JPH02135165A - Spray device for hot melt adhesive - Google Patents

Abstract

PURPOSE: To control the size of adhesive droplets by providing a sprayer with a means for discharging the jet of a molten thermoplastic adhesive from a discharge orifice, a means for finely breaking up the adhesive jet to droplets by injecting a spray air stream to the outside of this adhesive jet and a flow rate control means for the sprayed air stream. CONSTITUTION: A plunger control valve 186 and a prepressurized air control valve 68 are operated to supply the spray air to the region of a nozzle tip 126 prior to the start of the flow of the adhesive passing a nozzle. The adhesive stream 188 is then ejected from the discharge orifice 180 and meets the spray air injected from a spray air discharge flow passage 128. This spray air expands outward radially from the discharge flow passage 128 and collides against the outside surface of the adhesive stream 188 at a sufficient flow rate and velocity. As a result, the adhesive is finely ground to the adhesive steam 188 and the droplets 190 which deposit on a substrate 192. Further, the droplets 190 receive the collision of the pattern forming air ejected from the discharge orifice 146 of an air horn 148, there by, the pattern width of the droplets 190 deposited on the substrate 192 is controlled.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an apparatus for spraying hot melt adhesive,
More particularly, it relates to an apparatus for spraying droplets of molten thermoplastic adhesive onto substrates for bonding to other substrates.

[Prior art and problems to be solved] Hot melt thermoplastic adhesives are widely used in industry for bonding various types of products, and are particularly suitable for applications that require short curing times. . Such hot melt adhesives have been used with considerable commercial success, for example, in carton manufacturing (manufacturing of single cardboard boxes), where the rapid curing time of hot melt adhesives can be used to create high speed poles. The quick curing of hot melt adhesives is utilized in the assembly of pole box ears on the box manufacturing line.

For example, a series of dispensers are used to deposit hot melt adhesives onto carton flaps or other substrates where a rapid curing time is required.
Some adhesive dispensers are in the form of a gun, with an adhesive flow path connected to a nozzle with a discharge orifice. The adhesive is drawn through the gun and expelled from the discharge orifice of the nozzle in a relatively thick bead of molten thermoplastic adhesive that is applied to the substrate. The other substrate is then brought into contact with this first substrate, and the adhesive beads are distributed evenly over a larger surface area to obtain a sufficient bond between the substrates.

Adhesive dispensers that dispense such adhesive beads have the disadvantage that relatively large amounts of adhesive are required to achieve the desired bond. That is, the molten thermoplastic adhesive has a very high viscosity and does not spread quickly over the surface of one substrate when the other substrate is pressed against the adhesive bead. Therefore, a relatively large amount of adhesive is required if the bead is to be formed to provide sufficient bonding surface area between the substrates to bond them together.

In the past, many attempts have been made to reduce the amount of thermoplastic adhesive required to bond two substrates while still achieving sufficient bond strength between the substrates. The hot melt adhesive is delivered under pressure to the discharge orifice of the nozzle. When the hot melt adhesive is discharged into the surrounding atmosphere, the adhesive is atomized into a fine droplet spray. or form a mist, which are deposited on the substrate.These droplets are deposited over a larger surface area than the adhesive beads in the tun, and the bond strength depends on the portion of the surface area covered by the adhesive. Therefore, one droplet of adhesive less than that required in the case of adhesive beads can be used.

However, in devices such as these that spray droplets of molten thermoplastic material onto a substrate, the nozzle must be placed at a considerable distance from the mount in order to completely atomize the adhesive before it reaches the substrate. There is a problem. In this case, the droplets are exposed to ambient temperature and cooled before reaching the substrate. In some types of hot melt adhesives, the adhesive droplet hardens before contacting a substrate, or after reaching a substrate, it hardens to enable adhesion to another substrate. It has been found that sufficient specific heat cannot be maintained. Additionally, nozzles designed to atomize thermoplastic adhesives in the atomized state may produce elongated strings or fibers instead of droplets upon initial discharge and/or when cut off. This will form an adhesive. Such stretched adhesive strands can clog the nozzle and/or remain deposited on the substrate.

Lockwood (U.S. patent N.

No. 3.348.520 describes another method for reducing the amount of adhesive used in applications such as cartoning. The device shown in this Lockwood patent produces relatively large droplets of molten thermoplastic adhesive that are deposited onto one substrate for bonding to another substrate. Individual droplets of adhesive are obtained by alternately opening and closing a valve located in the adhesive supply line upstream from a nozzle connected to the supply line. However, in the device shown in Lockwood, in order to maintain the speed of the adhesive, carton boxing line, the valves that cause the adhesive droplets to form must be opened and closed at very high speeds, and therefore There is a problem that it wears out or breaks even during use.6Furthermore,
U.S. Patent N.

No. 4.721.252 describes another conventional method of spraying hot melt adhesives. In this patented device,
Molten thermoplastic adhesive is discharged through a discharge orifice of the nozzle, and a tube carrying pressurized air is positioned in the center of the adhesive stream discharged from the nozzle. When pressurized air is injected from the tube, this air expands radially outward and breaks up the hot melt adhesive in the flow to form adhesive droplets, which in turn deposited on a substrate. Multiple air delivery tubes can be used to control the width of the spray pattern of droplets formed.

However, there is a problem with the device shown in the Coulton patent, which is that when the device is stopped or shut off, adhesive dripping may occur, i.e., the adhesive flow is not interrupted. When it becomes continuous,
A problem arises in that stretched adhesive in the form of strings or fibers is formed in the area of the nozzle and air tube.

Additionally, since the pattern of adhesive deposited on the substrate depends on the number and location of the air delivery tubes, there is also the problem that entire nozzles must be removed or replaced to change the spray pattern.

It is therefore an object of the present invention to provide an apparatus for spraying droplets of molten thermoplastic adhesive which controls the size of the adhesive droplets and which is capable of being deposited on a substrate. It also controls the width of the spray pattern of the adhesive droplets, which further eliminates adhesive sag and string formation, and reduces adhesive droplets as they are deposited on one substrate and bonded to a second substrate. This allows the drops to maintain sufficient heat.

The foregoing objects are achieved by a device for atomizing molten hot melt thermoplastic adhesive, in which a stream of hot melt adhesive injected from a discharge orifice of a nozzle is impinged by a stream of atomizing air contacting the outside thereof. Forming droplets of adhesive such that these droplets retain sufficient heat when deposited on a substrate and subsequently bonding this substrate to another substrate placed in contact with this substrate. The droplet size is controlled by varying the atomizing air velocity and flow rate. A patterning air flow controlled separately from the atomizing air flow is directed at the adhesive droplets before they reach the substrate to vary the size and shape of the pattern of adhesive droplets on the substrate. Control.

According to one aspect of the invention, the use of the device eliminates cut sag, i.e., elongated fibers or threads of adhesive that form at the discharge orifice of the nozzle when the flow of adhesive is interrupted. include. This is accomplished in the present invention by a valve that controls the discharge of adhesive from the nozzle of the spray device and the supply of atomizing air and patterning air to the discharge orifice of the nozzle.

The spraying device according to the invention is formed with an applicator head having an adhesive flow path in which the adhesive is allowed to pass to the nozzle and in an open position allowing flow from the discharge refill. and a closed position in which adhesive flow is blocked. A plunger control valve is mounted on a pre-pressure air line connected to the applicator head to control movement of the plunger between open and closed positions.

Atomizing air is supplied to the nozzle through an atomizing air flow path to which an atomizing air regulating valve is connected. Additionally, patterning air is supplied to the nozzle region through a patterning air flow path which internally connects an adjustable patterning air regulating valve separate from the atomizing air regulating valve. Both the atomizing air regulating valve and the patterning air regulating valve communicate with a common supply line carrying heated or unheated air. The common supply line includes a pilot operated air supply valve located upstream of the regulating valve. The opening and closing of this pilot-operated (pre-pressure) air supply valve is controlled by an air control valve that communicates with a source of pressurized pilot air (pre-pressure air).

Movement of the plunger within the adhesive supply channel and air flow through both the atomizing air channel and the patterning air channel occurs before and after the adhesive flow is discharged from the discharge orifice. The atomizing and patterning air is also synchronized to be supplied to the area of the discharge orifice of the nozzle. The air control valve that operates the air supply valve is an unrestrained in/metered out funrestr.
icted inmeLered outl type valve, i.e., this control valve allows an unrestrained flow of pre-pressurized air to flow in one direction through it, which pressurizes the air supply valve and quickly opens it to atomize. Airflow and patterning airflow are allowed to flow toward the discharge orifice of the nozzle. On the other hand, the air control valve controls the airflow flowing in the opposite direction, and the air supply valve slowly reduces the pressure.
It is therefore slowly closed and metered to stop the flow of atomizing and patterning air after the flow of adhesive through the adhesive flow path has ceased. This eliminates the formation of adhesive "sag" or strings at the discharge orifice of the nozzle.

Plunger control valves that provide pre-pressure air to move the plunger axially between open and closed positions operate in the opposite manner to air control valves, i.e. such valves
unrestricted outimelpred 1n-unrestricted
out) J type valve. The plunger control valve controls the supply of pre-pressure air to the plunger through which the plunger moves from the closed position to the open position after the spray and pattern air flow begins to flow through the nozzle discharge orifice. so that the flow of agent is initiated.
delay. When the adhesive flow needs to be interrupted, the plunger control valve becomes ``unrestrained''.
Stricted outl J, i.e. the pre-pressure air flowing to the plunger is reversed along an unrestricted flow path through the plunger control valve, until the spring is in the plunger's quick closing position before the atomizing and slamming air flow path is made discontinuous. It is allowed to flow out so that it returns to normal.

Other aspects of the invention are based on controlling both the size of the droplets formed from the adhesive stream and the pattern of the droplets deposited on the substrate.

This is accomplished by air flow regulating valves in both the atomizing air flow path and the patterning air flow path that are independently controlled from each other to vary the air flow therein. Heated or unheated air is supplied to each of the regulating valves through an air supply valve, and such regulating valves are individually adjustable to direct selected portions of the airflow to the atomizing air flow path and the pattern air flow path. It is.

The air discharged from the atomizing air flow path impinges on the outside of the adhesive stream discharged from the nozzle, so that the adhesive stream is preferably about 1/4 to 7716 inches (0,615-1
, llIcm1 diameter nodules or droplets. The width of the pattern of these droplets on the substrate is primarily controlled by the patterning air that contacts the droplets after they are formed but before they reach the substrate.

The flow rate and velocity ratio of the atomizing air to the patterning air is adjustable by an air regulating valve.

Generally, the ratio of atomizing air to patterning air is
The flow rate and flow rate of the atomizing air are adjusted to increase while those of the patterning air are decreased so that a relatively narrow spray pattern containing relatively small adhesive droplets is formed. On the other hand, when the flow rate and flow rate ratio of the atomizing air to the patterning air is adjusted to decrease the flow rate and flow rate of the atomizing air and increase those of the patterning air, it is possible to include relatively large adhesive droplets. A relatively wide spray pattern is formed.

Another aspect of the invention resides in the versatility of the applicator head allowing different 14M4 sprayed NtIi fabrics. where the applicator head is configured to attach to the gun body of a hand-belt spray gun comprising a plunger control valve and an air control valve each connected to a source of pressurized air through a triggered supply valve. Ru. The applicator head is mounted on the gun body and connected to the air control valve and the plunger control valve for operation as described below.

On the other hand, a rod bearing mounting block is provided for connection to this applicator head. This mounting block carries the pneumatic and plunger control valves, as well as the adhesive supply lines, all of which are connected to the applicator as in the case of hand-belt (hand-operated) spray gun application. connected to the head. Prepressure air for the air control valve and the plunger control valve is supplied through a control device 1, e.g. a programmable control, a line connected to an ill device, which controls the primary applicator head to the mounting block. Pre-pressure airflow can be controlled automatically.

In yet other embodiments, a manifold is provided;
It is configured to control a series of individual applicator heads and the flow of pre-pressure air and adhesive to each of these heads.The supply of pre-pressure air and adhesive to the manifold is then controlled by a programmable controller. The adhesive is dispensed from each of the applicator heads in a desired pattern at desired time intervals.

Embodiment In FIG. 1, an adhesive spraying device 10 is constructed for hand-held operation and comprises a spray gun 12 having a handle 14 connected to a gun body 16. A trigger 18 (trigger) supported by a pivot 20 attached to the gun handle 14 is connected via an actuator 22 to a trigger rod 24 that is movable in the axial direction within the gun body 16. The end of trigger rod 24 is attached to connector plate 26, which in turn contacts valve plunger 28.

As shown in FIGS. 1 and 2, a three-way cartridge valve 30 is supported by the gun body 16 and the valve plunger 2
8.

One side of the cartridge valve 30 is connected through a supply line 32 to a source of actuating air (open circuit). The branch pipes 34 and 36 are
one each extending outwardly from the cartridge valve 30 at outlet ports 38, 40 formed within the cartridge valve.In the preferred embodiment, the cartridge valve 30 is commercially available and as such does not contain any of the features of the present invention. It does not form a part.

To open the cartridge 30 and allow air from the supply line 32 to enter each of the branch lines 34,36, the trigger 18 is first pulled to the left as viewed in FIG. move in the same direction. Upon movement of connector plate 26 relative to valve plunger 28.

The internal seat (open circuit) of the cartridge valve 30 is opened,
Air supplied from supply line 32 through cartridge valve 30 enters the items in branch lines 34 and 36. As shown in FIG. 1, releasing the trigger 18 causes the spring (open circuit) to return the trigger rod 24 and connector plate 26 to their initial closed position relative to the valve plunger 28, and the cartridge valve 30 to the closed position. will be placed in

Air entry into branch lines 34, 36 through cartridge valve 30 provides pre-pressure air, which controls adhesive flow and atomizing, patterning airflow, as described in detail below. Hereinafter, the structure for obtaining the air flow and the adhesive flow will be explained separately.

Atomizing air and patterning air First, as shown in FIGS. 1 and 2, the gun body 16
is connected to the service body 41 equipped with an applicator head 44. The service body 4I carries an adhesive heater and other electrical elements, which do not themselves constitute the invention and therefore will not be described here. A bearing block 42 is connected to an applicator head 44, which has an air supply valve 46 disposed at its base, which valve is operative to receive heated or unheated air from a supply line 48. The air supply valve 46 is connected to the support block 42
It consists of a plunger 50 extending between a pre-pressure air chamber 52 and an air inflow chamber 54 formed therein. T・Pressure air chamber 52
is formed with a port 55 connected to a pre-pressure air supply line 57, which in turn is connected to a branch line 36 from the cartridge valve 30. A sealing device 56 is interposed between the air inlet chambers 52,54, in which a lumen is formed in which the plunger 50 is axially slidable.

The end of the plunger 50 located within the pre-pressure air chamber 52 carries a head plate 58 and the opposite end of the plunger 50 located within the air inlet chamber 54 carries a plunger head 60. There is. This plunger head 60
is adapted to engage a seat 62 formed in the air inlet chamber 54 at the entrance to the channel 64 in the bearing block 42 . This channel 64 is connected to an air supply channel 66 formed in the applicator head 44 at the abutment surface of the support block 42 and the applicator head 44 . An O-ring 67 is arranged between the abutting surfaces of the bearing block 42 and the applicator head 44, forming 1.11F between them.

The flow of heated or unheated air into the air supply channel 66 of the applicator head 44 is obtained as follows. A pre-pressure air control valve 6 is provided between the 0-branch pipe 36 and the pre-pressure air supply pipe 57, through which pre-pressure air is supplied from the cartridge valve 30 to the protrusions of the branch pipes 34 and 36 in accordance with the movement of the trigger 18.
8 are connected. This pre-pressure air control valve 68 is a commercially available "unrestricted metering out" valve.
An in-metered out type actuated valve, i.e., pressurized pre-pressurized airflow is allowed to flow in one direction in an unrestricted flow path through valve 68, but airflow in the opposite direction through valve 68 is metered. When pressurized air is supplied from branch line 36 , preload air control valve 68 allows an unrestricted flow of preload air therethrough, and this flow is routed through preload air supply line 57 .
The air is sent to the pre-pressure air chamber 52 of the valve 46 through the air. When the pre-pressure air chamber 52 is pressurized, the head plate 5 of the plunger 50
8 is moved to the left as seen in FIG. 1, thereby releasing the plunger head 60 from its seating on the seat 62 of the air inlet chamber 54. As a result, the air supplied to the air inlet chamber 54 through the supply line 48 enters the flow passage 64 of the bearing block 42 and flows into the applicator head 44.
This allows the air to flow into the air supply channel 66 of the air.

When trigger 18 is released, air flow through cartridge valve 30 to branch line 34,36 is cut off.

In response, the pre-pressure air control valve 68 is operated to meter the airflow flowing therethrough, with this air flowing from the pre-pressure air chamber 52 of the valve 46 and from the pressure air supply line 57.
is gradually released in the opposite direction through the When the air pressure in the preloaded air chamber 52 gradually decreases, a spring 72 installed in the air inflow chamber 54 of the air supply valve 46 causes the plunger 5 to
0 plunger head 60 is biased into engagement with seat 62, thereby causing air flow from air inlet chamber 54 to flow path 64.
．． Air flow to 66 is stopped.

Referring now to FIG. 3, the applicator head 44 consists of an upper cylinder 74 connected to a base 76 having an air supply channel 66 formed therein, the base 76 having a stepped lumen 78 formed therein. The lumen has an upper end in which a sleeve 80 is mounted and a lower diameter end in which an adhesive channel 82 is formed. Sleeve 80 is formed with an annular slot 84 extending radially inwardly from its outer surface and communicating with air supply passage 66 formed in base 76 . Atomizing air branch line 88 is connected to annular slot 84 , and patterning air branch line 90 is also connected to annular slot 84 . These branch conduits 88,90 receive air from air passage 66 via annular slot 84 and are connected to base 7, as explained below.
6 and the air cap 94.

The base 76 receives the atomizing air regulating valve 98 therein.
A carved lumen 96 is formed. Regulating valve 98 includes a chamber 100 connected to a discharge orifice 102 .

Plunger 104 is carried by regulating valve 98, which has a rod 106 extending axially therethrough. The outer end of rod 106 is connected to cap 10B outside valve 98. The inner end of rod 106 includes a tapered edge 110 adapted to engage a seat 112 formed in regulator valve 98 at the intersection of chamber 100 and discharge orifice 102.

Atomizing air branch line 8 conveying air from supply line 57
A solid slot l-1 is provided on the outer surface of the regulating valve 98 connected to
14 is formed. A radial passage 116 connects the annular slot 114 to a chamber 100 of the regulating valve 98 in one flow to the discharge orifice 102 . Channel 64.
66 branch conduit 88, slot 114. Branch conduit 57 through the flow path defined by flow path 116 and chamber 100
The air flow from the is controlled as it passes through the discharge orifice 102 by rotating the cap 108 and thus by moving the rod 106 axially within the regulating valve 98. Axial movement of the rod 106 changes the spacing between the tapered edge 110 of the rod 106 and the seat 112 at the entrance to the discharge orifice 102, which in turn controls the flow rate of air between said edge and the seat.

From the discharge orifice 102 of the regulating valve 98 to the connector flow path 11 formed in the base 76 of the applicator head 44
Atomizing air is released at 8. This connector flow path 118
extends into an annular chamber 120 formed at the upper end of a threaded lumen 122 of the base 76, into which a nozzle 92 is mounted. The nozzle 92 has a plurality of radial flow passages 1 having an upper end communicating with an annular chamber 120.
24 is formed. The opposite lower end of the radial flow path 124 connects the outer surface of the nozzle tip 126 and the air cap 94.
to the tip 126 of the nozzle 92 within an annular atomizing air discharge channel 128 formed between opposing surfaces 130 of the nozzle 92 . As explained below, the atomizing air discharged from the atomizing air outlet channel 128 acts to impinge on the adhesive stream ejected from the nozzle 92 to form droplets of the adhesive and deposit them on the substrate. do.

Referring again to FIG. 3, the patterning air is
The air is conveyed to the nozzle 92 in the same way as the atomized air described above. A patterned air branch line 90 connected at one end to the air flow path 66 via an annular slot 84 communicates with a patterned air regulating valve 132 at its other end. The structure and operation of the patterning air regulating valve 132 is similar to that of the atomizing air regulating valve 98 and will not be described here. With respect to regulator valve 132, similar reference numerals will be used to indicate similar structure to regulator valve 98, except for the addition of "prime."

Discharge orifice 102 of patterned air regulating valve 132
' communicates with a connector channel 134 formed in the base 76 of the applicator head 44. The connector channel 134 reaches an annular chamber 136 formed in the base 76;
This annular chamber is connected to a plurality of radial passages 138 formed within the nozzle 92. In addition, the radial flow path 13
8 is connected to an annular chamber 140 formed around the nozzle 92. Chamber 140 communicates with one end of a pair of patterned air-forming channels 144 formed within air cap 94 . The other end of the pattern air forming channel terminates in at least one orifice 146 formed in each air horn 148 of air cap 94. As described in more detail below, patterning air is discharged from the discharge orifice 146 of each patterning air forming channel 144;
The atomizing air discharged from the atomizing air outlet channel 128 impinges on the hot melt adhesive droplets formed. This patterning air controls the width of the pattern of adhesive deposited on the substrate, ie, the height and width of the pattern of droplets on the substrate.

As best seen in FIGS. 1 and 3 (as shown, the image conditioning valve 98.132 is connected to the common air supply channel 66, so that the total airflow of the system is controlled by the atomizing air and patterning air branch lines 88.90). An important aspect of the invention is that the regulating valves 98, 132 are individually adjustable so that the flow rate of the air flow through them can be varied independently of each other.

Supply of Hot Melt Adhesive FIG. 3 shows a structure for conveying hot melt adhesive to the nozzle 92. In FIG. The upper cylinder 74 connects the adhesive connector flow path 1 from the adhesive source (enclosure) to the supply line 152.
A stepped lumen 156 is formed having a lower end connected by 50 .

Referring now also to FIG. 1, the lower end of the stepped lumen 156 is fitted with the upper portion of the sleeve 80, thereby allowing the adhesive to flow from the channel 150 in the upper cylinder 74 to the base 76 of the applicator head 44. A flow path for molten hot melt adhesive to flow path 82 is formed. Stepped lumen 1
A gasket cartridge 158 having a fitting portion 162 is attached to the upper end of the gasket 56 . A compression spring 163 is housed within the fitting 162 and is further connected to the plunger 165 carried by the packing cartridge 158.
It is mounted on the upper end 164 of the plunger and is movable in the axial direction along the plunger.

A ladder plate 166 is attached to the top of the plunger 165 with a nut 168, and a seal cartridge 158 is attached to the top of the plunger 165.
An air chamber 171 is formed between the header plate 166 and the header plate 166. The outer edge of header plate 166 is sealed against inner wall 169 of cap 170, applicator head 44.
form the top of the Pre-pressurized air is supplied to a flow path 154 formed in the upper cylinder 74 below the header plate 166 of the plunger 165 and to a supply conduit connected to the air chamber 171! 53. Regarding this, the first
Please also refer to Figures 2 and 2.

A lower end 172 of plunger 165 extends downwardly from upper cylinder 74 through adhesive channel 82 in base 76 to nozzle tip 126 of nozzle 92 . An adhesive discharge channel 178 (shown closed) is formed within the nozzle 92 and its upper end is connected to the adhesive channel 82 in the base 76 and the discharge orifice 180 in the nozzle tip 126. Nozzle tip 126 is tapered at discharge orifice 180 and engages a tapered tip 184 formed at lower end 172 of plunger 165 to control adhesive flow therethrough.

Adhesive flow through the spray device 10 is obtained by axial movement of the plunger 165 relative to the discharge orifice 180 of the nozzle 92, which movement is controlled as follows. As described above, air flowing into branch line 34 by operation of valve 30 flows toward plunger control valve 186 connected to branch line 34 . Next, the plunger control valve! 86 restricts the pre-pressure air flow into the supply line 153 and through the flow path 154 formed in the upper cylinder 74 below the header m166 of the plunger 165.

The plunger control valve 186 is a standard commercially available "metered in/unconstrained out" valve.
-unrestricted outl This is a J type operating valve. That is, the preloaded air flow from the branch pipe 34 is
It is metered in one direction through plunger control valve 186 to supply line 153 and through flow path 154 and then down plunger header plate 166 . Channel 15
4, the header plate 166 moves toward the upper cylinder 7.
The tapered tip 184 of the plunger 165 is then forced upward from the top of the plunger 165 toward the cap 170 above it, causing the adhesive flowing through the adhesive discharge channel 178 of the nozzle 92 to flow through the nozzle tip 126. It is lifted upward from the tapered seat of the nozzle tip 126 so that it is discharged from the discharge orifice 180. Plunger 165 compresses compression spring 163 against lower guide 160 as it moves upwardly as viewed in FIG.

To return the plunger 165 to the closed position relative to the nozzle 92, the plunger control valve 186 is operable to allow unrestricted flow of air through the control valve in the opposite direction, i.e. the header plate 166 below, air chamber 171.
The air contained within the flow path 154 and supply line 153 is allowed to escape in the original direction through the plunger control valve 186 without restriction and is then exhausted to the atmosphere through the 30,000 cartridge valve 30. Ru. When the upper air preload air passage to the plunger head plate 166 is depressurized, the compression spring 163 urges the plunger 172 downward as shown in FIG. 126 and is seated within the discharge orifice 180 of 126 .

Operation of the System An important aspect of the present invention is that plunger control valve 186 and pre-pressure air control valve 68 connected to branch lines 34 and 36, respectively, allow atomizing air and patterning air to flow through nozzle 92 to the adhesive. 126 before the flow of water is started and after this flow has ended. As mentioned above, the preload air control valve 68 is an "unrestricted in-metered out" valve.
Although it is a J type valve, the plunger control valve 186 is ``metered in ° unrestrained out fmetered''.
1n-unrestricted out) J type valve 6 Therefore, the prepressure air control valve 68 quickly supplies prepressure air to the air supply valve 46, which in turn supplies the atomizing air and patterning air as described above. flow into the area of the nozzle tip 126. At the same time, plunger control valve 186
@jeeredin)J, whereby the pressurization of the air chamber 171 of the upper cylinder 74 is slightly delayed. Accordingly, axial upward movement of plunger 165 and subsequent ejection of adhesive from nozzle 92 occurs after atomizing air and patterning air become present at nozzle tip 126. Unrestrained out fun
The restricted outlJ plunger control valve 186 allows the adhesive flow 5 from the nozzle 92 to be discharged by the preloaded air control valve 68 so that the preloaded air in the preloaded air chamber 52 of the air supply valve 46 is discharged by the This is ensured before the air supply valve 46 is allowed to close and stop air flow to the atomizing and patterning air line.

In this manner, operation of the valves 68, 186 substantially eliminates sag, ie, the formation of adhesive threads or fine fibers in the area of the nozzle tip 126. Because the atomizing air and patterning air continue to flow for some time after the adhesive flow is interrupted, no excess adhesive remains in the area of the discharge orifice 180 of the nozzle tip 126 after the adhesive flow is interrupted. Not acceptable. Similarly,
The atomizing air and patterning air are directed toward the nozzle tip 126 before the adhesive begins to flow;
Once adhesive flow begins, there is no initial shearing of the adhesive or formation of filaments.

As shown in FIG. 5, an adhesive stream 188 is ejected from the discharge orifice 180 of the nozzle tip 126 and is met by atomizing air ejected from the atomizing air discharge channel 128. The atomizing air expands radially outward from the discharge channel 128;
The outer surface of the adhesive stream 188 is impinged at a sufficient flow rate and velocity to cause the adhesive stream 188 to break up into droplets 190 and be deposited on the substrate 192. These droplets 190 then pass through the air horn. The width of the pattern of adhesive droplets 190 deposited on the substrate 192 is reduced by the impingement of patterning air ejected from the discharge orifices 146 of the adhesive droplets 148 .

An important aspect of the invention is that the applicator head 4 is capable of obtaining the desired size and pattern of adhesive droplets 190 using a series of different types of hot melt adhesives.
There are 4 types of diversity. Thermoplastic adhesives have a relatively long [open time] fopen timel J.

That is, it has enough time to be in a molten state to bond one substrate to another, but this release time varies depending on the temperature of the thermal lf bamboo adhesive. Additionally, some plastic adhesives are pressure sensitive, allowing for extended open times so that the adhesive can still provide effective adhesion after cooling.

To the applicator of the present invention, the adhesive 44 is applied to the base 1.
92 and in droplet form such that the individual droplets 190 maintain their specific heat sufficiently for a sufficient period of time to allow the second substrate 192 to adhere to the substrate 192. Acts as a spray of adhesive in droplets. This is accomplished in the present invention by providing separate control valves 98, 132 for atomizing and patterning air, respectively.

For example, the flow rate of the atomizing air and its velocity will be a factor in the size of the adhesive droplets produced by a given nozzle design. As the flow rate and velocity of the atomizing air increases, the size of the adhesive droplets 190 decreases because the adhesive stream 188 is more violently impinged by the higher velocity atomizing air and breaks up the adhesive stream into smaller droplets 190. The quality decreases. On the other hand, as the flow rate and velocity of the atomizing air is reduced, larger droplets 190 are formed due to less disturbance of the collision between the slower moving atomizing air and the adhesive stream 188.

In this way, the size of the droplet 190 can be adjusted for different hot melt adhesives to accommodate its opening time, and when the droplet 190 is deposited on the substrate 192, other Their opening time can be tailored to be large enough to maintain their specific heat for a sufficient time to obtain effective bonding with the substrate. Generally, hot melt adhesives with limited open times should be sprayed in relatively large droplets 190, and as the open time of the adhesive is increased, or pressure sensitive adhesives are used When this happens, the droplet size can be reduced.

The speed and flow rate of the patterning air is primarily regulated by the batten air regulating valve 132 to control the width of the droplet 190 deposited on the substrate 192. For example, as the velocity and flow rate of the patterning air increases, the pattern of droplets 190 becomes wider. On the other hand, as the flow rate and velocity of the patterning air decreases, the resulting pattern of droplets +90 becomes narrower on the substrate 1927.

In most cases, the ratio of atomizing air to patterning air to velocity can be adjusted instead of adjusting only one of the atomizing airflow or the patterning airflow while holding the other constant. For example, by adjusting the ratio of atomizing air to patterning air to increase the velocity and flow rate of the atomizing air, while decreasing the velocity and flow rate of the patterning air, A relatively narrow spray pattern is formed on the substrate 192.

Adjusting the ratio of atomizing air to batting air to decrease the velocity and flow rate of the atomizing air while increasing the velocity and flow rate of the patterning air produces a relatively wide spray consisting of relatively large droplets. A pattern is formed on substrate 192.

Given the many types of thermoplastic adhesives and the different requirements of the types of applications in which such adhesives are used, the flow rate and velocity ratio of atomizing air to patterning air for a particular application is It is envisioned that the settings for regulator valve 98 and patterned air regulator valve 132 will be determined experimentally. Furthermore, the specific configuration of the nozzle 92 used in the applicator rad 44 is such that the annular atomizing air path 1
24 and the two patterning air orifices 146 of the air horn 148 of the air cap 94 affect the velocity of the atomizing air and patterning air.

The following examples provide representative parameters for atomizing air and patterning air flow rates in a nozzle 92 and air cap 94 of the form shown in Figure 4, which have been experimentally determined to give acceptable results for a given application. is shown.

5-U adhesive type: Eastman A148 adhesive Adhesive temperature = 375°F Adhesive flow rate:
300 g/win nozzle spacing:
Atomizing air flow 12 inches from the base:
2.76 scfm patterning air flow rate 3.22 scfm Using the above adhesive type and adhesive flow rate, the adhesive stream discharged from the spray nozzle is impinged in this example by the atomizing air stream with a flow rate of 2.76 scfm. It was done. As a result, approximately 1/4 inch ~
A droplet or droplet 190 of adhesive with a lateral dimension of 7/16 inch was produced. The pattern of droplets 190 obtained with a patterning air flow of [3,22 scfm] is approximately 1
It had a width of 4 inches. The size of the droplets 190 relative to the type of adhesive used was considered sufficient to ensure that they had sufficient release time for the desired application.

Takumi) Adhesive type: Eastman A148 adhesive Adhesive temperature: 375°F Adhesive flow rate:
300 g/lll 1m nozzle depth: 12 inches from the base Atomizing air flow rate:
3.47 scfm Patterning Air Flow Rate: 3.21 scfm In this example, the same adhesive and adhesive flow rate as in Example 1 was used. The difference from Example 1 is that the atomizing air flow rate was increased relative to the patterning air flow. This produced adhesive droplets 190 with slightly smaller lateral dimensions than in Example 1, and the pattern width was reduced such that the droplets 190 were more tightly clustered.

System Structure Referring now to FIG. 4, an example of the suitability of applicator head 44 for various dispensing systems is illustrated. The applicator head 44 is useful for hand-head type operation as shown in FIGS. 1-3 and at the top of FIG. 4, and the applicator head 44 shown in the middle and bottom of FIG. , which is useful for more automated applications, mounted on various bearing means that supply pre-pressurized air, adhesives, and heated air.

In particular, the top portion of FIG. 4 shows the applicator head 44 in combination with the spray gun 12 shown in FIG. 1 and previously described in detail.
This is what is shown. This combination is utilized in hand belt applications for hand gripping the applicator head 44, such as during operation.

Referring to the center portion of FIG. 4, spray gun 12 is removed and mounting block 20 is supported by rod 202.
Replaced by 0. The mounting block 200 carries a service block 41, which in turn carries a bearing block 4.
The applicator head 44 is mounted at a position that supports 2. The service block 41 includes an applicator head 44
A boat 204 for receiving pre-compressed air for the plunger 165 and a photo 209 for receiving hot melt adhesive are formed. A boat 206 is formed within the bearing block 42 to receive air for the atomizing and patterning channels of the applicator head 44, and a boat 208 is also formed within the bearing block 42 to receive air supply valves such as air supply valve 46. It receives pre-pressurized air to operate the circuit (circle C). The embodiment in the center of FIG. 4 shows that the supply of pre-pressurized air and hot melt adhesive to this embodiment is preferably by a programmable controller instead of a hand trigger 18 as in the spray gun 12. It operates much the same as shown in FIGS. 1-3 and 5, except that it is controlled.

Referring to the bottom of FIG. 4, manifold 210 is shown supported on mounting rods 212.

This manifold 210 is configured to mount several applicator heads 44 on either side thereof;
Each of these heads is operated by a programmable controller.

In the illustrated manifold, a boat is provided on which two applicator heads are mounted on the side (1) and one applicator head is mounted on the opposite side. For this reason, the manifold 21
0 is configured so that the applicator head 4 is configured to provide pre-pressure air for moving the plunger within the applicator head 44.
Boat 2 configured to connect to boat 154 of Boat 4
14 is formed. Hot melt adhesive is boat 2
16 to the flow path 150 of the applicator head 44. Additionally, manifold 210 is formed with a boat 218 adapted to connect to boat 66 of applicator head 44, which provides air for the atomizing air and patterning air channels. The manifold 210 includes suitable flow paths connecting the control air supply line 215 with the boat 214, the Botmelt adhesive supply line 219 with the boat 216, and the forming and atomizing air supply line 219 with the boat 218. have.

Although the present invention has been described in terms of preferred embodiments, it will be apparent to those skilled in the art that various changes can be made without departing from the scope of the invention and elements can be substituted with equivalents. You can also. Therefore, the invention is not limited to the particular embodiment shown as the best mode of carrying out the invention, but includes all embodiments falling within the scope of the appended claims.

[Brief explanation of the drawing]

1 is a partial elevational view of one embodiment of an adhesive spraying device; FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1; and FIG. FIG. 4 is a cross-sectional view of the applicator head taken along line 3-3 in FIG. FIG. 5 is a schematic unincorporated drawing showing another structure; FIG. 5 is a schematic drawing showing the spray and forming air impinging on the dispensed hot melt adhesive stream; Drawing reference number 10 - - Spray device 2 - - 34, 36 5 2, 54 6 2, 11 Spray gun gun body trigger pivot actuator connector plate valve plunger 3-way cartridge valve supply line branch line service main body applicator Head Air Supply Valve Supply Pipe Plunger 11 Preload Air Chamber Head Plate Plunger Head 2 ---- Sheet Air Supply Channel Base Adhesive Channel Spray Air Branch Pipe Pattern Formation Air Branch Pipe Nozzle Spray Air Adjustment Valve 80 --- One discharge orifice compression spring plunger air chamber plunger control valve base 9 8 --- 102 , 1

Claims (1)

Claims: 1. An apparatus for spraying droplets of thermoplastic adhesive onto a substrate, comprising: a first means for discharging a jet of molten thermoplastic adhesive from a discharge orifice of a spray nozzle; a second means for injecting an atomizing air stream against the outside of the jet of adhesive to break the jet of molten thermoplastic adhesive into droplets; starting the flow of the atomizing air stream before beginning to discharge the jet of molten thermoplastic material from the orifice, and stopping the atomizing air flow rate after ceasing the flow of the jet of molten thermoplastic material from the discharge orifice; and a flow rate control means for controlling the flow rate. 2. said first means comprises a pre-loaded pneumatic actuated plunger carried within an adhesive channel formed in said spray nozzle;
2. The plunger is movable between an open position relative to the discharge orifice of the spray nozzle, which allows adhesive to pass therethrough, and a closed position relative to the orifice, which prevents passage of adhesive. The device described. 3. The flow rate control means includes: a first valve means for supplying pre-pressurized air to the plunger to move the plunger between the open position and the closed position; and the molten heat discharged from the spray nozzle. second valve means for directing atomizing air to the second means for directing atomizing air toward the flow of plastic adhesive; The second valve means is operative to initiate the supply of atomizing air to the second means before moving to the open position, and the second valve means is operable to move the atomizing air to the closed position in response to operation of the second valve means. 3. Apparatus according to claim 2, operative to terminate the supply of atomizing air to said second means following movement of the plunger. 4. The first valve means is a plunger control valve, the control valve directing pre-pressure air passing through the control valve into the plunger in a first direction to slowly move the plunger to the open position. said plunger control valve is effective for metering the flow of said plunger control valve through which an unrestrained flow of preloaded air flowing in an opposite second direction causes rapid expulsion of air from said plunger in said second direction; 4. The device of claim 3, wherein the device is effective to rapidly move the plunger to the closed position. 5. The second valve means is a pre-loaded (pilot operated) valve communicating with the second means, the valve being in an open position through which the atomizing air flow reaches the second means and to the second means. a preloaded valve movable between a closed position in which flow of the atomizing air stream is interrupted; an air control valve connected to the preloaded valve and a source of preloaded air; operative to allow unconstrained preloaded airflow to flow through this control valve in one direction, capable of rapidly moving said preloaded valve to said open position, and slowly releasing preloaded air from said preloaded valve. an air control valve operable to meter the flow of air through the control valve in a second direction opposite to the first direction and capable of slowly moving the preloaded valve to the closed position. 4. A device according to claim 3, characterized in that: 6. An apparatus for spraying droplets of thermoplastic material onto a substrate, the applicator head comprising: (i) an applicator body; (ii) attached to the applicator body, the applicator head comprises: (iii) a plunger carried within the adhesive flow path of the nozzle, the spray nozzle having an air flow path and an adhesive flow path having an outlet orifice; the adhesive discharge channel is movable between an open position relative to the outlet orifice that allows passage of a flow of thermoplastic adhesive therethrough and a closed position that stops the flow of thermoplastic adhesive through the outlet orifice; (iv) a pre-loaded pneumatically actuated air supply valve means connected to an atomizing air source and the atomizing air flow path of the nozzle to open and close atomizing air flow to the nozzle; and comprising bearing means for mounting said applicator head and supplying said head with pre-pressure air and molten thermoplastic adhesive, said bearing means (i) controlling pre-pressure air flow to said air supply valve means; (ii) controlling a pre-pressure air flow to the plunger to move the plunger to the open position and return the plunger to the closed position; (iii) means for continuously supplying adhesive to said spray nozzle. 7. The apparatus of claim 6, wherein said bearing means comprises a hand belt spray gun having means for manually operating said air control valve means and said plunger control valve means. 8. said bearing means comprising a manifold adapted to mount at least one of said applicator heads, said manifold having a first internal channel for conveying molten thermoplastic adhesive communicating with said nozzle; A second internal flow path that communicates with the plunger and conveys preloaded air, and a third internal flow path that communicates with the air supply valve means and conveys preloaded air. The device according to item 6. 9. A method of atomizing droplets of thermoplastic adhesive, the method comprising: directing a stream of atomizing air into the area of a discharge orifice of a spray nozzle; initiating a flow of material and impacting the outside of the thermoplastic material stream with the atomizing air stream to break up the thermoplastic adhesive into droplets, and dissolving the thermoplastic material stream from the discharge orifice. continuous and then discontinuous said atomizing air flow in the region of said discharge orifice of said nozzle.