The present invention relates to a joinery process for assembling parts to a joinery process using adhesive to produce cabinetry assemblies having fastener free joints.
The use of adhesive to assemble product assemblies is well-known. The joinery process used for an exemplary assembly may be defined by several characteristics, including the type of adhesive used, the application technique for the adhesive, the curing environment and conditions, and the properties of the individual assembly parts. As such, certain joinery processes are known in specific art fields, such as for example, processes for the assembly of cabinetry components.
Cabinets are in wide spread use in commercial and residential settings, including kitchens, baths and storage areas. Conventional kitchen and bathroom cabinets, cabinet doors, framing, and trim are assembled by use of tongue-and-groove structure or other indexing methods for attachment geometries. These tongue-and-groove assemblies are generally assembled with white glue (PVAc adhesive) or other wood adhesive, and are typically secured by one or more a mechanical fasteners, e.g., a nail, wire, or staple, to prevent relative part movement during the curing of the adhesive. The fastener acts to secure the parts together in the assembly, such that the parts remain joined during subsequent assembly work. This joinery technique relies upon the one or more metal fasteners to hold the assembled parts together after the parts are unclamped if curing is not sufficiently complete.
Another conventional method of assembly requires a set of external clamps to hold the parts in place, relative to each other, while the adhesive is curing. The clamping time must be of a sufficient length to achieve a bond strength adequate for subsequent handling. The curing time required may be minutes in length, causing this method to be relatively expensive and undesired. Further, many clamps are required for long periods of time. The number and variety of clamps also require considerable assembly line space.
The characteristics of some adhesives used in the art also cause undesired conditions. Some joinery adhesives cure slowly, and only when exposed to ambient conditions, so that no acceleration of cure is possible.
The specific application method of an adhesive is also an important characteristic. Conventional joinery technique uses adhesive dispensers that apply adhesive through a circular orifice, and are metered by pressure, regardless of temperature, viscosity of the adhesive, or the thixotropic condition of the adhesive. Generally, a bead of adhesive is applied to the groove side of the parts to be assembled, and then the parts are roughly assembled, and then clamped. Often, excess adhesive squeezes out of the joinery gaps, and the excess contaminates the visible surfaces, and results in the need for a repair or the marketing of a defective finish on the assembled part.
A method of making a fastener free cabinet component is disclosed. An embodiment of the invention includes assembling a plurality of cross rails and a plurality of stiles using a predetermined amount of adhesive. The amount of adhesive does not exceed a bond gap volume between the rails and the stiles. The embodiment offers reduction in material cost, cycle time and production costs over prior art processes.
Further features and advantages of the invention will become apparent from the following detailed description made with reference to the accompanying drawings.
a is a top view of a portion of the cross rail of
b is a top view of a portion of the cross rail of
This Detailed Description of the Invention merely describes embodiments of the invention and is not intended to limit the scope of the invention in any way. Indeed, the invention as described is broader than and unlimited by the discussed embodiments, and the terms used have their full ordinary meaning.
The present invention overcomes many deficiencies of the prior art. The present invention includes a process for manufacturer of a cabinet assembly. The assembly includes fastener free joints. The process features several advantages over the prior art, including reduced cycle time, reduced cure time, reduced number of external clamps, and reduced material cost without decreasing bond strength.
This invention is a joinery process in which an adhesive is metered, dispensed, and distributed, and the elements to be joined are clamped and the adhesive is dried or cured. The process achieves a low cost, high green strength, fast cure or dry, and high final-strength, with distribution and bond limited to the joint, rather than outside of the joint. The joinery may be mobile, within a moving clamp, for processing and can include the step of accelerating the cure of the adhesive. The joinery can be assembled without mechanical fasteners such as nails, screws or staples, because the high-strength and fast cure allows for fastener-free assembly. The joinery may include the application of a water mist to increase curing speed of certain adhesives.
For exemplary purposes only, the invention will be discussed in relation to a mortise and tenon joint design. It should be apparent to others with ordinary skill in the art that the invention could be practiced with other joint designs, such as for example, French dovetail, miter, and various wedge shaped designs. Furthermore, joint designs of various tolerances can be used in the practice of the present invention. This joint assembly is also applicable for regular mortise and tenon construction, miter construction, e.g. 45 degrees, or any intermediate angle joint or lap construction.
A preferred embodiment of the present invention includes the application of adhesive to the ends of the tenons, as opposed to the application of adhesive to the mortise of door and frame joints. In other words, the application of the adhesive is made to the tongue of the tongue-and-groove assembly, otherwise known as the tenon in a mortise-and-tenon joint. Various adhesives, bead application techniques, and application patterns may be used in the practice of this invention.
Referring now to the drawings,
It should be understood that the invention can be practiced to produce a wooden cabinet frame, a wooden cabinet door, or any other assembly having joints bound by an adhesive. It should also be understood that wood rails and wood panels are discussed for exemplary purposes only and the invention can be applied to a wide variety of structures, designs, and component materials, such as for example, plastic, corrugate, or metal. Further, the assembly produced can have any number of rails, dividers or styles and be shaped to include right angles, obtuse angles, acute angles, or any combination thereof.
The frame 12 of the wall cabinet 10 is formed by four mortise and tenon joints bonded only by an adhesive. No fasteners of any type are required to complete the bonds. The stiles are machined to form a mortise, or a groove, and the rails are machined to form a tenon, or a projecting tongue. Specifically, a tenon is formed on either end of the rails 14a, 14band a mortise is formed on one edge of the stiles 16a, 16b. In
Another example of a cabinet assembly having mortise and tenon joints is a cabinet door. A front perspective view of a cabinet door 30 constructed in accordance with an embodiment of the present invention is shown in
Referring now to
The profiles of an individual mortise and tenon need to be machined to a profile tolerance so that when the parts are mated, the gap between the parts is near to uniform. Consequently, the bond gap space will be uniform for adhesive consistency and strength optimization. For purposes of example only, a typical tolerance for a profile of a mortise or a tenon is in the range of +/−0.006″ across the entire width of the mortise and is +/−0.006″ across the entire width of the tenon. Consequently, the stack, i.e., the bond gap size or width, tolerance is +/−0.012″. The significance of a bond gap tolerance will be discussed later in further detail.
A perspective view of a cross rail 50 comparable to the cross rail 32bof
As best shown in
A preferred embodiment of the present invention includes the application of the adhesive to the cross rails 32a, 32brather than to the stiles 34a, 34b. Wood has a tendency to twist and bow after being cut into elongated pieces, such as cabinet door stiles. The application of adhesive to a door stile requires relatively high precision and control. By design, a cross rail of a cabinet door is typically shorter in length than a stile. As a result, applying adhesive to the shorter cross rail, rather than the longer stile, allows tighter control of the adhesive application because the effects of twisting and bowing are reduced.
Referring again to
In an embodiment of the invention, the amount of application in one area of the cross rail 50 may differ than in another area. Referring again to
The pattern of adhesive application can vary by other characteristics. The illustrated beads 60, 62 are a single continuous bead, although the adhesive can be applied in various patterns, such as for example, continuous bead, intermittent bead, flat extrusion, stitching or spotting. An example of an intermittent bead pattern in shown in
The engagement of the stile and cross rail occurs after application of the adhesive in a predetermined amount and pattern.
b is a top view of a portion of the cross rail 50 and the stile 80. During engagement, the cross rail 50 is slide into the stile 80 in the direction A1. In an embodiment of the invention, the beads 62, 60 are forced in the general directions A2, A3 toward the tenon contact surface 53. An exemplary adhesive distribution after engagement with the stile 80 is shown in
In an embodiment of the present invention, adhesive bond location is also controlled at least in part by a ratio between the bond gap volume (in3) to the tenon contact surface (in2). In a preferred embodiment, the ratio is between 0.0 and 0.012 inches. This ratio was determined and confirmed by use of a testing procedure where joints were tested in shear, a few seconds after assembly, to determine the appropriate green strengths of the joinery. In the case of the PVAc, and PUR adhesives, the strengths dropped significantly where the ratio was increased beyond 0.012 inches.
As discussed, a process step in this invention is the delivery of adhesive to desired locations on wooden cabinet components. In an embodiment of the invention, the adhesive is delivered via a balanced manifold to a plurality of dispensing nozzles. The manifold may be symmetrical, i.e., the channels that lead to the nozzles of similar diameter and length, so that all of the nozzles receive the same back-pressure and all of the nozzles receive equal flow of adhesive. Each nozzle may be circular, square or another shape, and include a pulsating head and an air knife to terminate residual flow after dispensing ends. The manifold and nozzle assembly is designed for delivery of adhesive to the tenon portion of the joint, but can be used for adhesive delivery to other locations.
A front perspective view of an exemplary nozzle apparatus used to dispense adhesive in accordance with an embodiment of the present invention is shown in
A cross-sectional view of the nozzle apparatus 90 is shown in
Another preferred embodiment of the present invention includes the step of applying adhesive to the tenons as the tenons move transverse to the nozzle. This technique positions the nozzles in a horizontal position, rather than vertical, and prevents the nozzle from dripping on stationary or moving cabinet parts. An example of such a technique is illustrated in
Various adhesives can be used in the practice of this invention. An embodiment of the present invention uses polyurethane reactive (PUR) adhesive. This adhesive is typically applied from a heated cartridge or roller coater. It is applied hot (about 250° F is typical), spread to a thin film, and sets quickly as it cools. In this respect, it is like a conventional hot melt adhesive. It achieves its ultimate strength several days after application by reacting with moisture in the surrounding air and/or in the substrates to form a significantly stronger bond than a conventional hot melt. Certain technologies cannot be used to accelerate the curing process. In cabinet processing, it is applied by various techniques and binds as a thin-film between two substrates.
Another embodiment of the present invention includes a process of applying an emulsion glue, such as for example, a conventional white wood glue. Polyvinyl acetates (PVAc's) are well-known adhesives that are used in a variety of formulas for many different applications. PVAc's are designed to work on porous materials only and are water based, so they clean up with warm soapy water. A PVAc adhesive needs pressure to adhere and must completely dry out to bind. In the wood processing industry, clamps are used to force the water out of the joining area.
The process steps of an embodiment of the present invention will now be discussed.
The process chart illustrated in
Alternatively, the mist of steam may be applied to the same surface upon which the adhesive is applied. In this technique, beads of adhesive are applied in a defined pattern. Subsequently or at the same time, mist is applied upon surface areas between the beads. When the glue beads are spread into a thin film substantially covering the surface, a thin film is formed over a surface of increased moisture content as compared to the substrate prior to the mist application.
These and other techniques within the scope of the invention use water to raise the moisture content of the substrate. Almost immediately after application, the substrates are pressed together so little moisture content is evaporated. After a short period in which the parts are being held by a mechanical clamp, the parts are unclamped and the assembly is transported for subsequent processing.
Returning to the flow chart, the PUR adhesive is applied by a nozzle system to the tenons as previously discussed, although any suitable nozzle system may be used. Because, the adhesive is applied to the tenons of the cross rails, the footprint of the machine assembly required to dispense the adhesive can be relatively small. For example, a machine of no more than 5 feet in length can be used for cross rails 36″ long. The adhesive is pumped into a known volume of space in a fluid cylinder, and then that exact amount of adhesive volume is transferred to the element to be bonded within the joinery. The adhesive is transported from the known volume cylinder to a manifold before the nozzles. The nozzles apply the adhesive in a predetermined amount and pattern, and then swipe the bead pattern to increase the wetting of the adhesive on the element, i.e., distribute the adhesive bead or beads into a thin film. The nozzles are positioned so that if unwanted dripping occurs after the swiping action, the dripping occurs within the machinery, and not on any of the elements of the joinery. There is a dwell time, such as for example, 20 to 40 seconds, after swiping where the assembly components can be orientated as desired.
Next, the clamping device is activated and the elements of the joints are brought closer until adhesive is squeezed into the bond gap between the elements. The clamp then moves to the next operational position where acceleration of cure time occurs. For example, in the case of PVAc adhesives, electromagnetic energy, such as for example, radio frequency (RF) energy, can now be applied to the joint to heat the PVAc adhesive to accelerate the cure. The adhesive is cured within the joinery, all within the movable clamp. RF energy is applied to PVAc adhesive because of its effects upon water within the adhesive. Water is a polar molecule, rather than a symmetric molecule. Water absorbs RF energy and converts it to heat. Consequently, the increase in temperature accelerates the drying of the PVAc adhesive.
Other forms of energy may be used to cure the adhesive, such as for example, microwave, ultrasonic, humidity, heat or sonic energy.
After a dwell time in which the bond has reached a desired green strength to allow for additional handling and assembly, the joinery moves to the next assembly position and generally is separated from the clamp, so that the clamp can cycle back to join another group of elements in the joinery process. Green strength is the adhesive joint strength immediately after the clamp is opened. Exemplary PUR adhesives may reach a strength of 60 psi in one minute and 200 psi in three minutes. After the clamping has been removed, the PUR adhesive continues to crosslink, resulting a joint strength of at least 475 psi for a bond gap of 0.012 inches.
While several embodiments of the invention have been illustrated and described in considerable detail, the present invention is not to be considered limited to the precise constructions disclosed. Various adaptations, modifications and uses of the invention may occur to those skilled in the arts to which the invention relates. It is the intention to cover all such adaptations, modifications and uses falling within the scope or spirit of the claims filed herewith.
This non-provisional application claims the benefit of U.S. Provisional Patent Application No. 60/709,175, entitled “Joinery Process,” filed Aug. 18, 2005, which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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60709175 | Aug 2005 | US |