US3465972A

US3465972A - Device for conducting crushing and screening operations simultaneously

Info

Publication number: US3465972A
Application number: US638701A
Authority: US
Inventors: Zane L Ardary
Original assignee: US Atomic Energy Commission (AEC)
Current assignee: US Atomic Energy Commission (AEC)
Priority date: 1967-05-10
Filing date: 1967-05-10
Publication date: 1969-09-09
Anticipated expiration: 1986-09-09

Description

Sept. 9, 1969 z. ARDARY 3,455,972

DEVICE FOR CONDUCTING CRUSHING AND SCREENING OPERATIONS SIMULTANEOUSLY Filed May 10, 1967 INVENTOR. Zane L. Ardary BY MQ.MM

.ATTORNE Y.

United States Patent US. Cl. 241-69 1 Claim ABSTRACT OF THE DISCLOSURE A hollow cylinder into which is placed a material to be crushed is mounted for rotation about its longitudinal axis. Crushing action is provided by a solid metal rod disposed inside the cylinder. As the cylinder rotates, the bar is picked up by a pair of dogs at the bottom of the cylinder and dropped from the top, thereby crushing any material caught between the bar and the wall. A portion of the wall of the cylinder is made of a selected size screen so that on each revolution of the cylinder the crushed material falls through the screen into a receptacle and is not left in the cylinder to produce fines from subsequent crushings. This device is quite useful in situations where it is desirous to obtain a narrow screen fraction of crushed particles in a very economical manner.

BACKGROUND OF THE INVENTION This invention relates to crushing and screening devices and more specifically to a low energy rotary crushing and screening device in which the material to be crushed is rotated in a cylinder together with a crushing element and screening takes place on each revolution of the cylinder.

This invention was made in the course of, or under, a contract with the U. S. Atomic Energy Commission.

When preparing spheroidal particles of uranium dicarbide for use in reactor fuel applications, one process comprises suspending uranium dicarbide particulates of -325 mesh in a carbon black matrix and applying sufficient heat to melt the uranium dicarbide. It has been found that, if the uranium dicarbide particulates are pre-sized to a narrow fraction prior to admixing with the lamp black, the yield of the desired size fraction in the product is increased.

The problem arises of how to economically obtain a high yield of a narrow screen fraction of uranium dicarbide particulates. The usual milling procedures and equipment will effectively reduce relatively large pieces of uranium dicarbide to small pieces through the action of crushing. However, the prior art mills and crushers utilize attrition extensively in conjunction with crushing. One result is the production of large quantities of fines. Further, since the prior art mills and the like produce particles varying in size over a large range, to obtain a narrow screen fraction one must crush, screen, and recharge the large particles to the crusher for further reduction in size. The obvious disadvantage is excessive labor and expense.

SUMMARY OF THE INVENTION The present invention is a mechanical device within which the dual functions of crushing and screening are performed and comprises a hollow cylinder rotatable about an axis disposed in a horizontal plane, means rotating the cylinder on its horizontal axis, passageway means penetrating a predetermined portion of the wall of the cylinder for conveying material below a predetermined size from the cylinder when the passageway means are in a lowermost location underlying the axis of the cylinder, material crushing means disposed in the cylinder for Patented Sept. 9, 1969 ice crushing material against the inner side wall of said cylinder, and means disposed in the cylinder for lifting the crushing means out of contact with the wall when said passageway means are in a lowermost location and for releasing the crushing means to effect crushing when said passageway means are rotated out of the lowermost location.

Accordingly, it is an object of this invention to provide a device for performing the dual functions of crushing and screening and for facilitating product removal after a minimum energy input to minimize fines generation.

Other objects and many of the attendant advantages of the present invention will become evident from the following description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic representation of a crusherscreener according to the present invention; and

FIGURE 2 is an enlarged, cutaway view of the cylinder element of FIGURE 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGURE 1, there is shown a hollow cylinder 5 closed at its ends by removable plates 7 and 9. Cylinder 5 is rotatably mounted in a horizontal plane by, and in frictional contact with, a pair of rollers 11 and 13. Rollers 11 and 13 are rotatably mounted on a frame assembly 15. A motor 17 is provided on frame 15 for driving roller 11 through a belt assembly 19, hence rotating cylinder 5.

For atmospheric control purposes, a housing 21 is pro vided having an upper hood portion 23 and a tapered portion 25 which extends downward below the cylinder for directing screened product into a receptacle 27.

Referring now to FIGURE 2, details of the construc tion of cylinder 5 are shown with plates 7 and 9 removed. A portion of the wall 29 of the hollow cylinder 5 comprises a screen 31 extending approximately the entire length of the wall but only extending over less than about one-half of the circumference thereof. Assuming clockwise rotation of cylinder 5, as shown in FIGURE 2, a pair of dogs 33 and 35 are provided on wall 29 at the leading edge of screen 31. Within the cylinder 5, a heavy solid rod 37 is provided as a crusher. Dogs 33 and 35 are generally L-shaped so that as the cylinder rotates rod 37 comes in contact with the dogs at the bottom of the cylinder and lifts the rod.

In operation, an appropriate amount of material to be crushed is loaded into cylinder 5 and as cylinder 5 rotates clockwise, dogs 33 and 35 pick up rod 37 at or near the bottom of cylinder 5 near the leading edge of screen 31, carry it in an arcuate path upward as the cylinder continues to rotate, and, as the dogs reach their uppermost position, the rod rolls off and falls to the bottom of the cylinder, crushing any material caught between the falling rod and the bottom portion of the cylinder wall. Preferably, the rod 37 is held by the dogs until the screen 31 has passed the lowermost position before the rod is dropped so that the screen at no time is subjected to the weight of the crusher rod or to its impact upon its falling from the dogs.

As cylinder 5 continues to rotate, the dogs again lift rod 37 at the leading edge of the screen. The screen now comes into the lowermost position and those particulates which are small enough fall through the screen into receptacle 27.

During each revolution of cylinder 5 there is a single crushing impact by the crusher rod and sized particulates are extracted. Due to the crushing and subsequent screening during each revolution a minimum amount of attrition occurs because the rod rolls upon the particles over only a short distance and the sized particles areextracted from the cylinder before significant attrition can occur. It should be noted, too, that the vibration creaed When the falling rod strikes the cylinder serves to clean the screen.

As an example, a typical crushing operation employed an S-inch-diameter cylinder, 14 inches long, having a SO-mesh screen covering 71 degrees of the cylinder surface and an 8-pound crusher rod. At a cylinder speed of 100 r.p.m., uranium dicarbide chunks of approximately Ar-inch diameter were crushed to produce 7 pounds per hour of particles, 40 weight percent of which were Within a desired 60 to 100 mesh range.

It will be seen that aunitary device is provided which performs the dual functions of crushing and screening with a minimum energy input which reduces fines gen eration and produces a high yield of a narrow screer fraction of particulates.

It will be understood that, while the preferred embodiment has been set forth, the invention is not limited thereto and various modifications may be made without departing from the spirit and scope of the invention as set forth in the appended claim.

What is claimed is:

1. A material crushing and screening device into which material to be crushed is loaded prior to operation, comprising: a hollow cylinder enclosed at the ends disposed for rotation with its longitudinal axis essentially horizontal; means for rotating said cylinder about its longitudinal axis, said cylinder having an opening longitudinally extending over substantially the length of said cylinder and extending circumferentially over less than half of the circumference of said cylinder; a screen having a predetermined mesh size disposed in said opening; a crushing rod disposed within said cylinder, said rod being substantially coextensive with the interior length of said cylinder; a pair of dogs mounted on said cylinder wall adjacent the leading edge of said opening, accor ing to the direction of rotation of said cylinder, said dogs having a configuration such that they engage said rod at a position underlying the longitudinal axis of said cylinder and lift said rod in an arcuate path upward upon each revolution of said cylinder to a position near the top of said cylinder where said rod is dropped so as to strike the material being crushed at a position on the underlying cylinder Wall adjacent the trailing edge of said opening.

References Cited UNITED STATES PATENTS 639,406 12/1899 Kreiss 241-91 741,606 10/1903 Zarniko 24l176 ROBERT C. RIORDON, Primary Examiner M. RASKIN, Assistant Examiner US. Cl. X.R. 241101, 178