Brush – broom – and mop making – Processes
Reexamination Certificate
1999-07-12
2001-04-24
Chin, Randall E. (Department: 1744)
Brush, broom, and mop making
Processes
C156S272800
Reexamination Certificate
active
06220673
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to toothbrushes and in particular a method of manufacture of toothbrush bodies, wherein pre-formed toothbrush heads and handles are joined together to form complete toothbrush bodies.
BACKGROUND OF THE INVENTION
Conventional toothbrush bodies comprise an elongated rod that functions as a handle, joined to a neck, which may be generally straight or curved, which is connected to a head having a flattened section to which tufts of bristles are fastened. Such toothbrush bodies are typically manufactured in one step by injection molding; wherein, a molten thermoplastic material is injected under high pressure into a steel mold. After the plastic solidifies, the mold is opened and the fully formed toothbrush body is removed. Such a conventional toothbrush body, formed of one material, lacks the desired different coloration and physical characteristics possible with toothbrush bodies having heads and bodies manufactured of different materials. For example, it is desirable to have a rigid handle for manipulating the toothbrush with a more flexible, i.e. less rigid, head that will flex and so tend to reduce the gingival trauma associated with excess brushing pressure by the user.
U.S. Pat. No. 2,445,657, discloses toothbrush bodies having heads of a resilient material, such as vulcanized rubber, secured to rigid handles. These toothbrush bodies are manufactured in a multi-step process, wherein the heads and handles are separately produced and subsequently cemented together. Such cementing, or in general adhesive bonding, takes significant surface preparation to provide an adequate/strong seal and takes a significant time interval for the adhesive to cure or otherwise set, adversely effecting the economics of mass production.
U.S. Pat. No. 5,121,520, discloses a toothbrush having twin side-by-side brushing heads attached to the toothbrush handle at a predetermined angle. The heads may be joined to the handle by gluing, i.e. adhesive bonding, or fusion, i.e. heating the head/handle joint surfaces to a softened thermoplastic state, bringing them into intimate contact and maintaining that contact to form a joining upon cooling. Fusion, unlike gluing, requires no surface preparation and no long set-up time; however, with fusion unless there is precise heating of both the head/handle joint surfaces, it is possible to experience degradation of the plastic toothbrush material, excessive softening and distortion of the plastic, as well as, excessive flash.
There is a need in the toothbrush manufacturing art for a means of bonding pre-formed toothbrush heads to handles of different materials, having different physical properties and/or coloration, in a time interval acceptable for mass production thereof and without any degradation, distortion, excessive flash, or other consumer unacceptable effect.
SUMMARY OF THE INVENTION
The present invention encompasses a method of joining preformed toothbrush head and handle components using laser beams of two particular wavelength ranges; wherein, these laser beams penetrate typical thermoplastic toothbrush material to heat the internal joint, to weld the part of the joint together, without significant absorption or heating of the material being penetrated.
The transmission, without absorption, of such particular wavelength ranges of laser light through typical toothbrush thermoplastic materials of construction, hereinafter “window effect”, is essential for the internal welding of toothbrush components of the present invention. This window effect can be demonstrated by the spectra of each such particular thermoplastic. The spectra of each thermoplastic is the measurement of the transmission ability of a range of wavelengths, such as the wavelenghts of particular lasers, through the thermoplastic. The
Atlas of Polymer and Plastic Analysis, Vol.
1,
Polymers: Structures and Spectra,
2
nd Edition,
by Dieter O. Hummel, published by Carl Hanser Verlag, Germany, 1982, (hereinafter the
Atlas
) contains such spectra; for polymers in a wavelength range from the bottom of the infrared, 2.5 micrometers, into the microwave range, 50 micrometers. As shown in the
Atlas,
the major bands of transmission through and absorption for typical polypropylene and polyethylene terephthalate toothbrush thermoplastics are shown in Table 1, below.
TABLE 1
Transmission Through/Absorption Wavelengths of Polypropylene
And Polyethylene Terephthalate
Transmission
Absorption
Applicable Lasers
Through Bands
Bands
with Wavelength
Material
(micrometers)
(micrometers)
(micrometers)
Polypropylene
1
2.5 to 3.22
N/A
3.22 to 4.0
N/A
4.0 to 6.45
CO, 5 to 6
6.45 and up
CO
2
, 10.6
Polyethylene
2.5 to 3.125
N/A
terephthalate
2
3.125 to 3.6
N/A
3.6 to 6.0
CO, 5 to 6
5 and up
CO
2
, 10.6
Notes: 1. Atlas, pages 6, Spectra 16, for poly(propylene), isotactic.
2. Atlas, page 232, Spectra 694.
For comparison, also shown in Table 1 are lasers which have wavelengths within the particular spectra ranges which either transmit or absorb energy within the wavelength ranges shown in Table 1. Accordingly, in accordance to the present invention, from the data shown in Table 1, a CO laser will transmit energy through such thermoplastics to an internal weld therein, while a CO
2
laser will not.
The particular two wavelength ranges unexpectedly found to provide this “window effect”, encompasses from about 0.7 to about 2.0 micrometers within the near-infrared, and from about 4.0 to about 6.0 micrometers within the infrared (IR) spectrum The method comprises selecting a first thermoplastic toothbrush component free of any material, such as a pigment or dye, capable of absorbing window effect wavelengths and selecting the other thermoplastic toothbrush component containing a material, such as a pigment or dye, capable of absorbing such about 0.7 to about 2.0 or about 4.0 to about 6.0 micrometer wavelength laser energy; aligning the two components in an tightly abutting relationship to form a joint; exposing the joint to a laser generating such a wavelength beam by penetrating the first thermoplastic component; thereby melting a surface layer of the component containing the laser absorbing material at the joint; with concurrent melting of the abutting surface layer of the first component, such that a weld is formed between the two components as the melted surface layers cool.
In an alternative embodiment of the method of the present invention, both the abutting toothbrush head and handle components are free of any material capable of absorbing from about 0.7 to about 2.0 micrometers or from about 4.0 to about 6.0 micrometers wavelength laser energy. In this embodiment, it has surprisingly been found that these components can be bonded together when briefly exposed to a laser beam having a wavelength of from about 0.7 to about 2.0 micrometers, or from about 4.0 to about 6.0 micrometers, when a relatively minute amount of such wavelength absorbing material is spread across the abutting surface of one of the components prior to exposure to such a laser beam. The use of such a relatively minute amount of such wavelength absorbing material provides a joint between the components wherein the particular wavelength absorbing material is not readily consumer noticeable.
REFERENCES:
patent: 3769117 (1973-10-01), Bowen
patent: 4441227 (1984-04-01), D'Ar Gembeau
patent: 4762373 (1988-08-01), Amos
Grimm Robert A.
Russell Bruce M.
Chin Randall E.
Colgate-Palmolive Company
Goldfine Henry S.
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