US3352278A

US3352278A - Hot melt glue applicator

Info

Publication number: US3352278A
Application number: US429264A
Authority: US
Inventors: Glynn H Lockwood
Original assignee: Tensor Corp
Current assignee: Tensor Corp
Priority date: 1965-02-01
Filing date: 1965-02-01
Publication date: 1967-11-14
Anticipated expiration: 1984-11-14

Description

Nov. 14, 1967 G. H. LOCKWOOD 3,352,278

HOT MELT GLUE APPLICATOR Filed Feb. 1, 1965 5 Sheets-Sheet 1 INVENTOR. (iv Aw bi [aczwaoa 1967 G. H. LOCKWOOD HOT MELT GLUE APPLICATOR 3 Sheets-Sheet 2 Filed Feb; 1, 1965 INVENTOR. 64W 19. Ava W000 Nov. 14, 1967 5. H. LOCKWOOD 3,352,278

HOT MELT GLUE APPLICATOR Filed Feb. 1, 1965 3 Sheets-Sheet 5 INVENTOR. 64 nviv fl. Z calm 00a yat r 22% I TTOiA/III United States Patent 3,352,278 HOT MELT GLUE APPLICATOR Glynn H. Lockwood, Carmel, Calif., assignor to The Tensor Corporation, a corporation of California Filed Feb. 1, 1965, Ser. No. 429,264 Claims. (Cl. 118-7) ABSTRACT OF THE DISCLOSURE A hot melt glue applicator has a reservoir open at one end and closed by a rotatable pattern wheel having a thin peripheral band defining an annular volume in which is disposed a heater stationary on the frame and heating the reservoir contents through the peripheral band. A thermostat in the reservoir is responsive to the conducted heat and controls the supply of glue to the reservoir.

My invention relates to means for utilizing glue originally in dry, approximately granular form, heating the glue to change it into a liquid form and then applying the liquid to devices to be glued, such as carton flaps and the like.

A device of a related nature is shown in the copending application of Lockwood, Panzer, Schleicher and Hudson, Ser. No. 259,074 filed Feb. 18, 1963.

In the present instance, it is primarily an object of the invention to provide a hot melt glue applicator in which the glue, although normally dry and solid in form, is converted into a liquid and is transported and applied in liquid form in an economical and efiicient fashion.

Another object of the invention is to provide a hot melt glue applicator in which there is a carefully regulated supply of glue to the applicator and in which the glue is well applied without becoming distributed in unwanted areas.

Another object of the invention is to provide a hot melt glue applicator which can be utilized as a unit for installation on carton machines and the like already in existence.

Another object of the invention is to provide a hot melt glue applicator utilizing a relatively small number of parts and which is easily accessible for servicing and attention, but which is relatively rugged and capable of operation for protracted periods without any difficulty.

Another object of the invention is to provide a hot melt glue applicator in which the supply of glue to the applicator is automatically maintained.

Other objects together with the foregoing are attained in the embodiment of the invention described in the accompanying description and illustrated in the accompanying drawings, in which:

FIGURE 1 is a side elevation of the hot melt glue applicator constructed pursuant to the invention, certain portions being shown diagrammatically;

FIGURE 2 is a cross section on a vertical axial plane through the liquefying unit of the hot melt glue applicator;

FIGURE 3 is a plan of a portion of the structure shown in FIGURE 2, certain enclosures and covers being removed;

FIGURE 4 is a cross section through the drive mechanism as indicated by the line 4-4 of FIGURE 1;

FIGURE 5 is a cross section through the applicator unit, the planes of section being indicated by the lines 55 of FIGURE 1; and

FIGURE 6 is a detailed cross section, the plane of which is indicated by the line 6-6 of FIGURE 5.

The hot melt glue applicator pursuant to the invention is readily installed in a number of different environments and in the present instance is illustrated as it is utilized ice for the application of liquid glue to the lower surface 6 of a flap 7 extended from a carton 8. This carton is usually of cardboard or fiberboard an is appropriately advanced on a conveyor 9 past the station at which the glue applicator is disposed. A cam shoe 11 is a part of the carton handling mechanism and affords a backing for the flap 7. The carton handling mechanism is no part of the present invention and is illustrated as being of standard nature. The result of the carton handling mechanism is to advance the carton 8 with the extended flap 7 travelling under the stationary cam shoe 11 and past the glue applicator mechanism.

Partially for ease in manufacture, partially for flexibility in installation, and also for thermal reasons, it is preferred that the hot melt glue applicator be fabricated in two main units. As particularly shown at the bottom of FIGURE 1, there is provided a base plate 12 having a bracket 13 secured thereto and supporting the feed body 14 of a glue supplier. Detachably mounted in an upstanding throat 16 forming part of the feed mechanism in a light metal hopper 17 open at the top and designed to receive cold glue. This material is capable of changing from dry, granular or flaky condition when cold to a moderately viscous liquid when hot. Dry glue in the hopper 17 flows by gravity into the throat 16. Means are provided for advancing the dry glue from the throat 16 into a generally circular cylindrical, horizontal feed housing 18 and therein exerting pressure upon the glue.

The driving means includes an open, helical screw 21. Preferably, the screw is formed as a helix from square section rod. While the helix is free at one end, it extends through the housing 18 and is anchored to a drive shaft 23. Appropriate bushings 24 mount the drive shaft 23 for rotation in a hub 26 of the body 14. A gear 27 fast on the end of the drive shaft 23 is in mesh with a gear 28 joined to one member 29 of a friction slip clutch 31. A facing 32 is interposed between the member 29 and a driving disc 33. These members are axially urged together by a spring washer 34 held in position by an adjusting nut 36 engaging a drive shaft 37 on the end of a reduction gear unit 38. An electric motor 39 turns the shaft 37 and unless the load is excessive, transmits rotary force through the friction members and the gears to the shaft 23 and the helix 21. In the event of overload, then the clutch slips and the mechanism is not injured. When the clutch slips for a considerable time, the local temperature is elevated and the heat affects the surroundings. To preclude premature heating of the glue, the slipping clutch is disposed on the motor shaft rather than on the drive shaft 23. Since there is good thermal isolation by the gears 27 and 28, the clutch heat does not disturb the glue.

As the helix 21 revolves, the dry, granular glue is on gaged by the convolutions of the helix. To make sure that the helix serves as an effective driver, the mass of glue is restrained from revolving with the helix by irregularities on the interior of the housing 18 such as axially extending splines 40. Thus, when the helix turns, the body of glue is advanced along the axis of the housing 18, building up some pressure as it does so. The tendency of the helix is to compact the glue into a dense body within the housing. There is no backflow even though the pressure at the leading portion of the body of glue is considerable. The term flow is utilized in connection with the granular material, since this behaves largely as a liquid although it is actually in a dry, flaky or granular form.

Coupled to the feeding mechanism is a liquefying unit 41. The liquefying unit 41 includes a massive metal body 42 of good heat conducting material such as cast aluminum and is provided with an interior tortuous channel 43 preferably in the form of a helix generated about an axis 44. The upper portion of the helix merges with an opening 46 serving as an inlet to the housing 18. Since it is desired to maintain good thermal isolation between the liquefying unit and the feeding unit, there is provided a thermally insulating hose 47, having some flexibility, connected between these units. The hose is clamped in place by bands 48 and 49 and itself surrounds part of the helix to serve as a part of or as a continuation of the cylindrical housing 18.

Part of the tortuous passage 43 is closed at its upper end by a plate 51 having a peripheral seal 53 and secured by a central bolt 52. The tortuous passage 43 winds downwardly from its inlet and extends into a chamber 54 having a clean-out plug 56 closing one end thereof. Insulating securing

bolts

57 and 58 pass through the base plate 12 and engages the body 42 to provide a firm mounting.

Arranged in the body 42, preferably crossing the axis 44 and in effect enveloped by the convolutions of the helical, tortuous passageway 43 is a bore 59. A heating element 61 having a conductor 62 extending to a suitable source of electricity is in elfect buried within the body and when energized transmits substantially all of its heat to the surrounding metal for transference to the walls of the passage 43, thus increasing the temperature of the material advanced through the passage by the operation of the feed screw 21. A standard temperature responsive controller 63 controls the operation of the heater 61. A thermal insulating blanket 64 overlies portions of the body 42 and is covered by a protecting jacket 65.

The temperature imparted to the glue within the body 42 is sufficient to liquefy the glue but is considerably below a proper temperature for glue application. Most of the glues utilized with this apparatus tend to cook, caramelize and form deleterious deposits as a function of temperature and time. Since it requires considerable time even at maximum output for the glue to travel through the machine, its temperature is kept as low as possible at the beginning of the flow and heat to application temperature is gradually applied as the glue advances through the machine so that the higher temperatures are effective over unimportant time periods.

By the time the relatively dry and solid glue has been advanced through the inlet 46 and has traveled at least part way through the tortuous passage in close thermal relationship with the heater element 61, the material has increased in temperature sufficiently to liquefy and become a continuous mass. The flow of the mass of now liquid glue then continues through the chamber 54. Flow cannot proceed toward the inlet because of the presence of an advancing body of dry glue impelled by the rotating helix. Flow of the liquid glue is thus into an outlet passageway 66 extending to a filter chamber 68 arranged vertically and having a closure plug 69 at the upper end thereof. Axially withdrawable from the filter chamber is a filter 71 having a peripheral screen 72 reinforced by an interior spring 73 and disposed between a pair of heads 74 and 75. The filter can be introduced and withdrawn as a body and is arrange in the path of flow of the melted glue so that all of the glue must flow through the filter and emerges therefrom clean. A drain valve 76 is located at the bottom of the chamber 68.

An outlet 77 from the body 42 is afforded through a connector 78 at one end of a flexible tube 79. This tube is a good thermal conductor and is jacketed with a flexible insulating material 80-. A heating wire 85 connected to a source of electricity is embedded within the jacket in conducting relationship to the tube 79 so that the temperature of the-material flowing therethrough is at least maintained and preferably is augmened. In this fashion, the viscosity of the heated, liquid glue is controlled after it leaves the passage or chamber 68.

i The other end of the flexible tube 79 extends to an applicator unit as shown in FIGURES 1 and 5, particularly. In this unit there is provided a mounting frame 81 suitably attached to the frame of the carton machine and including a clamp 82 grasping a tubular frame portion 83.

Rotatably mounted in a bushing 84 installed in the frame 83 is a driving shaft 86. At the outboard end of this shaft there is mounted a sprocket 87 adapted to be joined to the mechanism of the carton machine for rotation substantially in synchronism therewith. To avoid damage from overload, the sprocket 87 is not firmly connected to the shaft 86, but is freely journalled thereon and is driven through a ball 88 lodged in a driven disc 89 keyed to the shaft. The ball is pressed into a depression 90 in the sprocket 87 by a leaf spring 91, the assembly being secured by a central bolt 92. While the sprocket 87 and the shaft 86 normally revolve together, in the event of shaft overload, the ball 88 rides out of the socket 90 to release the drive.

At its inboard end, the shaft 86- carries a glue applicator or pattern wheel 94. This wheel includes a central hub 96 secured to the shaft 86 by an end bolt 97 and likewise includes a thin, peripheral band 98. This generally has a circular cylindrical exterior configuration and is spaced from the hub 96 to leave a semi-enclosed annular volume. The periphery of the wheel is for the most part truly circular cylindrical, but at intervals is provided with depressions 99 arranged in any suitable pattern, as desired, for the deposit of the melted glue on the carton flap 7.

In order to maintain and control the temperature of the pattern wheel, the interior annular volume thereof is largely occupied by a heater cage 101 at appropriately spaced points carrying a plurality of electric heaters 102 each having conductors 103 extending to a suitable source of electricity. The heaters and some of the attendant structure are appropriately held in position surrounding the tube 83 by insulating mountings 104 into which securing bolts 106 extend from a flange 107 on the tube 83.

In order to supply the glue pattern wheel with liquid glue at the appropriate, final temperature, a glue reservoir 111 is mounted on and extended from the frame. This reservoir is relatively small so that the temperature of the stored glue can easily be controlled and will be uniform. Heat is transferred to the reservoir walls and to the contained glue through the periphery of the wheel 94 from the heaters 102. The reservoir is formedof a bottom wall 112,

side walls

113 and 114 and an end wall 116.. The reservoir is at atmospheric pressure and is tightly related to the pattern wheel on and in alignment with the wall 114 by an applied thin plate of springy material 117. This is held in position by removable fastenings 118 so that there is virtually no leakage possible, between the plate 117 and the end face 119 of the pattern wheel. The reservoir is smaller then the glue pattern wheel so that either the top or bottom periphery of the pattern wheel can be brought against the material to receive the glue.

Somewhat similarly, the wall 112 is extended and leakage is largely prevented by the provision of a flexible, spring steel doctor blade 121 resting against the bottom wall 112 and slightly sprung into tight conta t with the periphery of the pattern wheel. The mounting and adjustment of the doctor blade 121 are arranged by a slide 122 adjustably secured to the frame of the device. The slide 122 has elongated slots 123 therein through which fastenings 124 extend. The slide also has an end ridge 126 designed to abut tightly against the doctor blade. Furthermore, the slide has an L end 127 through which bolts 128 extend and are screwed into the main body of the reservoir. When the fastenings 124 are loose, the bolts 12 8 can be operated to move the slide 122 toward the pattern wheel. A shoulder 129 on the slide abuts the end of the doctor blade and moves it toward the pattern wheel. When an appropriate position of adjustment has been arranged, the bolts 124 are tightened to hold the parts in position. The spring rate of the blade 121 is relatively high so that Bernouilli forces exerted between the pattern wheel 94 and the doctor blade during operation are resisted and no substantial leakage occurs.

The liquid, heated glue flowing through the heated, flexible line 79 passes through a drilled channel 131 in the body of the reservoir and discharges through lateral openings 132 into the reservoir.

Since it is desired to maintain substantially a predetermined level of glue in the reservoir despite variations in the speed with which the glue is Withdrawn by rotation of the pattern Wheel, there is mounted in the wall 116 a device responsive to level by sensing the temperature of the liquid glue in thermal contact with the device. For this reason the wall 116 is provided with an opening 133 communicating with the interior of the reservoir and partially sealed by an insulating Washer 134 clamped in place by a ring 136. Mounted on a separate plate 137 thermally distinct from or isolated from the reservoir is the probe 138 of a temperature responsive thermocouple or thermistor protected by a hood 139 and having a connection 141 for conductors leading to a control station, not shown.

When the level of the glue in the reservoir is low, the end of the sensing device 138 is exposed to the atmosphere and its temperature is relatively low. This initiates or increases the flow of material through the heating element of FIGURE 2 and through the connecting flexible hose to the reservoir. When suflicient glue has been received in the reservoir so that the level rises to the desired point, then the temperature of the sensing device 138 rises and the supply of glue is cut down or stopped. Thus, there is an automatic sensing arrangement for maintaining the desired glue level in the reservoir.

In the operation of this device, when the carton mechanism is running, all of the circuits are conditioned so that the motor 39 is energized and the feeding screw 21 is operated. The dry, pulverulent glue is then advanced in the form of a pressure compacted mass through the feeding portion of the machine and into the liquefying portion. The heater coil 61 therein converts the dry, solid glue into liquid form as it traverses the tortuous passage. After the glue has been filtered and has emerged from the chamber 68, it flows through the heated flexible hose to the applicator unit. The glue temperature is maintained or augmented. The glue forms a pool within the reservoir maintained at proper, preferably higher temperature, being retained by the reservoir walls and particularly by the doctor blade 121 and the side plate 117. The rotating wheel circulates the glue in the reservoir and tends to maintain a uniform temperature throughout the glue pool. The desired level of liquid glue in the reservoir is auto matically sustained.

Upon rotation of the sprocket 87, the shaft 86 is revolved and the applicator wheel likewise turns. As the periphery of the applicator wheel traverses the reservoir in contact with the glue therein, certain volumes of glue are trapped or lodged within the depressions 99 of the applicator wheel, any surplus being scraped off by the doctor blade. This glue is in close thermal contact with the heaters and is brought up to final temperature. The periphery of the applicator wheel is free of glue except in the depressions 99. As the applicator or pattern Wheel revolves in abutment with the tangent flap 7 of the carton, discrete bodies of liquid glue are deposited thereon. This flap promptly is advanced in the machine by the carton mechanism. The rotating pattern wheel depressions, being emptied of carried glue, then traverses the reservoir again, picking up further glue charges for subsequent carton flaps.

The glue on the pattern wheel that does not adhere to the carton flaps is returned by further rotation of the wheel to the reservoir, being directed to flow inwardly thereto by bevels 142 along the top edges of the

side walls

113 and 114 of the reservoir. Thus, no glue is lost and that not applied is reheated and recircu ated.

What is claimed is:

1. A hot melt glue applicator comprising a frame, a glue reservoir open at the top and on one end, means for mounting said glue reservoir on said frame, an applicator wheel, means for journalling said applicator wheel on said frame in position to form a Wall for said one end of said reservoir, said applicator Wheel being shaped to define an annular volume, a heater, means for mounting said heater stationarily on said frame within said volume, to transmit heat through said applicator Wheel to said reservoir, means responsive to temperature mounted on said frame and extending into the interior of said reservoir, and means controlled by said temperature responsive means for supplying said reservoir with hot liquid glue.

2. A hot melt glue applicator comprising a frame, a glue reservoir on said frame, said glue reservoir including a bottom wall and a pair of side walls at one end terminating in arcuate edges and at the other end terminating in an end wall having an opening therein, an applicator Wheel rotatably mounted on said frame with the pe riphery of said wheel making a close running fit with said edges, said applicator wheel having a thin peripheral band to define an annular volume, a heater fixed on said frame and disposed in said volume in thermal relationship with said wheel and with said reservoir through said band, means for supplying said reservoir with liquid glue, means on said frame thermally remote from said heater for supporting a temperature responsive device, a temperature responsive device on said supporting means and extending through said opening, and means for controlling said supplying means by said temperature responsive device.

3. A hot melt glue applicator comprising a tubular frame, a driving shaft journalled in and extending from said frame, a pattern wheel mounted on said shaft, said pattern wheel having a thin peripheral band surrounding but spaced from said tubular frame to leave an intervening annular volume, a heater frame including a heater cage substantially occupying said volume, means for supporting said heater frame stationarily on said tubular frame, a glue reservoir mounted on said heater frame at one side of said pattern wheel and having side walls extending substantially to the edges of said peripheral band leaving the central portion of said band exposed to the interior of said reservoir, and heaters in said heater cage and constituting the sole source of heat for said reservoir.

4. A device as in claim 3 in which said supporting means includes a thermal insulator for isolating said heater frame from said tubular frame.

5. A device as in claim 3 in which said reservoir has a height substantially less than the diameter of said pattern wheel whereby both the top and bottom of said pattern wheel can be contacted by horizontal sheets overlying and underlying said glue reservoir.

References Cited UNITED STATES PATENTS 2,861,159 11/1958 Seney 137-392 X 2,912,959 11/1959 Showalter 1185 3,030,915 4/1962 Shannon ll8-202 3,028,833 4/1962 Hummel 118-7 3,206,125 9/1965 Farrell 2l9301 X 3,255,727 6/1966 Boothroyd 1l87 FOREIGN PATENTS 901,592 7/ 1962 Great Britain.

CHARLES A. WILLMUTH, Primary Examiner. L. G. MACHLIN, Assistant Examiner,

Claims

1. A HOT MELT GLUE APPLICATOR COMPRISING A FRAME, A GLUE RESERVOIR OPEN AT THE TOP AND ON ONE END, MEANS FOR MOUNTING SAID FLUE RESERVOIR ON SAID FRAME, AN APPLICATOR WHEEL, MEANS FOR JOURNALLING SAID APPLICATOR WHEEL ON SAID FRAME IN POSITION TO FORM A WALL FOR SAID ONE END OF SAID RESERVOIR, SAID APPLICATOR WHEEL BEING SHAPED TO DEFINE AN ANNULAR VOLUME, A HEATER, MEANS FOR MOUNTING SAID HEATER STATIONARILY ON SAID FRAME WITHIN SAID VOLUME, TO TRANSMIT HEAT THROUGH SAID APPLICATOR WHEEL TO SAID RESERVOIR, MEANS RESPONSIVE TO TEMPERATURE MOUNTED ON SAID FRAME AND EXTENDING INTO THE INTERIOR OF SAID RESERVOIR, AND MEANS CONTROLLED BY SAID TEMPERATURE RESPONSIVE MEANS FOR SUPPLYING SAID RESERVOIR WITH HOT LIQUID GLUE.