Music – Instruments – Drums
Reexamination Certificate
2000-01-20
2002-04-02
Nappi, Robert E. (Department: 2837)
Music
Instruments
Drums
C084S413000, C084S418000
Reexamination Certificate
active
06365812
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a new type of drumhead material which has improved properties over known materials.
A problem experienced by most all drumheads is excessive stretch and the resultant effect on tonal quality. Drumheads that stretch too much don't have the correct sound -often not as high as might be desired. The excessive stretch can also affect the ability to properly tension a drumhead material.
In addition to providing the proper tonal qualities, a drumhead should be resistant to failure due to delamination or abrasion failure due simply to the normal and natural use of the drum. Unfortunately, the desire to achieve proper tone by simply further tightening conventional drumheads can overly stress those materials. A review of the prior art indicates that the various inventors have noted that one improvement in defined properties often fails to address weaknesses in others.
Drumheads must be able to resist stresses of a number of different kinds. Again, this is in addition to achieving the proper tonal quality. A good drumhead provides good tome and resists the various stresses normally encountered. As will be familiar to drummers, there are a variety of drum strokes and striking implements. Among the implements are all wooden and plastic-tipped sticks, brushes and mallets. Each of these is used for characteristic strokes. For example, drumsticks might be used for single strokes, double strokes and rolls. Of these, the single strokes are often the sharpest in terms of impact force, but slowest in frequency. The roll, of course, is not particularly high in impact, but is high in frequency. The mallets have a high total force, which is usually spread out somewhat due to the nature of the mallet head. The brushes, on the other hand, produce little impact force but, being typically of metal, will be a source of abrasion. Thus, a drumhead, to be successfully used, must be able to absorb and resist a number of stressful and abrasive contacts. It must also be resistant to a number of environmentally-induced stresses, such as humidity and temperature changes. It would be advantageous to provide a drumhead material which had reliable resistance to each of these stresses and a good balance of resistance to all.
In an early attempt to make a drumhead of a synthetic material, Heybeck, in U.S. Pat. No. 729,936, stiffened woven fabric with a shellac-based material. Later, in U.S. Pat. No. 1,018,767, Logan used two or more layers of a fabric such as linen, treated with a cement formed of fish glue, rubber, turpentine, shellac, white of eggs, gum arabic, and linseed oil. In a later patent, U.S. Pat. No. 1,809,050, Logan states that the material of his earlier patent must be made too thick to reproduce higher or sharp tones. To achieve this effect, he describes a material having a layer of fabric and a layer of skin, united by glue.
More recently, in U.S. Pat. No. 2,667,098, McMullen attempted to solve the problems experienced with animal skins and substitutes for them and proposed a material comprised of a woven acrylonitrile fiber fabric coated with an alkyd resin before stretching and another layer of alkyd resin after stretching. He noted that peeling and cracking of the surface was prevented while the material was essentially insensitive to changes in humidity.
In another attempt to provide a synthetic drumhead material, Elzas, et al., in U.S. Pat. No. 3,425,309, utilized a sheet of polyester yarn woven fabric. The procedure they described, called for the fabric to be pretensioned and/or stabilized and/or heat sealed under pressure to enhance the dimensional stability of the fabric. The stabilized fabric was then subjected to a silica treatment, tensioned and sprayed with additional resin. In U.S. Pat. No. 3,668,296, Crisculo described a molded drumhead that could include an embedded layer of woven fabric material. These two patents were referenced in U.S. Pat. No. 4,282,793 to Muchnick which described a composite drumhead comprising polyaramid fiber fabric impregnated with a rigidifying amount of epoxy polymer. Muchnick also discussed the problems with polyester films, such as those made from Mylar brand film.
In two U.S. Pat. Nos. 4,308,782 and 4,362,081, Hartry attempted to finally solve the problems with known hide and synthetic drumheads. In each he utilized materials having good strength and resilience, but the disclosures utilize fabric forms and construction methods that are now found to fall short of their potential in achieving a satisfactory drumhead material.
In the first, U.S. Pat. No. 4,308,782, Hartry provided a sheet of synthetic plastic material and a synthetic fabric material having a random fiber orientation. He applied a water-based resin emulsion to the fabric to assure that the nonoriented individual fibers were elastomerically bonded together. The version illustrated in the patent had a top surface of fabric over a bottom surface of a polyester film. He indicated that the fibers were elastomerically bonded together rather than rigidly bonded so as not to transfer stress into the plastic sheet material and to aid the “cushion” effect by distributing load. Thus, although he had proposed high strength materials for the fabric layer, the layer inherently avoids the benefit of the strength by permitting the elastomeric binder rather than the fibers of the fabric to take on the initial load applied during use.
In the latter patent, U.S. Pat. No. 4,362,018, Hartry described a drumhead material which employed top and bottom sheets of polyester film and an intermediate layer of woven fabric of high modulus of elasticity, such as a polyaramid sold under the Kevlar brand name. The mobility of the individual fibers throughout the synthetic woven fabric layer was maintained. The synthetic woven fabric material was not wetted through, or impregnated, by the adhesive resin composition employed in the lamination process to allow the individual fibers in the woven fabric to move freely. Therefore, the adhesive resin composition preferably was chosen to have a high molecular weight, high viscosity, and correspondingly low mobility to minimize its penetration of the fabric layer during the lamination process. Thus, in each of Hartry's arrangements, the movement of the fibers was assured prior to their being tensioned in use to fully utilize their high modulus properties.
In a distinct approach from that of Hartry, Donohoe indicated in U.S. Pat. No. 4,798,121, that in both of the above-identified Hartry patents the entire drumhead is laminated with the specified materials. Donohoe indicates that this produces a sound quality substantially different from that achievable with an unlaminated polyester film. To improve this, Donohoe employed an overlay consisting of two sheets or lamina of woven synthetic plastic fibers, which were coated with a synthetic plastic material. The two sheets were cross-laminated together with their woof directions perpendicular to one another, and then fastened to the upper surface of a central region of a drumhead made of plastic film, thereby increasing the impact resistance on the drumhead. The plastic coating on the upper surface of the upper lamina was said to enhance impact resistance, and also result in a crisp impact sound when struck by a drumstick. It can be seen that only a small impact area is covered to preserve the sound of the unlaminated film.
In U.S. Pat. No. 5,091,248, to Balli, in discussing the Hartry patents, it was stated that the Hartry invention did not address a very critical problem in the technology relative to the delamination of the nonorientated polyethylene fibers in the fabric material. He described his improvement as lamination comprising an upper fabric layer made of nonorientated polyester fibers, a lower plastic layer, and a substance which, when applied to the fabric, creates a seal on the surface and impregnates the material acting to further create a bond among the fibers. This combination of elements, he indicated, would preclude delamination of the polyester fibers, partic
Dimension Polyant Sailcloth, Inc.
Lockett Kim
Nappi Robert E.
St. Onge Steward Johnston & Reens LLC
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