Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ackground_of Inventio!l ~ 0 3 G 3 9 9
Bodies or drums of banjos consist, ususally, of
three major concentric ringed portions which fit together
under tension, as tightly as possible. Threaded hooks or
brackets hold the components together and hold the drum
head in a stretched position. The three ringed portions are
the tone ring, shell and flange, the latter is called
"lower bracket ring" if there is no resonator on the parti-
cular banjo.
Since the quality and volume of the sounds from
the instrument are directly related to the way these com-
ponents fit against each other, it is critical that these
components fit snugly together, with even pressure in all
directions between all contacting surfaces. If there is not
such contact between the parts, vibrations are dampened and
distorted. Lower volume and a poorer tone result. Since the
quality and volume of the sound created is all important,
and since the construction of the instrument directly relates
thereto, significant improvements in construction are very
desirable.
Except for the most expensive instruments, there
is a lack of optimum quality and volume of sound. This is be-
cause said components cannot easily and economically be made
to fit together, in perfect unison. Even if they did,
shrinkage of the shell, due to dehydration of the wood over
a period of years will cause an undesirable loose fitting.
Banjo manufacturers have tried to avoid the problem
of imperfect fitting by substitution of a single piece part
for the described components. However, this gives rise to a
loss of desirable tone quality for another reason. As is well
known in the trade, banjos are best made of different materials,
specifically, shells of hard wood, while the contacting tone
ring and flange are best made of metal.
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Before my inventio~ common problems of otherwlse imperfcct
fitting were best solve~ by excellent workmanshlp, tedious
machinework, use of high quality materials, and well seasoned
wood Obviously, all thls is very expensive and results in a
high cost of manufacture and a relatively high price to the con-
sumer.
I have solved the above mentioned problems by a novel assem-
bly which does not require sea~oned wood for the shell, nor does
it require close machining, to exact tolerance9 on two dimensions,
~0 a9 19 presently required. The result is an instrument which has
the tone and volume comparable to the most expensive in~truments,
but which can be sold for a much less price because of a lower
cost of manufacture.
Summary of_Invention
In place and instead of the usual vertical and lateral dimen-
sion~, at right angles to each other, on the inside of the tone
ring and flange, and the mating outside dimensions of the shell,
I have provided tapered surfaces on the components which, when
assembled, abut each other, whereby u9ual force applied by
tightening usual threaded hook~, automatically causes a snug fit
due to a wedging action. Any two of the components may utilize
my invention. If all three components ha~e the tapered construc-
tion optimum results will be obtained.
Thus, in one aspect, my invention consists of a banjo
body assembly comprising a body shell and a tone ring in contact
with said shell wherein at least a portion of the outer surface
of the upper portion of the body shell is sloped inwardly and at
least a portion of the under surface of the tone ring has
angulation matching the said sloping surface to provide a
wedging fit when the tone ring is placed on said body shell.
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In a more specific form the invention can be defined as
a banjo body assembly comprising a cylindrical body shell
having upper, mid- and lower wall portions, said shell having
a downwardly sloping outer surface on the upper portion of
said shell, a tone ring having at least one lower internal
surface beveled to wedgingly mate with said outwardly sloping
surface when said ring is placed on said shell, and a ring-
shaped sheli flange having an inner surface at least a portion
of which wedgingly mates with a sloping outer surface of the
mid-portion of said shell.
Description of drawings
In the accompanying drawings:
Figure 1 is a top view of the body and portion of neck of
a banjo embodying my invention;
Figure 2 is an exploded perspective view of the components
thereof;
Figure 3 is a cross sectional exploded view of these
components;
Figure 4 is the same as in Fig. 3, except the components
are in contact with each other, as in use.
Description of the Preferred Embodiment ~-
Referring to the drawings wherein like numerals represent -;
like parts throughout, the numeral 14 indicates my novel shell.
It is formed on one of the usual hardwoods and has the familiar
configuration of a cylindrical section. Unlike the convenional,
however, I have caused the outer surface of its upper portion to
slope uniformly inwardly around the entire periphery thereof,
this is tapered surface 14a. The angle of inclination may
vary. An angle of 45 degrees is suitable. Preferably
provided at both ends of such inclinatlon are raised portions
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to form rims around the circu ~ ~e~c3e9 Between lower rim 14f
and upper rim 14b I have placed tone ring 12. It too has the
conventional cylindrical section shape and is made of metal, as
usual. Unlike the prior art however, this ring has a slanted
circular surface 12c uniformly and inwardly from its base. For
snug abutment with the shell, the angulation of 12d is the same
as that of surface 14a. This permits the two beveled surfaces
to interface as can best be seen in Fig. 4. Upper rim or bead
14b serves as a guide and retainer for tone ring 12 on the shell
14 when the parts are being assembled. The tone ring fits
between the rim 14b and point 14c of Fig. 4. The tone ring 12
has usual inside beveled surface 12a at the top without change.
Its function is unrelated to my invention. As usual~ the skin
head 10 is retained thereon by a tension hoop (not illustrated).
The upper portion 12b may be a continuation of surface 12d if
and when the surface is continuous and not a modified conventional
ring, a8 8hown.
An oppositely disposed tapered portion 14d is provided on
the outer underside of the 8hell. For mating therewith, I have
prov~ded an otherwise conventional flange 16 with a flange
beveled portion 16a of the same angle as shell portion 14d. As
can be seen, all beveled portions align with and slideably abut
mating surfaces on adjoining components. The head is held
together with the usual threaded brackets (not shown).
Imperfections in manufacture and/or seasoning of the shell do
not result in misfits, because the brackets need only be
tightenened and through the obvious wedging action of my novel
beveled parts, the desired close, tight fit will always result.
As a further novel contribution, I have provided a generally
outwardly sloping surface 14e uniformly around the inner upper
portion of the shell. This further improves the sound by
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reflecting sound waves in the direction of arrows 14g.
Those skilled in the art may readily see that some, but not
all, tapered surfaces may be resorted to without departing from
the scope of my invention. With only abuting beveled surfaces
on the tone ring and upper portion of the shell, for example, an
lmprovement over the prior art will be provided.
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SUPPLEMENTAR~ DISCLOSURE
Further aspects of the invention are illustrated in Figures
5 to 13 in which:
Figure 5 is a perspective view of a modified tone ring;
Figure 6 is an elevation view of the tone ring of Figure 5,
the tone ring having the identical appearance whether viewed
from the front, back left or right sides;
Figure 7 is a cross-section of the tone ring taken along
the plane 7-7 in Figure 5;
Figure 8 is a top plan view of this tone ring, it being
understood that the bottom plan view would be identical; and
Figures 9 to 13 illustrate other triangular cross-sectional
forms which the tone ring may take.
Referring to Figures 5 to 8, the tone ring T will be seen to
have a vertical outer wall 1, an inwardly and downwardly sloping
upper surface 2 and an upwardly and inwardly lower surface 3.
These two surfaces meet at an apex 4.
While it will be noticed in the drawings that the apex 4,
4', 4" and 4"' (Figures 9 to 11) as well as the top edges 7, 7',
7" and 7"' and bottom edges 8~ 8', 8" and 8"' are depicted as sharp
intersections, in actual practice these edges are slightly
rounded. The rings are cast and then are machined to remove any
imperfections in the casting and also to present a more polished
surface. It is difficult to cast sharp edges and the machining
and polishing also is most difficult to carry out and produce
sharp edges. Edges 7 and 8 as seen in Figure 7 should be rounded
; slightly in order to prevent cutting the drum head when it is
placed across the tone ring. -~
A tone ring having an isosceles triangular cross-section
as seen in Figure 7 or an equilateral triangular cross-section as
seen in Figure 10 is obviously reversible upon the banjo body.
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The cross-section of the tone ring may also be in the
form of a truncated triangular form as seen in Figures 9 to 11
at 6, 6' and 6". This form may be required because of the
thickness of the banjo body shell when it is desired to use a
particular size tone ring and the surfaces 2 and 3 of a particular
form might have too great a length if the conventional triangular
cross-section were utilized. Even when so truncated, the tone
ring is considered to be substantially triangular in cross-
section.
The tone ring is preferably of solid cross-section as shown
in the drawings. However, it would be feasible to make a
triangular cross-section that was not solid but was rather formed
of a two-sided casting to which a third side is then braised or
otherwise permanently secured to the cast portion.
The slope of the under surface 3, 3', 3", 3'" will always
match the slope of the corresponding part of the banjo body ~ ~ .
ghell upon which it is placed. Generally speaking, the cross-
section of the tone ring is determined, the ring is cast,
-~ machined and poli8hed and then the banjo body surface is shaped
; 20 to provide the tapering, wedging fit between the tone ring and
the banjo body.
Figures 12 and 13 show two other embodiments of the tone
ring whic~h reflect a slight modification of the under surface. ~ -
In Figure ~ the under surface 3a, since this is an equilateral
cross-section as seen in Figure ~, has been modified by a recess 9
formed therein extending downwardly from the apex 4". In
Figure 13 the recess 9' is formed in the lower portion of the
- under surface 3b extending upwardly from the edge 8". The
` recess 9 or 9' could be formed when it is desired to provide a
sealing block or portion of the sloping surface of the banjo body
shell. Even with these recesses the tone ring is considered to
be substantially triangular in cross-section. The embodiments
of Figures 12 and 13 may include the truncated feature shown
at 6 etc. 7
