GB1592799A - Hotmelt dispenser - Google Patents

Description

(54) HOT MELT DISPENSER (t1) We, NORDSEN CORPORA TION, a corporation of the State of Ohio, United States of America, of Jackson Street, Amherst, Ohio 44001, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to the art of hot melt pumping and dispensing apparatus, and pertains more particularly to an improved heater construction for such apparatus.

The prior art describes a number of hot melt dispensers which liquefy and dispense plastic materials which are normally solid or semi-solid at room temperature, and which materials become sufficiently plastic or liquid at elevated temperatures to permit dispensing directly from the shipping container or barrel.

Commonly, such devices include an arrangement for lowering a combined heating element and pump directly into the open end of the shipping container for liquefying or melting the plastic material in the region directly below a heated platen for delivery by pump of the heated and liquefied material to a remote location. Such apparatus is shown, for example, in the United States patents of Von Haase, 2,522,652 or 1960; Hooker, 3,031,106 of 1962; Weitzel, 3,113,705 of 1963; Skonberg, 3,282,469 of 1966; Van Riper, Jr. et al, 3,412,903 of 1968; and McCreary, 3,637,111 of 1972.

Commonly, the dispensing apparatus includes a heated follower plate assembly which supports a pair of gaskets about its periphery, which carries supports or incorporates a pump, and which carries, supports or incorporates a heater or beater segments on the bottom thereof exposed directly to the plastic material within the container, for liquefying the plastic material which is exposed directly to the heater, and for delivery of such plastic material through suitable passageways to the inlet of a pump. Either a platform may be provided by means of which the container is elevated or a mechanism may be provided by means of which the plate assembly is lowered into the container.

Commonly, such heating assemblies are pro vided with heating elements which present flat heated surfaces to the plastic material to be melted. While such apparatus has proven to be highly useful with material which is readily elevated to a flowable temperature, and where the demand for such material is relatively low, such heating elements have proven to be less than fully effective when applied to material which requires a higher melt tem perature or when applied to installations where greater flow rates are required, or both.

Hot melt materials which are dispensed by the apparatus of this invention are an exten sion of the thermoplastic family of products.

Commonly, higher melt index polymers are being. used in blends. These materials compries a series of families including butyl rubber, meltable rubbers, and the "low end" of common polymers such as polyethylene, acrylics, polypropylene, polyesters, and polyamides. Melt temperatures can range anywhere from the ambient up through 500 F or more, with the bulk of applications being in the 250"F to 3500F range. However, there are many materials which move more readily by the addition of temperature even though they, in themselves, are not considered in the hot melt family of products. In other words, warming the product decreases its viscosity and allows it to be handled more readily.A product which, as an example, would be impossible to pump at 60"F, may very well be the type of product that when elevated to the temperature of 90"F or so would be a pumpable material.

Characteristics of the pumped material range from a sharp melting product through those products which essentially only change in viscosity having no sharply defined transition temperature between the "sclid" and molten phases. Chemists blend in many types of additional compounds to provide tackiness, providing a series of compounds which are considered pressure sensitive. They behave much like the equivalent materials in the rubber based families which require the elimination of solvent for their inherent pressure sensitive characteristics.

Viscosities can range anywhere from light syrup through the butyl family which can be handled at temperatures which permit, for example, extruding a bead which retains its circular cross-section as it cools.

The present invention consists in a hot melt pumping and dispensing apparatus in which a platen assembly carrying a pump and a plastic material heater is lowered into a barrel of hot melt material or the like for melting and dispensing the same from the barrel, characterized in that the heater comprises a plurality of substantially identical sector-shaped heater segments arranged generally in a circle on said platen assembly, said segments having lower material heat transferring surfaces and defining at their common apex a pump inlet opening, and passageways between said segments for conduction of molten material to said opening.

One of the difficulties in normally applying heat to hot melt materials is of applying heaters above the product, with the usual arrangements requiring the heat to be transferred through a variety of surfaces into the final product to be heated. By using cast-in electric heaters formed in segments, it is pos sible to change any one of the segments in the event of a failure. Also, the radial gaps between the segments can be controlled to provide flow passageways for transferring material which is already molten into a centrally-located pump. Also, the relatively axially thick heater segments assures that the heat is transferred from the heater elements to the material, increasing the life of the electric elements.

Each of the heater segments is preferably formed with a plurality of depending, heat conducting projections which terminate at a common plane. The projections precede the main segment bodies into the material and provide a greatly increased area for dissipation of heat, so that the material underlying the segment bodies is preheated and softened. The projections serve to remove heat from the heater segments directly into the material or product. The projections further define therebetween a multitude of flow passages which provide for the flow of melted plastic material inwardly into the pump inlet.

In the preferred embodiment, the projections are formed as solid, vertically-extending substantially cylindrical members, each of the same dimensions and arranged in equally spaced relationship from each other on each of the heater segments. They are formed with axial lengths which substantially exceed their diameters, and are also formed as an integral portion of the main body of the heater.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings, in which: Fig. 1 is an elevational view of hot melt pumping and dispensing apparatus in accordance with this invention; Fig. 2 is an enlarged vertical cross section through a platent assembly showing the heater elements in elevation, with a portion thereof being broken away; Fig. 3 is a bottom plan view of one of the heater segments; and Fig. 4 is a top plan view thereof.

Referring first to Fig. 1, the improved hot melt dispensing apparatus according to this invention includes a base plate 10 on which are supported a plurality of uprights, including a pair of upright support cylinders 12 and 14. The base 10 supports a barrel 15 of hot melt material to be dispensed by the apparatus of this invention.

Tbe cvlinders 12 and 14 are supported at their upper ends at a transfer support 16.

Also, a control box 20 may be supnorted on the base 10 and support 16 for including the electrical and temperature-monitoring controls of the dispensing apparatus.

A pair of cylinder rods 22 and 24 extend upwardly respectively from the cylinders 12 and 14. The rods are joined and connected at their tops by a crosshead 25. The crosshead 25 also supports a pump drive motor 26 and a right angle drive gear box 27.

The crosshead 25 further supports a depending tube 30. A platen assembly indicated generally at 32 in Fig. 1 is carried by the tube 30, and is shown in the raised or elevated position prior to entering the barrel 15. Air under pressure may be admitted into the cylinders 12 and 14 to cause the rods 22 and 24 to extend and lift the crosshead 25 and the associated structure supported thereon to an elevated or raised position, as shown in Fig. 1. Similarly, air under pressure may be anDlied to the opposite ends of the cylinders 12 and 14 to cause the platen assembly 32 to be lowered into the barrel with a predetermined force or pressure against material in the barrel 1S.

Referring to Fig. 2, the platen assembly 32 is shown as including a generally cylindrical bottom plate 40 on which is mounted a cvlindrical bodv 42. which supports a cover plate 43. The body 42 is formed with a pair of peripheral grooves which respectively support a pair of hollow elastomer seals 45. The seals 45 engage the inside walls of the barrel 15 and provide a fluid-tight seal therewith.

The support tube 30 is joined to the assembly 32 by a flange 46 and an annular spacer 47.

The spacer 47 preferably receives a gear-type positive displacement cartridge type pump 48.

The pump 48 is directly driven by the motor 26 and the drive 27 through a drive shaft 50 within the tube 30, as coupled by a universal joint 52.

There are supported on the lower surface of the plate 40 a plurality of essentially identical sector-shaped heater segments 60 as shown in Figs. 3 and 4. Each heater segment 60 is formed with a curved outer peripheral wall 62, generally radially extending sides 64 and a truncated apex 65. Each heater element 60 is preferably formed of cast aluminum and incorporates a cast-in heating element 68 as shown in broken view in Fig. 2. The electrical terminals 66 extend upwardly through access openings 70 formed in the plate 40. Bolts 72 extend downwardly through the plate 40 into the bodies of the heater segments 60 for securing the segments in underlying relation to the bottom plate 40.

The individual heater segments 60 are arranged side-by-side in a circle on the plate 40, and define, at a common apex formed by the truncated surfaces 65, a central pump inlet opening 75 as shown in Fig. 2. Narrow radial flow passages 76 are defined between the adjacent walls 54 of the heater segments. In the embodiment shown, six heater segments 60 are employed each subtending an approximate arc of 60". However, it is within the scope of this invention to arrange the beater into a fewer or greater number of sectorshaped heaters.

The lower heat conducting surfaces of the heater segments 60 are preferably formed with a plurality of depending, integral heat conducting projections 80. In the embodiment shown, the projections 80 are all the same diameter, and are generally cylindrical in shape, but may be formed as tapered cones with about a 1-1/2 taper wider at their bases when joined with the segments 60 than at their tips 82. The tips of the projections preferably terminate at a common plane and are arranged in a regular grid or pattem as shown in Fig.

3 to define therebetween a multitude of flow passages. The generally cylindrical pin-shaped projections provide a heating area which is greatly increased over the planar area which would otherwise be presented to the plastic material and may extend a depth of approximately 2", for example, below the surface of the heater body itself. The pins or projections 80 thus precede the main bodies of the segments 60 and extend into the plastic material in advance to preheat and soften the plastic material for flow therebetween and flow through the radial passages 76 into the central inlet space 75 and from there into the inlet of the pump 48. The pump outlet opens into a fitting 90 to which a tube 92 (Fig. 1) is attached for delivery of the hot melt material to a remote location.

The segmented heater construction of the present invention has been found substantially to increase the capacity of the dispensing apparatus. For example, when a platen assembly 32 of 22" in diameter is provided with 738 pins 2" long, a heating surface of approximately 2,400 square inches is formed.

The employment of the pins provides a seven to eight times increase in effective area over that of a simple or flat annular heating plate of the same diameter. A 27 000 watt heater constmcted according to this invention can provide a flow rate for example, of 10 gallons per minute. However, the flow rate is, itself, a function of many factors including the specific heat of the material and the ability of the material to conduct energy. Preferably, the projections 80 are each formed of the same diameter and are arranged in substantially equal spacing from each other and for an axial length which substantially exceeds their diameter.

While the preferred embodiment as shown and described herein incorporates a plurality of generally cylindrically shaped depending pins 82, it is to be understood that in the broader aspects of the invention, the pins may be eliminated and suitable heating channels or grooves formed in place thereof, or a flat lower surface may be provided for the segments 60. The individual segments 60 permit ease of maintenance by removal and replacement of any one segment which has become inoperative. Further, by controlling the arcuate widths of the segments, the capacity of the radial channels or passages 76 may be controlled or varied, and the depth of such passages also be varied, to accommodate a quantity of the liqufied material for delivery to the inlet of the pump 48. It will also be noted that the principal body of the heater Se. omeot 60 is relatively deep, as shown in Fig. 2, providing a mass of aluminum for conduction of heat from the heating element 68 for the protection of the heating element.

The increased surface such as provided by the pins 82 assures constant direction of energy flow from the element into the underlying material within the barrel 15.

While the form of apparatus herein described constitutes a preferred embodiment of this invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention as defined by the appended

Claims (6)

claims. WHAT WE CLAIM IS:

1. A hot melt pumping and dispensing apparatus in which a platen assembly carrying a pump and a plastic material heater is lowered into the barrel of hot melt material or the like for melting and dispensing the same from the barrel, characterised in that the heater comprises a plurality of substantially identical sector-shaped heater segments arranged gener ally in a circle on said platen assembly, said segments having lower material heat transferring surfaces and defining at their common apex a pump inlet opening, and passageways between said segments for conduction of molten material to said opening.

2. The apparatus of claim 1, in which said surfaces are formed to include a plurality of downwardly extending projections.

3. The apparatus of claim 2, in which said projections define solid vertically extending cylindrical members each substantially of the same diameter, and arranged on said segments in substantially equal spacing from each other and having an axial length which substantially exceeds their diameter.

4. The apparatus of claim 1, 2 or 3, in which heater segments are formed of cast aluminum having a cast-in electric heater element.

5. The apparatus of claims 2 or 3, in which said projections etxend downwardly from said segments and terminate substantially at a common plane, and said projections defining therebetween multiple flow passages providing for material flow into said passageways and into said inlet.

6. Hot melt pumping and dispensing apparatus constructed and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings.