Patent Application
20060225832
The present invention generally relates to an adhesive dispensing system, and more particularly, to an adhesive dispensing system for temporarily unitizing substrate surfaces.
When cartons, packages or bags are adjacently stacked, it is often desirable that the items remain temporarily in a stable group, or unitized. Unitization is particularly advantageous in the context of warehousing, palletizing and transportation operations. For example, large numbers of packages may be piled onto wooden pallets and moved from different locations on forklifts. The pallets are raised on elevators for warehouse storage, or for long distance transport. When the stored item is actually used, the cartons are de-unitized, or separated, so that a single package can be picked up and carried, for example, by a plant operator.
Conventional materials used to unitize package, bag, pallet and other substrate surfaces include tape, glues, hot melt adhesives, plastic straps and stretch wrap films. While these materials and their associated application processes generally succeed in securing packages to each other and/or a pallet, the subsequent de-unitizing of the substrates can be problematic. For example, conventional adhesives may damage package surfaces upon separation. Conventional adhesives routinely leave sticky balls or other residue along formerly bonded surfaces when packages are removed from each other or the pallet. Adhesive placement and tackiness often makes carton removal from a pallet difficult, requiring exertion and/or tools, such as shears or a crowbar. Such separation practices can damage graphics and compromise package integrity.
There is consequently a need for improved bonding methods that bond substrate surfaces in a manner that facilitates de-unitization.
The present invention provides improved fluid dispensing processes configured to securely unitize substrates in manners that address the problems of the prior art. In one aspect, the invention includes a method for applying an energy reactive adhesive to a first surface of a surface on a substrate. For instance, the energy reactive adhesive may be sprayed or otherwise applied onto the substrate as it moves along a conveyor. The first surface of the substrate is temporarily bonded to a second surface using the energy reactive adhesive. The first and second surfaces may then be moved as a single unit. For example, a number of cartons can be adhesively secured together for movement or storage.
The bonding capability of the energy reactive adhesive is reduced when exposed to a source for radiating energy within the electromagnetic spectrum, excluding infrared radiation. A typical source for radiating energy radiates ultraviolet light. The reactive adhesive is exposed to the source for radiating energy when de-unitized. To this end, a mechanical arm may be used to separate the first and second surfaces in order to better expose the energy reactive adhesive to the source for radiating energy. The radiation exposure causes the temporary bonding characteristics of the light reactive adhesive to be reduced, so that a package, bag, carton, box or other container, and/or a pallet or other substrate may consequently be easily separated without tearing or defacing their outer surfaces. As such, substrates are economically and efficiently unitized and de-unitized in a manner that mitigates or eliminates residue and surface damage.
These and other objects and advantages of the present invention will become more readily apparent during the following detailed description taken in conjunction with the drawings herein.
The system 20 applies the energy reactive adhesive 26 on and/or between substrate surfaces, and upon setting (which may be immediate or nearly immediate), yields a bond having high shear strength and tensile forces. The bond helps prevent the substrates 28 from sliding across one another during warehousing operations, such as forklift maneuvers, palletizing, storage and/or subsequent transport.
Conversely, the temporary bond formed between the substrate surfaces is readily reduced from exposure to a positioned source for radiating energy. After the subsequent exposure to the radiated energy, the substrates separate and lift off of a pallet or other substrate surface easily, causing little or no damage to package graphics. While suitable energy radiating sources may include devices that radiate energies having wavelengths of less than about 700 nanometers, the system 20 shown in
The dispensing system 20 of
Referring more particularly to
Particularly advantageous temporary bonding characteristics may be achieved using high vinyl styrene-butadiene-styrene (SBS) or rubber-based pressure sensitive adhesives mixed with a photoinitiator. For example, a commercially available formulation of energy reactive adhesive available from Kraton Polymers, Inc. of Houston, Tex., which comprises KX-222 high vinyl SBS with at least five parts per hundred of Ergacure 651 photoinitiator, has proven to be particularly effective in temporarily unitizing substrates. One skilled in the art will further appreciate that while a combination of SBS-based pressure sensitive adhesive with a photoinitiator may have particular advantages in certain embodiments, other energy reactive adhesives may be substituted in accordance with the principles of the underlying invention. For instance, while radical photoinitiators may be particularly advantageous in certain embodiments, one skilled in the art will appreciate that other photoinitiators, including cationic photoinitiators, may have equal application.
In any case, the photoinitiator of the energy reactive adhesive 26 will not react with a mixing agent by itself. The photoinitiator of one preferred embodiment must absorb ultraviolet light before the photoinitiator will undergo a chemical reaction. That reaction may produce byproducts that cause the energy reactive adhesive 26 to harden. More particularly, the light transforms the tacky (adhering) energy reactive adhesive 26 into a hard and non-tacky (non-adhering) cross-linked polymer network.
A conveyor 30 of the system 20 carries the substrate 28 past the dispensing gun 22. The conveyor 30 is mechanically coupled to a conveyor drive having a conveyor motor 32. A conveyor feedback device 34, for example, an encoder, resolver, etc., is mechanically coupled to the conveyor 30 and detects conveyor motion. The feedback device 34 is used by a system control 40 to determine the position of the substrate 28. This positional information, in turn, may be used to determine when processes for applying light reactive adhesive should be initiated for optimal adhesive placement.
The system control 40 generally functions to coordinate the operation of the overall dispensing system 20. For example, the system control 40 typically controls the operation of the conveyor motor 32 and also provides a system user input/output interface (not shown) in a known manner. Further, the system control 40 manages the dispensing gun 22 as a function of a particular application and/or part being run.
The system control 40 receives, on an input 46, a part present or trigger signal from a trigger sensor 38. The trigger sensor 38 is positioned to detect a feature, for example, a leading edge 99 of the substrate 28 moving on the conveyor 30. For instance, the trigger sensor 38 may detect the leading edge of a carton flap or pallet. The trigger sensor 38 may comprise a photocell or other proximity sensor.
A gun driver 48 is responsive to command signals 50 from the control 40 and provides output signals 56 to a dispensing gun coil 54. The output signals 56 energize and de-energize the gun coil 54 to operate the dispensing gun 22 as a function of the timing and duration of the command signals 50 from the system control 40. More particularly, the signals 56 from the gun driver 48 creates current flow through the gun coil 54, thereby building up a magnetic field that lifts an armature 58 and a dispensing valve 60 connected thereto, applying the energy reactive adhesive 26 onto the moving substrate 28. While the above-described gun coil embodiment is effective in dispensing energy reactive adhesive, other dispensers known in the art may be used to dispense energy reactive adhesive in accordance with the principles of the present invention.
As shown in
A memory 43 of the system control 40 typically stores an adhesive dispensing pattern 44. The adhesive dispensing pattern 44 represents a series of dispensing cycles associated with a substrate 28 that result in a desired pattern of energy reactive adhesive deposits 26 thereon. For instance, the pattern 44 is used along with the dispensing program 45 to accurately place the energy reactive adhesive 26 in a manner that optimizes both temporary adhesion and eventual exposure to radiating energy.
Through conveyance and other automated processes, the package substrate 28a and adhesive 26 may have been subsequently oriented and/or contacted with the surface 64b of the second package substrate 28b. While shown in
The energy reactive adhesive 26 shown in
The upward movement of the arm 98 may communicate forces to the bottom surfaces 97a, 97b of the substrates 28a, 28b causing the top surfaces 99a, 99b of the substrates 28a, 28b to separate. This separation allows energy radiating from the source 95 for radiating energy to reach the energy reactive adhesive 26. In another embodiment, the arm may be stationary and the substrates may be made to bump into or slide over the arm to achieve a similar separation. In any case, the system 93 uses mechanical forces transferred by the arm 98 to the substrates 28a, 28b to achieve communication between the radiating energy source 95 and the energy reactive adhesive 26.
More particularly, the arm 98 shown in
The arm 98 may return to its original, lowered position after the reactive adhesive 26 has been exposed. In another embodiment, a comparable arm, or ridge may continuously remain above the surface of the conveyor surfaces to create a gap between the substrates as they roll over the ridge. One skilled in the art will recognize that there are a number of other manners in which a gap between substrate surfaces may be formed to facilitate light exposure in accordance with the principles of the present invention.
Where the radiating source comprises an ultraviolet light, for example, the temporary bond of the light reactive adhesive 26 begins to destabilize, or weaken, in response to the light exposure. For instance, the photoinitiator of the energy reactive adhesive 26 may become activated, cross-linking the styrene-butadiene-styrene. This cross-linking dramatically reduces the tackiness of the adhesive 26.
Only a short light exposure is typically required to sufficiently destabilize the temporary bond. Once destabilized, substrates 28a, 28b may be readily separated off of the conveyor 96a, 96b or pallet. Moreover, the energy reactive adhesive 26 does not damage graphics or form sticky balls associated with some fugitive adhesives and tape, among other conventional unitizing materials.
The adhesive sets at block 106, temporarily bonding the substrate surfaces 64a and 64b. The time needed for curing the adhesive 26 may vary and/or be accelerated using blowers and temperature variance, as is known in the art.
Once unitized at block 106, the bonded substrates 28 may be manipulated at block 108 as a single unit. For instance, the unitized substrates 28a and 28b may be conveyed or otherwise transported to a next processing station, e.g., a machine for palletizing substrates that more efficiently processes two substrates at a time. Another example may include a scenario where it is more efficient to transport palletized or otherwise unitized substrates in a warehouse while they await shipment.
The system 20 applies the energy reactive adhesive 26 in a manner that takes into account that the adhesive 26 must ultimately be exposed to a radiating source 95. The placement and amount of the energy reactive adhesive 26 applied may consequently be influenced by the manner in which the energy radiating source 95 is intended to communicate with the substrates 28a, 28b and adhesive 26. For instance, the adhesive 26 may be dispensed on a portion of a surface of a substrate that will be closest and/or most exposed to the source during de-unitization.
At such time as it becomes desirable to de-unitize the substrates 28a, 28b, the energy reactive adhesive 26 is exposed at block 110 to energy from a source 95. The radiating source 95 typically emits ultraviolet light, but for purposes of this specification may alternatively produce energy having any wavelength and frequency of the electromagnetic spectrum, other than of infrared radiation. That is, wavelengths are typically near ultraviolet light (40-400 nanometers range), but energies associated with other wavelengths may alternatively be used. For instance, photoinitiators expanding into the visible light range, or on the blue side to deep ultraviolet, may be commonly used. In any case, the radiated energy is suited to reduce the bonding characteristics of the energy reactive adhesive 26.
The unitized substrates 28a and 29b may be manipulated to increase the exposure of the light reactive adhesive 26. For example, the substrates 28a, 28b may have mechanical forces automatically or manually applied to them in order to maximize the light exposure of the light reactive adhesive 26.
The de-unitized substrates 28a and 28b are separated at block 112 of
An aspect of the invention capitalizes on the accuracy of dispenser systems 20 to strategically and efficiently apply the energy reactive adhesive 26 on and/or between substrate surfaces 28a, 28b. The placement and properties of the adhesive 26 yield a bond having high shear strength and tensile forces upon curing. The bond helps prevent the substrates 28a, 28b from sliding across one another during warehousing operations, such as forklift maneuvers, storage, pre-palletizing and/or subsequent transport. Conversely, the temporary bond formed between the substrate surfaces 28a, 28b is readily reduced from exposure to the positioned radiating source.
The reactive adhesive 26 provides a number of advantages over known unitizing systems, providing packagers with relatively inexpensive and stable method of temporary bonding substrate surfaces. Moreover, this unitizing is accomplished without the residue and adverse affects of some cold glues, scored tape or hot melt adhesives. Further, the reactive adhesive 26 typically does not include any volatile organic compounds.
Because the reactive adhesive produces neither solid waste nor surface damage, the adhesive 26 does not interfere with the reading of graphics or product codes. Moreover, the reactive adhesive 26 can be applied in a very thin layer. The layer may be clean and clear when set. Substrate surfaces 28a, 28b do not re-bond to one another after they are separated.
The reactive adhesive 26 is further ideal for automated dispensing operations or integration into automatic palletizers, increasing throughput. The reactive adhesive may be prepared and stored for long periods. In one embodiment, the de-unitized adhesive layer is chemically and physically resistant, providing additional protection to cardboard, paper, plastics, wood or metal substrate.
While the present invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail in order to describe a mode of practicing the invention, it is not the intention of Applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications within the spirit and scope of the invention will readily appear to those skilled in the art.
