Extended riffle structure for a dry washer

Abstract

A generally elastic riffle assembly useful with a dry washer is provided with a frame that is receivable within the washer opening through which the mined particulates descend while the washer is agitated to separate the denser particulates and a set of inclined transverse riffles aligned across the frame to form wedge shaped transverse cavities in which the descending particulates are collected. Each of the riffles further include a plurality of generally vertical posts attached to their elevated edges which assist in the separation of the particulate flow and in setting off of the various modes of elastic motion of their corresponding riffle.

Claims

1. A riffle assembly useful in separating the denser particulates from a particulate stream descending through an inclined trough, comprising: a frame including a pair of substantially parallel side pieces dimensioned for conforming receipt within said trough, each said side piece being connected to a respective end of a transversely aligned elongate riffle provided with a raised leading edge directed in cantilever towards said particulate stream in a direction substantially opposite to the descent thereof through said trough and an oppositely directed trailing edge; and a plurality of posts mounted substantially orthogonally on said leading edge to project beyond said frame.

2. A riffle assembly according to claim 1, wherein: said frame is receivable within said trough at a depth exposing the ends of said posts above said particulate stream.

3. A riffle assembly according to claim 2, wherein: said raised leading edge of each said riffle is conformed as a generally planar strip for providing elastic support for said posts mounted thereon.

4. A riffle assembly according to claim 3, further comprising agitation means operatively connected to said frame for imparting reciprocal movement thereto whereby said riffle assembly transmits said reciprocal movement to said posts.

5. A riffle assembly according to claim 4, wherein: said transmitted reciprocal movement of said posts is transferred to said particulate matter in the course of the descent thereof within said inclined trough.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective illustration of the inventive dry washer assembly in its fully deployed configuration at the prospected site;

(2) FIG. 2 is yet another perspective illustration of the inventive dry washer assembly, separated by its parts, illustrating the operative elements of the present invention;

(3) FIG. 3 is a further perspective illustration of a riffle frame in accordance with the present invention; and

(4) FIG. 4 is a sectional detail view depicting the use of vertical posts mounted in cantilever to extend from portions of a riffle structure to promote particulate separation and induced elastic modes therein in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

(5) As Shown in FIGS. 1 through 4 the inventive dry washer assembly, generally designated by the numeral 10, comprises a hopper 11 formed as a rectangular thin-walled structure 11ST open at its top and provided with a set of inclined panels 11PS extending outwardly from the periphery of its upper opening to guide whatever material is shoveled into its interior so that it slides down and falls onto a classifying screen 12 spaced from its bottom surface 11BS. An erectable support frame 14 comprising a plurality of tubular segments 14-1 through 14-n that are pinned to each other to form a generally triangulated assembly that is attachable at its upper ends to selected points on the hopper 11 provides an inclined supporting alignment for the hopper so that the particulates comprising the material shoveled into it are separated, or classified, by size according to the openings in the screen 12 with the larger particulates rolling down the screen 12 to fall over its lower edge 12LE onto the ground surface GS along the direction indicated by the arrow AA. The classified smaller particulates that pass through the screen 12, in turn, slide down the bottom surface 11BS of the hopper 11 to fall over its lower edge 11LE along the arrow BB into the upper opening of a dry washer assembly 21 resiliently suspended on suspension cables 22-1 through 22-m within the support frame 14 directly below hopper 11 with the receiving opening of the dry washer assembly 21, similar to the hopper 11, including an inclined shielding panel 21PS that guides these particulates into its interior in the course of this fall.

(6) The dry washer assembly 21, itself, also includes a thin-walled, generally rectangular housing structure 21HS open at the top and including a bottom surface 21BS supporting a fan enclosure 31 communicating into the interior of housing 21HS the air conveyed through a hose 32 from a portable blower 33 to drive an unbalanced fan 31F mounted for air flow driven rotation that by its unbalance then induces agitating forces that shake the whole of the dry washer assembly 21, setting off the various elastic modes in each of the components thereof. The air flow AF, reduced in its intensity by the parasitic losses associated with the fan rotation, is then trapped within the lower part of housing 21HS by a dimensionally conforming diffuser plate 41 extending across the whole of the housing planform to pass through the plurality of diffusing openings 41DO in the plate into the interstices of a conforming fibrous mat 51 held in intimate contact on the diffuser plate 41 by a fitted riffle frame assembly 61 pivotally fixed by a set of pivot pins 61PP retaining its upper or front end adjacent the shielding panel 21PS that deflects the classified particulates falling from the hopper 11 into the dry washer assembly 21.

(7) By particular reference to FIGS. 3 and 4, the riffle frame assembly 61 comprises two generally parallel, flat side pieces 61SP in the form of metal straps spaced to face each other at a distance matching the interior width of the washer housing 21HS by way of welded attachments to the ends of a transversely spanning forward partial riffle 61PR and a rear end baffle 61RB, with the front ends of both side pieces perforated to engage the pivot pins 61PP while straddling a front baffle plate 61FB covering the front portion of the subjacent mat 51 so that all air flow escape out of the ends of the fibrous mat is prevented when the riffle assembly is fully seated thereon. Preferably, each of the side pieces 61SP are of a width selected to coincide with the top edges of the housing structure 21HS when resting on mat 51, a receiving depth determined by the placement of supporting brackets 21SB within the housing structure on which the diffuser plate 41 is mounted, determining the depth for the descent progression of the particulate stream within the riffle frame assembly. Of course, this also determines the maximum useful depth of the particulate mass as it descends by gravity along the downwardly along the path shown by the double phantom descent vector DD in FIG. 4 to accommodate the further mounting of a plurality of inventive riffle structures 71 that include portions extending above this particulate flow to avoid what are often its supercritical damping. By limiting the particulate depth at each riffle location in the foregoing manner the elastic modes of motion of unrestrained riffle panels can then be utilized for their forcing impact downward on the denser particulates that may be trapped beneath them. Of course, the same riffle portions that extend above this friction inducing particulate mass also create trailing voids in the particulate flow through which the much lighter particulates are blown away, eliminating the burden of the unproductive particulates.

(8) To achieve the foregoing effects each of the inventive riffles 71 is formed as an elongate segment fixed transversely in spaced increments between the side pieces 61 SP and convolved in the form of a stepped section defined by a trailing edge strip 71TE aligned for contiguous contact with the subjacent mat 51 and a generally parallel leading edge strip 71LE spaced at an offset from the trailing edge strip to extend in cantilever above the mat, the leading edge and trailing edge designations respectively corresponding to an alignment into and away from the path of the descending particulates as indicated by the vector DD. An inclined bridging surface portion 71BS extending between the leading and trailing edge strips then completes the riffle structure to form a transverse, forward facing cavity that opposes a substantial portion of the particulate descent driven by the agitation and the inclined washer alignment to approximate the stochastic processes sometimes referred to as ‘random walk’ or ‘Markoff process’ in mathematical modeling. Notably, the resulting forward facing cavities that are thus formed by each of the riffles approximate a rearward tapering wedge in which the elastic modes induced in the riffle structure assist in the downward progression of the denser particulates into the fibrous mat 51 and to obtain the effects set out above each of the leading edge strips 71LE supports a plurality of vertically projecting posts or pins 71PO that extend substantially above the particulate descent to minimize the attenuation of these elastic modes by friction while also opening ventilation pathways through the particulate mass through which the lighter particulates are blown away.

(9) The benefits of the foregoing effects can be further extended by staggering the mounting locations of the posts 71PO on each of the successive riffles so that the whole of the descending particulate mass is exposed to the process. Moreover, by varying the vertical height of each of the leading edge strips 71LE the effects of any potential stratification in the particulate descent flow can be minimized, providing a convenient mechanism to resolve the occasional stochastic interlocks by the simple expedient of small dimensional variations in the several riffle structures.

(10) The foregoing structural arrangement thus effectively conserves the levels of energy that need to be transported to the remote prospecting sites while also rendering convenient the periodic collection of the accumulated denser particulates by pivotally raising the riffle assembly 71 to remove the particulate laden mat 51 and shaking out its contents into a pan PA to be collected along with any particulates that may have migrated into the housing structure 21HS and then periodically processed in the conventional panning process, a sequence that may be repeated until the energy source is consumed. In this manner the inventive dry washer assembly effectively conserves both the manual burden of prospecting and also its efficacy in a structure that is simple, easily fabricated and fully adapted to the rugged settings of its use.

(11) Obviously many modifications and variations of the instant invention can be effected without departing from the spirit of the teachings herein. It is therefore intended that the scope of the invention be determined solely by the claims appended hereto.