US2721647A - Paper machinery - Google Patents

Description

Oct. 25, 1955 o. R. WITWORTH 2,721,647

PAPER MACHINERY Filed July 127, 1951 65 INVENTOR. By 0175 E. WITWOETH ATTORNE Y5 United States Patent PAPER MACHINERY Otis R. Witworth, Middletown, Ohio, assignor to The Black-Clawson Company, Hamilton, Ohio, a corporation of Ohio Application July 27, 1951, Serial No. 238,987

4 Claims. (Cl. 198213) This invention relates to apparatus for separating grit and other solid particles from a liquid suspension such as paper making stock, and the invention has special relation to the removal of the separated reject particles from cleaning and separating apparatus of this character, including both centrifugally operated apparatus and devices such as settling troughs wherein gravity is relied upon for the separating action.

It has in the past been a common practice to remove the separated reject material by continuously or intermittently bleeding off a small quantity of liquid from the separating apparatus at a point where the separated reject material collects within the apparatus, but in such operations it then becomes necessary either to conduct the resulting mixture of liquid and reject to the sewer, or else to concentrate by a further straining or drying treatment. In either case, the liquid lost with the reject material or the further concentrating treatment add undesirably to the cost of the separating operation and correspondingly reduce efficiency.

Improved results from the standpoint of simplicity, convenience and economy have been obtained by equipping cleaning and separating apparatus of the above character exteriorly of the apparatus and counterbalanced to a normally closed position, examples of such constructions being disclosed, for example, in the copending applications of Joseph Baxter Jr., Serial No. 57,559 filed October 30, 1948 and now Patent No. 2,622,795, and Stephen A. Staege et al., Serial No. 163,112 filed May 20, 1950 and now Patent No. 2,645,346 and both assigned to the same assignee as this application. In operation, the conveyor screw collects and compacts the reject material into the form of a relatively solid slug between the end of the screw and the closure door, and then as additional reject accumulates and is forced against this slug, the door will be opened against its counterbalance to effect gradual discharge of the reject, in the form of a damp sludge roughly comparable in consistency to sand and readily handled for disposal by a shovel or the like. During this discharging action, however, a substantial slug of reject material remains between the end of the screw and the opened door and acts eifectively as a seal against free discharge.

Several factors are important in obtaining optimum efficiency in the operation of a reject removing device of this character. For example, the closure door should be suificiently counterbalanced to provide an adequately tight seal against the maximum hydraulic pressure within the body of the apparatus in order to assure that no leakage of liquid occur, particularly when the device is starting up and before there has been suflicient time for the slug of reject material to accumulate. Also, the closure door should provide sufficient resistance to movement of the slug of accumulated reject material to cause proper compaction of the slug beforethe door opens in order to the. screw tip; I

assure that this slug will provide the desired continuously eflective seal after the door opens, and on the other hand the door should not offer such high resistance to opening as to cause compaction of the reject to such extent that it will lock in place against the desired discharging movement.

These factors with respect to the closure door also affect the conveyor screw. In particular, the comparatively large counterbalancing force required for proper operation of the door as described imposes a corresponding load on the screw, and especially on the end portion of the screw which is required to drive the accumulated slug of reject material through the reject tube with sufficient force to open the door and to hold it open for the desired continuous extrusion of reject material. When apparatus of this character is utilized for cleaning paper making stock, and particularly waste paper and other com paratively dirty stocks in which the reject includes a high percentage of gritty particles, the abrasive forces on the screw tend to be severe, especially on the end portion of the screw in contact with the slug, and sometimes may be so severe as actually to wear away the end flight of the screw in a comparatively short time if the device is not operating properly.

It is accordingly a principal object of the present invention to provide a reject removing device of the above character wherein the conveyor screw for compacting and discharging the reject material is constructed to offer high resistance to both the abrasion and torsional stresses thereon in operation and thereby to give eflicient service over a long useful life.

It is also an object of the invention to provide a conveyor screw for use in a reject removing device as discussed above which includes a main body portion of relatively mild and tough material for withstanding the torsional stresses incident thereon in use and which also includes a tip portion at its outer end of substantially harder material for withstanding the abrasive forces encountered in operation, and it is a particular object of the invention to provide such a conveyor screw wherein the hard tip portion is separately formed from the main body of the screw and separately removable and replaceable if worn without requiring replacement of the whole screw.

An additional object of the invention is to provide a conveyor screw for the above use which is simple and economical to construct and assemble initially and which in addition is of such construction that the hard portion thereof may be readily removed and replaced in the field with comparatively simple shop equipment in order to give a renewed useful life to the screw at substantially lower cost than would be required to replace the entire screw.

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

In the drawing Fig. 1 is a view in side elevation, partly broken away, showing a vortex type of cleaning and separating apparatus embodying a reject removing device constructed in accordance with the present invention;

Fig. 2 is a detail view of the conveyor screw in the reject removing device of Fig. 1;

Fig. 3 is an enlarged fragmentary section of the working end of the screw;

able hard tip portion of the screw;

Fig. 6 is a fragmentary transverse section on the line 6--6 of Fig. 3;

Fig. 7 is a detail elevational view of the outer end of Fig. 8 is a diagrammatic view illustrating the operation of replacing the hard tip on the main body of the screw.

Referring to the drawing, which illustrates a preferred embodiment of the invention, Fig. 1 shows a vortex separator generally of the construction disclosed in the above noted Staege et al. application, which includes a main base 10 supporting a cylindrical casing 11 enclosing a separating chamber 12. A center section 13 is positioned between the casing 11 and base 10 to form an extension of chamber 12, and it includes an outlet conduit 15 which projects upwardly for a substantial distance within chamber 12 and is curved forwardly through section 13 for attachment at 16 to a suitable discharge pipe. An inlet conduit 20' is mounted on the upper end of casing 11, and it includes a tangentially arranged inlet connection 21 at its upper end. A helix comprising a core 22 and a helical vane 23 is mounted within the inlet conduit 20, and the core 22 extends downwardly through the upper part of the chamber 12 and into the upper end of the outlet conduit 15 as shown.

The adjacent ends of the inlet and outlet conduits 15 and 20 are spaced axially to provide an annular gap 25 between the lower end of the inlet conduit and the upper end of the outlet conduit, and in operation, the stock entering the apparatus is provided with a whirling motion by the tangential arrangement of the inlet connection 21 and the helical vane 23 before it reaches the chamber 12. The centrifugal force resulting from this whirling motion causes heavy particles in the stock to be thrown radially outward through the discharge passage or gap 25 as the clean stock flows across this gap into the upper end of the outlet conduit 15. These discharged heavy particles will also whirl in a larger spiral as they are discharged into the outer part of the chamber 12 and as they settle towards the bottom of the chamber.

The base 10 includes a tapered throat portion which forms the bottom of the separating chamber 12, and a cylindrical passage 31 extends horizontally through the base below and in communication with this tapered thrc at 30, the passage 31 being lined with a cylindrical sleeve 32 which is cut away in alignment with throat 30. Within the passage 31 is a conveyor screw indicated generally at 33 which is connected at its rearward end with a drive motor 35 mounted at the back of the base. The forward end of the passage 31 is provided with an outlet extension casting 36 which extends forwardly beyond the end of the screw 33, and a closure door 40 for this outlet is pivoted in a bracket 41 at the top of the casting 36.

At either side of the base is a counterweight 42 adjustably mounted on a lever arm 43 pivoted by means of a shaft 44 in a bracket portion of casting 36. Two levers 45 are pinned to this shaft 44 and each of these levers is connected with the door 40 by a link 46, the arrangement being such as shown that the counterweights 42 act through their associated levers and links to hold the closure door normally in sealing position on the outer end of the outlet 36. In this connection, cross reference is made to the copending application of Ray Schrock, Serial No. 23 8,988, filed of even date herewith and now Patent No. 2,681,610 and assigned to the same assignee as this application, which discloses a door construction especially satisfactory for this purpose wherein the door is mounted on parallel links for movement in a substantially straight line.

The reject material discharged through gap 25 into the chamber 12 ultimately settles to the bottom of the chamber and into the sleeve 32 where it is carried by the screw 33 towards its outlet 36. In practice it is desirable to have the screw terminate at a position spaced from the closure door 40 by an appreciable distance as shown, for example 6 to 8 inches, so that the accumulated reject first forms the desired relatively solid slug between the end of the screw and the door. Then as additional reject accumulates and is forced against this slug, the door 40 will be opened against its counterweights 42 to efiect gradual extrusion of the reject, but since there still remains a substantial slug of reject within the outlet passage 36 which acts effectively as a seal, the discharged material is in the form of a damp sludge containing practically no more liquid than adheres to the individual particles therein.

It is essential for operation of the device as described that there be relative movement of the screw and the accumulated slug of reject material in order to force the latter forward towards the outlet, and maximum wear from this cause occurs at the front end of the screw which withstands the major thrust against the frictional resistance between the reject slug and the inner surface of sleeve 32 as well as against the counterbalance weights 40. Also as noted, many grades of paper making stock, such particularly as waste paper stock and the like, which may be treated in the illustrated vortex separator contain a large percentage of gritty particles in the junk entrained therewith such, for example, as sand, bits of glass, paper clips, staples and the like, all of which tend to have a relatively severe abrasive action on the screw.

In order therefore to meet these operating conditions, the present invention provides a special construction for the screw 33 such that while the major portion of its length is of sufliciently tough metal to withstand the torsional stresses thereon in use, the tip portion at its working end is of hard metal strongiy resistant to the abrasive forces incident to its use as described, and this tip portion is also readily removable if it should become worn down. Referring first to Fig. 2, the screw 33 is shown as including a main body portion 50 having a conveyor flight 51 thereon and having a bore in its rearward end for receiving the end portion of the shaft 52 through which it is connected with the drive motor 35, the end of this shaft being pinned or otherwise secured to screw body 50 as indicated at 53.

The tip portion 55 of the screw is initially formed separately from the main body portion 5%) and is formed of a very hard and abrasion resistant steel or other metal in contrast with the mild steel or cast iron satisfactory for use in the screw body 59. This screw tip 55 includes a conveyor flight 56 matching the conveyor flight 51 to form a continuous flight along the composite screw. It will also be noted that while the center part of the screw body 50 is of uniformly cylindrical section, except for the enlarged rearward end portion connected to the shaft 52, the center portion of the screw tip 55 is tapered to a substantially smaller diameter at its forward end than at its rearward end. As shown in Fig. 7, this tapered construction of the screw provides substantially increased effective flight area at the forward end of the screw for maximum thrust at the area of engagement between the end of the screw and the reject slug in operation as described.

A releasable driving interconnection is provided between the two portions 50 and 55 of the screw 33. At the forward end of the main screw body 50 is a non-circular projection 60 of reduced diameter with respect to the remainder of the screw body. This projection 60 is shown as of tapered hexagonal section, and at its forward end it is formed with a pair of notches 61 on opposite sides thereof providing a reverse wedge shape. The screw tip 55 is formed with a non-circular bore 65 extending completely therethrough and complementary in cross-section to the projection 60, being also shown as hexagonal. The overall length of the screw tip 50 is somewhat longer than the projection 60, and also the cross-sectional dimensions of the bore 65 are materially larger than those of the projection 60 to provide radial clearance therebetween, for example an average clearance of inch at the widest parts thereof, sufficient for limited relative angular movement therebetween. Also the bore 65 is provided with enlarged notches 66 adapted to match the notches 61 in the projection 60.

In assembling and securing together these two parts of the screw, the tip 55 is fitted over projection 60, and the clearance for this projection in bore 65 makes it readily possible to adjust the two screw sections both laterally and angularly into accurate alignment of the conveyor flights 51 and 56. An accurate fit is also facilitated by machining the annular end portion or shoulder 70 on the screw body 50 surrounding the base of the projection 60, and by correspondingly grinding the annular end portion 71 of the screw tip 55 so that these two surfaces will fit smoothly together in their assembled relation. The two screw portions are readily held in this aligned relation by means such as the parallel bars indicated at 75 in Fig. 8, and while so held together, a low melting point bonding material 77, such for example as Babbitt metal, is poured into the open end of bore 65 to fill the clearance in the bore around projection 60 and thus to bond the two screw 5 portions firmly together in their desired aligned relation. Also as shown in Fig. 3, this material will be received between the notches 61 and 62 to provide a thicker section of bonding material in this area than between the other opposite surface portions of the projection 60 and bore 65 for resisting axial separation of the screw portions.

It will be apparent that the metals employed in forming the two parts 50 and 55 of the screw may be selected in accordance with the conditions of torsional and abrasive stresses expected to be encountered in use, with toughness and readily machinability being a desired characteristic for the part 50, while the part 55 should be formed of a very hard metal which will be strongly resistant to abrasion. By way of illustrative example of suitable metals for use in the practice of the invention, satisfactory results have been obtained in practice with the body portion of the screw formed of cast iron or a mild steel and with the screw tip formed of a hard steel of either of the followin anal ses.

t. 5 '2. 7 Chromium I 1. 5 13. 0 Iron Balance Balance Percent Carbon 2.25-2.75 Cobalt 45.25 55 Chromium 30-3 5 Tungsten 12-17 This composite screw constructed as disclosed is highly effective for handling the reject materials commonly encountered in the cleaning of paper stock and for like uses. Since as pointed out, the major thrust and abrasion load is directly on the end flights of the screw, maximum resistance to wear is provided by the provision of the hard tip portion 55, while the mild steel main body portion 50 provides adequate support for the hard tip. In addition, this screw construction has the important advantage of easy replacement of the hard tip portion if it should become worn or damaged and without requiring special equipment or return of the screw to the no factory. In order to renew the tip, the user will be provided with a spare tip portion formed and ground as described for interconnection with the projection 60 on the screw part 50. The renewing operation merely requires heating of the end parts of the screw sufficiently to melt the Babbitt or other bonding metal while the screw'is held with its hard end pointed downwardly to permit the melting bonding material to flow out. Thereafter the screw is reversed and the new tip set in place as described in connection with the initial formation of the screw, and the same or an additional quantity of bonding metal may be poured back into place to complete the renewing operation.

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

What is claimed is:

1. A conveyor screw of the character described adapted for use in handling gritty particles, comprising a main screw body having a conveyor flight thereon, an end portion on said screw body having a conveyor flight thereon matching said flight on said main body, said screw body having a projection of non-circular crosssection atthe forward end thereof, said end portion having a bore therethrough substantially complementary in cross-sectional dimensions to said projection for cooperation therewith to form a driving interconnection between said end portion and said screw body, said bore being of predetermined larger section than said projection to provide radial clearance therebetween for adjustment of said body and said end portion into abutting relation and relative positions of accurate alignment between said flights thereon, a quantity of low melting bonding material received within said clearance to bond said projection within said bore and thereby to maintain said screw portions in said interconnected and aligned relation, and said bore being open completely through said end portion to receive said bonding material through the forward end thereof.

2. A conveyor screw of the character described adapted for use in handling gritty particles, comprising a main screw body having a conveyor flight thereon, an end portion on said screw body having a conveyor flight thereon matching said flight on said main body, said screw body having a projection of non-circular crosssection at the forward end thereof, said projection being tapered towards the forward end thereof, said end portion having a bore therethrough substantially complementary in cross-sectional dimensions and in taper to said projection for cooperation therewith to form a driving interconnection between said end portion and said screw body, said bore being of predetermined larger section than said projection to provide radial clearance therebetween for adjustment of said body and said end portion into abutting relation and relative positions of accurate alignment between said flights thereon, a quantity of low melting bonding material received within said clearance to bond said projection within said bore and thereby to maintain said screw portions in said interconnected and aligned relation, and said bore being open completely through said end portion to receive said bonding material through the forward end thereof.

3. A conveyor screw of the character described adapted for use in handling gritty particles, comprising a main screw body having a conveyor flight thereon, an end portion on said screw body having a conveyor flight thereon matching said flight on said main body, said screw body having a projection of non-circular crosssection at the forward .end thereof, said end portion having a bore therethrough substantially complementary in cross-sectional dimensions to said projection for cooperation therewith to form a driving interconnection between said end portion and said screw body, said bore being of predetermined larger section than said projection to provide radial clearance therebetween for adjustment of said body and said end portion into abutting relation and relative positions of accurate alignment between said flights thereon, a quantity of low melting bonding material received within said clearance to bond said projection within said bore and thereby to maintain said screw portions in said interconnected and aligned relation, said projection being of shorter axial length than said bore to terminate at a position spaced inwardly from the forward end of said end portion, said projectiori having a notch in the side thereof adjacent the forward end thereof, said bore having a matching notch therein cooperating with said notch in said projection to receive a thicker section of said bonding material between said notches than between the other opposite surface portions of said projection and said bore for resisting axial separation of said screw and said end portion thereof, and said bore being open completely through said end portion to receive said bonding material through the forward end thereof.

4. A conveyor screw of the character described adapted for use in handling gritty particles, comprising a main screw body having a conveyor flight thereon, an end portion on said screw body having a conveyor flight thereon matching said flight on said main body, said screw body having a projection of non-circular cross-section at the forward end thereof, said projection being tapered towards the forward end thereof, said end portion having a bore therethrough substantially complementary in cross-sectional dimensions and in taper to said projection for cooperation therewith to form a driving interconnection between said end portion and said screw body, said bore being of predetermined larger section than said projection to provide radial clearance therebetween for adjustment of said body and said end portion into abutting relation and relative positions of accurate alignment between said flights thereon, a quantity of low melting bonding material received within said clearance to bond said projection within said bore and thereby to maintain said screw portions in said interconnected and aligned relation, said projection having at the forward end thereof a relatively short portion tapered in the opposite direction from the remainder of said projection to form a circumferential notch thereon, said bore having a portion thereof radially overlying said notch and tapered at a greater angle than the remainder thereof to form a similar circumferential notch cooperating with said notch in said projection to receive a thicker section of said bonding material between said notches than between the other opposite portions of said projection and said bore for resisting axial separation of said screw and said end portion, and said bore being open completely through said end portion to receive said bonding material through the forward end thereof.

Ackerman et a1. Jan. 24, 1928 Turner May 11, 1929

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