US3420208A - Pneumatically controlled applicator system for adhesive and the like - Google Patents

Description

J. W. GUTHRIE Jan. 7, 1969 m "//l//f s v. s Tm I HLW NM1 l/ AT D mu L W. mno J T www @2 CHI M1 H F R L0 MF I M. m W. N f P j. L. .w

Va/re was YCQMK1- United States Patent Ofi ice 3,420,208 Patented Jan. 7, 1969 9 Claims ABSTRACT OF THE DISCLOSURE Liquids such as hot melt adhesives are applied to a work surface through orifices connected in parallel and controlled by individual needle valves actuable in response to pneumatic signals. The same pneumatic signals control the valves and the pump mechanism by which the adhesive is intermittently pressurized.

This invention has to do generally with the application of a liquid material to a relatively moving work surface in a definite and controllable application pattern.

The invention is especially useful for applying hot melt adhesive to such work surfaces as the liaps of paperboard cartons or cases to effect sealing. The invention will be described with special reference to such systems, but without implying limitation to any particular type of liquid or work surface.

lt has previously been suggested to control the application pattern of such liquids by intermittently pressurizing the uid by means of a pump mechanism controlled by a pneumatic actuator. Systems are also known in which the fluid to be applied is mentioned under continuous pressure, and its supply to the applicator nozzles is controlled by intermittent actuation of valve mechanism at the applicator head.

One aspect of the present invention provides improved accuracy and reliability of the cutoff of uid liow by combining intermittent pressurization with intermittent valve actuation, timing of the pump and valve controls being coordinated by making them both responsive to the same control signals.

A further aspect of the invention utilizes pneumatic signals for combined control of the type just described.

Another aspect of the invention employs individual shutoff valves for each nozzle orifice, each valve being located immediately adjacent the orice outlet. With that arrangement particularly accurate and positive control is provided. Moreover, each valve can be separately adjusted, facilitating the selection of different patterns of application.

The invention also provides valve structures and valve operating mechanisms that are particularly well adapted for systems of the present type.

A full understanding of the invention and of its further objects and advantages will be had from the following description of illustrative manners in which it may be carried out. The particulars of that description, as of the accompanying drawings which form a part of it, are intended only as illustration and not as a limitation upon the scope of the invention, which is described in the appended claims.

In the drawings:

FIG. 1 is a schematic drawing representing an illustrative system in accordance with the invention, with uid supply mechanism and part of an applicator head shown in section; and

FIG. 2 is a schematic drawing representing a modification.

Referring rst particularly to FIGURE l, the numeral 10 represents illustrative means for providing a continuous supply of hot melt adhesive or similar lluid. The container 12 has an open top through which solid adhesive can be added, and is heated by electrical elements represented schematically at 14. The temperature of the resulting liquid in tank 12 is preferably controlled, aS by a thermostat 15 of conventional type.

Fluid from tank 12 is withdrawn through the check valve 20 by the pump mechanism 22, and is supplied under pressure through the supply conduit 24. Pump mechanism 22 typically comprises the pump cylinder 26 with pi ton 27, and the actuating cylinder 30 with pif ton 32. The two pistons 27 and 32 are positively coupled by the rod 34 which passes in sealed relation through the partition 35 between the two cylinders. Actuator piston 32 is driven in its reciprocating motion by admission of pressurized air to one end or the other of cylinder 30 via the respective control conduits 36 and 38. Control air is supplied to those conduits from the conventional source of compressed air indicated schematically at 40 Via the solenoid controlled four-way valve 42. The solenoid mechanism indicated schematically at 44 maintains valve 42 normally in position to supply air to control conduit 36, and opens conduit 38 to the atmosphere. Electrical energization of the solenoid shifts the valve to supply control air to conduit 3S and to open conduit 36 to the atmosphere. Current for solenoid 44 is supplied intermittently in any suitable manner to produce the desired pattern of uid application.

In the present illustrative system the work surface 50 represents typically a ap of a carton to be sealed, and is moved continuously by conventional mechanism, not explicitly shown, along the support 52. A control switch 54 is operated in response to presence of the work surface at support 52 by a mechanism indicated schematically by the dashed line 56. Switch closure completes an energizing circuit through solenoid 44 and a suitable power source, shown as the battery 58. Valve 42 is thereby shifted to pump operating position, admitting air to the right of actuator piston 32 and driving pump piston 27 to the left as seen in FIGURE 1. Fluid is thereby forced under pressure into conduit 24. Upon release of switch 54, valve 42 returns to normal position, causing pump piston 27 to be positively retracted, typically drawing fresh fluid from tank 12 via check valve 20.

The present invention is concerned more particularly with the applicator valve structure shown illustratively at 60. That structure comprises the block 62 with the working face 63 and with parallel valve bores 64 which open inwardly from face 63 and in which the applicator nozzles 66 are threaded. Each of the nozzles 66 has a small axial orifice 68 which opens outwardly from an annular conical valve seat 70. Valve bore 64 extends coaxially inwardly, forming the valve chamber 65 and the valve actuating chamber at 72, in which the valve actuating piston 74 is slidably contained, with suitable sealing means shown as the two axially spaced O-rings 76. An elongated spindle 78 projects axially from piston 74 and carries at its outer end the needle valve 80. The Working surface of valve 80 is conically tapered to engage valve seat 70 in positively sealing relation in response to downward movement of piston 74. Seating of valve 80l on its conical seat 70 is facilitated by lateral lflexure of the relatively slender spindle 78. Control piston 74 and valve 80 are yieldingly urged toward valve closing position by the coil spring 82, which acts between the upper end of the piston and block 62.

Upward movement of piston 74 is positively limited by Contact of the coaxial boss `84 with the end of the valve bore at 86, that contact limiting the degree of opening of valve 80. The effective position of stop surface 86 with respect to the valve action is adjustable by screwing nozzle 66 in or out of block 62. The O-ring 67 typically exerts suflicient resistane to nozzle rotation to effectively lock that adjustment. Whereas such adjustment might be used for regulating the rate of delivery of fluid through orice 68, it is normally preferred to make the valve opening large compared to the cross section of the orifice. If it is desired to modify the rate of ow, the entire nozzle 66 can readily be removed and replaced with a nozzle having an orifice of the desired diameter. In practice the described stop adjustment is conveniently made by screwing in nozzle 66 until boss 84 engages stop surface 86, and then unscrewing the nozzle through a predetermined angle.

A system of passages 90 is provided within block 62 interconnecting the valve bores 64 at points between their respective nozzles 66 and pistons 74. Passages 90 are connected, as indicated by the dashed line 92, to fluid conduit 24, already described. Hence pressurized uid from pump mechanism 22 is supplied in parallel to all of the valves 80 and their orices 68. Fluid in each valve chamber 65 also lills the lower portion of valve actuating chamber 72, exerting upward force on the piston 74.

The passage structure 100 interconnects the upper portions of actuator chambers 72 above pistons 74. Passages 100 are connected, as indicated by the dashed line 102, to the line 103 and control conduit 36, already described, which supplies control air from control valve 42 to the left side of pump actuating piston 32. That control air drivels valve piston 74 down, as seen in FIG. 1, positively closing valve 80 during the periods when the tluid in passages 90 is relieved of pressure. When the fluid in valve chamber 65 is again pressurized by pump mechanism 22 air passages 100 are vented to atmosphere via control valve 42. Hence valve 80 is opened by the fluid pressure on the lower side of piston 74, applying adhesive to surface 50.

lf desired, the valve-piston element can be resiliently biased in either direction. As illustrated, the spring 82 supplements the action of control air in closing the valve, reducing the air pressure required for that purpose. Springl 82 also holds the valve positively closed when the apparatus is shut down with air pressure turned off. With suitable values of spring bias and air pressure, the adhesive pressure can be maintained continuously in chamber 65, selective application being controlled entirely by the single pneumatic signal pulses applied to chamber 72 above the control piston. Also, with suitable spring bias, the system may be operated successfully without supplying pneumatic signals to` passages 100, those passages -then forming a buter chamber that permits piston movement without excessive pressure variation.

In the modified structure of FIG. 2 the mechanism 10 for providing hot melt adhesive and pump mechanism 22 for intermittently pressurizing that liquid are typically as described in connection with FIG. 1, and are indicated only schematically. Air supply 40, control valve 42 and solenoid 44 and its control :circuit are typically as already described.

.The applicator block 60a of FIG. 2 is provided with parallel bores 104, which extend coaxially through the entire thickness of the block. 'I'he forward portions of those bores form the valve chambers 105 with the nozzles 106 xedly mounted in them, as by coaxial threads. Nozzles 106 are provided with the orifices 108 with the conical valve seats 110 immediately adjacent them. The needle valves 120 are mounted by means of the elongated spindles 118 on the valve plungers 122, guided in the relatively small guide portions 123 of bores 104, and sealed by the two O-rings 125. Plungers 122 are directly coupled to the valve actuating pistons 134 which work in the cylinders 132 with sealing O-rings 135. Inward movement of each entire piston and valve member is limited by the positive stop 136 which is adjustably threaded in a coaxial bore in the plug member 138. Adjustment of the stop in plug 138 is locked by the nut 139, and the stop member is sealed at 140.

CII

The liquid adhesive to be dispensed through orifice 108 is supplied to all the Valve chambers in parallel via the passage system 142, which is connected to pump outlet conduit 24 as indicated at 144. Control air is supplied selectively "to each valve actuator chamber 132 on both sides of piston 134 via the respective passage systems 146 and 148. Passage 146 on the inner side of piston134 is connected via the -tube indicated at v147 to control conduit 36, essentially as in the structure of FIGURE 1. Passage 148 on the outer side of piston 134 is connected via the tube 149 to control conduit 38. Control air is thus supplied under pressure from valve 42 to passage 148 during periods of adhesive pressurization.

Operation of the mechanism of FIG. 2 is generally similar to that of FIG. l except that the operation of each needle valve is essentially independent of the fluid pressure in passage 142 and valve chamber 105. Each valve is opened by the pressure of control air from passage 148 on the outer face of piston 134, and is closed by pressure of control air from passage 146 on the inner face of piston 134. Thus each valve is positively actuated in both directions in response to control air pressure from control valve 42. Since that control air pressure also controls pump mechanism 22, accurate synchronization of the pump and valve operations is reliably maintained. The mechanism is ythus capable of providing extremely rapid and clean projection and cutoff of the liquid that is dispensed.

In accordance with a further aspect of the invention 1t has been found that under the severe service conditions presented by the relatively high temperature and pressure typically employed in adhesive applicators the live seals at and 135 tend to give only limited service. I have found that the life of such O-ring seals can be greatly extended by mounting them in grooves whose axial dimension is appreciably less than-that normally employed. Rather than providing axial clearance between the rings and the sides of the groove, I preferably reduce the normal groove dimension by from l5 to 30%. The O-ring is then appreciably flattened 0n its axial faces by the opposing sides of the groove. Under that condition, and with the relatively short valve stroke, typically only 0.010 t0 0.030 inch, the O-ring is restrained against rolling and is merely laterally distorted by the valve movement. With the described O-ring channel dimensions satisfactory life of the live seals is obtained.

In order to provide prompt indication of deterioration of the uid seals, I preferably provide an indicator orifice 146 leading from the exterior of applicator block into each valve containing bore 104 at a point between the two piston seals 76 in FIG. 1 and between the two plunger seals 125 in FIG. 2. If the outer one of those seals, which is exposed to the full uid pressure, should start to fail, the-resulting le-ak is made visible promptly by oozing of liquid from orifice 146. That flow is sharply limited by the small orice diameter, shown at its inner end.

The applicator structure of FIG. 2 has the particular advantage that it can be effectively employed either with intermittent pressurization of the dispensed liquid, as has been described, or with continuous pressurization of that liquid. For example, adhesiveA source 10 and pump 22 of FIG. 2 may be considered to represent any suitable means for supplying adhesive under continuous pressure to supply conduit 24, being then isolated from both control conduits 36 and 38` The latter conduits then supply pneumatic control signals from valve 42 only to the passages 146 and 148 of applicator block 60a. With that arrangement the applicator needle valves 120 are operated as already described, and selectively control the intermittent application of the continuously pressurized fluid.

1. A system for selectively applying a fluid to a relatively moving work surface, comprising in combination structure forming a plurality of nozzle orifices mounted adjacent the path of the work surface for projecting pressurized fluid thereon,

first conduit means communicating with all the orifices in parallel,

pump means for supplying a pressurized fluid to the conduit means intermittently in response to pneumatic control signals,

individual valves connected in series between the conduit means and the respective orifices,

a piston mechanism coupled to each of said valves for operating the same,

second conduit means for supplying said pneumatic signals to the piston mechanisms for controlling said valves to permit fluid flow to the respective orifices only during periods of said fluid pressurization,

and means for developing said pneumatic signals in controlled relation to the movement of the work surface.

2. A system as defined in claim 1, and in which said pneumatic signals comprise on signals and ofi signals, the pump means acting to supply pressurized fiuid in response to the pneumatic on signals and to relieve the fiuid pressure in response to the pneumatic off signals,

and said second conduit means supply the off signals to said piston mechanisms in a direction tending to close the valves in response to the pneumatic off signals.

3. A system as defined in claim 2, and in which said piston mechanisms comprise a piston for each valve exposed on one side to the pneumatic off signals for closing the valves during periods of fiuid pressure relief, and exposed on the other side to the fluid pressure in said first conduit means, for opening the valves during periods of said fluid pressurization.

4. A system as defined in claim 1, and in which said valves comprise generally annular valve seats surrounding the respective said orifices immediately inward thereof, and needle valves axially movable with respect to the valve seats and coupled to the respective piston mechanisms.

5. A system as defined in claim 4, and in which said piston mechanisms comprise structure forming cylinders coaxial with the respective orifices, pistons slidable in the cylinders and directly coupled to the respective needle valves, said second conduit means supplying pneumatic signals to the cylinders on at least one side of the pistons.

6. A system as defined in claim S, and in which said second conduit means supply pneumatic pressure signals to the cylinders on the side of the pistons remote from the orifices only during fluid pressure relief,

the sides of the pistons toward the orifices being exposed to uid pressure in the first conduit means.

7. A system as defined in claim 5, and in which said second conduit means supply pneumatic pressure signals to the cylinders on the side of the pistons toward the orifices during said fiuid pressurization, and supply pneumatic pressure signals to the cylinders on the side of the pistons away from the orifices during fluid pressure relief. 8. A system for selectively applying a fiuid to a relatively moving work surface, comprising in combination structure forming a nozzle orifice mounted adjacent the path of the Work surface for projecting pressurized fluid thereon, pump means for intermittently supplying pressurized fluid to the nozzle orifice in response to a control signal, a valve means connected in series between the pump means and the orifice, said valve means comprising a valve actuating piston slidable in a cylinder coaxial with the orifice, a needle valve adapted for closing the orifice and and directly coupled to the piston, control conduit means communicating with at least one side ofthe piston, and sealing means for isolating the control conduit means from the orifice, and control means for supplying control air under pressure intermittently in controlled relation to the movement of the work surface both to the pump means as said control signal to supply pressurized fluid and to the control conduit means to operate the valve. 9. A system as defined in claim 8, and in which said control conduit means comprise valve opening conduit means communicating with the piston on the side toward said orifice and valve closing conduit means communicating with the piston on the side away from said orifice, and said control means act to supply control Iair under pressure intermittently and simultaneously to the pump means as said control signal and to said valve opening conduit means to apply fluid to the work surface, and act to supply control air under pressure intermittently to said valve closing conduit means to terminate fluid application to the Work surface, said air supply to the valve closing conduit means alternating with said air supply to the pump means and to the valve opening conduit means.

References Cited UNITED STATES PATENTS 1,987,046 l/1935 Bergner 118-323 X 2,804,764 9/1957 Runton 118-313 X 3,081,947 3/1963 Walter 239-533 X 3,152,923 10/1954 Marshall et al. 118-2 3,250,247 5/1966 Beaman 118-315 X 3,286,689 11/1966 Ziemba 118-411 3,348,520 10/1967 Lockwood 118-411 X WALTER A. SCHEEL, Primary Examiner.

JOHN P. MCINTOSH, Assistant Examiner.

U.S. Cl. X.R. 118-411

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