US2119595A - Screening device - Google Patents

Description

June 7, 1938. J. w. M NEELY- SCREENING DEVICE Filed Dec. 22, 1934 2 Sheets-Sheet l J. I: v 1 I- Jar/5 h. M112 Y, 62-) June 7, 1938. J. w. McNEELY S CREENING DEVI CE 22, 1934 2 Sheets-Shet 2 Filed Dec.

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Patented June 7, 1938 UNITED sTATl-zs PATENT OFFICE 3 Claims.

This invention relates to improvements in methods of screening and in arrangement of elements whereby eflicient, durable and substantially fool-proof screening devices are obtained. The term "screening as used hereinafter relates to the art of separating solids diflering in particle size from mixtures of solids, the term also including the separation of solids from a fluid by mechanically retaining the solids on a foraminous member.

The invention particularly relates to screening devices in which a vibration is imparted to a screen member, said screen member being preferably retained in a rigid frame.

Heretofore, vibrating screens necessitated continual replacement of the screen fabrics, particularly when woven screen fabrics of relatively fine mesh were employed. I have found that the disruption, tearing or breakage of the screens is due to improper application of the vibrating force and therefore an unequal distribution of vibrations over the screen area.- For example, the vibrating screens of the prior art have practically always exhibited areas of the screen surface which were not being effectively vibrated and which were therefore substantially dead and ineffective in the screening operation. Furthermore, inadequate and ineffective means for supporting the screen were provided. I have discovered that by properly supporting the screen fabric and by applying the vibrations to certain portions of the screen as hereinafter described in detail, the breakage and wear of the screen cloth can be prevented and thecapacity of a given screen materially increased. Moreover, I have found that in order to produce most effective results, the screen frame should" be anchored in such manner as to permit its free movement in a vertical plane without restricting upward movement of the screen frame.

Generally stated, the present invention relates to a screening apparatus in which a screen fabric is suitably supported within a rigid frame, the vibrating means being attached to the frame at a point between 50% and 80% of the frame length from the feed end thereof. Moreover, the vibrating means should be attached to a transverse member positioned as'stated hereinabove with respect to the frame length, the vibrating means being attached to said transverse member at points spaced from the side of the frame, said points being located at between 10% and 60% of the distance between side members.

In addition, the device of this invention includes means for supporting the screen cloth in such manner as to produce a progressively increasing curvature to the cloth (from the feed to the discharge end), the radius of curvature of the screen thus progressively decreasing from the feed to the discharge end. Moreover, the device 5 of this invention includes an anchoring construction in which annular res'ilient rings firmly mounted on a base slidably and loosely receive anchoring pins carried by the screen frame.

These and other characteristics of the invention will become apparent to those skilled in the art from the following detailed description of one preferred embodiment of the invention.

In illustrating the invention, reference will be had to the appended drawings, in which:

Fig. 1 is a plan view of a-screening device embodying the concepts of this invention.

Fig. 2 is a side'elevation of the device shown in Fig. 1.

Fig. 3 is .an enlarged vertical section taken along the plane III -III of Fig. 1.

Fig. 4 is an enlarged vertical section taken along the plane IV-IV of Fig. 1.

Fig. 5 is a front view of the screen shown in Fig. 1, the housing being partly brokenaway.

Fig. 6 is an enlarged view of the screen tensioning device.

Referring to the drawings, the apparatus comprises a screen .frame having side members I and a central longitudinal partition 2 joined .by cross members 3 forming a rigid frame. Arranged transversely of this frame on each side of the partition 2 is a plurality of transverse screen supporting members I. These members are arranged in progressively displaced relation to each other along the frame so as to provide supporting means for a-screen fabric 5 stretched thereover, adapted to contour the screen fabric,

as shown in Fig. 2. .The screen fabric 5 is secured at its rearward end between clamping bars 6 suitably fixed in the frame. The contour of the fabric surface is such that said surface is a relatively flat adjacentthe feed end, namely, the right-hand end of Fig. 2, while gradually increasing in curvature downwardly toward the forward end, the radius of curvature of the screen thus progressively decreasing. The members 4 are so displaced with respect to one another that preferably a tangent of the operative screen surface adjacent the discharge end .wiil intercept the tangent of the screen surface adjacent the feed end by an angle of not less than 10 and preferably between 20 and 30. Obviously, the precise arrangement of supporting members 4 and the maximum angulation imparted to the v bar or body portion I by welding or the like, the

screen fabric will vary with the characteristics 4 of the materials which it is desired to screen.

The forward end of a length of screen fabric substantially equal to the length of the frame, is

secured'to a tensioning means including a bar I rotatably and adjustably mounted in clamping screen being held to the clamping face 3I by means of the clamping bar 32 and bolts 33. Re-

silient gaskets 34 may be placed between the screen cloth and the clamping members so as to insure a firm grip on the cloth. .In order to I stiffen the body bar I, a stiffening web 30 may be welded thereto, as shown in Fig. 6. Partial rotation of the bar I will therefore cause the fabric to contact with the circular body portion -of the device, the bar being clamped in desired position by means of the clamping studs 9 connecting the ends of the clamp brackets 8. By providing the tensioning device with a flat face adapted to receive the screen and a cylindrical body portion, the screen may be tensioned without injury. After the screen is tensioned the clamping bar 32 is out of the path of the material being screened.

Screen fabrics of similar texture may be mounted on both sides of the partition 2 or different textures maybe mounted on the different sides. The partition 2 divides the screening surface longitudinally so as to provide laterally adjacent sections on opposite sides of the partition. Mounted on the side members I and center member 2 is a transverse support or supports I 0 which distribute and apply vibrations to the.

verse member or'members III with respect to the length of the screen frame I is quite important. Preferably, the transverse member I 0 is at a point between 50% and of the frame length from the feed end thereof as it has been found thatvibration is more effectively and. uniformly distributed over the entire area of the screen when such location is used.

The vibrating device, generally indicated at II and illustrated specifically in Fig. .5, is of the type in which the vibration is produced by an unbalanced weight or by a weight rotating eccentrically. A plurality of weights is shown at 35, these weights being mounted eccentrically on a shaft 36 having a pulley 3'I' to which a suitable belt may be attached, such as the belt I2 (Fig. 1). The shaft 36 is mounted in bearings 31 which are in turn connected to the transverse members Ill. The entire shaft may be enclosed in a housing, as shown.

The location of the bearings 31 with respect to the width of the screen frame I is also important. The transverse members I 0 are connected to the side plates as well as the intermediate partition 2 of the screen frame, the screen supporting members 4 being also attached to the side plates and partition. It has been .found that if the bearings 31 are located at between 10% and 60% of the distance between the side members and partition 2 (this distance being measured from the side members), that the vibrating effect is distributed uniformly over'the entire screen surface. of connection between the transverse members III In other words, the points and the vibration generating element are preferably located at between 5% and 30% of the total width of the screen frame, measuring from the side members. a

If, for example, the bearings 31 are positioned directly above the side plates of the screen frame, then vibration would be intensive in the center of the screen but ineffective in regionsgadjacent the side plates. Similarly, if the bearings 31 are attached to the transverse member III at a point closely adjacent the central-partition 2, the screen 5 will readily exhibit dead areas which do not exert a screening action, other areas exhibiting intensive vibration which destroys or weakens the screen at such points.

As shown in Fig. 5, it has been found that when the bearings 31 are at a distance from the side plates representing approximately 30% of the distance between the side plates and the'central partition, very effective and uniform distribution of vibration occurs. Obviously, the precise location of the bearings 31 may be influenced by the speed at which the vibrator shaft 36 is run and the mass of the weights 35.

As the'screen fabric 5 rests upon the supports 4, the latter are preferably protected by rubber channel members I3 arranged to slip over the upper edge of the member 4 as illustrated in Fig. 4. These rubber channels provide resilient members upon which the screen cloth may rest. They assist in providing an eventension in the screen fabric so as to produce a smooth and even surface free from wrinkles. ping strips I3 are under compression, they tend to keep the screen 5 taut for a long period of time. They protect the screen fabric from ex cessive wear and also the members 4. These channels are easily renewable at slight expense.

The entire screen frame I is suitably anchored to a fixed base, such as the base or sub-frame 2|. This sub-frame may be mounted on any suitable base 22 and provided with means, such as the adiusting screws 23, whereby the inclination of the sub-frame 2| may be varied. The

frame I in any suitable manner, as by means of brackets I5. The pins or stub shafts I4 are preferably four in number at the end portions of the .side plates.

The pins loosely extend into bores formed in' annular rings I6 of a solid resilient material, such as rubber or rubber composition. Each of the rings I6 is preferably provided with a bore larger in diameter than the diameter of the stub shaft I4, said bore being flared at each end as shown in Fig. 3. The annular rings I6 are retained within split housings I9 secured by bolts 20 or other suitable means to the sub-frame 2 I. Opposing cones I'I may be carried by each of the stub'shafts I4, the cones being adapted to cooperate with the countersunk portions-of the rings I6. The cones may be retained on the stub shaft by means of lock nuts I8.

It has been found that the bore of the rings I6 may be from to A; inch larger in diameter than the cooperating portion of the anchoring pin or stub shaft I4." In operation, the entire screen screen.

has been found that this method of anchoring the screen frame upon a base or sub-frame results in the most effective application of vertical vibrations to the screen. Although the fabric or screen proper 5 vibrates, the entire screen frame I also vibrates and floats within the rubber rings, the maximum movement of the screen frameitself consisting of a vertical displacement which is most effective for screening operation.

Any suitable means for feeding materials to be screened upon the device may be employed. A form of feeder or feeding gate including a chute 24 and gates or vanes 25 pivotally mounted on vertical shafts 26 is illustrated but such feeding gate forms no specific part of the present invention.

In the operation of this device, the screen fabric 5 is adjusted to the desired tension by means of the roller 1, if desired, and the inclination of the entire device is adjusted by means of the'screw 23. The vanes 25 are adjusted to suitable angles so as to distribute the flow of material between the laterally adjacent screen sections and the operation of the vibrating device I l is started. The device H sets the screen frame I into vibration. This vibration takes place in a vertical plane through the longitudinal axis of the device. The form of vibration may be of any desired type withinthis plane. The rubber support rings l6 are adapted to accommodate any type of vibration whether circular, elliptical or simply oscillatory which may be induced by the device II. This vibration is imparted to the screen fabric 5 and the material flowing thereover is separated accordingly. It will be noted' slope of the screen fabric increases progressively so that as the material is cleaned it movesfaster over the screen. This arrangement is such as to utilize the screening material at its highest eificiency and accordinglyan increased amount of material can be handled in a given time.

The arrangement of the partition 2 makes it permissible to screen different kinds of materials on the same apparatus. Furthermore, the screen fabric is subdivided so that wear of one portion involves renewal of only that portion without rendering it necessary to renew a full size screen fabric. A considerable economy is,-therefore, effected by this construction.

The resilient members l6, being uniform in texture, are equally resilient in all directions. Accordingly, these supports will respond to any type of vibration which may be imposed on the device by the particular type of vibrator H.

While a definite and particular structure has been illustrated in the drawings, it will be understood that this is for the purpose of description only, and that any other suitable type of construction embodying the features of this inven-' tion may be used. 'It is also understood that various individual features or sub-combinations of the device may be useful of themselves without reference to other features and that the use of such individual features or sub-combinations is contemplated by this invention and within the scope of the appended claims.

It is further obvious that various changes may be made, within the scope of the appended claims, in the details of construction without departin After this point has been passed, the' from the spirit of this invention; it is to be understood, therefore, that this invention is not specific details shown and/or desupports, said supports being adapted to contour the screen fabric to a progressively decreasing radius of curvature from the feed end to the discharge-end of the frame.

2. In a screen construction, the combination of a frame provided with longitudinal side members, a transverse vibration-distributing member connecting said side members, said transverse member being positioned at a point between 50% and of the frame length from the feed end thereof, a vibration-generating element carried by said transverse member and attached thereto at points spaced from said side members a distance of between 5% and 30% of the total frame width, a plurality of transverse spaced supports carried by said screen frame, and a screen fabric mounted in said frame and supported by said transverse supports, said supports being adapted to contour the screen fabric to a progressively decreasing radius of curvature from the feed end to the discharge end of the frame.

3. In a screen construction, the combination of a screen frame provided with longitudinal side members, a longitudinally extending medial partition, transverse members connecting the lower portions of said side members and partition, a transverse stationary vibration-distributing member fixed to the upper portions of said side members and longitudinal partition and connecting the same, said vibration-distributing member being positioned at a point between 50% and 80% of the frame length from the feed end thereof, a pair of transversely spaced separate bearings carried by said stationary transverse vibration-distributing member, each of said spaced bearings being attached to said member at a point between 10% and 60% of the distance between a side member and said partition, measurin from a side member, said bearings being located on opposite sides of said longitudinal partition, an unbalanced rotating vibration-generating shaft journaled in saidbearings, a plurality of transverse spaced supports carried by said screen frame and connecting said side members and longitudinal partition, and a screen fabric mounted in said frame and supported by said transverse supports, said supports being adapted to contour the screen fabric to a progressively decreasing radius of curvature from the feed end of the frame to the discharge end thereof, said reduction in radius of curvature being such that a tangent of the screen surface adjoining the discharge end intercepts a tangent of the screen surface adjoining the feed end by an angle of between about 20 and 30.

JAMES w. mums.

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