Patent Application
20150231655
When applying water-based adhesives by hand spray techniques of the prior art or automated/machine controlled spray techniques for assembly of cushioning materials, such as for the furniture and bedding industries, there is a problem with adhesive overspray. This is because the prior art teaches that water based adhesives are sprayed using air-atomized spraying systems. The overspray presents itself as a “fog” in the factory that can carry long distances from the actual application area of the factory. This fog also creates a nuisance dust health hazard for the employees. Lastly, the fog or overspray wastes resources as the adhesive is lost and not used for its intended purpose. This overspray not only gets onto the employees that apply the adhesive, but also contaminates nearby equipment, finished products or raw materials in inventory, air conditioners, heaters, and lighting.
One solution has been to set up air extraction hoods in the spray area. This works relatively well when the filters are maintained and the types of parts that are being assembled are small. However, when making larger items such as mattresses or large sofa cushions, the usefulness of an air extraction hoods is negated.
Also there have been attempts to control the overspray “fog” by using low fogging air-atomized guns such as the DUX or EasyFlow Laminair spray gun. Although these spray devices minimize the overspray when adjusted properly, they are dependent on the spray operators not adjusting the settings as they can easily be misadjusted and create fog.
Another solution has been to use different types of adhesive bases other than water base. Solvent-based adhesives and hot melt adhesives when sprayed do not create a “fog.” These types of adhesives work well to eliminate the overspray but present other problems.
Solvent-based adhesives contain hazardous materials and often are flammable. They require air-extraction equipment to reduce the flammability hazard as well as the health hazards to employees. Also, solvent adhesives do not adhere to some types of visco-elastic foams.
Hot melt adhesives typically do not bond foam cushion substrates as well as water-based or solvent-based products. Hot melts also require melt tanks and heated hoses and this equipment is more expensive on a per gun basis than water-based or solvent adhesives.
Another solution is the roll coating of water-based adhesive rather than spray application. Roll coating eliminates the overspray, but suffers additional problems because the rollers are exposed to the atmosphere. As such, during any down time at all, the adhesive on the rollers can coagulate, causing inconsistent application of the adhesive. In addition, at the end of a shift, the workers must clean the rollers which adds to the system downtime and taking away working time from the workers. Further still, rollers do not allow a control of the application rate over a surface. Although roll coating provides a consistent application of adhesive across an entire surface, sometimes it is advantageous to vary the application rate of the adhesive. For example, it may be advantageous to use more adhesive in one area and less in another, thereby using less adhesive overall.
The subject matter of this application may involve, in some cases, interrelated products, alternative solutions to a particular problem, and/or a plurality of different uses of a single system or article.
In one aspect, the present invention comprises an airless adhesive spray gun system. The system may have an airless adhesive spray gun, and a quantity of water-based adhesive connected to the spray gun. The spray gun comprises a handle, a trigger attached to the handle which controls the position of an actuating needle, the needle being movable between a closed position and an open position. The spray gun further comprises an adhesive inlet port through which the quantity of adhesive is connected, a nozzle interior portion comprising an inlet end, outlet end, and an interior, the interior having an increased width portion, an orifice, and a needle seat configured to sealingly receive the actuating needle when the needle is in the closed position, the needle exposing the orifice when in an open position, allowing flow of the adhesive through the orifice. As noted, the quantity of adhesive is connected to the airless adhesive spray gun through the adhesive inlet port, the quantity of adhesive being a water-based adhesive, a pressurizing structure providing the quantity of adhesive to the airless adhesive spray gun under pressure of less than 150 psi. The nozzle configuration, as well as gun structure such as a nozzle interior portion, is such that it atomizes a quantity of adhesive as the adhesive passes through the nozzle orifice when provided to the airless adhesive spray gun at a pressure of under 150 psi.
In another aspect, a mechanized, or automated, airless adhesive spray gun system is provided. The mechanized system may have an airless adhesive spray gun and a quantity of adhesive connected to the spray gun. The spray gun comprises a mechanically controlled handle, a mechanically controlled trigger, the trigger controlling the position of an actuating needle, the needle movable between a closed position and an open position. The spray gun further comprises an adhesive inlet port, through which the quantity of adhesive is connected, a nozzle interior portion comprising an inlet end, outlet end, and an interior, the interior having a substantially straight fluid flow portion, an orifice, and a needle seat configured to sealingly receive the actuating needle when the needle is in the closed position, the needle exposing the orifice when in an open position, allowing flow of the adhesive through the orifice. In some embodiments, the nozzle interior portion orifice may be formed as part of the needle seat. As noted, the quantity of adhesive is connected to the airless adhesive spray gun through the adhesive inlet port, the quantity of adhesive being a water-based adhesive, a pressurizing structure providing the quantity of adhesive to the airless adhesive spray gun under pressure of less than 150 psi. The nozzle, nozzle interior portion, and spray gun configuration is such that it atomizes a quantity of adhesive as the adhesive passes through the outer nozzle orifice when provided to the airless adhesive spray gun at a pressure of under 150 psi.
The present invention concerns a water-based adhesive that can be applied by “airless” spray techniques. In one embodiment, this adhesive can be supplied in a ready to use aerosol can. The can may use bag-in-can technology, or the adhesive may be stored directly within the container. In a bag-in-can embodiment, the adhesive is injected into the bag. The bag is placed inside of a can that can hold pressure. In the space between the bag and the can, nitrogen or carbon dioxide or some other gas is inserted until sufficient pressure is reached to cause the adhesive to be expelled and atomized properly. In other embodiments, the adhesive can be supplied by bulk means and pumped, pressure pot-supplied, or by other similar pressurizing structure provided, to an “airless” spray gun. For example, bulk containers sized between one gallon to a tank wagon-sized container may be used. The adhesive may be stored directly in the tanks (as opposed to in a “bag-in-a-can” embodiment). The adhesive in the tank is provided in either pressurized or non-pressurized containers. The tank is connected to the spray gun by at least one hose and the adhesive is pumped or otherwise provided under pressure to the spray gun to provide the pressure required for operation.
Generally it is the case for sprayed adhesives that the better an adhesive works to adhere, the worse it performs in a sprayed application. This is because the application of pressure, as well as the shear forces caused by forcing the adhesive through piping, spray gun internal flow paths, and a spray nozzle, all cause the adhesive to coagulate and start acting as an adhesive as opposed to a fluid. The air-atomized spray guns used in the prior art seek to limit the forces on the adhesive by using air atomization, and using low pressure feeds. An airless spray gun/system only magnifies the problems faced above: Airless spray guns and systems use higher pressure, have faster moving fluid (causing higher shear forces), and force the adhesive through a very small hole to cause it to atomize without the use of an air curtain or air stream. As such, airless spray guns have not been considered as an option in this field. The present invention unexpectedly overcomes these issues, using an airless spray gun with a specially designed adhesive to achieve airless spraying without the downfalls that would normally be expected and, further, resulting in a process that overcomes the issues of air-atomized spray guns, namely overspray.
The atomization of the adhesive is caused when the adhesive is expelled through the airless gun tip that atomizes and spreads the adhesive into a controlled spray pattern. This is in contrast to an air-atomized spray gun which atomizes the adhesive using an air stream or air curtain. The airless spray gun and adhesive sprayed through it eliminates the problem of overspray fog seen in the prior art. In particular, it has been observed that the present invention saves 30-40% of adhesive used compared to air-atomized spray guns, in large part because of the elimination of this overspray. While typical airless spray guns operate at 300 psi or above, the present invention achieves an airless spray at under 150 psi. In a particular embodiment, the present invention achieves an airless spray at approximately 20-60 psi. In a particular embodiment, the spray gun may achieve spray at an interior pressure of approximately 20-40 psi. In another particular embodiment, the spray gun may operate at an interior pressure of approximately 20-25 psi. The pressure is provided to the adhesive by some sort of pressurizing structure, which could be the adhesive stored under pressure, a pump, gravity, or any other structure or system that may provide a fluid under pressure. It has also been observed that bonding is faster and stronger with the present airless spray gun adhesive application than in the air-atomized spray gun found in the prior art. This may be because of larger droplets in the airless spray gun system (compared to an air-atomized system), which penetrate further into the material to be bonded, resulting in a stronger bond at a lower adhesive application rate. The strength of this bonding can be seen in the chart provided in
In further embodiments, the airless spray gun may be replaced with a mechanized or automated spraying machine. In this embodiment, the spray device may be automated, as opposed to controlled by a person using a hand spray gun. In this embodiment, sensors such as optical, location-based, thermal, and the like, may control the activation of the spray nozzle, activating the spraying onto the desired surface. Robotic assembly may also be involved in these embodiments. It may be particularly important to avoid overspray in mechanized embodiments because the expensive machinery will be fouled by the adhesive cloud, jamming the machinery and otherwise leading to wear and tear or malfunction.
Typically the water-based adhesives that are designed to work for foam fabricating tend to have reduced mechanical stability. This foam fabricating may be performed in the present invention as wet bonding, allowing more rapid assembly of the adhered components so that there is no waiting time between spraying and adhering, which there would be if the adhesive had to dry to be operational. This reduction in mechanical stability causes many water-based adhesives to clog or coagulate when pumping or pressure-pot delivering to spray guns. Also, the small size of the airless spray nozzles causes the nozzles to clog and therefore not spray consistently or effectively. As such, water based adhesives, particularly for foam adhesion and other product manufacturing processes including lamination adhesion processes (such as assembly of counter tops, and the like) are not used in airless spray applications.
However, the adhesive used herein is mechanically stable enough to withstand the mechanical shear forces encountered with airless spraying, yet it has enough instability to work in the application by providing instant grab or tack.
It is known that water-based glues that work in this market are not stable enough to be sprayed using airless technology. Also the viscosities of current adhesives tend to be too high to atomize well using airless technology. They also tend to clog the nozzles of the airless gun as well as coagulate inside the airless gun due to the higher shear forces encountered during the airless spraying.
When using airless guns to deliver our water-based adhesive, the overspray fog is eliminated. Spray operators are not exposed to “nuisance dust” hazards. The factory, equipment, inventory, lighting and air-handling systems remain adhesive free. Also it was unexpectedly found that the final bonding of the adhesive was faster when sprayed using airless guns than with air-atomized guns. Further, airless spray guns are limited to have minimal or no adjustments that a spray operator can easily make to the spray device. This eliminates the problems associated with the adjustments that can be made with air-atomized spray guns. Air-atomized spray guns can have the following adjustments: Atomization air, fan width air, and fluid needle. Any changes in these adjustments can cause overspray fogging or over-application of adhesive.
The adhesive is selected and intended for use in the present invention is a water-based dispersion with no co-solvents. The spray gun, and particularly the nozzle therein, is configured to carefully destabilize the selected dispersion so that it coagulates very quickly with shear forces from the spraying process. In many cases, this destabilization prevents similar adhesives from being used with an airless spray gun. However, the particular water-based dispersion selected is resilient enough to maintain its flow properties under the shear forces of the spraying. Further, the water-based dispersion adhesive selected and used herein in the airless spray gun has a low viscosity and is somewhat more stable to shear forces than other formulations known in the art. However, the adhesive used herein also has enough instability to cause the emulsion to break quickly after spraying under the shear forces from the nozzle of the spray gun. This breaking allows the adhesive to be able to adhere quickly and hold strongly enough for its applications. In one embodiment, the adhesive may be used in foam fabrication such as that used in the furniture and bedding industries.
Particularly, the adhesive contemplated herein is a polychloroprene latex base that can have other lattices such as styrene butadiene rubber (SBR), Acrylic, Vinyl Acetate Ethylene (VAE), Poly-Vinyl Acetate (PVA), Vinyl Acrylic, Nitrile, and the like added as well. A pH of the adhesive is lowered using Glycine, or other acid such as glycolic, lactic, citric, ascorbic, boric, and the like. Stabilizers are further added. The stabilizers may be any of: Anionic soaps, nonionic surfactants, polymeric thickeners, and water. In a particular embodiment, the adhesive used herein may be Fabond 1226, 1404, or equivalent from Worthen Industries.
The unique nozzle of the present invention may be configured to allow a metal needle of the spray gun to fit into a metallic seat of the nozzle. This allows the adhesive to be more closely controlled without being damaged or deformed during operation. While other materials may be used to seat the needle of the spray gun as long as the needle moves perpendicularly to the nozzle opening, metal has been determined to be superior, particularly over the life of the spray gun. However, in another embodiment, a plastic material may be used to form the entire interior nozzle, therefore the present invention is not limited to a metallic seat for the nozzle. Generally, the needle and seat may be configured in any manner to prevent leakage of a lower viscosity adhesive that is also capable of providing a clean seal when stopping the spraying process. As noted above, the prior art teaches that adhesives of the types described above cannot be used in airless spray gun applications because they are not stable enough to withstand the shearing forces of the spray gun without coagulating and jamming the spray gun. However, it has been unexpectedly observed that with a proper balance of adhesive properties, an airless spray gun may indeed be used with the right adhesive, proper nozzle sizing and spray gun configuration. In a particular embodiment, the nozzle may have an inner orifice and outer spray tip. This nozzle may have an outer spray tip orifice size of approximately 0.127 mm to 1.35 mm. In a further embodiment, the outer spray tip orifice size may be approximately 0.66 mm. In some embodiments, the orifice may have an orifice outer size of 0.28 mm to 5.16 mm (0.011″-0.203″) measured horizontally across the nozzle when straight up and down. In a particular embodiment the orifice outer size may be approximately 0.51 mm-0.76 mm (0.020″-0.030″). However, it should be understood that other varying orifice sizes may be used without straying from the scope of the invention. The nozzle may be angled to provide a desired pattern and pattern width at a certain distance. Some non-limiting examples of nozzle angle include 110, 95, 80, 73, 65, 50, 40, 25, and 15 degrees.
In one embodiment, a spray gun configured for air-atomization was modified to be an airless spray gun by using a nozzle having orifice sizes within the ranges noted above, as opposed to the larger orifice sizes used in air-atomized spray guns. The specially selected adhesive was then used through this particular modified spray gun, yielding positive results. Many air-atomized spray guns have larger internal fluid (adhesive) flow paths than their airless counterparts, as such, this aided in the airless spraying by exposing the adhesive to fewer shear forces.
In summary, the present invention involves a combination of adhesive formulation, with the modification of an airless spray gun in order to come up with a unique invention. The problems of water-based airless sprays are numerous such as: Corrosion to the container that ruins the adhesive, problems with gun tip cleanliness, incompatibility with propellants, need for high solids for fast drying, the need for high pressure, typically above 300 psi to achieve atomization (which will immediately destabilize a water based one-component adhesive-clogging the spray gun), valve seat leakages, clogging of spray gun internal chambers, and the like. The combination of our adhesive with the modified gun has solved all of the problems with airless spray and has also solved the overspray issue seen in the air-atomized spray guns for product assembly where adhesive is applied to one or both surfaces to be bonded and the parts are either immediately put together or are allowed to dry some period of time before assembly.
Turning now to
While several variations of the present invention have been illustrated by way of example in preferred or particular embodiments, it is apparent that further embodiments could be developed within the spirit and scope of the present invention, or the inventive concept thereof. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present invention and are inclusive, but not limited to, the following appended claims as set forth.
| Number | Date | Country | |
|---|---|---|---|
| 61941952 | Feb 2014 | US |
