Injection-molding apparatus

Claim 2

Apparatus for injection molding of material into a mold comprising: cylinder means for holding said molding material, including upper and lower end portions, said cylinder means comprising walls defining an elongated chamber of circular cross section; means for guiding said cylinder means substantially in up and down motion; means for upwardly biasing said cylinder means; nozzle means mounted on said lower end portion of said cylinder means for substantially up and down movement with respect to said cylinder means, said nozzle means including means alternately communicating with and sealed off from the inside of said cylinder means when said nozzle means is moved to upward and downward positions, respectively, with respect to said cylinder means; means for biasing said nozzle means downwardly with respect to said cylinder means; piston means for movement downwardly into said cylinder means, said piston means being constructed of a thermoplastic material with an initial diameter larger than the inner diameter of said cylinder means, for hot sizing to a close fit with said cylinder walls; means for applying downward force to said piston means; and means for heating said cylinder means to an elevated temperature.

Claim 3

Injection-molding apparatus comprising: a stand having a base for supporting a mold; a housing mounted on said stand above said base; a cylinder mounted on said housing for movement toward and away from said base; means for biasing said cylinder away from said base; a piston for moving down in said cylinder; means for moving said piston down in said cylinder; valve means slideably mounted at the lower end of said cylinder for up and down movement, including a hollow stem with an open lower end for discharging molding material into a mold and an upper end with an aperture for receiving molding material from said cylinder only when said stem is in an upward position; means for biasing said valve means downwardly with respect to said cylinder; and piston-receiving means mounted on said housing for movement between a first position over said cylinder and a second position spaced from said first position, said piston-receiving means having an opening, said means for moving said piston comprising a handle and an elongated member extending through said opening in said piston-receiving means, with one end attached to said handle and an opposite end attached to said piston.

Claim 4

The apparatus described in claim 2 wherein said cover means is transparent, whereby to enable observation of seating of said nozzle means on a mold.

Claim 5

The apparatus described in claim 1 wherein said nozzle means includes a hollow stem with a lower end portion, said lower end portion having walls which are less than one-twentieth of an inch in thickness, whereby to prevent severe burns when said lower end portion is touched while it is an elevated temperature.

Claim 6

The apparatus described in claim 3 wherein said thermoplastic material includes numerous small pieces of a material that is solid at a temperature when said thermoplastic material is hot sizable.

Claim 7

The apparatus described in claim 3 including a multiplicity of glass fibers dispersed in said thermoplastic material.

Claim 8

The apparatus described in claim 1 including heating means disposed about said cylinder means, said heating means including a cylindrical insulator that comprises a layer of corrugated insulating material sandwiched between a pair of layers of insulating material.

Claim 9

The apparatus described in claim 4 including: means for heating said cylinder; and a protective cover mounted below said cylinder, said cover having an aperture for allowing the passage of said stem of said valve means.