SPIRAL ORE CONCENTRATING PAD APPARATUS AND METHOD

Abstract: A spiral ore concentrating pad apparatus (A) and fabrication method (B) for the production of spiral concentrating pads of any size or configuration. Resilient strips (C) having variable cross section (D) are disposed in planar and spiral orientation and glued tightly together to a backing plate (E). The strips are made of flexible material (F). The strips can also be secured to each other by providing the strips with configurations (G) that when pressed together will interlock. The strips are saw toothed (H) in cross section, are designed for use in the wheel (I) of an ore concentrator, and are oriented outwardly from a hub (J).

Description: SPIRAL ORE CONCENTRATING PAD APPARATUS AND METHOD FIELD OF THE INVENTION The present invention relates in general to mining, equipment and, in particular, to spiral concentrating wheels. BACKGROUND OF THE INVENTION Spiral concentrating wheels are a specific type of automatic panning machines. Such machines have been used for many years by both professional and amateur gold miners to remove trace amounts of gold from the surface of the earth. The principle of operation of these machines is relatively simple. The spiral concentrating wheel has a spiral groove running from the center to the periphery of the wheel. The wheel is spun, and earth in either a wet or dry state is placed upon the wheel. Separation is accomp¬ lished when a combination of gravitational and frictional forces act on the material placed in the wheel. These forces cause the material to move toward the vertical centerline of the wheel, where the lighter material is washed away by cascading water. While in this off center position, the heavier material rides the spiral recess toward the center of the concentrating wheel. The center of the wheel generally has a hole passing therethrough. Accordingly, the gold drops through the hole into a collec- tion pan or the like. Spiral concentrating wheels have been made from various materials. Steel, aluminum, rubber, and injected molded plastic have been used. Few materials have survived the wrath of the mining community and the test of time. Those wheels which have survived and proven themselves the most worthy have been those constructed of steel. The attributes of the steel wheels have been high efficiency, longevity, and good throughput capability. Steel wheels have also characteristically been as heavy and costly as they have been efficient. The expense of a steel concentrating wheel relates primarily to the fact that modern versions of the wheel have been machined out of solid steel. This process -is expensive both in terms of materials and labor. More recent automatic panning machines have used modern technology and materials to reduce the weight and increase • the portability and efficiency of the wheel. The most recent addition to the field of spiral concentrating wheels has been a metal wheel which utilizes a one-piece compres¬ sion molded rubber centerpiece or pad in place of the tradi- tional machined steel spirals. From a production stand¬ point, a one-piece compression molded rubber centerpiece or pad has tremendous advantages over customized steel machin¬ ing. Use of the rubber inserts allows lower production costs plus much lighter weight. The negative side of the compression molded rubber centerpiece or pad has been the difficulty of fabricating the original metal compression mold from which the rubber pads are made. As the size of the pad being fabricated increases, the cost of the mold goes up exponentially. For example, a compression mold for a rubber pad on the order of a foot in diameter can cost several thousand dollars, while a mold for a pad approximately six feet in diameter can cost hundreds of thousands of dollars. A primary difficulty in producing such a mold, even if one has the requisite capital, lies in the fact that the production of such a mold requires very special tooling which is very difficult to find. Accordingly, it is the principal object of the present invention to produce a spiral rubber concentrating pad with- out using the standard compression molding techniques. It is another object of the present invention to pro¬ duce spiral rubber concentrating pads of unlimited size. It is a further object of the present invention to pro¬ duce spiral concentrating pads having internal spirals of different cross sectional variation. It is yet another object of the present invention to produce a compression-molded spiral concentrating pad with¬ out the need for : an original metal compression mold. Yet another- object of the present invention is to produce a spiral concentrating pad utilizing either pour- molding techniques, strip-molding techniques, or vacuum forming techniques adapted to thermoplastic. SUMMARY OF THE INVENTION The present invention provides a novel spiral ore con- centrating pad and fabrication method thereof based upon the recognition of the fact that in any device utilizing spiral riffles, any given spiral in the device has a nearly triangular cross section which is in the shape of a saw¬ tooth. More specifically, when one of the compression- molded spiral pads is completely cut in half, the pad appears in cross section as a plurality of sawteeth. Any one of these sawteeth can be thought of as a cross section of a long thin piece of extruded material. Accordingly, in a broad aspect, the invention comprises a technique for making a mold to produce a spiral concentrating pad and the production of the pad using the mold. More specifically, the invention comprises a technique for making an original or master pad having strips of indeterminate cross section; making a molded part from the original pad; and making pads from the molded part. According to one feature of the invention, a method for producing a spiral concentrating pad with a planar and spiral groove between the center and the periphery of the pad utilizes the following steps. First, elongated flexible stripping is arranged and maintained in a planar and spiral orientation. Next, a hardenable material is formed over the stripping. The strips are then removed from the material after it is hardened, thereby exposing a molded part having an internal contour in the image of the stripping. Lastly, resilient material is formed in the molded part, thereby producing a pad having an outer contour identical to that of the stripping originally in the molded part in the plana and spiral orientation. In accordance with another feature of the invention the flexible stripping comprises a plurality of elongate strips of resilient material which are maintained in generally concentric and spiral orientation prior to th hardenable material being formed thereover. The strips ar maintained in this orientation by being mutually bonded t an adjacent strip and by being bonded to a rigid backin plate. The strips can be generally sawtoothed in cros section, whereby the outer contour of the pad produced wit the molded part comprises a continuous and spiral sawtoothe recess disposed between the center and the periphery of th pad. In accordance with yet another feature of the inven tion, the forming of the hardenable material over the strip ping can comprise the step of fiberglassing the stripping Alternately, other techniques may also be used, such a vacuum forming a sheet of hardenable material over th stripping. In accordance with yet another feature of the inven tion, the forming of the resilient material in the molde part to produce the pad can be done in several ways. First compression molding may be utilized, wherein the molded par may be used in place of the traditional steel mold. Second a pouring technique may be used whereby liquid material suc as latex may be poured into the molded part and thereafte cured or vulcanized. Third, the pad may be formed b vacuum-forming a resilient material over the molded part Fourth, a strip forming technique could be wound into th internal contour of the molded part. A backing plate coul then be affixed to these strips to maintain them' in th appropriate arrangement. The completed pad would then b removed from the mold and glued to an appropriate support. In accordance with a further feature of the invention a novel ore concentrating pad is provided with the latte technique. The pad comprises a central open hub, resilien stripping disposed in spiral and planar orientation outward from the hub, and a means for maintaining the stripping in that orientation. This produces an ore concentrating pad having stripping spiralling outwardly from the hub. The strips can be of flexible and elongated material and the size of the pad is limited only by the number of strips utilized. The cross section of the stripping can vary in accordance with the desired cross sectional shape of the pad. Other objects, features, and advantages of the present invention will become apparent from a consideration of the following detailed description and from the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the spiral concentrat¬ ing wheel portion of an automatic panning machine as known in the prior art; FIG. 2 is a fragmentary cross sectional view of the wheel of Fig. 1, taken through the plane II - II, the view showing a spiral ore concentrating pad as known in the prior art; FIG. 3 is a plan view of the spiral concentrating pad of Fig. 2, taken through the plane III - III; FIG. 4 is a perspective view of a section of resilient stripping used to form a molded part for producing a spiral concentrating pad according to the present invention; FIG. 5 is a plan view of elongated flexible stripping disposed in a spiral and planar orientation for producing the molded part from which the spiral concentrating pad is made according to the present invention; FIG. 6 is a fragmentary cross sectional view of the stripping of Fig. 5, taken through the plane VI - VI; FIG. 7 is a fragmentary cross sectional view of the production of the molded part for producing a spiral pad according to the present invention, said view showing the forming of a hardenable material over the stripping shown in O PI Figs. 5 and 6; FIG. 8 shows a fragmentary cross sectional view of t molded part produced in Fig. 7; FIG. 9 shows a fragmentary cross sectional view of t forming of a spiral pad according to the present inventi using the molded part of Fig. 8 by the pouring of a harde able material into the molded part and allowing the materi to harden; FIG. 10 is a fragmentary cross sectional view of t spiral concentrating pad formed with hardenable material shown in Fig. 9, after the material has been removed fr the molded part; FIG. 11 shows a plan view of the forming of a spir concentrating pad according to the present invention placing elongated flexible stripping into the molded part Fig. 8 and bonding the stripping together and to a flexib backing plate placed thereover; FIG. 12 shows a fragmentary cross sectional view take on plane XII - XII of Fig. 11; FIG. 13 shows a fragmentary cross sectional view of section of the spiral concentrating pad produced accordi to the present invention, after removal from the molded par shown in Fig 11; and FIG. 14 shows a cross sectional view of an alternat embodiment of the flexible stripping used in the producti of the spiral concentrating pad according to the presen invention. DETAILED DESCRIPTION Referring more particularly to the drawings. Fig. shows a spiral ore concentrating wheel 10 as known in th prior art. Such wheels generally comprise an open pa having in the bottom thereof a continuous spiral between th periphery of the pan and a hub or hole in the middle there of. In operation, the wheel is rotated in a tilted orienta tion, and material from the surface of the earth is place upon the wheel in a wet or dry state. As the pan rotates the lighter material moves toward the periphery of the pan 14, while the heavier material travels in the spiral groove to the opening in the center of the pan. As mentioned hereinabove " , various materials have been used in the prior art to fabricate the spiral concentrating wheel. For example, steel, aluminum, rubber and injection molded plastic have been used. Of these, only steel wheels have proven successful. Steel wheels are very expensive to fabricate, however, because of both materials and labor. Figs. 1-3 show a more recent design of a spiral concen¬ trating wheel 10. In contrast to the solid, machined steel wheel of the prior art, the design of Figs. 1-3 uses a flat and nongrooved pan 14 into which is placed a compression molded rubber centerpiece or pad 12 having the necessary spiral between the center opening or hub 16 and the edge of the pan 14. As shown in Fig. 2, the pad 12 is generally flat on its underside for bonding to the bottom of the pan. Additionally, in cross section, the continuous spiral be¬ tween the center opening 16 and the periphery of the pan appears as a plurality of sawteeth 12' . As also discussed hereinabove, while the compression molded rubber centerpiece or pad has a lower production cost than a completely machined steel wheel, the original metal compression mold from which the rubber pads are made is extremely expensive. The cost of the metal compression mold almost increases exponentially as the diameter of the rubber pad increases. • The present invention is directed toward the production of a rubber spiral concentrating pad without need for an original metal compression mold. Referring to Fig. 2, the present invention is based upon the recognition of the fact that, in cross section, the single continuous sprial groove of the rubber concentrating pad 12 appears as a plurality of sawteeth 12'. If the vertical line of each of the sawteeth 12" is envisioned as extending down to the bottom of the pad, then any one of the sawteeth can be thought of as a separate section of rubber stripping having generally saw- toothed or triangular cross section. Therefore, if hardenable material is formed over such stripping, a mold part will be produced which can be used to strip-form, pour form, or compression-mold a spiral concentrating pad replace those currently manufactured with metal compressi molds. The present invention therefore comprises both a nov method of forming a molded part from which a spiral conce trating pad can be fabricated in a number of ways, but al a novel spiral concentrating pad apparatus made from th molded part. Regarding the molded part, Figs. 4-8 show the produc tion thereof. Several steps are required to make the mold part. First, strips of flexible extruded material 18 ar arranged on a flat backing plate 20 in a planar and spir orientation in a manner whereby they fit together snugl Next, the strips 18 are bonded together and also attached the backing plate 20. The stripping 18 is arranged to for a central opening or hub 22 passing through the sections stripping 18 and the backing plate 20. The arrangement the stripping 18 on the plate 20 produces a master conce trating pad or template 24 from which the molded part i produced. As shown in Fig. 6, each of the strips is generall triangular or sawtoothed in cross section, in order t provide the molded part to be formed thereover with a internal contour identical to that of the outer contour the prior art spiral concentrating pad 12 shown in Fig. The stripping 18 may be of any flexible material such a rubber. It has been found that rubber extrusions of approx imately 15 feet in length may be commercially fabricated a very low cost. The backing plate 20 may be likewise fabri cated from any convenient material which is generally stiff Wood, metal, or the like may be utilized. As seen from the foregoing, with the novel technique o the present invention, a template 24 of any diameter may formed by simply adding more lengths of stripping 18 Therefore, the cost of a very large template is only slight¬ ly more than a smaller template because of the extremely low cost of the material comprising the template 24. Moreover, since the outer contour of the template is determined by the cross sections of the rubber stripping, the template 24 may have an outer contour which is deeply grooved by the use of stripping 18 having a sawtoothed or triangular cross section. Similarly, the outer contour may comprise a con¬ tinuous rounded groove by the use of stripping 18 with a rounded cross section. Once the template 24 has been fabricated as shown in Fig. 6, a molded part 26 is produced from the template by forming a hardenable material thereover. The internal con¬ tour of the molded part 26 is identical to the outer contour of the template 24. Accordingly, the resulting mold can be used as a guide in producing the novel spiral concentrating pad according to the present invention. Various materials may be used to form the molded part 26 from the template. In particular, fiberglass 28 may be laid up over the template 24 and allowed to harden. Alternately, a sheet of harden¬ able material may be vacuumed formed over the template. When the template 24 is fiberglassed, a stiff backing plate 30 can be attached to the fiberglass material 28 to increase its rigidity and strength. Figs. 8 and 11, respectively, show cross sectional and plan views of the molded part 26 produced by forming harden¬ able material such as fiberglass 28 over the template 24. As shown in Fig. 8, the internal contour of the molded part 26 is sawtoothed in cross section, corresponding to the outer contour of the template 24. Additionally, a lip portion 28' has also been formed in the hardenable material to act as a vertical guide in the forming of the pad. As shown in Fig. 11, the outer shape of the molded part 26 'may be generally square in cross section, although this feature is not particularly critical. Once the molded part 26 has been so produced, spiral concentrating pads may be formed from it with a variety of methods. Four methods are particularly contemplated. With the first method, the molded part 26 may be used as a com¬ pression mold in the place of the metal compression mold. With this method, and as shown in Fig. 9, rubber material 32 would simply be compressed into the molded part 26 to produce a spiral concentrating pad 34 {Fig. 10) which is substantially identical to the rubber spiral concentrating pad 12 of the prior art (Fig. 2) . With the second method, resilient material could be vacuum formed over the molded part 26. With the third method, a spiral concentrating pad could be formed by pouring a hardenable material into the molded part 26 and allowing the material to harden. Natural liquid rubber (latex) or some form of two-part catalytic urethane could be used. The pad so produced could be cured or vulcanized either in the mold or after removal for hardening purposes. A pad produced with such a pour molding would be substantially identical in appearance to the pad 34 produced by compression molding, as shown in Fig. 10. With the fourth and particularly contemplated method of the present invention, the molded part 26 may be used to strip-form a spiral concentrating pad as shown in Figs. 11- 13. With this method, strips of extruded material 36 sub¬ stantially identical to those used to form the template 24 are wound into the recessed spiral groove of the molded part 26. As shown in Figs. 11 and 13, after the strips 36 have been wound into the molded part 26, a flexible thin backing sheet 38 is glued to the spirals, thereby forming a spiral concentrating pad 40, shown in cross section in Fig. 12. The completed pad 40 may be heated prior to removal from the molded part 26 in order to promote complete and rapid drying. After the strip-formed spiral concentrating pad has been removed from the molded part 26, it may be affixed to a spiral concentrating wheel 14 as known in the prior art and shown in Fig. 1. The use of the strips 36 to strip mold a spiral concentrating pad 40 is particularly advantageous because the stripping 36 may be obtained commercially at a very reasonable cost. 11 Regardless of the technique used to produce the spiral concentrating pad, the finished pad is substantially identical in appearance and quality to the rubber concen¬ trating pads 12 of the prior art, as shown in Figs. 1-3. Moreover, the novel spiral concentrating pad apparatus and method has several advantages over the rubber concentrating pads currently produced with metal compression molds. First, the cost of the molded part 26 is very inexpensive compared to the great expense of the metal compression mold. It is estimated that fabricating time and cost for the molded part 26 are approximately one-tenth the cost of a metal compression mold. Second, the novel spiral concen¬ trating pad of the present invention can be of relatively unlimited size because of the ease with which the molded part 26 may be produced. The ability to produce a very large concentrating pad will result in increased ore throughput with less labor. Third, the cross sectional shape of the novel spiral concentrating pad may be easily changed due to the ease with which the molded part may be produced. The ability to vary the cross section of the molded part also allows the width of the spiral groove to be varied. As the processing of larger material requires larger grooves, while the processing of small material is most beneficial with smaller grooves, the configuration of the pad may be matched to its use. Fig. 14 shows an alternate embodiment of the rubber stripping used to form the template 24 for the production of the molded part 26, as well as for the strip-forming of the spiral concentrating pad from the molded part 26. As shown therein, the stripping 42 has a cross section with a saw¬ toothed portion 44 adjacent a dovetail section 46. On the underside of the stripping 42 is a dovetail opening,48. As can be easily envisioned, the forming of the template 24 would be done by simply snapping the dovetail projections 46 into the dovetail opening 48 of an adjacent section of stripping. The use of such stripping 42 would result in a semirigid structure. Accordingly, when the stripping 42 was 12 used to form the template 24, the backing plate 20 could b eliminated. Similarly, when the spiral concentrating pa was strip molded in the molded part 26, the interlocking o the stripping 42 would also eliminate the necessity for th flexible backing sheet 38. While the dovetail stripping 4 will most likely eliminate the backing sheet sheet 38 an the backing plate 20, it is unlikely that use of the molde part 21 could be eliminated. As an additional contemplated variation of the inven tion described herein, the pads 34 and 40 may be provide with means to allow the pads to be removably attached to rigid and generally circular backing wheel similar to th prior art wheel 10 shown in Fig. 1, but without the spiral 12. Such a backing wheel could have various curvatures t tilt the spirals of the pad at different angles. Moreover this feature would allow the pads to be changed after wear and would also allow pads having different cross sectiona configurations for the spirals in the pads to be used fo specialized applications. Such removal means could be bolt or the like, VELCRO fastening devices, glue, etc. In the foregoing description of the present invention several embodiments of the invention have been dislcosed It is to be understood that other mechanical and desig variations are within the scope of the present invention Thus, by way of example and not of limitation, the formin of the template from which the molded part is produced coul be done by other methods than by placing flexible strippin in a generally spiral and planar orientation; the productio of the molded part over the template could be done b methods other than fiberglassing or vacuum forming; the pro duction of the rubber pad using the molded part could b done by methods other than pour-molding, strip-molding o compression molding; and different cross sectional shape could be employed in the flexible stripping to produc spiral concentrating pads having grooves of various config urations. Accordingly, the invention is not limited to th particular arrangements which have been illustrated an 13 described in detail herein. What is claimed is:

Claims: 1. An ore concentrating pad comprising: central hub means; resilient stripping means disposed in spiral and planar orientation outwardly from said hub means; and means for maintaining said stripping means in said orientation, thereby producing an ore concentrating pad of stripping means spiralling outward from said hub means, said maintaining means comprising a backing plate of flexible material affixed to said stripping means. 2. A pad as defined in claim 1, wherein: said stripping is generally sawtoothed in cross section, whereby said pad comprises a continuous and spiral sawtoothed recess extending outwardly from said hub means. 3. A pad as defined in claim 2, wherein said resilient stripping means comprises: a plurality of strips of flexible and elongated material, said strips being disposed in a generally concentric and spiral orientation. 4. A pad as defined in claim 1, wherein: said resilient stripping means comprises a plurality of elongated flexible members, each of said members including a sawtoothed-shaped surface disposed longitudinally along said member; and said maintaining means comprises a dovetail-shaped member projecting from said elongated flexible member and disposed longitudinally adjacent said sawtoothed-shaped surface, and a dovetail-shaped recess disposed longitu¬ dinally beneath said sawtoothed-shaped surface, whereby said dovetail-shaped member of one of said elongated flexible members interlocks with said dovetail-shaped recess of an adjacent flexible member as said flexible members are disposed in said spiral and planar orientation. 15 5. A pad as defined in claim 1, wherein said hub means comprises: a generally circular opening at the center of said pad defined by said stripping. 6. An ore concentrating pad comprising: central hub means; resilient stripping means disposed in spiral orienta¬ tion outwardly from said hub means, said stripping being generally sawtoothed in cross section, each portion of said stripping means having a relatively wide side, having a relatively narrow side, having an inclined side which extends between upper edges of said wide and narrow sides, and also having a bottom side which extends between lower edges of said wide and narrow sides, the wide side of each of said portions of said strip¬ ping means being closely adjacent the narrow side of another of said portions thereof, whereby said inclined sides and proximate portions of said wide sides define grooves adapted to receive ore; and means for maintaining said stripping means in said orientation, thereby producing an ore concentrating pad of stripping means spiralling outwardly from said hub means. 7. The invention as claimed in claim 6, in which said maintaining means comprises a backing plate secured to said stripping means. 8. The invention as claimed in claim 7, in which said backing plate is flexible material and is adhesively secured to said stripping means. 9. The invention as claimed in claim 6, in which said maintaining means comprises means for securing each portion of said stripping means to each adjacent portion thereof. ITURE-ATT 16 10. The invention as claimed in claim 9, in which said means for securing comprises interlocking portions of said stripping means. 11. The invention as claimed in claim 6, in which said stripping means comprises a plurality of strips of flexible and elongated rubber extrusions disposed in generally concentric and spiral orientation. 12. The invention as claimed in claim 1 or claim 6, in which said ore concentrator pad is combined with a concentrator wheel adapted to be rotated about its axis when in a tilted orientation. 13. A method for producing a pad for use in ore- concentration apparatus, comprising: arranging elongated flexible stripping, comprising a plurality of elongated strips of resilient material, in a spiral orientation by positioning said plurality of strips in a general concentric and spiral orientation; and maintaining said stripping in said orientation by securing said stripping to a backing sheet. 14. The invention as claimed in claim 13, in which said method further comprises mounting the combination stripping and backing sheet, after completion of said above- stated steps, in the wheel of an ore-concentration apparatus. 15. The invention as claimed in claim 13, in which said strips are elongated rubber extrusions disposed closely adjacent each other in saw-tooth relationship. 16. The invention as claimed in claim 14, in which said backing sheet is flexible. 17 17. A method for producing a pad for use in ore- concentration apparatus, comprising: arranging elongated flexible stripping, comprising a plurality of elongated strips of resilient material, in a spiral orientation by securing said strips to each other. 18. The invention as claimed in claim 17, in which said securing is effected by causing said strips to have such conf gurations that when pressed together they will interlock longitudinally, and then effecting said longitu¬ dinal interlocking.

Inventors: CLELAND KEITH
Applicants: CLELAND KEITH
Application year: 1981
Main classification: B03B5
IPC codes: B03B5, B29C33, B29C39