Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SPIRAL ORE CONCENTRATING PAD APPAR~TUS AND METHOD
The present invention relates in gene~al to lnining
equipment and, in par-ticular, to spiral concentrating
wheels.
Spiral concentrating wheels are a specific type of
automatic panning machines. Such machines have been used
Eor many years by both professlonal and amateur gold miners
to remove trace amounts of gold flom the ~urface of ~he
earth. The principle of operation of these machines is
relatively simple~ The ~piral concentrating wheel has a
spiral groove running ~rom the center to the periphery of
the wheel. The wheel is spun, and earth in elther a wet or
dry state is placed upon the wheel. Separation is
accomplished when a combination of gravitational and
~Erictional forces act on the material placed in the wheel.
These Eorces cau~e the material to move toward the vertical
centerline of the wheel, where the lighter material is
washed away he 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 general1y has a hole passiny therethrough.
Accordingly, the gold drops through the hole into a
collection pan or the like.
,Spiral concentrating wheels have been made from
variou~ ma~erial~. Steel, aluminum, rubber, and injected
molded pl,~stlc have been used. Few materials have ~urvived
the wrath oE the mining community and the test of time~
Those wheels which have survived and proven themselves the
mo~t worthy h~ve been th~e con~t~ucted of ~teel. The
attrlbute~ oE the ~teel wheels have been high eEficiency,
longevity, and good throughput capability. Steel wheels
have also characterlstically 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 ol~t of
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solid steel. This process is expensive both in terms of
material~ and labor.
More recent automatic panning machines have used
modern technology and materials to recluce 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
compression molded rubber centerpiece or pad in place of
the traditional machined steel spirals. From a production
standpoint, a one-piece compression molded rubber
centerpiece or pad has tremendous advantages over
customized steel machining. Use of the rubber inserts
allows lower production costs plus muc'n ligllter weight.
The negative side of the compression molded rubber
centerpiece or pad has been the difficulty of fabricating
the original metal compression mold from whic~h the rubber
pads are Inade. As the size oE 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
oE a foot in diameter can cost several thousand dollars,
while a mold for a pad approximately six feet in diameter
can cost hundreds of t'nousands o~ dollars. A primary
di~ficulty in producing such a mold, even if one has the
requisite capital, lies in the fact that the production o
such a mold require~ very special tooling which is very
die~icult to ~ind.
Accordingly, it i~ the principal object of the
pre~ent invention to produce a splral rubber concentrating
pads o~ virtually unlimlted size without using the standard
compre~slan moldin~ techniques, which generally utilize
ne~cll mold~.
Tt is a Eurther object o~ the present invention to
produce spiral concentrating pads havlng internal spirals
of different cross sectional variation.
Yet another object of the present invention is to
produce a spiral concentrating pad utilizing either
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pour-molding techniques, strip-molding techniques, or
vacuum forming techniques adapted to t'nermoplastic.
The present invention provides a novel spiral ore
concentrating pad and -~abrication method thereof based upon
the recognition of the fact that in any device utilizing
spiral rifEles, any given spiral in the device has a nearly
triangular cross section which is in the shape of a
sawtooth. More specifically, when one of the
compression-molded spiral pads is completely cut in halE,
the pad appears in cross section as a plurality of
sawteeth. Any one of these sawteeth can be thought of a~ 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
lS 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
~rom the original pad; and making pads ~rom the molded
part.
According to the invention, a method for producing a
spiral concentrating pad with a planar and spiral yroove
between the center and the periphery of the pad utilizes
the following steps. First, elongated flexible stripping
ls arranged and maintained in a planar and spiral
orientation. Next, a hardenable material is formed over
the st~ipping. The strips are then removed ~rom the
material after it is harclened, thereby expo~ing a molcled
part having an internal contour in the image Oe the
~trlpplng. Lastly, ~esilient material i~ formed in the
molded part, therehy producing a pad having an outer
conkour identical to that oE the stripping originally in
the molcded part in the planar and spiral orientation.
In accordance with a further feature of the inven-
tion, a novel ore concentrating pad is provided with the
latter technic~ue. The pa~ comprises a central open hub,
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resilient stripping dispos~d i~ spiral and planar orien-
tation outward ~rom 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 ~ize of the pad is limited only by the
number of strips utilized~ The cross section oE the
stripping can vary in accordance with t'ne desired cross
sectional shape of the pad.
The present invention is further illustrated in the
accompanying drawings, in whicho
FIG. 1 is a perspective view of the spiral
concentrating wheel portion of an automatic panning machine
as known in the prior art;
FIG. 2 is a ~raymentary cross sectional view of the
wheel of Fics~ 1, taken through the plane II - II, the view
showing a spiral ore concentrating pad as known in the
pclor art;
FIG. 3 i~ a plan view of the spiral concentrating pad
of Fig. ~, 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 o~ elongated flexible stripping
dispo~ed in a ~piral and planar orientation for producing
the molded part from whlch the spiral concentrating pad is
made accordiny to the present invention;
FIG. 6 is a eragmentary cros~ sectional view of the
strlpping o~ Fig. 5, taken through the plane VI ~ VI;
FIG. 7 i~ a Eragmentary cro~s ~ectlonal view oE the
producti4n oE the molded part Eoc producing a spiral pad
according to the present invention, said view showing the
~orming of a hardenable snaterial over the stripping shown
in Figs. S and 6;
FIG. 8 shows a fraymentary cro~ sectional view of
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the molded part produced in Fig. 7;
FIG. 9 shows a Eragmentary cross sectional view of
the forming of a spiral pad according to the present
invention using the molded part of Fig. 8 by the pouring of
a hardenable material into the molded part and allowing the
~naterial to harden;
FIG. 10 is a fragmentary cross sectional view oE the
spiral concentrating pad formed with hardenable material as
shown in Fig. 9, after the material has been removed from
the molded part;
FIG. ll shows a ~r3gmentary cross sectional view of
the forming of a spiral concentrating pad according to the
present invention by placing elongated flexible stripping
into the molded part of Fig. 8 and bonding the stripping
together and to a flexible backing plate placed thereover;
FIG. 12 shows a plan view of Fig. ll;
FIG. 13 shows a fragmentary cross sectional view Oe a
sectiorl of the spiral concentrating pad produced according
to the present invention, after removal from the molded
part shown in ~ig. ll; and
Fig. 14 shows an cross sectional view of alternate
emboaiment of the flexible stripping used in the production
oE the spiral concentrating pad according to the present
invention.
ReEerring more particularly to the drawings, Fig. l
~hows a spiral ore concentrating wheel lO as known in the
prior art. Such wheels yenerally comprise an open pan
h~vlng ln the bottom thereoe a continuou~ .5pkal, between
the periphery oE khe pan and a hub or hole in the middle
thereo~. In operatlon, the wheel i~ rotated in a tilted
orlentation, and material from the surEace oE the earth is
placed upon thc wheel in a wet or dry state. As the pan
rotatesl the lighter material moves toward the pertphery o~
the pan 14, while the heavier material travels in the
spiral groove to the opening ih the center of the pan.
As mentioned hereinabove, varLous materials have been
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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.
Fi~s. 1-3 show a more recent design of a spiral
concentrating wheel 10. In contrast to the solid, machined
steel wheel of the prior art, the design of FigsO 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
oE the pan. Additionally, in cross section, the continuous
spiral between the center opening 16 and the periphery oE
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
ls extremely expen~ive. The cost of the metal compression
mold almost increases exponentially as the diameter of the
ruhb~r pad increases.
The present invention is directed toward the
production o~ a rubber spiral concentrating pad without the
need ~or an orlginal metal compression rnold. Referring to
Fig. 2, the present lnvention is based upon the recoqnition
of the act that, in cross section, the single continuous
spiral groove of the rubber concentrating pad 12 appear3 as
a plurality o~ sawteeth 12'. IE the vertical line oE each
oE the ~awteeth l~' ls envisloned as ex~ending down to the
bottom oE the pad, then any one oE the sawteeth can be
thought of as a separate section o rubber stripping having
generally sawtoothed or triangular cross section.
Therefore, iE a hardenable material is Eor~ed over such
stripping, a molded part will be produced which can be used
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to strip-form, pour-form, or compres~ion mold a spiral
concentrating pad to replace tho~e currently manuEactured
with metal compression molds.
The present invention therefore comprises both a
novel method of forming a molded part rom which a spiral
concentrating pad can be fabricated in a number of ways,
but also a novel spiral concentrating pad apparat:us made
from the ~olded part.
~egarding the molded part, Figs. 4-8 show the
production thereof. Several steps are required to make the
molded part. First, strips of flexible extruded material
18 are arranged on a flat backing plate 20 in a planar and
spiral orientation in a manner whereby they fit together
snugly. Wext, the strips 18 are bonded together and also
attached ~o the backing plate 20. The stripping 18 is
arranged to form a central opening or hub 22 passing
through the sections of stripping 18 and the backing plate
20. The arrangement of the stripping 18 on the plate 20
pro~uces a master concentrating pad or template 24 from
which the molded part i8 produced.
As shown in Fig. 6l each of the strips is generally
triangular or sawtoothed in cross section, in ordar to
provi~3e the molded part to be formed thereover with an
internal contour identical to that of the outer contour of
the prior art spiral concentrating pad 12 shown in Fig. 2.
The ~tripping 18 may be oE any flexible material such as
rubher. It ha~ been Eound that rubber extru~ions of
approximately lS Eeet in length may be comme~cially
~abrlcated at very low cost. The backing plate 20 may be
lik~wl~e eabrlca~e~ ~rom any convenient material which is
generally ~tlE~ Wood, metal, or the like may be ~tilized.
As ~een from the foregoing, with the novel technique
of the present invention, a template 24 of any diameter may
be ~ormed by ~imply adding more lengths of stripping 18.
ThereEore, the cost oE a very large template is only
sllghtly more than a Emaller template becau~e oE the
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extremely low cost of the material comprising the template
24. Moreover, since the outer contour of the tegnplate is
determined by the cross sections of the rubber stripping,
the template 24 may have an outer contour which i5 deeply
grooved by the use of stripping 18 having a sawtooi7led or
triahgular cross section. Similarly, the outer contour may
comprise a continuous 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
contour oE 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, ~iberglass 28 may be
laid up over the template 24 and allowed to harden.
Alternately, a sheet of hardenable material may be vacuumed
formed over the template. When the template 24 is
flberglassed, a stiff backing plate 30 can be attached to
the fiberglass material 2~ to increase its rigidity and
strength.
Figs~ 8 and ll, respectively, show cross sectional
and plan view~ of the molded part 26 produced by forming
hardenahle materlal such as Piberglass 2~ over the template
24. As shown in Flg. 8, the interna:L contour oE the molded
part 26 is sawtoothed in cross section, corresponding to
the outer contour o~ the template 24. Additionally, a li~
por~lon 2~ also b~en ~ormed in the hardenable material
to act a~ a vertical guide in the forming of the pad. As
~hown in Fig. ll, 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 ~o produced, spiral
concentrating pads may be formed from it with a variety of
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me-thods. Four methods are particularly contemplated. Wikh
the Eirst method, the molded part 26 may be used as a
compression mold in place of the metal compression mold.
With this method, and as shown in Fig. 9, rubber rnaterial
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,
r~silient 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 ~orm 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 a such
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
substantially identical to those used to form the template
24 are wound into the recessed spLral 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 ~orming a
spiral concentrating pad 40/ shown in cross section in Fig.
12. The completed pad 40 may be heated prior to removal
erom the molded part 26 in order to promote complete and
rapid dryiny. A~ter the strlp-formed spiral concentrating
pad ha~ 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 o~ the strips 36 to
strip mold a spiral concentrating pad 40 is particularly
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advantageous because the stripping 36 may be obtained
commercially at a very reasonable cost.
Regardless oE the technique used to produce the
spiral concentrating pad, the finished pad is substantially
identical in appearance and quality to the rubber
concentrating pads 12 of the prior art, as shown in Figs.
1-3. Morever, 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 concentrating 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 produc~ 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 varied. As the processing of larger
material requires larger grooves, while the processing of
small material is mo3t beneficial with smaller grooves, the
configuration Oe the pad ma~ be matched to it~ use.
Fig. 14 ~hows an alternate embodiment oE the rubber
stripplng u~ed to ~orm the templa~e 24 Eor the production
oE the molded park 26, a~ well as Eor the strlp-Eorming o~
the spical concentratlng pad ~rom khe molded part ~6. ~8
shown therein, the stripping 42 has a cross section with a
sawtoothed portion 44 adjacent a dovetail section 46. On
the underside of the stripping 42 is a dovetail opening 48.
As can be easil~ envisioned, the forming of the template 24
would be done by simpl~ snapping the dovetail projections
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46 into the dovetail opening 48 of an adjacent section o~
stripping. The use of such stripping 42 would resul-t in a
semiriyid structure. Accordingly, when the stripping ~2
was used to form the template 24, the backing plate 20
could ~e eliminated. Similarly, when the spiral concentrating
pad was strip molded in the molded part 26, the in-terlocking
o~ the stripping 42 would also eliminate the necessity for
the flexible ~acking sheet 38. While the dovetail stripping
42 will most likely eliminate the backing sheet 38 and the
backing plate 20, it is unlikely that use of the molded part
21 could be eliminated.
As an additional contemplated variation of the inven-
tion described herein, the pads 34 and 40 may be provided
with means to allow thl_ pads to he removably attached to a
rigid and generally circular hacking wheel similar to the
prior art wheel 10 shol~n in Fig. 1, but without the spirals
12. Such a hacking wheel could have various curvatures to
tilt the spirals o~ the pad at difEerent anyles. Moreover,
this Eeature would allow the pads to be changed after wear,
~0 and would also a:Llow pads having di~ferent cross sectional
conEigurations for the spirals in the pads to be used for
~pecialized applications. Such removal means could be a
separabLe hook and loop type ~astener such as is sold under
the trade mark VELCRO, bolts or the like, glue, etc.
In the foregoing description of the present
invention, several embodiments of the invention have been
disclosed. It is to be understood that other mechanical
and design varlations are within the scope of -the present
invention. ~ccorcl.i~nctl!,7, i:he invent.iorl ls not 1imited to
the partlcular arrangemerits w~lich have been illu~trated
and described in detai:L herein.
