Note: Descriptions are shown in the official language in which they were submitted.
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TTTT F
DRUMSTICKS MADE FROM LIQUID CRYSTALLINE POLYMER
FIELD OF THE INVENTION
Liquid crystalline polymers (LCPs) are useful in drumsticks, the drumstick
being completely made from a LCP (plus any fillers, antioxidants, reinforcing
agents, pigments dyes or other materials normally found in thermoplastics.),
or the
drumstick may have one or more LCP inserts.
TECHNICAL BACKGROUND
Drumsticks for percussionists have traditionally been most often made
l0 from wood, usually a hardwood such as American hickory which is straight
grained and readily shaped. Usually a rod of the wood is turned to produce the
desired shape, the wood is smoothed if necessary, and then coated with a
finish.
Although wood sticks have been used for many years, and have been found
satisfactory, they have some drawbacks, such as a tendency to break along the
grain. Therefore improved drumsticks are needed.
Thermoplastics have been thought of for drumsticks, but the stiffness and
other properties of most thermoplastics are too low to afford good drumsticks.
Recently [see Modern Plastics, vol. 76, No. 10, p. 41 (Oct. 1999)] it has been
reported that oriented polymers, such as oriented polypropylene, can be used
for
2o drumsticks, but these sticks are relatively expensive to form, requiring
one or
more orientation steps, then turning (much as in making wood drumsticks) to
form the final shape. This manufacturing process does not allow for taking
advantage of some of properties of thermoplastics, such as inexpensive and
easy
formability. Drumsticks which are made from LCPs, or which contain LCP
inserts, may be simply melt formed, as by injection molding, and have the
requisite properties for drumsticks without further processing.
SUMMARY OF THE INVENTION
This invention concerns a drumstick, comprising, a one or more
thermotropic liquid crystalline polymer (s).
3o The invention also includes an embodiment wherein a thermotropic liquid
crystalline polymer forms a core overmolded with a second polymer, which may
be either a thermoplastic polymer or a thermoset polymer.
A further embodiment features a thermotropic liquid crystalline polymer
overmolded over an isotropic polymer, preferably a thermoplastic core.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a cross section of a drumstick towards the handle end
having an LCP core.
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Figure 2 shows a longitudinal cross section of a drumstick having an LCP
core and a partial thermoplastic overmolding.
DETAILS OF THE INVENTION
The drumstick described herein comprises a thermotropic liquid crystalline
polymer. By comprises is meant that the drumstick contains at least some LCP,
and may contain other materials, such as other thermoplastics. The LCP (or
other
polymer) may be blended with one or more fillers, antioxidants, reinforcing
agents, pigments, dyes, or other materials normally found in thermoplastics.
The
other ingredients (if any) in the LCP or other polymer may be used to change
the
to appearance (color for instance) of the drumstick, physical properties,
and/or may
also affect the acoustical properties of the drumstick.
Blends of LCPs with other thermoplastics may be also be used in the
drumstick in place of "pure" LCP. If such a blend is used, it preferred that
the
LCP be in a continuous phase.
By an LCP is meant a polymer that is anisotropic when tested in the "TOT
Test" described in U.S. Patent 4,118,372. Any thermotropic LCP may be used in
this process. Suitable thermotropic LCPs, for example, are described in U.S.
Patents 3,991,013, 3,991,014 4,011,199, 4,048,148, 4,075,262, 4,083,829,
4,118,372, 4,122,070, 4,130;545, 4,153,779, 4,159,365, 4,161,470, 4,169,933,
2o 4,184,996, 4,189,549, 4,219,461, 4,232,143, 4,232,144, 4,245,082,
4,256,624,
4,269,965, 4,272,625, 4,370,466, 4,383,105, 4,447,592, 4,522,974, 4,617,369,
4,664,972, 4,684,712, 4,727,129, 4,727,131, 4,728,714, 4,749,769, 4,762,907,
4,778,927, 4,816,555, 4,849,499, 4,851,496, 4,851,497, 4,857,626, 4,864,013,
4,868,278, 4,882,410, 4,923,947, 4,999,416, 5,015,721, 5,015,722, 5,025,082,
5,086,158, 5,102,935, 5,110,896, and 5,143,956, and European Patent
Application
356,226. Useful thermotropic LCPs include polyesters, polyester-amides),
polyester-imides), and polyazomethines. Preferred thermotropic LCPs are
polyesters or polyester-amides), and it is especially preferred that the
polyester or
polyester-amide) is partly or fully aromatic.
3o If the drumstick is made completely from LCP or an LCP composition
(meaning the LCP plus any fillers, antioxidants, reinforcing agents, pigments
dyes
or other materials normally found in thermoplastic.) the drumstick may simply
be
melt formed in any desired shape or size from the LCP (see for instance H.
Mark,
et al., Ed., Encyclopedia of Polymer Science and Engineering, Vol. 8, John
Wiley
& Sons, New York, 1987, p. 102-139, which is included herein by reference).
For
example, the drumstick may be injection molded. In order to achieve a high
degree of stiffness along the length of the drumstick (as it is in a wood
drumstick),
it is preferred to place the gate of the mold at one end of drumstick cavity,
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preferably the end which is the handle (not the end for hitting the drum or
other
instrument). In this instance it is preferred that the LCP contain a filler or
reinforcing agent, such as talc, (hollow) glass spheres. or sawdust (the
latter may
allow the drumstick to look like wood). The filler or other added ingredients
may
be chosen to adjust the weight of the stick, by choosing a filler/reinforcing
agent
with an appropriately low or high density. It is preferred that the fillers)
and
other ingredients present (but not including any polymer in an LCP/other
polymer
blend) be about 5 to about 40 percent by weight of that mixture.
The LCP may also be present as one or more cores (also called inserts or
to insert molding) or the outer material of the drumstick. In either case the
LCP
lends stiffness and other desirable properties to the drumstick, while
reducing the
amount of (often) relatively expensive LCP in favor of a cheaper
thermoplastic. If
the LCP _is used as a core, it may have a cross section (through at least most
of the
length) as shown in Figure 1. The core, 1, in spline form, may be formed by
melt
15 forming, for example by extrusion or injection molding, much as a drumstick
formed completely from LCP would be formed. The core may then be
overmolded with another thermoplastic, 2. Useful thermoplastics include
polyolefins such as polyethylene, polypropylene and polystyrene, polyesters
such
as polyethylene terephthalate) and poly(butylene terephthalate), polyamides
such
20 as nylon-6 and nylon-6,6, and other thermoplastics such as polysulfones,
polyethers, polyurethanes. Thermosets may also be used. Useful thermosets
include epoxy, urethane and phenolic resins. The LCP core may be overmolded
by any usual technique used to overmold thermoplastics or thermosets.
Conversely, a (nonLCP) thermoplastic or thermoset or other material may
25 be used for a core, and an LCP overmolded over that core to form the
drumstick.
Again any normal method of overmolding may be used. In this process it is
often
preferred that the LCP have a relatively low melting point so as not to melt
or
otherwise damage the already existing core. Whichever material is used for the
core, the core may be mechanically "locked" to the overmolding by molding into
3o the core shape appropriate angles, overlaps or other discontinuities that
cause such
mechanical locking.
The drumstick may also be constructed where part of the exposed surface
is an LCP or LCP polymer blend "core", and part of the length of the drumstick
is
overmolded with another polymer, as is shown in Figure 2. In Figure 2, which
is
35 a longitudinal cross section of a drum stick, the LCP core, 3, extends
beyond the
overmolded thermoplastic jacket 4, and this core also is the tip of the
drumstick.
The LCP core in Figure 2 may have a cross section similar to that shown in
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Figure 1, until the point where it emerges from under 4. The LCP and non-LCP
polymers in Figure 2 may also be reversed.
As some wooden drumsticks are now made, the striking end of the LCP
containing drumstick may be covered by another material such as another
thermoplastic, for example a polyamide such as nylon-6 or nylon-6,6. The
striking end of the molded drumstick may be configured so that the added tip
may
slip over that end and be locked onto the end by mechanical means (so-called
snap
fit). The drumstick may have fastened to it at its end felt or other material
which
is the surface that actually strikes the drum, as is typical with tympani
mallets
(sticks).
The LCP drumstick may also be hollow to some extent (through part of all
or the length, especially the hand held section) to adjust the weight of the
drumstick, adjust the acoustical response, and/or reduce the amount of
relatively
expensive LCP used. Alternatively for the same reasons the LCP drumstick may
15 be partially or fully foamed to form a rigid foam. Since LCPs maintain
their
rigidity in foams, the stick's stiffness is not greatly compromised.
Unlike turned drumsticks, such as most wooden drumsticks and oriented
polymer drumsticks, the cross section of molded LCP drumsticks need not be
circular, and contoured and/or curved drumsticks, which may be easier or less
2o tiring to grip, may be readily formed. Such drumsticks may be ergonomically
superior to the classical straight drumstick, and/or the cross section may be
varied
to change the balance of the drumstick. For a drumstick, such as shown in
Figure
2, the outer layer may also be a thermoplastic or thermoset elastomer,
preferably a
thermoplastic elastomer. The use of an elastomeric outer layer may allow the
25 drumstick to be used with less fatigue by the percussionist, and/or change
the
acoustical properties of the drumstick. A useful thermoplastic elastomer is a
block copolymer containing polyester segments and polyether segments, such as
is available under the tradename Hytrel~ from the DuPont Co., Wilmington, DE,
U.S.A. LCP containing drumsticks are durable, and their acoustical properties
3o may sometimes be adjusted.
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