CA1092802A - Extrusion nozzle for molten adhesive dispensing device - Google Patents

Abstract

EXTRUSION NOZZLE FOR MOLTEN
ADHESIVE DISPENSING DEVICE

Abstract of the Disclosure An extrusion nozzle of an extended length, that nozzle being directly connected in heat transfer relation with a heater block in the discharge head of a molten adhesive dispensing device. The elongated nozzle is comprised of an inner tube of steel, and an outer casing of copper or aluminum, to establish optimum strength and heat transfer characteristics for the nozzle along the length thereof from one end to the other. The molten adhesive gun's heater block provides the heat source for the nozzle's casing, the heated casing preventing the molten adhesive from solidifying within the inner tube prior to discharge of the adhesive from the nozzle.

Description

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This invention relates to molten adhesive dispensing devices. More particularly, this invention relates to a molten adhesive dispensing device with a novel nozzle structure.
IIot melt adhesive, i.e., molten adhesives of the ther-moplastic type, have recently become quite commonplace in cer-tain industries. For example, hot melt adhesives are widely used in the assembly and manufacture of automobiles, ~urniture, aircarft sub-assemblies, textile articles, and the like. One basic type of molten adhesive dispensing device is in the nature of a hand gun so the operator can have freedom to move the applicator in and out or back and forth as required during use.
The hand gun, of course, may be manually moved relative to a stationary workpiece. Another basic type of molten adhesive dispensing device is in the nature of a stationary piece of equipment located at a fixed work station. With the station-ary dispensing device, the workpiece may be automatically moved past the dispensing device in assembly-line fashion, the device discharging molten adhesive thereon as the workpiece moves past.
As the scope of use of molten adhesive dispensing de-vices has increased due to acceptability thereof throughout in-custry, the various products at least partially assembled with molten or hot melt adhesives, i.e., the number of end uses of those dispensing devices, has also increased. In this connection, oftentimes it is highly desirable to direct the dispensing device's nozzle into very small nooks and crannies of an assembly or sub-assembly so as to deposit the hot melt adhesive in the exact location required to accomplish the desired bonding result.
Such nooks and crannies may be of quite limited dimensional size, or of limiting geometrical configuration, so that an extended length nozzle is required. I~hether the hot melt adhesive dm/'~ 2-80;~

dispensing device ;s of the hand gun type, or of the stationary or fixed equipment type, the extended length nozzle permits the molten adhesive to be discharged into nooks and crannies which might not be otherwise accessible to hot melt adhesive without the extended length nozzle.
Extended length extension nozzles for molten adhesive devices may have a linear axis configuration or may have a curved axis configuration. In other words, the extended length nozzle may have a discharge ~ore that is linear, or may have a discharge bore that is curved. Whether a linear nozzle or a curved nozzle is used upon the workpiece is, of course, dictated by the structural configuration and dimensions of the workpiece, and by the spatial or work area within which the nozzle has to reach the desired bonding location on the workpiece. A typical nozzle of the ~type known to the prior art, which nozzle is curved at its outer end relative to the axis of the bore, is illustrated in U. S. Patent No. 3,901, 181 at Figures 6 and 7, and in British Patent No. 1,392,285, see Figure 3~
The major problem with an extended length nozzle on a molten adhesive~dispensing device, where the nozzle is fabricated of steel for structural rigidity purposes, is that the molten adhesive tends to solidify within the nozzle's bore toward the output end thereof. In other words, and as molten adhesive pass-es through the steel nozzle's bore from the device's discharge head to the nozzle's output end, that adhesive cools and may solidify at the nozzle's output end unless the molten adhesive throughput is substantially continuous and of significant quantity. Thus, and in an extended length steel nozzle, the molten adhesive tends to soldify at the outer end or tip of the nozzle, thereby plugging up the nozzle and preventing further discharge from the nozzle dm/ ~ 3-~U9~8(~2 until the nozzle is cleared. One approach to this solid-ifying problem has been to fabricate an extended length nozzle of a high heat transfer coefficient material, e.g~
of copper. This approach to the solidifying problem has effectively eliminated that problem, but this approach has given rise to perhaps an even more serious problem.
When the extended length nozzle is fabricated of a material such as copper, the nozzle will bend or deform quite easily. Thus, and if the nozzle is bumped against a workpiece during use (as certainly would be expected to occur in connection with a manually operated dispensing device), the nozzle's bore may be pinched closed or the nozzle bent so severely that the nozzle i5 rendered in-effective or useless.
It has been one objective of this invention to provide a molten adhesive dispensing device having a novel nozzle structure, that novel nozzle being structured in a manner that permits hot melt adhesive to be discharged therefrom on a continuous or on an intermittent basis, as desired, without freeze-up of the hot melt adhesive within the nozzle's bore.
It has been another objective of this invention to provide an improved nozzle structure for a hot melt ad-hesive dispensing device, that nozzle comprising an inner tube of steel and an outer casing of copper or aluminum, that outer casing being fixedly connected to and surrounding the inner tube, and that outer casing being connected with the heater block of the molten adhesive dispensing device's discharge head, thereby preventing solidification of molten adhesive within the nozzle as long as the discharge head's heater block is heated.

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In summary of the above, the PXesent invention broadly provides a molten adhesive dispensing device, the device including a discharge head, a heater body within the discharge head, and the improvement comprising a long tapered nozzle of extended length having a length to inside diameter ratio of at least twenty to one, the nozzle being connected at one end in conductive heat ex-change relation with the heater body, the tapered nozzle having a tapered outer casing, the casing having an axial bore therein and being fabricated of one of copper and aluminum, one end of the casing being structured to re-movably connect,with the heater body, and an inner steel tube contained within the bore of the nozzle outer casing, the steel tube e~tending from ad~acent the one end of the casing slightly beyond the outer casing at the other out-put end thereof.
Other objectives and advantages of this inven-tion will be more apparent from the following detailed des-cription taken in conjunction with the drawings in which:
Figure 1 is a perspective view illustrating an extended length nozzle in combination with a hand held molten adhesive gun in accord with the principles of this inventioni Figure 2 is an enlarged view illustrating assembly of the extended length nozzle with the heater block of that hand held molten adhesive gun illustrated in Figure l;
Figure 3 is an axial cross-sectional view of the extended length nozzle shown in Figures 1 and 2; and Figure 4 is an axial cross-sectional view similar to Figure 3, but illustrating a second embodiment of the extended length nozzle.
A molten adhesive device 10 with a novel elong~ted nozzle 11 structure, in accord with the principles of this Pg/ ~ 5 -invention, is particularly illustrated in Fi~ures 1 and 2. The molten adhesive devi`ce 10 illustrated in those Figures is in the nature of a hand held gun.
The hand held gun shown in Figure 1, and partially shown in Figure 2, is particularly described and illustrated in detail in Scholl et al Patent No.
4,006,845, assigned to the assignee of this appli-cation. Thc deecript~

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It is particularly apparent upon viewing Figure 1 that the hahd gun type molten adhesive dispenser 10 shown permits an operator to grip manually and to manipulate, i.e., to use manually, the gun to direct the molten adhesive discharge through the gun's nozzle 11 at the desired location. E~oweve~ the imprcved e~-tended length nozzle 11 is also adapted for use with a molten adhesive dispenser which is not of the hand gun type, i. e., a dispenser located at a fixed location or work station. In this type molten adhesive dispensing device the workpiece moves past the devi~e. A typical such molten adhesive dispensing de-vice, with multip]e adhesive discharge heads, is illustrated in Baker et al Reissue Patent No. 27,865, also assigned to the assignee of this application.
The improved extended length nozzle 11, as previously mentioned, is illustrated in Figures 1 and 2 in combination with a molten adhesive dispenser 10 of the hand gun type. The hand gun 10 constitutes a discharge head, and is adapted to discharge a molten adhesive feedstock as desired by an operator. The gun 10 basically comprises a gun housing 12 having a barrel portion 13 and an adhesive feed portion 14, the longi~udinal axes 15, 16 of the barrel and adhesive feed portions, respect-ively, being oriented in an acute angle relative one to the other. A heater body 17 is positioned within the gun housing.
The heater body 17 includes at least one heater cartridge 18 thermostatically controlled to maintain the molten adhesive feed-stock within the gun at the desired temperature level. In other words, the heater body 17, which is in the gun or dis-charge head 10, is a heat source that maintains the adhesive in the molten state. A discharge valve 19 is positioned within the gun housing 12, and is connected with that heater body 17. The discharge valve l9 is operable by an operator to control dis-charge of the molten adhesive feedstock through the nozzle 11.

dm/ ~ ~'` -6-.: -The gun housing 12 includes a handle 20 fixed to the barrel por-tion 13 at the a~ end thereof, and extending rearwardly thereof.
The handle 20 includes trigger 21, and the trigger is connected to discharge valve 19 so that actuation of trigger 21 also opens the discharge valve.
More particularly, and as illustrated in Figure 2, the heater body 17 (which is fabricated of a heat conductive material) defines the discharge head's discharge bore 22 for the hot melt adhesive. The extended length nozzle 11 is threaded, as at 23, into the interior of the heater body's discharge bore 22 at the output end of that bore 22. The discharge end of the heater body 17 is retained in ~ixed location relative to the gun's housing 12 by nut 24 and washer 25, the nut 24 being threaded as at 26 onto the exterior surface of the heater body 17. An insulator ring 27 is interposed between the heater body's discharge end 28 and the housing 12 ~o insulate the housing from the hot heater body 17 during operation of the gun 10. The discharge valve 19 is positioned within the discharge bore 22 interiorly of the heater body 17, see also Figure 2. The discharge valve l9 includes a valve stem 29 interconnected with the gun's trigger 21, a valve head 30 being fixed thereto. The valve head 30 is adapted to seat against valve seat 31 in sealing fashion, the valve seat being press fit into the heater body's bore 22 against bore shoulder 32. Use of trigger 21 by the gun's operator permits the valve head 30 to be lifted off the valve seat 31, thereby permitting discharge of molten adhesive from the heater block 17 through the extended length nozzle 11.
The hot melt adhesive gun 10 illustrated in Figures 1 and 2 is of that type where the hot melt or thermoplastic feed-stock is translated from a solid into the molten state ~t a sup-ply source, i.e., at a molten feedstock reservoir, remote from the gun. This may be accomplished by apparatus such as is il-dm/~ 7-, ,8(~Z

lustrated in Reighard et al Patent Nos. 3,827~603 and 3,815,788, both assigned to the assignee of this application. The molten adhesive feedstock is transmitted to the gun 10 through feed hose 33, and is maintained therein in the molten state because of the heater body 17 and cartridge heater 18 mounted therein, as previously mentioned, within the gun's housing 12.
The structural details of one embodiment of the ex-tended length nozzle 11 are particularly illustrated in Figures

2 and 3. As shown in those two figures, the extended length nozzle 11 is comprised of a cylindrical tube 40 of steel. The steel tube 40 is encased or enclosed in an outer tube or casing 41 of copper or aluminum. The copper or aluminum (which may be in the alloy form) casing 41 has a high heat conductivity co-efficient so that it effectively transfers heat from the base to the outer end of the nozzle. The axis 46 of the casing 41 and the axis 47 of the tube 40 are coaxially disposed, these axes 46, 47 being linear. The outer casing 41 is tapered or conical in cross-sectional configuration, the inner end 42 of the conical casing being provided with a neck portion 43 having threads 44 exteriorly thereof. The threaded neck portion 43 of the outer casing 41 is adapted to be threadedly received in threaded bore 23 in the discharge end of the gun's heater block 17 so as to interconnect the nozzle 11 in direct heat conductive -relation with the heater block 17 itself. To facilitate thread-ed assembly of the nozzle 11 into the heater block 17, opposed flats 34 are provided on the periphery of the nozzle adjacent the neck portion 43.
In lieu of the threaded connector 44, 23, a conven--tional flange and nut connection may be utilized for securing the nozzle to the heater body 17. Such a conventional flange and nut connector for securing a nozzle to a dispenser is il-lustrated in United States Reissue Patent No. 27,865, which dm/ ' ~; -8-109~8(~2 patent is assign~d to the assignee of this application.
Assembly of the steel tube 40 with the copper or aluminum casing 41 is achieved by slip-fitting or telescoping the steel tube into the copper or aluminum casing. The steel tube 40 is maintained in fixed combination with the copper or aluminum casing 41 by the silver brazing at the innermost end as at 48. The inner tube 40 is silver brazed to the outer cas-ing 41 at the inner end thereof so as to insure a seal between the tube and the casing since innermost face 49 of the extended length nozzle 11 is e~posed directly to molten adhesive. Al-ternatively, the tube 40 may also be maintained in fixed rela-tion with the casing 41 by crimping or swaging the casing at a point between the inner 42 and outer 50 ends thereof. This crimping or swaging of the inner tube 40 and outer casing 41, once same have been assembled, serves to provide a mechanical seal between the two component parts so that same do not become disassembled upon use. Note particularly that the tube 40 ex-tends slightly beyond the free or outer end 50 of the casing 41 as illustrated particularly in Fi~ure 3. The tube 40 ex~
tends beyond the casing 41 at the outer end so as to define a sharp output orifice 51 for the nozzle. A sharp output orifice 51 does not permit molten adhesive to collect or build up at the tip 50 of the nozzle 11 as would normally occur in a blunt nose nozzle. Further, the sharp nose or tapered end 50 of the nozzle 11 is provided so that the nozzle can be easily man-euvered into very small dimensioned work areas where necessary to de~osit the molten adhesive.
As a matter of reference relative to the use of the term -~extended length nozzle in this application, the te~m is used in a relative sense which is relative to the inside dia- -meter ID of the nozzle 11 and the length L of the nozzle. For purposes of this application, the term extended length nozzle dm/\~

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will be considered to mean any nozzle having a length 'co inside diameter ratio of at least 20 to 1. As an illustrative example of a particular embodiment of a nozzle 11, from a dimensional standpoint, which nozzle is adapted for use with a hand gun of the type shown in Figure 1, and for that embodiment illustrated in Figures 2 and 3, the nozzle is 2.530 inches in length L with a .075 inch inside diameter ID. This provides a length to in-side diameter ratio of about 34 to 1. Further, the Figure 3 embodiment includes a wall thickness for the tube 40 of .032 --inches, and the outside diameter of the casing 41 at the gun end42 is about .50 inches. The free end of the tube 40 may extend beyond the free end of the casing 41 a distance about equal to 0.10 inches.
It is preferred under certain circumstances to provide a plating or cover 55 for the extrusion nozzle 11, that plating having surface characteristics that prevent the nozzle from being dented or marred. In other words, the plated cover 55 presents a hard surface to the exterior face of the nozzle 11 so that the nozzle is not easily dented. Further, the exterior surface coating 55 may function to prevent the hot melt material from sticking to the nozzle 11 itself. A preferred coating or plating material, when the casing is fabricated of copper, is nickel.
A second embodiment 60 of the improved nozzle according to the principles of this invention is illustrated in Figure 4.
The nozzle 60 of Figure 4 is, in effect, the nozzle 11 of Figure

3 but with the tip 61 thereof angled on an axis 62 relative to the longitudinal axis 63 of the nozzle. As illustrated in Figure 4, the tip 61 of the nozzle 60 is angled at a 45 angle, and this angulated tip geometry may be desirable under certain use conditions. The tip 61 of the nozzle 60 may be angled or bent to the desired attitude at the work site as directed by the dm/

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dimensional and geometrical configurations of the workpiece, and this is another advantage of the nozzle structure )f this invention. With ~ steel tube 64 interiorly positioned within a copper or aluminum casing 65, the tip 61 of the nozzle 60 can be relatively easily bent without severly disfiguring or other-wise adversely effecting the nozzle's bore 66. Without the steel tube 64, i.e., if only the copper or aluminum casing 65 defined the nozzle bore 66, it is quite possibe that bending of the nozzle's tip 61 would cause the bore to collapse, in effect, thereby rendering the nozzle useless. But the pre-sence of the tube 64 within the casing 65 provides sufficient strength to the bore 66 so that such collapse or bore dis-figurement does not occur.
From a practical standpoint, the improved extended length nozzle 11 of this invention provides several desirable advantages vis-a-vis those extended length nozzles known to the prior art when in actual use or work environment. In the first instance, the copper or aluminum casing 41, 65 surrounds the steel tube 40, 64 of the nozzle 11, 60 provides a high de-gree of heat transfer from the discharge head 15 heater block 17 to the outer reaches or tip 61 of the nozzle since the copper or aluminum casing is of a highly heat conductive nature.
Thus, the casing 41, 65 functions as a heat sink to accept heat from the gun's heater block 17 due to the direct or conductive heat transfer connection therebetween, and to maintain a heat envelope around the nozzle bore 66 from the heater block end 42 all the way out to the free tip end 50 of the nozzle 11. This prevents the molten adhesive material from chilling or solid-ifying at the free tip end 50 of the nozzle 11, 60 even when discharge of the molten adhesive from that nozzle is on a sporadic or intermittent, i.e., not continuous, basis. Further, the nature of the steel tube 40, 64 as the inner tube provides dm/~

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a longer useful l;fe to the nozzle 11, 60 in the sense that the steel tube resists corrosion due to the continuous passage of molten thermoplastic adhesive material therethrough, i.e., it is a more highly corrosion resistant material, relative to the high heat conductive materials such as aluminum or copper.
Further, the high strength steel tube 40, 64 tends to resist bending of the nozzle 11, 60 if that nozzle is inadvertently knocked against an immobile object by a careless operator, thereby providing structural inte~rity to the nozzle. Further, the use of the steel tube 40, 64 permits a smaller orifice 51 to be used in practice because the bore 66 erosion problem is substantially eliminated; such small outlet orifices are des-irable in certain use conditions. Thus, the improved nozzle 11 structure of this invention provides a significantly improved useful life, as well as significant practical advanatages in a work environment, over extended length nozzles currently known to the prior art.
Having described in detail the preferred embodiments of my invention, what I desire to claim and protect by Letters Patent is:

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Claims (2)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A molten adhesive dispensing device, said device including a discharge head, a heater body within said discharge head, and the improvement comprising a long tapered nozzle of extended length having a length to inside diameter ratio of at least twenty to one, said nozzle being connected at one end in conductive heat exchange relation with said heater body, said tapered nozzle having a tapered outer casing, said casing having an axial bore therein and being fabricated of one of copper and aluminum, one end of said casing being structured to removably connect with said heater body, and an inner steel tube contained within the bore of said nozzle outer casing, said steel tube extending from adjacent said one end of said casing slightly beyond said outer casing at the other output end thereof.

2. The molten adhesive dispensing device as set forth in Claim 1 wherein said casing is threaded on said one end thereof, said threaded casing section being threadably engaged with said heater body.