US2700470A - Sifting apparatus - Google Patents

Description

M. 1.. DE GA,

SIFTING APPARATUS Jan. 25, 1955 2 Sheets-Sheet 1 Filed April 10, 1951 Jan. 25, 1955 M. L. DE GAIL SIFTING APPARATUS 2 Sheets-Sheet 2 Filed April 10, 1951 United States Patent SIFIIN G APPARATUS Marc Lamort de Gail, Vitry-le-Francois, France, as-

signor to E & M Lamort Fils, Vitry-le-Francois, France, a French company Application April 10, 1951, Serial No. 220,190

Claims priority, application France April 15, 1950 8 Claims. (01. 209-287) This invention relates to sifting or screening apparatus.

More particularly, this invention relates to a vibrating sifting or screening apparatus which is provided with a novel arrangement for controlling the vibration thereof.

There exists in the art sifting or screening apparatus used for separating or filtering fibrous materials, such as paper-pulp, in which a sifting drum is resiliently mounted on a support by means of springs, rubber strips, or other shock-absorbers, and in which vibrations are generated by means of an unbalanced shaft or the like. In such devices the vibrations are dependent upon the elasticity of the resilient mountings as well as the speed of rotation of the unbalanced shaft, the normal period of oscillation or vibration of the sifting 'drum, and several other factors. Consequently, the exact mechanical characteristics of known sifters cannot readily be determined in advance of actual construction of the device. Also, in order to stabilize known apparatus, i. e., to prevent the same from vibrating at undesirable frequencies or according to undesirable patterns it has been necessary to decrease the elasticity of the'shock absorbers. As a result, the efficiency of the sifting device is greatly reduced.

Furthermore, the shock-absorbers commonly used in known sifting or screening devices, such'as springs, pistons and the like, are adapted to yield in one direction only so that during normal operation of the device the shock-absorbers are subjected to undesirable stresses. As a result, the useful life of the shock-absorbersis materially reduced.

It is therefore one of the objects of the present invention to overcome the above disadvantages by providing a sifting or screening apparatus the mechanical characteristics of which may be very easily determined and controlled.

It is another object of this invention to provide a sifting apparatus, the amplitude of vibration of which may be controlled while the apparatus is in operation;

It is also an object of this invention to provide a sifting device wherein it is possible to control the vibratory path or ellipse during operation of the device.

It is also among the objects of the present invention to providea sifting or screening mechanism with'shockabsorbers capable of yielding in any direction.

The objects of this invention also include the providing of a sifting device with suitable control means for con- 1 trolling the elasticity and resiliency of the shock-absorbers by means of which a vibrating drum is supported on a stationary support.

Also an object of this invention is the providing of a sifting device wherein the elasticity of the shock-absorbers by means of which a vibrating sifting drum is supported is controlled by variations of fluid pressure.

It is further an object of this invention to provide a screening or sifting arrangement which can be adjusted so as to perform at the optimum operating point by controlling the elasticity of' the shock-absorbers by means of which the vibrating sifting drum is supported.

With the above objects in view the present invention mainly consists of a stationary framework fixedly supporting a tub or pan in which a rotatable sifting or screening drum is at least-partially located. This drum is rotatably supported ona symmetrical movable framework which has an even number of tires distributed on opposite sides of a vertical plane passing through the drum axis.

These tires, which may be filled with air or the like, are

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mounted in cages forming part of the stationary framework, and the pneumatic pressure in the tires may be varied so as to regulate the tightness or looseness with which the tires are held in the cages. Vibrations are imparted to the rotating drum by means of an unbalanced shaft supported by the movable framework, which shaft is located in the vertical plane passing through the drum axis. A similar result may be obtained by running such a shaft eccentrically about an axis located in the vertical p ane.

A first source of fluid pressure is operatively connected only to the pneumatic tires located on one side of the vertical plane so as automatically to maintain an equal pressure in all tires on this one side of the vertical plane, and a second source of fluid pressure is operatively connected only to the pneumatic tires located on the other side of the vertical plane so as automatically to maintain an equal pressure in all tires on this other side of the vertical plane, which last-mentioned pressure may be different from the first-mentioned pressure.

The framework may comprise a pair of members, each of which has a horizontal arm and a vertical arm intersecting the horizontal arm, the pair of members being respectively locatedat opposite ends of the drum and having upper end portions of the vertical arms connected to the drum. The vertical arms of each of the members may be substantially shorter than the horizontal arms thereof, and be substantially equal to one half the length thereof.

The tires may be connected to the outer end portions of the horizontal arms, so that vibrations are transmitted to the support only through the tires.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 is a schematic side view of a preferred embodiment of the present invention; and

Fig. 2 is a schematic top view of the embodiment illustrated in Fig. l.

Referring now to the drawing there is shown a tub or pan 1 fixedly mounted on a stationary support. A sifting or screening drum 2 is rotatably supported by a framework consisting of two identical cross-shaped members 3.

Each cross-shaped member has a horizontal arm which is intersected by a vertical arm which is substantially shorter than the horizontal arm. In the preferred embodiment the vertical arm is substantially equal to one llz alf tlhe length of the horizontal arm, as can be seen in The drum 2 is rotatably supported by the vertical arms at the upper ends thereof. Suitable vibration means, such as an unbalanced shaft 4, are provided to vibrate the drum 2. The shaft is located in the vertical plane passing through the axis of the drum and is supported for rotation by the lower portion of the vertical arms of the cross-shaped members 3.

The free ends of the horizontal arms of the crossshaped members 3 carry the axles 5 which supported four pneumatic tires 6, as shown in Fig. 2. The tires are mounted in cages 7 which are fixedly secured to the stationary support. The tires may either simply rest on supporting surfaces, or they may be firmly pressed against the inner wall surfaces of the respective cages 7 which are round and adapted to receive the outer rim portions of the tires.

The pneumatic tires on the left side of the vertical plane passing through the axis of the drum 2, as seen in Fig. 2, are in communication with a source of fluid under pressure such as a compressed air container 9. Suitable conduits means 8 connect the tires to the compressed air container 9.

The pneumatic tires on the right side of the vertical plane are in communication with another source of fluid under pressure 9 which may be similar to the compressed air container mentioned above. Similarly, suitable conduit means 8 are provided to connect the tires with the source of fluid.

Each of the compressed air containers are provided with suitable gauges and valves so that the pressure within the tires can be controlled. It will be understood that the pressure prevailing within the two containers 9 need not be identical so that the tires on either side of the vertical plane passing through the axis of the drum 2 may be inflated to different pressures.

In operation, the tires pressures may be chosen so that when the sifting or screening drum 2 rotates at a few revolutions per minute, it vibrates at approximately 1,500 vibrations per minute. The amplitude of the vibration is preferably of the order of a few millimeters.

By varying the tires pressures, the amplitude of the vibrations of the drum 2, as well the path along which the axis of the drum moves under the influence of the vibrations may be controlled. It is well known that the vibrating or oscillating movement described by the drum of an apparatus of the character described is elliptical, the inclination of the axis of the ellipse being determined by the direction of rotation of the unbalanced shaft 4 as Well as the intensity of the vibration. The direction of rotation of the unbalanced shaft determines on which side of the vertical plane passing through the axis of rotation of the drum the major axis of the ellipse inclines whereas the intensity of the vibrations determines the degree of inclination of the axis of the ellipse relative to this vertical plane. Inasmuch as in the present in vention the shock-absorbers supporting the framework which carries the drum 2 are particularly adapted to yield in any direction the drum is ideally supported for vtilbration regardless of the direction of rotation of the s aft.

Also, since the amplitude of the vibration is dependent upon the elasticity of the shock-absorbers, the amplitude may very readily be controlled by varying the pressure prevailing in the tires. Suitable valve means may be provided to keep the tire pressure within predetermined limits by equipping the containers 9 with valve devices to keep the tire pressure below a predetermined value. Also, automatic tire inflation systems may be provided which shut off in case of excessive vibration of the drum Furthermore, by varying the pressure in the right or left group of tires, as seen in Fig. 2, it is possible to vary the major and minor axes of the elliptical path along which the drum 2 moves. As a result, the mechanical characteristics of the device according to the present invention may be controlled by varying the tire pressure in either the right or the left group of tires, or in both simultaneously.

All of the above adjustments may be made while the device is in operation, without it being necessary to interrupt the sifting or screening processes.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of sifting or screening apparatus differing from the types described above.

While the invention has been illustrated and described as embodied in a sifting apparatus equipped with pneumatic tires, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of thegeneric or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. Screening apparatus comprising, in combination, a screening drum; a framework rotatably supporting said drum; an even number of pneumatic tires mounted on said framework and being symmetrically distributed on opposite sides of a vertical plane passing through the axis of. said drum: a stationary support operatively connected only to said tires so as to support to said framework;.and-vibration means located in said vertical plane passing through the axis of said drum, said vibration means being connected to and supported by said framework to impart vibrations to said drum, so that vibrations are transmitted to said support only through said pneumatic tires.

2. Screening apparatus comprising, in combination, a screening drum; a framework rotatably supporting said drum; an even number of pneumatic tires mounted on said framework and being symmetrically distributed on opposite sides of a vertical plane passing through the axis of said drum; a stationary support operatively connected only to said tires so as to support said framework; vibration means located in said vertical plane passing through the axis of said drum, said vibration means being connected to and supported by said framework to impart vibrations to said drum, so that vibrations are transmitted to said support only through said pneumatic tires; a first source of fluid pressure operatively connected only to the pneumatic tires located on one side of said plane to automatically maintain an equal pressure in all tires on said one side of said plane; and a second source of fluid pressure operatively connected to the pneumatic tires located on the opposite side of said plane to automatically maintain in all tires on said opposite side of said plane an equal pressure which may be different from the pressure in said tires on said one side of said plane.

3. A screening apparatus as defined in claim 2 and wherein said framework comprises a pair of members each of which has a horizontal arm and a vertical arm intersecting said horizontal arm, said members being respectively located at opposite ends of said drum and having upper end portions of said vertical arms connected to said drum, said tires being connected to outer end portions of said horizontal arms, and said vibrati n means being connected to lower end portions of said vertical arms.

4. A screening apparatus as defined in claim 1 and wherein said framework comprises a pair of members each of which has a horizontal arm and a vertical arm intersecting said horizontal arm, said members being respectively located at opposite ends of said drum and having upper end portions of said vertical arms connected to said drum, said tires being connected to outer end portions of said horizontal arms, and said vibration means being connected to lower end portions of said vertical arms.

5. A screening apparatus as defined in claim 4 and wherein said vertical arms of each of said members are substantially shorter than said horizontal arms thereof.

6. A screening apparatus as defined in claim 5 and wherein said vertical arms are substantially equal to one half the length of said horizontal arms.

7. Screening apparatus comprising, .in combination, a screening drum; a pair of framework members respectively located at opposite ends of said drum in planes normal to the axis of said drum and each having an upper end portion turnably supporting said drum for rotation about its own axis, each of said framework members being of a symmetrical construction and having identical halves respectively located on opposite sides of a vertical plane including said drum axis; a pair of tires mounted on each framework member, all of said tires being symmetrically distributed and symmetrically arranged on opposite sides of said vertical plane including said drum axis; a stationary support operatively engaging only said tires so as to support said framework members and drum; and vibration means located in said vertical plane including said drum axis and being carried by lower portions of said framework members, so that vibrations are transmitted to said support only through said pneumatic tires.

8. Screening apparatus .comprising, in combination, a screening drum; a pair of framework members respectively located at opposite ends of said drum in planes normal to the axis of said drum and each having an upper end portion turnably supporting .said drum for rotation about its own axis, each of said framework members being of a symmetrical'construction and having identical halves respectively located on opposite sides of a vertical plane including said drum axis; a pair of tires mounted on each framework member, allof said tires being symmetrically distributed and symmetrically arranged on opposite sides of said vertical plane including said drum axis; a stationary support operatively engaging only said tires so as to support said framework members and drum; vibration means located in said vertical plane including said drum axis and being carried by lower portions of said framework members, so that vibrations are transmitted to said support only through said pneumatic tires; a first source of fluid pressure operatively connected only to the pneumatic tires located on one side of said vertical plane including said drum axis; and a second source of fluid pressure operatively connected to the pneumatic tires located on the opposite side of said vertical plane including said drum axis.

References Cited in the file of this patent UNITED STATES PATENTS 1,131,599 Clarke Mar. 9, 1915 6 Beaumont Aug. 3, Daman May 22, Stroud Oct. 21, Maginn Dec. 9, Burls June 19,

FOREIGN PATENTS Germany Feb. 15, Germany Apr. 10, France Aug. 26,

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