Rotary Feeder Construction

This invention relates to the transfer of particulate matter, and more particularly pertains to a rotary feeder construction which efficiently transfers said matter at desirably high, controlled rates to a zone of use from a supply source.

In prior art processes for feeding particulate material by means of rotary feeders, various expedients have been employed to effect desired feeding of such material to a zone of use. Thus, in Kidd U.S. Pat. No. 3,593,891 which issued July 20, 1971, a star feeder is provided in which a rotatable wheel is eccentrically mounted relative to the surrounding casing wall whereby the teeth thereof form an air seal when approaching the incoming material to be fed and are subsequently spaced from the casing wall in the course of rotation. Conveying pockets formed by the wheel teeth may thus carry the material into a feed line.

In Stern U.S. Pat. No. 3,223,288 which issued Dec. 14, 1965, a feeder employing rotating vanes having fluid passageways is employed in which the clearance between each of the vane distal edges and the housing wall is maintained as small as possible. In Woods U.S. Pat. No. 3,556,606 which issued Jan. 19, 1971, the flow of carbon black from a rotary feeder is maintained uniformly by a by-pass loop disposed about the rotary valve inter-connecting a supply hopper and zone of use whereby excessive pressure build-up in said supply hopper may be relieved.

The apparatus of this invention comprises a rotary feeder employing a rotatable valve having radially extending vanes secured at their proximal ends to a central rotatable shaft. The valve is rotatable within a feeder housing communicating with a supply source of the particulate material to be fed, such as a hopper, and a conduit leading to a zone of use for such particulate material.

In accordance with this invention alternate vanes of the rotatable valve have clearances interposed such vanes and the surrounding housing wall. Such clearances may take the form of notches in the vane edges, apertures through the vane bodies or intervals between the vane distal edges and the casing wall.

It is an object of this invention, therefore, to provide a rotary feeder construction for particulate material, interposed a supply source for such material and a zone of use which provides desirable, even feeding of the particulate material into said zone of use.

It is another object of this invention to provide a rotary feeder construction for particulate material in which consistent, even feeding is provided over varying rates of feed necessitated by varying consumption rates in a zone of use in communication with said feeder.

It is yet another object of this invention to provide a rotary feeder construction adapted to uniformly feed particulate material at exceedingly high rates of flow by a simple modification of the radial vanes employed in the rotatable valve of such feeder.

The above and other objects of this invention will become more apparent from the following description when read in the light of the appended claims and the drawing in which:

FIG. 1 is a fragmentary, schematic, vertical elevation of a feeding system employing a rotary feeder made in accordance with this invention;

FIG. 2 is a perspective view of a rotatable valve made in accordance with invention;

FIG. 3 is a side elevational view of a modified rotatable valve made in accordance with this invention; and

FIG. 4 is an end view of a second modified rotatable valve made in accordance with this invention disposed in a housing illustrated in section.

This invention is particularly adapted for use in apparatus employed in a system wherein loose carbon black is fed to carbon black pelleting apparatus. In such pelleting operation it is necessary to provide a precise feed into the pelleter to maintain a proper load and proper pelleting conditions in the apparatus which will assure a desirably uniform pellet product.

Referring now to the drawing and more particularly to FIG. 1, a hopper 10 is fragmentarily illustrated which receives carbon black from a conveyor or cyclone collector (not illustrated) communicating with a source of carbon black. Hopper 10 has a lower conical section 12 which discharges carbon black contained in the hopper 10 through rotary feeder 14 into conduit 16 which enters the top of pelleter 18. Pelleter 18 is powered by motor 20 through shaft 22. The pelleted carbon black is discharged from the pelleter 18 through discharge conduit 19.

The rotary feeder normally employed in systems such as that illustrated in FIG. 1 comprise a rotatable valve having a central rotatable shaft from which material-engaging vanes radially extend. The vanes comprise plates having planar material-engaging faces. The opposed shaft ends may be journalled in bearings disposed in opposite wall portions of the housing. The feeder housing has a curved inner wall surface over which the vanes pass in the course of sweeping the carbon black or other particulate material to be fed from the housing inlet to the housing outlet.

In accordance with this invention it has been found that the rate of feeding particulate material by means of such a rotary feeder from a supply source to a zone of use may be dramatically increased if clearances are provided in the rotary feeder between the feeder housing inner wall and alternate vanes of the rotatable valve disposed in the feeder.

Thus, it will be noted from FIG. 4 that alternate vanes 24 of rotatable valve 26 have distal edge portions spaced from surrounding housing wall 28 of feeder 14 so as to form clearances, whereas vanes 30 are in close proximity or touching engagement with curved wall 28 and, as shown in FIG. 2, are imperforate. Vanes 24 and 30 radially extend from rotatable shaft 32 journalled at opposed ends in bearings disposed in housing side portions of the feeder 14. In the valve embodiment of FIG. 4 the clearances between the alternate vanes 24 and housing wall 28 are effected by shortening the vane widths.

The clearances between the alternate vanes and encompassing housing surface portions may take the form of V-shaped notches formed in the distal edges of the vanes. Notches 34 in valve 26A (illustrated in FIG. 2) are formed in alternate vanes 24A in the form of equilateral triangles. The vane-housing wall clearances provided by the notches effect a desired increase in feed rate through the feeder while enabling the particulate material to be fed uniformly and under control effected by regulation of the speed of rotation of the valve. As will be seen from the drawing, the clearances are preferably uniformly arranged across the width of the alternate vanes effecting clearances with the housing wall.

The "clearances" between the valve alternate vanes and the housing curved wall portions may be of any configuration and disposed on the leading or side edges, or may comprise apertures in the bodies of the vanes themselves such as apertures 36 illustrated in vanes 24B of valve 26B of FIG. 3.

It has been found that the range of open area or clearance between each alternate vane and the surrounding housing surface of the feeder should be preferably about 0.5% to 5% of the normal full vane surface area. By way of example, a rotary feeder having a diameter of 18 inches could employ an open or clearance area in the alternate vanes of approximately 2 square inches or approximately 1.2% of the normal area of 162 square inches. It has been found that the number of vanes in the feeder valves should preferably be of a number between six and 12.

Utilizing a rotary feeder employing the normal vane-housing wall, substantially-touching relationship to permit free rotation of the rotary valve in the feeder housing, the rate of feeding carbon black to a pelleter through an 18 inch rotary feeder could not exceed 3,000 pounds per hour. The formation of clearances amounting to 1.2% of the total vane area in the form for instance of the notches 34 illustrated in FIG. 2 increased the feed rates to over 4,000 pounds per hour.

It is believed that the clearances may serve as a pressure equalizing means between the system portions on opposite sides of the rotary feeder 14. In the course of attempting to feed particulate matter at a constant rate by means such as a rotary feeder rotating at a constant speed, gas pockets often accumulate in the source of the particulate matter which obstruct the free passage of such particles through the system thereby rendering feeding erratic. Gases may also be intentionally introduced into the system to break down bridging which may occur in the particle source portion of the system such as in hopper 10 of FIG. 1. Such introduced gases, however, although eliminating bridging, may form flow-obstructing pressure pockets. By providing regularly recurring clearances in the rotary feeder by means of the alternate vanes having the reduced surface areas, gas passage through the rotary feeder is permitted. Such passage eliminates pockets and enables feeding of the particulate matter to carry on in an efficient uniform manner through the rotary feeder. Thus, a simple expedient is provided in a basic rotary feeder construction for relieving gaseous pressure opposing flow which is located upstream of the rotary feeder.

The provided invention may employ any of a variety of clearance forms between the alternate vanes and the surrounding housing as above noted. As has also been above noted the workable clearances in terms of vane area are also variable.

The valves of this invention require nothing unique in the way of unusual manufacturing techniques or manufacturing apparatus and may readily be inserted in feeders disposed in systems already operating in the field. Although the rotatable valves disclosed employ planar vanes or impellers of rectilinear peripheral configuration, other vane configurations may be employed to advantage for purposes of obtaining the benefits of this invention.