Coating implements with material supply – With means to impart heat to material
Patent
1985-08-02
1987-01-27
Apley, Richard J.
Coating implements with material supply
With means to impart heat to material
401 2, 2221461, 2221462, B67D 532
Patent
active
046391550
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to melt dispensers.
Various proposals have been made to provide apparatus for melting and dispensing thermoplastic material supplied in the form of a rod. Such apparatus is usually provided with a melt body having a melt chamber in which thermoplastic material is melted, an inlet for the rod and an outlet comprising an orifice for dispensing melted material, and means for heating the melt body so that composition fed as a rod into the melt chamber may be dispensed in molten condition from the orifice. Such apparatus finds use in various fields of application, an important example being hand held glue guns having provision for feeding a rod of adhesive to the melt body for example by direct thumb pressure or by trigger operated means.
BACKGROUND ART
A persistent problem associated with hot melt dispensers which rely on feeding of the rod to cause outflow of molten composition from the orifice is the drooling of cement from the orifice which tends to occur when feeding of the rod ceases and the melt body remains hot. This drooling is wasteful, inconvenient and messy. While the employment of check valves has assisted in reducing drool, it remains highly desirable to provide an inexpensive means for further reducing or eliminating drool. Proposals have been made to physically pull the rod of adhesive out of the melt body to a limited extent, but such proposals require complications in the mechanism of the apparatus with consequent increase in its weight and/or cost and furthermore such proposals are ineffective when there is a discontinuity in the rod between the pulling mechanism and the melt chamber, as may occur for example when the rod is made up of short sticks of adhesive held together merely by pressure exerted to feed the rod, as is the case particularly for example in the case of glue guns normally used by "do it yourself" enthusiasts.
It is one of the various objects of the present invention to provide an improved device for melting and dispensing thermoplastic material supplied in the form of a rod.
DISCLOSURE OF INVENTION
The invention provides as one of its aspects a device for melting and dispensing thermoplastic material supplied in the form of a rod comprising a melt body having an inlet end and an outlet end and a melt chamber within the melt body, the inlet end being adapted to receive a solid rod of composition as it is fed to the melt chamber, and the outlet end having an orifice, means for heating the melt body so that composition fed into the melt chamber via the inlet end in the form of a rod may be dispensed in molten condition from the orifice in response to application of a feeding force on the rod to urge it in a direction towards the melt body, and resilient means located within the melt body arranged to exert sufficient force in a reverse direction to move the rod outwardly of the melt body when the feeding force is not applied.
In a device according to the invention, the resilient means is preferably provided by a coil spring trapped in the melt body and arranged to act directly or indirectly upon a solid portion of a rod fed into the melt chamber. As a first embodiment of the invention hereinafter described, the coil spring is arranged to bear directly on the advancing solid end of the rod. As a second embodiment of the invention, the coil spring is arranged to bear upon a melt chamber element which is slidable in the melt body, whereby to move the melt chamber element and the advancing solid end of the rod entering the melt chamber outwardly of the melt body when the feeding force is not applied.
Preferably the spring does not reduce the melting capacity of the melt body and thus, the spring preferably is in heat conductive contact with the melt body, so that it may be heated by transfer of heat from the melt body, and so contribute to melting of the thermoplastic material.
In a simple form of the invention, for example the first embodiment hereinafter described, preferably a coil of the spring furthermost from the inlet end is locat
REFERENCES:
patent: 3743142 (1973-07-01), Elliott et al.
patent: 4032046 (1977-06-01), Elliott et al.
patent: 4378076 (1983-03-01), Stirnweiss
Press Gerd
Schuster Heinz
Apley Richard J.
Szatkowski Thomas S.
USM Corporation
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