US3537653A - Adhesive applicators - Google Patents

Description

Nov. 3, 1970 R. was, 3,537,653

ADHESIVE APPLICATORS Filed July 30, 1968 United States Patent 3,537,653 ADHESIVE APPLICATORS Reginald Jones, Sheflield, England, assignor to Stabilag Engineering Limited Continuation-impart of application Ser. No. 637,294, May 9, 1967. This application July 30, 1968, Ser. No. 748,783 Claims priority, application (resat Britain, May 10, 1966,

Int. Cl: Bb 1/30 US. Cl. 239533 2 Claims ABSTRACT OF THE DISCLOSURE This invention relates to apparatus for applying a hot melt adhesive to a surface where adhesive is required, for example a carton, cigarette packet or continuous web, and is a continuation-in-part of US. specification 637,294 filed May 9, 1967, now abandoned, in which apparatus for applying a hot melt adhesive includes a container and means for melting'the adhesive in the container, at circulating line for leading the melted adhesive to one or more application points, and a pump for driving the adhesive through the line, a nozzle at the or each application point arranged to be operated in response to rise in pressure of the adhesive in the line above a preset pressure, and means enabling the pressure in the lines to be selectively raised above the set pressure. Such apparatus will hereinafter be referred to as of the type defined.

It is the case with the apparatus of US. specification 637,294 that the control of the nozzles is solely by the pressurising device, so that if it is required that one or more nozzles connected in the line is or are not required to dispense adhesive then the pressure control device is prevented from causing the build-up in pressure required to operate the nozzles, with the result that none of the nozzles connected in the line are able to dispense adhesive.

It has now been found that in certain circumstances it is desirable to have additional control means to that provided by the pressure control device so that should the need arise, an individual nozzle can be prevented from dispensing adhesive while the remainder of the nozzles in the line continue to function in response to the buildup ofpressure caused by the pressure control device.

According to the present invention, apparatus of the type defined for applying a hot melt adhesive comprises a simple shut-off valve in the or each nozzle operated by a pressure responsive device which is biassed towards the closed position of the valve, there being an air inlet to the side of the pressure responsive device remote from the valve for the selective admission of pressure air to prevent opening of the valve in response to the rise in pressure of the adhesive created by the pressure control device.

The pressure responsive device may be biassed towards the closed position of the valve by a spring, but preferably, the pressure responsive device is air biassed. In either case, the load on the pressure responsive device is Patented Nov. 3, 1970 such as can be overcome by the rise in pressure of the adhesive, and to prevent actuation of an individual nozzle, pressure air is admitted in the first case, or additional pressure air in the second case, so that the load on the pressure responsive device is such that it will not be overcome by a rise in pressure in the adhesive.

In this way, individual nozzles in a series of nozzles fed by a common line can be selectively prevented from dispensing adhesive if, for example, supply of articles (to receive adhesive) to any one or more nozzles becomes discontinuous, and which does not warrant closing down the whole apparatus.

One embodiment of the invention will now be described with reference to the single figure in the drawings, which is a sectional side elevation of a nozzle for dispensing adhesive to be used in conjunction with the apparatus fully described in US. specification 637,294.

The nozzle 1 has a straight sided orifice 2 which is normally closed by a tungsten carbide pad 3 on a stem 4 forming an extension of a piston 5 sealed by rings 6 in a cylinder 7 formed in the body of the nozzle. The stem 4 continues above the piston 5 to a piston 8 in a cylinder 9, an inlet 10 admitting pressure air at a constant pressure to bear on the piston 8 to urge the valve member 3 against the orifice 2 to close the nozzle. The air inlet 10 is connected to a source of pressure air by a line 11.

It will be seen that the pressurised adhesive circulating through the chamber 12 through inlet and outlet passages 14 and 15, respectively from the pressurising device (not shown) passes through a chamber 12, one wall of which is defined by the piston 5, so that if the pressure in the line rises sufficiently to overcome the restraint of the air bias, the piston 5 will move against the spring 16 to open the valve 3 and allow the adhesive to be applied through the orifice 2. However, if for any reason adhesive is not to be applied by any one of the series of nozzles, e.g., because a carton or the like is not in position below the nozzle, then the supply of pressure air is actuated to admit additional pressure air to the cylinder 12 to hold the valve closed against the increased pressure in the adhesive. By this means, any abnormalities in the supply of, e.g., cartons to the nozzles does not necessitate the halting of the means creating the increased pressure in the adhesive.

The valve member 3 has a flat valve closing surface and the orifice 2 is a circular straight-sided opening through a flat lower wall of the valve chamber. The length of the orifice is equal to or greater than four times its diameter and this ensures that the vena contracta connecting adhesive flowing through the orifice with the mass of adhesive in the chamber occurs in the length of the nozzle and not outside it, so that severing of the applied adhesive from the main body is simplified when the pressure drops and the valve closes. The tungsten carbide valve member is advantageous in that it does not deform under the relatively high pressures at which the system operates.

Despite the precautions taken to seal the piston 5, it is always the case that a small proportion of adhesive leaks past it and into the cylinder 7 above it. Therefore bleed holes '13 are provided through which adhesive can be ejected as the piston 5 is raised. Also, similar bleed holes 13 are provided in the wall of the cylinder 9 to provide for ejection of any adhesive that has leaked into that cylinder.

What I claim is:

1. Apparatus for applying a hot melt adhesive to workpieces, comprising a first cylinder having a first piston disposed for axial movement therein, said piston and cylinder defining beneath said piston an adhesive chamher with a nozzle orifice at the lower axial end thereof, a valve member carried by said piston for movement into and from sealing relation with respect to said orifice, there being adhesive inlet and outlet passages communicating with said chamber in all positions of said valve member for constantly circulating liquid adhesive through said chamber, said liquid adhesve being under pressure and exerting force on said piston in a direction tending to unseat said valve member, a second cylinder axially aligned with said first cylinder, means interconnecting said first and second pistons for movement together, and means for conducting pressurized fluid into said second cylinder only on the side of said second piston remote from the first piston, for thereby applying a force to said second piston in a direction to seat said valve member.

2. Apparatus as in claim 1, including a spring within said second cylinder thrusting against said second piston in a direction to seat said valve member.

References Cited UNITED STATES PATENTS 1,311,760 7/1919 Davis 239-412 X 1,332,544 3/1920 Davis 2394ll 1,380,866 6/1921 Day 239-412 10 M. HENSON WOOD, JR., Primary Examiner.

M. Y. MAR, Assistant Examiner US. Cl. X.R.

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