Hot melt machine

• US 3,876,105 A
• Filed: 02/25/1974
• Issued: 04/08/1975
• Est. Priority Date: 02/25/1974
• Status: Expired due to Term

• Current Assignee: Gordon L. Kelling
• Original Assignee: Gordon L. Kelling
• Inventors: Kelling, Gordon L.
• Primary Examiner(s): Reeves, Robert B.
• Assistant Examiner(s): Handren, Frederick R.
• Application Number:
  US05/445,151
• Time in Patent Office: 407 Days
• Field of Search: 222/146HE,56 219/421,422 118/202 126/343.5A
• US Class Current: 222/56
• CPC Class Codes: B29B 13/022 Melting the material to be shaped

Abstract

A hot melt machine comprises a hopper for granular thermoplastic resin having a bottom outlet across which an electrically heated melting grid extends. A funnel beneath the grid collects molten resin and guides it to fall into a small, open-topped heated reservoir spaced below it. A gear pump, driven by a constant torque motor and having its inlet communicated with a bottom outlet in the reservoir, forces the melt towards points of use. A sensor in the reservoir controls grid energization in accordance with reservoir liquid level. A heat shield between funnel and reservoir, having a hole through which melt falls, prevents reservoir heat from affecting grid operation.

Claims

1. In hot melt apparatus that comprises a hopper for holding a store of thermoplastic material in a solid state and delivery means for conducting material from the hopper, in molten state, to a point of use at which it is dispensed, hot melt supply means by which the solid material is brought to the molten state at a rate substantially in step with the rate at which molten material is dispensed and by which a substantially constant-volume supply of the molten material is kept available for immediate dispensing, said hot melt supply means comprising:

A. a melting heater extending across an outlet at the bottom of the hopper and arranged to support thermoplastic material in its solid state but to permit molten thermoplastic material to fall;

B. means for electrically energizing the melting heater to heat the same to a temperature high enough to melt thermoplastic material;

C. an open topped reservoir spaced beneath the melting heater, the area of the open top of said reservoir being substantially smaller than the area of the melting heater, and said reservoir having an outlet at its bottom that communicates with said delivery means;

D. a funnel beneath the melting heater for collecting molten material falling therefrom, said funnel having an outlet over the open top of the reservoir for constraining the molten material to fall into the same;

E. heater means for heating the reservoir contents to maintain the same in molten condition;

E. heat shield means above the top of the reservoir and underlying the funnel, to prevent transmission to the melting heater of heat from the reservoir, said heat shield means having a hole therethrough which is vertically aligned with the outlet of the funnel to allow molten material to drop into the reservoir from the outlet in the funnel;

G. sensing means in the reservoir at a level spaced from both the top and the bottom thereof, for detecting the presence of molten thermoplastic material at said level in the reservoir; and

H. means operatively connecting said sensing means with said means for electrically energizing the melting heater, to initiate energization of the melting heater whenever molten material in the reservoir is below said level and to terminate such energization when such molten material reaches said level.

2. The apparatus of claim 1, further characterized by:

said heat shield means comprising a plate-like baffle spaced beneath the funnel and spaced above the top of the reservoir.

3. enclosure means having a. a flat bottom surface upon which the pump rests and b. thermally insulating walls in outwardly spaced relation to the pump and reservoir extending upwardly from said bottom surface to a level above the melting heater to protectively enclose hot parts of the machine;

4. The apparatus of claim 1, further characterized by:

1. said reservoir comprising a substantially cylindrical one piece metal vessel having integral fins projecting into its interior from its walls, to distribute heat through its contents; and

2. said heater means comprising an electrical heating element embracing the lower portion of said vessel at the exterior thereof.

5. The apparatus of claim 4, further characterized by:

3. said vessel having a flat bottom surface to which its outlet opens;

4. said delivery means comprising a gear pump having an inlet portion with a flat top surface to which an inlet port opens; and

6. The apparatus of claim 5, further characterized by:

6. a constant torque motor drivingly connected with the gear pump.

7. Hot melt apparatus by which thermoplastic resin from a supply thereof in solid state is heated to its melting temperature and, while molten, is delivered under pressure to a point of use to be available for dispensing, said hot melt apparatus comprising:

A. an open topped reservoir for molten material having an outlet at its bottom;

B. heater means associated with the reservoir for heating the contents thereof to maintain the same in molten condition;

C. a hopper for holding a supply of solid resin, spaced a distance above the reservoir and having an outlet at its bottom that is of substantially larger area than the open top of the reservoir;

D. an electrically energizable melting heater extending across said outlet in the hopper, for supporting the solid contents of the hopper and melting a lowermost portion of the same, and which permits molten resin to drop towards the reservoir;

E. a funnel beneath the melting heater by which molten resin dropping from the melting heater is collected and constrained to fall into the reservoir;

F. a sensor in the reservoir, intermediate the top and bottom thereof, responsive to the level of liquid in the reservoir;

G. means connected between said sensor and the melting heater for initiating energization of the latter whenever molten resin in the reservoir falls below a predetermined level and for terminating such energization when the reservoir has been replenished to said level;

H. a heat shield between the funnel and the reservoir by which heat from said heater means is prevented from reaching the melting heater, to assure that melting of resin will terminate promptly upon termination of energization of the melting heater;

said heat shield having a hole therein through which molten material falls from the funnel into the reservoir;

I. a positive displacement rotary pump having an inlet communicated with said outlet in the reservoir and having an outlet communicated with said point of use; and

J. constant torque drive means for said pump.

8. The hot melt apparatus of claim 7, wherein said outlet in the reservoir is in the bottom wall thereof and opens downwardly, further characterized by:

1. the pump having its inlet opening upwardly; and

2. the reservoir being mounted on top of the pump, with its outlet communicating with the inlet of the pump, to make available to the pump a head of molten material adequate to prevent cavitation thereof.

9. The hot melt apparatus of claim 8, further characterized by:

10. Hot melt apparatus of the type comprising a hopper for thermoplastic resin in its solid state, an electrically energizable melting heater extending across an outlet in the bottom of the hopper to support solid state resin in the hopper and by which a lower portion of such resin can be melted and permitted to fall to a lower level, a heated open-topped reservoir beneath the melting heater in which molten resin is temporarily stored before its delivery to a point of utilization, and a sensor in the reservoir, responsive to the level of molten resin therein, for controlling energization of the melting heater by initiating such energization when molten resin in the reservoir falls below a predetermined level and terminating such energization when the reservoir is replenished to said level, said hot melt apparatus being characterized by:

A. the area of the open top of said reservoir being substantially smaller than the area of said melting heater, so that the melting heater can melt resin at a rate that quickly replenishes the reservoir but the reservoir has a small volume for its depth and causes a small area of molten material surface to be exposed to air;

B. a funnel beneath the melting heater with an outlet over the reservoir for collecting molten material falling from the melting heater and constraining it to drop into the reservoir; and

C. heat shield means between the reservoir and the funnel by which heat from the reservoir is substantially prevented from reaching the melting heater, to insure that melting of solid resin terminates promptly upon termination of energization of the melting heater, said heat shield means having a hole through which molten resin passes in dropping from the funnel into the reservoir.

11. The apparatus of claim 10, further characterized by:

D. a pump by which molten material from the reservoir is delivered under pressure to said point of utilization; and

E. said pump being mounted at a level below the reservoir, 1. the pump having an upwardly opening inlet, and 2. the reservoir having a downwardly opening outlet in its bottom that communicates with said inlet to insure that an adequate head of molten resin will be available to the pump to prevent cavitation thereof.