Multi-function heat exchanger

Abstract

A multi-function heat exchanger for use with a dispensing gun for dispensing hybrid plastisol hot melt material, the heat exchanger having an elongated tubular high temperature heater assembly having a front end hydraulically connected to an inlet port of a dispensing gun and a rear end connected to a heat dissipating assembly which in turn is connected to the outlet end of a supply hose for providing hybrid plastisol material which is liquid at room temperature and under sufficient hydraulic pressure to move the plastisol material through the heat dissipating assembly and the high temperature heater assembly into the dispensing gun when the gun is operated. The heater assembly has a heat source providing sufficient heat to turn the plastisol into a molten liquid as it passes into the dispensing gun. The heat dissipating assembly prevents heat from the high temperature heater assembly from migrating back into the plastisol supply hose.

Description

FIELD OF THE INVENTION

This invention relates to a heating apparatus that will heat a hybrid plastisol hot melt that is a flowable liquid at room temperature to a temperature wherein the material becomes molten at approximately 280 degrees F. to 350 degrees F. In addition, the device statically mixes the molten liquid converting it to a hot melt as it exits from the apparatus into commercially available hot melt dispensing heads. Once the molten material is dispensed, it has adhesive properties identical to packaging hot melt.

BACKGROUND OF THE INVENTION

U.S. patent application #20040029980 describes a hybrid plastisol hot melt composition that is liquid at room temperature. The hybrid plastisol is comprised of various micron-size resins and chemicals suspended in a liquid carrier. When this liquid is heated and mixed, it becomes a 100 percent solid hot melt that produces fiber-tear bonds when it is compressed and cooled between two cellulosic substrates.

This liquid hybrid plastisol exists in three distinct physical states at room temperature, it is a liquid. When it is heated from 150° F. to approximately 270° F., it becomes a solid. When it is heated to approximately 280° F. and above, it becomes a molten liquid. When this molten liquid is mixed, it becomes a molten hot melt.

In order for this hybrid plastisol to be useful as a hot melt, it must be pumped under pressure through a device that heats the material to molten temperature and mixes it's discrete molten ingredients to becomes a homogenous blend and supplied under pressure to a manual or automatic dispenser. Unfortunately, before the hybrid plastisol reaches its melting point, it must pass through a temperature range between 150° F. and 270° F. during which it is a solid.

There are difficult challenges to overcome in order to elevate the temperature of this material from its liquid state at room temperature to its molten state at approximately 280° F. and above.

One specific problem to overcome is that between its room temperature liquid state and molten state at +300° F., the material is an un-pumpable solid. Therefore, an apparatus had to be developed that would minimize the volume of material existing in its solid state so that it could flow through supply hoses and piping via plug flow.

One method to achieve a minimal volume solid zone is to direct cooling compressed air at the supply piping feeding the heat exchanger. Heat migrating is mitigated by a 3 to 5 cfm air nozzle directed at the pipe nipple. The result is that the portion of material at its solid state is only 50 to 100 cc's within the pipe nipple, so it is easily forced into the heat exchanger by plug flow hydraulic pressure from the liquid contacting the solid plug.

One major disadvantage to the above is the requirement for compressed air which is a very expensive utility that would have to be supplied to multiple heat exchangers in a manufacturing environment. A further disadvantage is if plant air availability is interrupted for any reason heat will migrate from the ⅛ inch supply nipple into the supply hose causing material to solidify in the pipe and hose in sufficient volume that it cannot be moved by hydraulic pressure; therefore, material supply is stopped.

The present invention is a combination heat exchanger heat dissipater that minimizes the volume of material held at its solid phase temperature range of 150° F. to 270° F. The heat dissipater is static and does not require the use of compressed air.

The heat exchanger combination performs three functions simultaneously, heat the incoming material to its melting temperature, statically mix the molten material as it exits from the heat exchanger and statically dissipate thermal energy so that it does not migrate into the room temperature supply hose; thus minimizing the volume of material held at its solid phase temperature range of 150° F. to 270° F.

OBJECTS OF THE INVENTION

One of the objects of the invention is to provide a means to heat a room temperature liquid hybrid plastisol to its molten temperature of 270 degrees F. and above and simultaneously mix the molten material so that it becomes a homogeneous hot melt before it exit's the heating device.

Another objective of this invention is to provide a means to minimize the volume of the hybrid plastisol held resident in the heater at the temperature at which the material is a solid so that it could still be pumped by plug flow.

Another objective of this invention is to prevent thermal energy from migrating from the heating device into the supply hose so that the liquid resident in the supply hose will not be heated to its solidification temperature.

BRIEF SUMMARY OF THE INVENTION

This invention is a heat exchanger that simultaneously performs the following functions:

• 1. Heats incoming room temperature liquid hybrid plastisol to its melting temperature on a first-in first-out flow path.
• 2. Statically mixes the molten material so that it is transformed into a hot melt as it exit's the heat exchanger.
• 3. Minimizes the volume of material held at a temperature at which it is a non-flowable solid.
• 4. Prevents thermal energy from migrating from the heat exchanger to the supply hose and piping so that the material held in residence therein does not reach its solidification temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational assembly drawing of the invention with part of the heat exchanger broken away to show a vertical cross section through the heat exchanger body and end caps and including a side view of the thermal dissipater and an outline drawing of a commercially available manual dispensing gun for hot melt;

FIG. 2 is an end view of the heat exchanger body;

FIG. 3 is a sectional side view of the Brass End Cap attached to the upper end of a fragmentary portion of the heat exchanger body; and

FIG. 4 is an end view of the upper mixer end cap looking into the end that fits on the upper end of the heat exchanger body as show in FIGS. 1 and 3.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings and in particular to FIG. 1, the entire heat exchanger assembly is indicated by the numeral 8 which is attached to a commercially available manual dispensing gun 9 for dispensing hot melt material. The gun 9 has a trigger 9a and a dispensing nozzle 9b. Since the gun is a commercially available gun a further description of its interior working parts should not be necessary.

The heat exchanger assembly 8 has an elongated tubular aluminum body 10 which has a front end cap 11 and a rear end cap 12. As shown in FIGS. 1 and 2, the body 10 has eight symmetrically space fluid ports 13 and a centrally located hole 14 extending longitudinally through the body 10 and retaining therein a heating cartridge 15. The front end cap 11 is made from a thermally conductive metal such as copper or aluminum so as to conduct heat into the heated dispensing gun 9.

The front end cap 11 has eight, 90° mixing channels 16 and 17 that statically mix the molten material as it exit's the heat exchanger through an axial port 18 in communication with an intake port 19 in the dispensing gun 9.

The heating cartridge 15 heats the entire body 10 and end caps 11 and 12. The end cap 12 is made of a poor thermally conductive metal such as stainless steel to reduce the rearward transfer of heat from the heat exchanger assembly 8.

An annular fluid channel 20 in end cap 12 feeds fluid to the 8 fluid ports 13. The channel groove 20 is milled into the body 10 so that a temperature sensor (not shown) may be located therein as close to the heating cartridge 15 as possible. Wire retainer 21 is mechanically attached to the body 10 providing a cavity for wire nuts 21a and mechanical clamping of armored cord set 21b. “O” rings 22 and 23 hydraulically seal the end caps 11 and 12 to the body 10. In both FIGS. 3 and 4, the arrows indicate the fluid flow as it passes through mixing channels 16 and 17 and exits the end cap 11 through the exit port 18 to pass into the dispensing gun 9.

A heat dissipating assembly 24 has one-eighth inch stainless steel pipe nipples 25 and 26 connected together by an elbow 27. The nipple 25 is connected to the rear end cap 12 of the 300+° F. heat exchanger 8 and the nipple 26 is connected to a supply hose 30 which provides hybrid plastisol which is liquid at room temperature.

Six (6) aluminum heat dissipating discs 28 are press-fit onto stainless steel pipe nipple 26. The diameter of thickness and spacing and quantity of discs can vary considerably, but in the present example; there are six (6) aluminum discs 1.25 inches in diameter and 0.064) inches thick press-fit onto a one-eighth (⅛) inch stainless steel pipe nipple 26. Spacing between discs 287 is 0.300 inches. The temperature differential between elbow 27 and the front end cap 11 is a minimum of 200 degrees F.

The heat dissipating assembly 24 prevents the 300+° F. heat from the heat exchanger 8 from migrating rearwardly into the supply hose 30 where the hybrid plastisol is at room temperature.

In operation, when the trigger 9a is squeezed, a valve (not shown) in the gun 9 is opened to permit molten hybrid plastisol to flow from the outlet port 18 of the heart exchanger 8 and into the inlet port 19 of the gun 9 where it passes through the dispensing nozzle 9b where it is deposited onto a surface to receive the hot melt adhesive. The pressure in the supply hose forces the hybrid plasisol through the heat dissipating assembly 24, the heat exchanger assembly 8 and the dispensing gun 9.

Variations can be made in the arrangement of the parts in the heat exchanger assembly and the heat dissipating assembly without departing from the scope of the invention so long as the apparatus maintains the temperature differentials mentioned herein between the plastisol material when in the supply hose and when it is in the heat exchanger assembly. For example it should be recognized that the heat dissipating assembly could be made from a single piece of pipe which is straight or curved with the heat dissipating disks or fins mounted thereon.

Claims

1. A multi-function heat exchanger comprising: a heat exchanger assembly having a front end that is hydraulically connectable to an inlet port of a dispensing gun; anda heat dissipating assembly that is connected to a rear end of the heat exchanger assembly and is connectable to an outlet end of a supply hose through which a hot melt adhesive material having a lower temperature flowable liquid state and a higher temperature molten liquid state can be supplied under sufficient hydraulic pressure to move the material through the heat dissipating assembly and the heat exchanger assembly into the dispensing gun when the gun is operated,

2. The multi-function heat exchanger as claimed in claim 1 wherein the heat exchanger assembly comprises a tubular body having an axial center hole extending throughout its length and wherein the heat source comprises an electrical heating element disposed therein.

3. The multi-function heat exchanger as claimed in claim 2 wherein a plurality of longitudinal holes are located around the axial center hole and extend for the full length of the tubular body and wherein a front end cap and a rear end cap are attached to the tubular body, the front and rear end caps having fluid channels that communicate with the plurality of longitudinal holes to permit the material to flow through the tubular body member and into the dispensing gun.

4. The multi-function heat exchanger as claimed as claimed in claim 3 wherein the fluid channels in the front end cap are positioned in communication with the longitudinal holes to mix the material before it passes into the dispensing gun.

5. The multi-function heat exchanger as claimed in claim 3 wherein the front end cap is made of a thermally conductive metal to conduct heat into the dispensing gun and the rear end cap is made of a poor thermally conductive metal to the reduce the rearward transfer of heat from the heat exchanger assembly.

6. The multi-function heat exchanger as claimed in claim 1 wherein the heat dissipating assembly includes at least one pipe nipple having a plurality of heat dissipating annular disks mounted thereon.

7. The multi-function heat exchanger as claimed in claim 1 wherein the heat exchanger assembly heats the material flowing therethrough to a temperature of between 280° F. and 350° F.

8. The multi-function heat exchanger as claimed in claim 1 wherein the heat dissipating assembly permits the material to exist in a solid state therein at a temperature of between 150° F. and 270° F.

9. The heat multi-function exchanger as claimed in claim 1 further comprising a static mixer at the front end for mixing the material in the higher temperature molten liquid state.

10. A multi-function heat exchanger for use with a dispensing gun for dispensing a hot melt adhesive material having a lower temperature flowable liquid state and a higher temperature molten liquid state, the multi-function heat exchanger comprising: a heat dissipating portion that is connectable to a supply hose; andheat exchanger portion comprising a heat source that is capable of heating the material to a temperature at which it is in the molten liquid state as, the heat exchanger a rear end that is a front end that is connectable to a dispensing gun, and a static mixing portion proximal to the front end for mixing the material in the molten liquid state;

11. The multi-function heat exchanger as claimed in claim 10 wherein the heat exchanger portion comprises a tubular body having an axial center hole extending throughout its length and further comprises an electrical heating element therein as a heat source.

12. The multi-function heat exchanger as claimed in claim 11 wherein the tubular body further comprises a plurality of longitudinal holes located around the axial center hole and extending for the full length of the tubular body and wherein the heat exchanger portion further comprises a front end cap and a rear end cap attached to ends of the tubular body, the end caps being provided with fluid channels that communicate with the longitudinal holes to permit the flow of the material through the tubular body to the dispensing gun.

13. The multi-function heat exchanger as claimed as claimed in claim 12 wherein the fluid channels in the front end cap are positioned in communication with the longitudinal holes to statically mix the molten material before it passes from the heat exchanger portion to the dispensing gun.

14. The multi-function heat exchanger as claimed in claim 12 wherein the front end cap is made of a thermally conductive metal to conduct heat into the dispensing gun and the rear end cap is made of a poor thermally conductive metal to the reduce the rearward transfer of heat from the heat exchanger assembly.

15. The multi-function heat exchanger as claimed in claim 10 wherein the heat dissipating portion includes at least one pipe nipple having a plurality of heat dissipating annular disks mounted thereon.

16. The multi-function heat exchanger as claimed in claim 10 wherein the heat exchanger portion heats the material to a temperature of between 280° F. and 350° F.

17. The multi-function heat exchanger as claimed in claim 10 wherein the heat dissipating portion permits the material to exist in a solid state therein at a temperature of between 150° F. and 270° F.

18. The multi-function heat exchanger as claimed in claim 10 wherein the static mixer is built into an outlet at the front end.

19. A multi-function heat exchanger comprising: a heat dissipating portion connected to a supply hose;a heat exchanger portion comprising a heat source that is capable of heating a hot melt adhesive material to a molten liquid state at a temperature of 280° F. to 350° F. as it passes therethrough, the heat exchanger portion having a rear end that is connected to the heat dissipating portion and a front end comprising a static mixing portion that is connectable to a dispensing gun;

20. The multi-function heat exchanger as claimed in claim 19 wherein the static mixing portion is formed by the combination of a front end cap and a plurality of longitudinal holes that extend through the heat exchanger portion.