Device For Distributing Hot-melt Adhesive

Abstract

This invention relates to a device for applying discrete amounts of hot-melt adhesive on surfaces of materials such as paper, cardboard, and the like. More particularly, the invention relates to a device enabling a nozzle to be utilized for applying small or large amounts of hot-melt adhesive on surfaces. The amounts may be deposited in the form of spots on in the form of continuous layers.

Description

In the particular art to which the present invention relates there are known devices for applying on the surfaces of materials such as paper lines or spots of hot-melt adhesive. The term "spot" is intended to refer to application of adhesive to a small definitive area having a substantially circular configuration. In order to apply such spots, there are devices which include a premelting chamber and a melting chamber, these chambers being separated from each other by a filter. The hot-melt adhesive is melted by means of electrical heating resistances, and then the melted adhesive passes through the filter in order to reach the melting chamber where the temperature of the melted adhesive is maintained at the required value through the use of a thermostatically controlled heating resistance. A pneumatic piston pump provides by way of its reciprocating motion for the supply of suitable amounts of adhesive, such amounts being supplied to a head which includes a fixed dispensing nozzle controlled by a needle valve. A return line or duct which leads to the melting chamber is connected to the head. As a result, two tubes, namely a supply tube and a return tube, are connected to the latter head. During use of such a structure, the opening of the needle valve enables desired amounts of adhesive to be dispensed. When this valve is closed, and inasmuch as the pneumatic pump continues to operate, the adhesive is first delivered to the head and then returns to the melting chamber.

A first disadvantage of a circuit of this latter type resides in the fact that it must include return and supply pipes. In addition there is the disadvantage that inasmuch as the nozzle is stationary it is necessary, in order to provide adhesive spots in an accurate manner, that the nozzle be vertically directed with respect to a horizontal surface with the jet issuing from the nozzle being directed downwardly.

It is therefore an object of the present invention to provide a device for applying lines or spots of hot-melt adhesive on surfaces, while being capable of utilizing for this purpose a jet which is directed in a direction other than a vertically downward direction.

A still further object of the present invention is to provide a device which enables only a single duct to be used for connecting the nozzle with the melting chamber.

A still further object of the present invention is to provide a device which avoids the necessity of utilizing a source of compressed air in order to supply the molten adhesive to the nozzle.

A device according to the present invention includes a premelting chamber, a melting chamber, a pump, and a nozzle, and is characterized in that the nozzle is movable and during dispensing of the adhesive is in substantial contact with the surface on which the adhesive is applied.

According to a particular aspect of the present invention, the pump is a gear pump driven by an electric motor through a reducer, and the outlet of the pump is connected to the nozzle by way of an overpressure valve and a relief valve which, together with the pump, are located within the melting chamber. In this way any portion of the pump fluid which discharges from the pump without being dispensed by the nozzle will return back into the melting chamber through the relief valve, so that in this way only a single duct is required to connect the nozzle to the pump.

According to a preferred embodiment of the invention a gear pump includes a gear mounted on a shaft driven by the motor, while a second gear is supported in a floating manner within the chamber of the pump.

The invention will be better understood from the following detailed description of a preferred embodiment, illustrated by way of a non-limiting example in the accompanying drawings, in which:

FIG. 1 is a schematic partly vertical sectional view showing the device of the present invention, with the nozzle being operated by a solenoid;

FIG. 2 shows schematically a detail of a pressure control valve;

FIG. 3 illustrates the flow circuit of the device of the invention;

FIG. 4 is a vertical sectional view of details of the nozzle; and

FIG. 5 is a schematic illustration of a different embodiment of the nozzle as utilized in connection with a gun-type of device held by the operator.

Referring to FIGS. 1-3, the device illustrated therein according to the present invention comprises a body or reservoir 1, preferably made of aluminum. Against the exterior surface of the bottom 2 of the reservoir there are electrical heating resistances 3 controlled by an unillustrated thermostat.

The interior of the reservoir 1 is divided into two portions by a wire mesh 4 which acts as a filter and which has incorporated therein a preheating resistance which is controlled by the thermostat. The space 5 situated above the mesh 4 forms the premelting chamber in which solid adhesive may be melted. Upon melting the adhesive will filter through the mesh 4 while dropping down into the lower chamber 6 which is situated beneath the mesh 4 and which forms the chamber in which the adhesive is maintained in a molten condition. Within this lower chamber 6 is a gear pump 7 having a delivery or outlet conduit 8 which communicates with a relief valve 10. As may be seen from FIG. 3, a conduit 8A is connected in parallel with the pump 7 and carries an overpressure valve 9. The gear pump 7 is driven by a variable speed electric motor 11 through a toothed-belt reduction drive 12.

As may be seen from FIG. 2, the pressure regulator or relief valve 10 is located in a conduit 13 branching from the delivery or outlet conduit 8 of the pump. This conduit 13 is closed at its top open end by a ball 14 which is loaded by and thus under the pressure of a spring 15 the convolutions of which become gradually smaller in a downward direction, as viewed in FIG. 2. The other end of the spring 15 presses against a piston 16 which slides within a cylinder 17. A cam 18 presses against the top surface of the piston 16 and is carried by a rotary spindle 19 supported within the casing of the pressure regulator. The spindle 19 projects laterally to the exterior of the reservoir 1 and at its projecting end it carries a knob or handle 20. Thus the operator can grasp the handle or knob 20 in order to change the angular position of the cam 18 and thus change the force with which the spring 15 acts on the ball 14. The chamber 17, in which the ball 14 is accommodated, is connected directly through the conduit 21 with the lower portion 6 of the reservoir 1.

The delivery conduit 8 is connected downstream of the pressure regulator 10 through a conventional swivel joint 22 with a flexible hose 23 around which a thermostatically controlled heating wire resistance 24' is wound. The hose 23 terminates in the nozzle head 24.

As may be seen from FIGS. 1, 3, and 4, the head 24 includes a housing above which an electromagnet 25 is mounted, this electromagnet 25 having a movable core 26 (FIG. 4) pressing against the head 26A of a slidably mounted nozzle 27 urged toward the core 26 by a spring 28. This spring 28 is situated within a tubular element 29 secured in a known way within an aperture 30 formed in the head 24.

The nozzle 27 has a pair of opposed inclined surfaces 31 which converge downwardly toward each other, as viewed in FIG. 4, with these surfaces 31 joining at their lower ends a pair of opposed parallel surfaces 32 which extend parallel to the axis of the nozzle 27. At these inclined surfaces 31 the nozzle 27 is formed with a transverse bore 33 which communicates with an axial bore 34 formed in the nozzle 27 and opening at its lower end, as viewed in FIG. 4, into the interior of an internally threaded outer nozzle member 34A, which is threaded onto the outer end of the nozzle 27 and which is provided with a small nozzle opening 35. The fluid jet will issue to the exterior through the opening 35.

The tubular member 29 which supports the nozzle 27 is formed with a pair of apertures 36 respectively aligned with the zones 31, 32 of the nozzle 27. A ball 37 is situated in each of these apertures, and the force of a spring 38 is transmitted to each ball 37 through a member 39 so that the balls 37 engage the inner circular edges of member 29 at the inner smaller ends of the apertures 36 thereof. These apertures 36 extend inwardly from an annular groove 41 formed around the exterior of the member 29, this groove 41 communicating with a conduit 40 as shown in dotted lines in FIG. 4. It is to this conduit 40 that the hose 23 is connected.

Assuming that an electrical pulse is applied to the electromagnet 25, the core 26 thereof will move downwardly, as viewed in FIG. 4, thus displacing the nozzle 27 downwardly in oppossition to the spring 28 with the head 26A acting as an abutment against which the core 26 acts. Therefore, the inclined surfaces 31 will become situated between the balls 37 to displace the latter outwardly in opposition to the springs 38, with the result that the fluid adhesive supplied by the pump 7 can now flow from the annular groove 41 into and through the apertures 36 to reach the transverse bore 33 so as to flow from the latter along the axial bore 34. In this way the adhesive will reach the nozzle outlet 35 so as to flow from the latter into contact with the surface to which the adhesive is to be applied. During this stage of the operation the lower end of the nozzle 27, or in other words the member 34A thereof, will be held by the operator in engagement with the surface which is to receive the adhesive so that in this way an adhesive spot or line can be applied. When the energizing of the solenoid 25 is terminated, the spring 28 will expand to displace the inclined surfaces 31 away from their position between the balls 37 so that the latter will again be pressed by the springs 38 through the members 39 into the positions where these balls 37 close the apertures 36, and thus the flow of adhesive will be terminated. It is apparent, therefore, that with this construction the distributing head can be utilized in any position.

FIG. 5 illustrates an embodiment wherein the head is a gun-type of component capable of being held by the operator. In this case the conduit 23 is connected to a conduit 50 which extends through the gun-type of dispenser. As is shown at the right of FIG. 5, the conduit 50 opens into an annular groove 51 formed at the exterior of a tubular element 52 which is secured in the gun-type of dispenser in any suitable way. A nozzle 53, corresponding to nozzle 27, slides within this tubular element 52. A ball valve 54, substantially similar to the ball valve 37, normally closes an aperture 55 formed in the tubular element 52 and serves to connect the annular chamber 51 with the bore 56 of the nozzle. This bore 56 of course extends to the exterior of the nozzle through a small nozzle outlet as was the case with the embodiment of FIG. 4.

In connection with the nozzle of FIG. 5, the nozzle 53 is urged by a spring 57 toward a slidable push member or wire 58 which engages a head 61 against which the spring 57 presses, this head 61 being fixed to the inner or upper end of the nozzle 53. The pusher 58 is encased within a sheath 59, forming a Bowden cable, and, as shown at the lower part of FIG. 5, when the trigger 60 is turned in a clockwise direction, as viewed in FIG. 5, the inner wire 58 of the Bowden cable assembly will be pushed within its sheath so as to cause the nozzle 53 to be depressed in opposition to the force of the spring 57. In this way the molten adhesive will discharge from the nozzle as described above in connection with FIG. 4.

Thus it will be seen that with the invention there is a reservoir means 1 defining the chamber 6 for the hot-melt adhesive as well as the premelting chamber 5 separated from chamber 6 by the wire filter 4 which includes additional heating wires. The hot-melt adhesive is delivered to the desired location by way of the nozzle means 24 which includes the housing of FIG. 4 or FIG. 5 together with the combined nozzle and valve unit which is shifted in its entirety with respect to the housing in order to open or close the flow of hot-melt adhesive to the outlet of the nozzle. In the case of FIGS. 3 and 4, the combined nozzle and valve unit is shifted in its entirety in an electrical manner by way of the solenoid 25 while in FIG. 5 the combined nozzle and valve unit is shifted in its entirety as a result of manual operation of elements 58-60. Thus in FIGS. 3 and 4 there is an electrical means for shifting the combined nozzle and valve unit from its closed to its open position while in FIG. 5 there is a manual means for shifting the combined nozzle and valve unit from its closed to its open position, with the unit being returned in each case to its closed position by way of a spring means. The nozzle means can be moved about as desired as a result of the flexible hose 23 which forms part of a supply means for supplying the hot-melt adhesive from the reservoir means 1 to the nozzle means 24. This supply means includes not only the flexible hose 23 but also the pump means 7 which serves to urge the hot-melt adhesive continuously toward the nozzle means 24 so that whenever the combined nozzle and valve unit is shifted to its open position there will be an immediate discharge of hot-melt adhesive. In order to maintain this constant readiness to supply hot-melt adhesive during operation of the device, the pump means is operatively connected on the one hand with the adjustable relief valve means 10 and on the other hand the suction and delivery portions of the conduit 8 leading to and from the pump means 7 are interconnected by the parallel-connected conduit 8A which includes the over-pressure valve 9. Furthermore, it is to be noted that all of the supply means except the flexible hose 23 is situated within the chamber 6 of the reservoir means 1.

Although only two embodiments of the invention have been described, those skilled in the art can now readily devise many changes and modifications, all of which are intended to be within the scope of the invention.

According to a further feature of the invention, while one gear of the pump is carried by a shaft, the other gear thereof is mounted in a floating manner within the pump chamber.

Claims

What I claim is:

1. A device for distributing a hot-melt adhesive, comprising reservoir means defining an interior chamber for containing a supply of hot-melt adhesive, nozzle means for applying the hot-melt adhesive to a desired location, and supply means communicating on the one hand with said chamber and on the other hand with said nozzle means for continuously urging the hot-melt adhesive to flow from said reservoir means to said nozzle means, said supply means including a flexible hose operatively connected with said nozzle means so that the latter may be freely moved with respect to a surface to which the hot-melt adhesive is distributed, said nozzle means including a housing, a combined valve and nozzle unit shiftable with respect to said housing between a closed position preventing the adhesive from issuing from said nozzle means and an open position opening said nozzle means to permit the adhesive to be distributed by said nozzle means, spring means urging said unit to its closed position, and means operatively connected with said nozzle means for shifting said unit in opposition to said spring means from said closed to said open position thereof.

2. The combination of claim 1 and wherein a manually operable means is operatively connected with said nozzle means for operating the latter.

3. The combination of claim 1 and wherein an electrical means is operatively connected with said nozzle means for operating the latter.

4. The combination of claim 1 and wherein said supply means includes a pump for continuously urging the adhesive to flow from said chamber to said nozzle means and a pressure-relief valve means communicating with the outlet of said pump and with said reservoir means for returning adhesive to said reservoir means when a given pressure at the outlet of said pump is exceeded, said pump and said pressure-relief valve means both being situated in said interior chamber of said reservoir means at an elevation low enough to be immersed in a supply of hot-melt adhesive.

5. The combination of claim 4 and wherein an adjusting means operatively connected with said pressure-relief valve means for adjusting said given pressure.

6. The combination of claim 1 and wherein said supply means includes a pump in said interior chamber of said reservoir means for continuously urging the adhesive to flow from said reservoir means to said nozzle means, said pump having an inlet and an outlet and said supply means including a conduit in said interior chamber of said reservoir means connected in parallel with said pump and communicating with said inlet and outlet thereof, said conduit carrying an overpressure valve in said interior chamber of said reservoir means which acts for automatically returning adhesive from said outlet to said inlet when a given pressure is exceeded, said pump, conduit, and overpressure valve being situated at an elevation in said interior chamber low enough to be immersed in a hot-melt adhesive contained by said reservoir means.

7. The combination of claim 1 and wherein said chamber of said reservoir means is a main chamber thereof, said reservoir means including a premelting chamber and a filter situated between said premelting chamber and said main chamber, said filter being in the form of a wire mesh including at least some wires which form heating elements.

8. The combination of claim 1 and wherein said supply means includes a gear pump.

9. The combination of claim 8 and wherein said gear pump includes a driven pump gear and a floating pump gear.

10. The combination of claim 1 and wherein said housing of said nozzle means includes an interior tubular guide, said combined valve and nozzle unit being shiftable in said tubular guide and being in the form of an elongated body formed with an axial bore which at one end is provided with a nozzle outlet, and said body being formed inwardly of said nozzle outlet with a transverse bore communicating with said axial bore, said tubular guide being formed with an opening passing therethrough at the region of said transverse bore and said opening communicating with the interior of said hose so that hot-melt adhesive can flow through said opening into said transverse bore and from the latter through said axial bore to said nozzle outlet, and a spring-pressed ball member situated in said opening of said tubular guide for closing said opening to prevent the hot-melt adhesive from reaching said transverse bore when said unit is in said closed position thereof, said body having at the region of said transverse bore thereof an exterior camming surface which engages said spring-pressed ball member to displace the latter to a position unblocking said opening when said unit is shifted to said open position for then providing flow of the hot-melt adhesive past said spring-pressed ball member through said opening into said transverse bore to flow from the latter through said axial bore out through said nozzle outlet.