dewatering press, rotatable screw conveyor means consisting of a shaft having disconnected conveyor flights secured to the same, a cylindrical screen assembly surrounding the screw conveyor means, means for supplying material to be dewatered to one end portion of the screw conveyor means whereby the material is caused to progress through the screen with progressive dewatering, discharge means at the other end of the screw conveyor means, said discharge means serving to permit discharge of dewatered cake under pressure, stationary interrupter bars having portions extending into the screen assembly and disposed be tween interrupted flights, each of the interrupted flights having a trailing edge and a face serving to act upon material to urge the same toward the discharge means. and material engaging means fixed to said face of at least one of the interrupted flights, said means forming a shoulder protruding from said flight face and faced in the direction of rotation and extending in a general radial direction from the inner portion of said one flight to a region near the outer perimeter of the same, said means serving to act upon the material in conjunction with interruptor bar portions express water from the material.

2. A press as in claim 1 in which said last-named means consists of at least one bead bar fixed to said face of said one interrupted flight and disposed near the trailing edge of the same, the leading edge of the bead bar forming said shoulder.

3. A press as in claim 2 in which said bead bar has its outer end portion bent in a direction opposite to the direction of rotation.

4. A press as in claim 1 in which said last-named means is carried by the flights located nearest to te discharge means.

5. A press as in claim 1 in which said last-named means is secured to two sets of flights located nearest to the discharge means.

6. A press as in claim 1 in which said means consists of at least two bead bars fixed to the said faces of each of two sets of flights located nearest the discharge means, the bead bars in each instance being angularly displaced and disposed near the trailing edge of the flight, the outer end portions of the bead bars being curved in the direction opposite to the direction of rotation.

7. A press as in claim 3 in which a bead bar is fixed to each of two interrupted flights located near the discharge means and in regions angularly displaced substantially with respect to the axis of the shaft.

Claims

1. In a dewatering press, rotatable screw conveyor means consisting of a shaft having disconnected conveyor flights secured to the same, a cylindrical screen assembly surrounding the screw conveyor means, means for supplying material to be dewatered to one end portion of the screw conveyor means whereby the material is caused to progress through the screen with progressive dewatering, discharge means at the other end of the screw conveyor means, said discharge means serving to permit discharge of dewatered cake under pressure, stationary interrupter bars having portions extending into the screen assembly and disposed between interrupted flights, each of the interrupted flights having a trailing edge and a face serving to act upon material to urge the same toward the discharge means, and material engaging means fixed to said face of at least one of the interrupted flights, said means forming a shoulder protruding from said flight face and faced in the direction of rotation and extending in a general radial direction from the inner portion of said one flight to a region near the outer perimeter of the same, said means serving to act upon the material in conjunction with interruptor bar portions express water from the material.

7. A press as in claim 3 in which a bead bar is fixed to each of two interrupted flights located near the discharge means and in regions angularly displaced substantially 180* with respect to the axis of the shaft.