US2215818A - Screening mechanism - Google Patents

Description

c. J. LINDEQUlsT 2,215,818

SCREENING MECHANISM sept. 24, 1940.l

5 Sheets-Sheet l lFiled July 1o. 19s? Sept., 24, 1940- c. J. LINDEQUIST SCREENING MECHANISM Filed July 1o, `19:57

5 Sheets-Sheet 2 1722/6/ '7 zdzywi MM i y f [kyk/QU) N wwwfsm sept 24 l940. c. .1, LINDEQUIST 2,215,818

SCREENING MECHANISM Filed VJuly 10, 1957 5 sheets-sheet s www Mr/www2 Sept. 24, l940=.

C. J. I INDEQUIST SCREENING MECHANISM 5 Sheets-Sheet 4v Filed July 10, 1937 Sept. 24, 1940.

c. J, lflNDl-:Qurs'r SCREENING' MECHANISM Filed July l0, 1937 5 Sheets-Sheet 5 Patented Sept. 24, 1940 UUNITED STATES `PA'rsN'r oFFlcE scnEaNING MECHANISM Application July 10, 1937, Serial No. 152,940

2 Claims. (Cl. 92-36) This invention relates to improvements in rotary screens of the inilow type which are employed for separating knots, lumps and foreign matter from paper pulp stock. Such screens are customarily employed to purify streams of pulp stock immediately prior totheir being fed into paper-making machines. type usually consist of a horizontal cylinder having a large number of small slits in its surface through which the pulp can pass but which are of such a size as to prevent the passage of knots or lumps of pulp fibers, and lother undesirable matter. The cylindrical screen is rotated on a horizontal axis within a suitable vat, the stock being 'fed into the vat so as to pass inwardly through the screen to the interior thereof, the purified stock owing out of one end of the screen and through a discharge port in one end of the supporting frame for the vat. means are provided for the screen, such means being customarily located at the end opposite to that through which the purified stock is discharged from the screen.

According to the present invention, the gearing customarily mounted upon the end frame to drive the cylindrical screen is changed so that a considerable portion of the end frame is accessible, this portion being provided with one or more manholes through which access may be had-to the interior of the vat for purposes of cleaning. Instead of the large gear wheel normally mounted on the screen shaft, a small gear wheel is employed, this wheel being connected through one or more reducing gears to a driving motor which can be mounted on the upper portion of the end frame. The use of a central gear of relatively small diameter permits access to one or more manholes, preferably three, in the lower portion of the end frame. Preferably, one manhole is directly below the screen shaft, the other manholes being on either side of the central manhole. The manholes are preferably .closed by hinged doors, the inner faces of which are rubber covered so that separate gaskets are not required. These doors may be secured in closed position by any suitable means such as hinged bolts.

. ln order to avoid clogging of the slits through which the stock must pass, it is customary to vibrate the vat as the screen rotates therein. These vibrations should be of sufficient amplitude to prevent the pulp fibers from catching on the edges of the slits but should not be too violent. Excessive vibration tends to force dirt through the slits and imparts severe mechanical strains on the Screens of this Suitable driving entire apparatus whereas a gentle sifting motion is desirable. Furthermore, vibrations which are too rapid cause the pulp stock to approach a state of equilibrium which reduces the screening Vaction and hence the capacity of the screen. 6

An object of the invention is to provide improved vibrating mechanism which is adjustable to vary the speed of vibration of the vat and which automatically varies the amplitude of vibration in accordance with changes of speed. To 10 this end separate drives are preferably providedfor the screen and vibrating mechanism, and-the latter includes a spring connection device as hereinafter described in detail.

Stock to be purified has heretofore been sup- 16 plied either by a pipe leading in through an end frame or through a flow box suspended above and at one side of the vat, the flow being supported on the stationary end frames which also support the vat. According to the invention, an 20 improved flow box is provided, this flow box being mounted beside the vat at such an elevation as to supply a stream of stock below the'surface of the pool within the vat, this stream extending from one end of the vat to the other. Since the vat is vibrating when in use and the flow box is preferably stationary, a exible connection or apron is provided to connect the ow box with the vat. This apron serves as a threshold over which the stream flows from the flow box into the vat, and also leaves the vat free to vibrate without vibrating the flow box. The flow box is provided with a baille arranged longitudinally near the connecting apron. Pulp stock to be purified is fed into the flow box behind this baille and must flow beneath the baille to enter the vat. The lower edge of the baille is below the surface level 'ithe pool within the vat so that the stock enters the vat below the surface of the pool, thus avoiding the formation of foam. If desired, the 40 baille plate may be adjustable to vary its height and also to tilt the plate if it is desired to have a deeper stream entering the vat at one end than at the other end. The flow box may be made double, if desired, to supply two screen vats which may be installed side by side.n In such case, the box is provided with two bailies, the stock being fed into the box between these baffles. A further object of the invention is to provide adjustable spillways for the continuous removal of floating impurities from the vat.

These and other novel and useful features will be apparent to one skilled in the art from the following description of an embodiment of the invention, and from the drawings, of which Figure 1 is a side elevation of a screening mechanism embodying the invention.

Figure 2 is an end elevation of the same. Figure 3 is a section on the line 3 3 of Figure 2. Figure 4 is a section on the line 4 4 of Figure 2. Figure 5 is a section on the line 5 5 of Figure l. Figure 6 is a section on the line 6 6 of Figure 5. Figure '7 is a section on the line 1 1 of Figure 5. Figure 8 is a fragmentary front elevation of a screening mechanism showing two flow boxes.

Figure 9 is a fragmentary front elevation of two screening mechanisms which are supplied from a single flow box.

Figure 10 is a plan View of a portion of the screening mechanism shown in Figure l.

Figure 11 is a section on the line |I of Figure 10.

Figure 12 is a section on the line I2 18 of Figure 10.

Figure 13 is a perspective view of the Weir shown in Figure 12.

The screen mechanism illustrated on the drawings includes a vat 20 which consists of stationary end walls 22 and 24 between which is a body portion 26 mounted on a pair of semi-cir cular frames 28 and 30. These frames are each carried on a pair of sets of vertical laminated springs 32 so that the body portion 26 of the vat can be laterally vibrated. Since theend walls are fixed and stationary, a flexible connection 34, preferably consisting of'a strip of rubber of suitable thickness, is secured between the body portion 26 and each of the end walls 22 and 24. Within the vat 20 is rotatably mounted a cylindrical screen 40. One end of this screen is closed and carries a shaft 42 which projects through the end wall 22 and is journaled in a suitable bearing 44 carried by the end wall. This end wall also carries suitable drive means for rotating the cylinder. As indicated in Figures 2 and 4, such drive means includes a source of power such as an electric motor 46 which drives a worm 48 meshing with a worm gear 50. The worm gear is mounted on a shaft 52 on which is also mounted a pinion 54 meshing with a gear wheel 56. This gear wheel is mounted on a shaft 58 on which is also mounted a pinion 60 meshing with a large gear wheel 62. The gear wheel 62 is secured directly on the shaft 42. Heretofore, the screen shaft has carried a gear wheel having a diameter approximately as great as that of the screen itself, the gear wheel thus covering substantially the entire end wall of the vat at the dry end of the machine. According to the present invention, the compound reducing gearing which has been described makes possible the use of the gear wheel 62 which is considerably smaller in diameter than the screen itself so that considerable area of the end wall 22 is exposed and accessible. In the machine illustrated on the drawings, the diameter of the gear wheel 62 is approximately half that of the screen. The end wall is provided with a plurality of manholes which are normally closed by covers or doors 64, 66 and 68. These covers or doors may be of any suitable or convenient construction, such, for example, as is illustrated in Figure 3. As therein shown, the cover 66 is pivotally mounted on an arm 7l) which is hinged at 'l2 to a bracket 14 mounted on the front wall 22 of the vat. The inner face of the cover 66 mai7 be supplied with a lining 'i6 of sheet rubber, or a gasket may be used to make a water-tight closure. The end of the arm i0 is notched as at 18 to receive a securing bolt S6 which carries a nut 82 to set up the cover 66 tightly against the opening of the manhole. The distribution of these manholes is such as to provide convenient access to the clearance between the bottom and sides of the screen and the adjacent portions of the vat 26. This facilitates the thorough cleaning of the vat when the type of stock going through the screen is to be changed.

In order to facilitate the ilow of stock through the ne slits in the screen, the vat is laterally vibrated. For this purpose, the body portion 26 of the vat is, as previously mentioned, mounted on vertical leaf springs 32. As indicated in Figure 5, the frames 28 and 30, which carry the body portion 26 of the vat, are connected by a longitudinal member 86. Midway between the frames is a hollow boss 88 on the member 86, through which passes a longitudinally adjustable rod 90 as indicated in Figure 6. Secured to the rod 90 within the hollow boss 88 is a collar 92. The ends of the hollow boss 88 are perforated and threaded to receive a pair of threaded sleeves 94 and 96, these sleeves having suitable hand wheels 98 and |00 thereon by which the sleeves can be screwed into or out of the boss 88. A pair of springs |02 and |04 surround the rod 90 within the boss 88 and are compressed between the collar 92 and the inner ends of the respective sleeves 94 and 96, so

that, by turning the hand wheels 98 and |00, the compression of the springs |02 and |04 can be adjustably varied. In order to clamp the sleeves 94 and 96 in adjusted position, the end walls of the boss 88 may be split and bolted together as by suitable bolts- |06 and |08 so as to bind the sleeves 94 and 96 when the bolts are set up tightly. The rod 90 is longitudinally and positively vibrated by suitable means so as to impart lateral vibrations to the body of the vat. Reciprocating means are illustrated in Figures 5 and 6 and may include an eccentric I0 which is mounted on a rotatable shaft l2 so as to reciprocate an eccentric which has a pair of pitman arms H6 extending to an articulated joint. The ends of the pitman arms H6 are clamped tightly to a pair of sleeves |I'| which are shrunk on a pin I8 (Figures 6 and 7). This pin has a drive t within an inner sleeve |20 of a compound bushing consisting of this inner sleeve, an outer sleeve |22 with an outer diameter equal to that of the sleeves H1, and an intermediate sleeve |24, the latter being of rubbei' which is vulcanized directly to the inner and outer sleeves. A connecting member |26 is clamped to the outer sleeve |22 and is secured to the rod 90. The use of the compound bushing, with the rubber between the two metal sleeves to take up the slight relative angular movement between the two metal sleeves, obviates lubricating diiculties. Rotation of the shaft ||2 at a suitable speed results in longitudinal oscillation of the rod 90 by which the vat is vibrated through the springs |02 and |04 acting on the member 86 which is rigidly attached to the frames 28 and 30. The shaft H2 is preferably connected by a belt |30 to a suitable source of power such as an electric motor |32. As shown, the belt |30 may consist of a plurality of V-shaped belts in parallel, these belts protecting the motor from the inequalities of the pulsating load resulting from the vibration of the vat through the eccentric H0. The use of separateldriving means for the vibrating mechanism and for rotating the screen permits suitable adjustment of the speed of vibration without interfering with the speed of rotation of the screen. Any suitable change-speed device may be used in the drive for the vibrating mechanism. For example, the pulley wheels,

over which the belt runs, can be replaced by other wheels of different relative sizes. Where a spring connection is employed between the reciprocating mechanism and the vat, the amplitude of the vibration of the vat may be controlled in a large measure by varying the speed of vibration. This control may be modified by tightening or loosening the compression of the springs |02 and |04, so that, by the use of the mechanism shown in Figures 1, 5 and 6, the vibration of the vat-may be readily modified to suit the particular fiber length and character of the pulp stock which is being screened. I have found that, when using vibrating apparatus such as herein described, an increase in the speed of vibration tends to shorten the amplitude thereof. In general, a relatively long slow stroke of vibration is preferred for pulp stock characterized by long fibers of a relatively thick consistency, a faster and shorter shake being preferred for shorter fibers and more dilute consistencies.

According to the present invention, improved means are provided for introducing pulp stock into the vat to be screened. Heretofore, pulp stock has been introduced either at an end of the vat or has been cascaded into one side of the vat from. a flow box overhanging a side of the vat. According to the invention, a flow box is mounted on the end walls 22 and 24 so as to extend along one side ofthe vat and to open into the vat as indicated in Figure 11. Since the box is rigidly mounted on the end walls of the vat, it is stationary and does not vibrate. Hence the box is connected to the intermediate portion 26 of the vat as by an apron |42 which may consist of a heavy strip of rubber. The side of the box toward the vat is cut away to a level below the normal liquid level within the vat so that stock from the box flows into the vat at its normal liquid level instead of falling into the vat as heretofore practiced. This avoids foam in the vat. In order to regulate the flow of stock from the box into the vat, a suitable baiiie plate |44 is mounted within the box and extends from one end to the other thereof, stock being supplied to the box behind the baille as by a supply pipe |45 or other suitable means. The lower edge |46 of the baiiie plate is spaced above the bottom |48 of the box so that the stock which is introduced into the box behind the baille plate must now under the lower edge of the plate and then above the apron or threshold |42 into the vat. The battle plate |44 is supported at its ends by suitable bolts |58 which extend through slots |52 (Figure 1), so that ends of the plate |44 may be independently adjusted up or down. Thus the clearance between the lower edge |46 of the plate and the bottom of the box may be increased or diminished uniformly or the bottom edge of the plate may be inclined so that the clearance at one end is greater than that o! the other end, thus admitting a larger ow of stock to the vat at one end thereof than enters at the other end thereof. l

Stock may be supplied to the vat through a single ilow box |40 on one side thereof, or through two such boxes as illustrated in Figure 8. If two or more screening mechanisms are installed side by side, a single box |66 may be used to supply two machines. In such case, the box is supplied with two banle plates |44, the incoming stock being introduced into the box between these plates.

At the end of the vat opposite to that at which the driving is located, the end wall Y resulting in a gradual componentof flow of the stock in this clearance toward the wet end of the vat. Since pulp stock usually contains floating impurities, these impurities gather at the surface of the stock between the vat and the screen and work gradually toward the wet end of the vat. Beyond the slitted portion of the screen a chamber |62 is provided on each side of the vat. The liquid in this chamber is relatively undisturbed so that floating impurities tend to collect here. In order to provide for the continuous removal of such impurities, the chamber |62 at each side of the vat may be provided with a suitable dam or weir |64 having an opening |66 through which the surface stock may iiow into a discharge chamber |68, as indicated in Figure 12. The Weir |64 is vertically adjustable and is secured in position by a setscrew |10. A handle |12 at the upper end of the weir facilitates the adjustment of the weir when the screw |10 is backed off to release it. Heavy impurities which sink to the bottom of the vat are caught in a narrow chamber |16 extending along the bottom of the intermediate portion 26 of the vat and discharging into a suitable pipe |18. The screen is preferably provided with the customary spray and catch pan (not shown) for cleaning the screen as it revolves.

It is evident that various modifications and changes may be made in the structure herein shown and described without departing from the spirit or scope of the invention as defined in. the following claims.

I claim:

1. A screening mechanism for paper stock and the like. comprising a vat with stationary end walls and a vibratable intermediate portion, nexible connections between said intermediate portion and said end walls, a cylindrical screen rotatably supported in said vat by said end walls, means for rotating said screen, and separate means for vibrating said intermediate portion, said vibrating means including a positively vibratable member, a pair of opposed compressed springs through which vibrations are imparted by said member to said intermediate portion of the vat, power means vibrating said member, and means for controlling the rate of vibration of said vibratable member independently of the rate of rotation of `the screen.

2. A screening mechanism for paper stock and vthe like, comprising a vat with a rotatable screen vat, and means for adjusting the normal tension lo of said springs.

CHARLES JOHN LINDEQUIST.

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