Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2001-02-05
2001-10-16
Pelham, Joseph (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S436000, C607S086000, C607S114000, C004S545000
Reexamination Certificate
active
06303910
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of making a paraffin bath and to a paraffin bath apparatus made according to the method.
BACKGROUND ART
A paraffin bath is an appliance that is used to melt paraffin for therapeutic purposes. Warm paraffin wax melted in the bath is used to treat dry, chapped hands and may provide pain relief for stiff or aching joints that may be caused by bursitis and arthritis.
Paraffin baths are known that include a metal inner tub in which the paraffin wax is melted. Paraffin baths made of metal are relatively expensive to manufacture and can be dented if improperly handled.
Applicants' assignees' prior paraffin bath of application Ser. No. 09/523,506 discloses a method of making a paraffin bath having a plastic inner tub and having heating elements that comprise braided wire sandwiched between layers of foil that are assembled to the side walls of the inner tub and base wall of the inner tub.
The prior art also includes devices such as foot baths that have a rope heater attached to integrally formed flanges on a base wall. An example of such a device is disclosed in U.S. patent application Ser. No. 09/631,643, filed Aug. 2, 2000 that is assigned to the assignee of this application. The prior art foot baths do not have side wall mounted heating elements and are intended to heat water or at least prevent previously heated water from cooling down.
There is a need for a paraffin bath in which all major structural components are formed by a simple, reliable and inexpensive process. For example, there is a need for a paraffin bath manufactured from structural parts that are injection molded of a temperature resistant plastic such as polypropylene. There is also a need for a manufacturing process utilizing injection molded parts that are assembled with a heating element and controller in an efficient and cost effective manner. There is also a need for a simple, durable paraffin bath appliance that is inexpensive to manufacture.
These and other problems and objectives are addressed by applicant's invention as will be summarized below.
DISCLOSURE OF INVENTION
According to the present invention, a paraffin bath apparatus for melting paraffin is disclosed that has a housing having a base wall, side wall and an upper opening. A polymeric inner tub is received within the housing and is a generally cup-shaped member having a bottom wall, an upstanding wall and an open top. The inner tub is received within the upper opening of the housing with the bottom wall overlying the base wall of the housing. A heating element is mounted on an outer wall of the inner tub between the inner tub and the housing. The heating element provides heat through the inner tub that is sufficient to melt the paraffin but is limited to a temperature that is below the temperature that would adversely effect the polymeric material of the inner tub. The heating element comprises a wire that is at least partially retained in a series of loops between paired flanges that are integrally molded of the same polymeric material forming the inner tub walls. The paired flanges are spaced apart to receive the wire. A thermostat is electrically connected to the heating element to control the heat provided to the inner tub.
According to another aspect of the invention, the heating element includes a base heating element that is located between the base wall of the housing and the bottom wall of the inner tub. A side heating element is located between the side wall of the housing and the upstanding wall of the inner tub. The base heating element is received by flanges formed on the bottom wall of the inner tub.
According to a further aspect of the invention, a thermostatic sensor is remotely mounted on the inner tub and is connected to a thermally conductive element that is coated with a refractive sealant that provides a heat conduction path between the thermally conductive element and the base wall of the inner tub.
According to yet another aspect of the invention, at least one metal wire guide is provided on the upstanding wall of the inner tub that has projections extending outwardly from the upstanding wall. The heating element is wrapped around the upstanding wall and retained by the projections. At least one layer of adhesive coated foil is wrapped around the wire after the wire is wrapped around the upstanding wall and the metal wire guide.
According to another aspect of the invention the major structural parts of the paraffin bath are all formed of polypropylene. The housing, a control panel, base and removable lid all may be formed of polypropylene.
A thermostat or other electronic temperature control circuit is assembled to one or both of the inner tub and the control panel. The control panel is attached to an opening formed in part by the inner tub and in part by the housing.
According to the method of the present invention, a method of making a molded polymeric paraffin bath appliance is provided. A housing is provided that has a base wall and a side wall defining an upper opening. An inner tub is injection molded and includes a base having inner and outer sides and a wall extending from the base to an upper opening. A plurality of wire retainer flanges are simultaneously molded on the outer side of the base of the inner tub. A wire is assembled to the wire retainer flanges. The wires are connected to a voltage source and the voltage source is connected to a controller for controlling the current provided to the voltage source and thereby control the heat generated by the wire. The inner tub is assembled to the housing to provide an enclosed space between the inner tub and the outer tub for containing the wire heating element.
According to another aspect of the method of the present invention, at least some of the flanges are deformed by partially melting the flanges after the wire is assembled to the flanges to retain the wire within the flanges.
According to a further aspect of the method of the invention, the housing is injection molded of a polymeric material. The base is also injection molded and assembled to the housing. The control panel is molded of polymeric material. A temperature controller is attached to a heat transfer element that is mounted on the inner tub before the control panel is attached to the housing. A removable lid is also injection molded of polymeric material and is adapted to be removably placed on the upper opening of the housing.
According to yet another aspect of the method of the invention, at least one wire guide is assembled to the outer surface of the wall of the inner tub. A wire is wrapped around the inner tub a plurality of times with the wire guide retaining the wire. Foil having an adhesive coating is wrapped around the inner tub over the wire and wire retainer so that it adheres to portions of the wire and the inner tub to hold the wire on the inner tub. The foil also functions to disperse heat from the wire about the sides of the inner tub. The wire is connected to the voltage source as previously described.
These and other aspects and advantages of the invention will be better understood in view of the attached drawings and following detailed description of the invention.
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Ferber Roman S.
Glucksman Dov
Brooks & Kushman P.C.
HoMedics, Inc.
Pelham Joseph
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