Patent Application
20060013417
1. Field of the Invention
The invention relates in general to an acoustical panel assembly, and in particular to an acoustical panel assembly comprising a panel made of a material formed by a reaction injection molding (RIM) process, a reinforced reaction injection molding (RRIM) process, or a structural reaction injection molding (SRIM) process with an acoustic device, such as a loudspeaker, an exciter, a piezoelectric transducer, and the like, mounted thereon.
2. Description of the Related Art
Traditionally, auto manufacturers have made sole use of traditional cone speakers that have a minimum depth requirement that has demanded a minimum packaging space. This requirement has ensured that audio speaker placement has often been determined not by optimum in-car sound quality, but by available space. Thus, most vehicles audio speakers are tucked away down by the occupants' knees and not necessarily located for optimum listening.
An acoustic device, such as a piezoelectric transducer, an electrodynamic device, a flat panel loudspeaker, distributed mode loudspeaker (DML), and the like, applies bending wave energy to a panel to cause the panel to resonate and produce an acoustic output (i.e., sound). One such acoustic device is commercially available from New Transducers Limited (NXT™) of Huntingdon, England. A typical electrodynamic device, for example, comprises a magnet assembly rigidly fixed to a housing to define an annular gap, and a voice coil and coil former assembly disposed in the annular gap and rigidly fixed to the panel near to the geometric center thereof.
Typically, the acoustic device is mounted to the panel by using a separate mounting member, such as a mounting plate, that is fixedly attached to the panel using one or more fasteners, such as screws, adhesives, double-side tape, or the like. After the separate mounting member is fixedly attached to the panel, the acoustic device can be fixedly attached to the panel via the mounting member.
It has been found that a suitable conventional material for the panel that will produce an acceptable frequency response is made of an extremely low-density, rigid plastic foam material commercially available under the tradename ROHACELL® sold by Roehm GMBH Limited located in the Fed. Rep. of Germany. ROHACELL® is a polymethacrylimide (PMI) hard foam, that is used as a core material for sandwich constructions. For example, ROHACELL® is typically used as a modeling material for architects and sculptors, and in some cases, as a building insulation. ROHACELL® is available with densities ranging from 2.0 to 6.87 lbs/ft3 (32 to 110 kg/m3). However, such a material may not have the necessary structural properties, such as stiffness, rigidity, and the like, that is suitable for use in most home, office and/or automotive applications, such as for use in vehicular door panels, instrument panels, trim panels, residential and commercial floor and ceiling panels, and the like.
The inventors of the present invention have recognized these and other problems associated with conventional materials used for panels that resonate and produce an acoustic output, while providing the structural characteristics that are suitable for automotive applications. To this end, the inventors have developed a material for use as a panel made of a material formed by a Reaction Injection Molding (RIM) process, a Reinforced Reaction Injection Molding (RRIM) process, or a Structural Reaction Injection Molding (SRIM) process that can widely be used in automotive applications, and unexpectedly produces an acceptable acoustic output when the acoustic device is mounted thereon.
In an embodiment of the invention, an acoustical panel assembly comprises a panel having a core made of synthetic material comprising a mixture of isocynate and polyol, and an acoustic device mounted to an exterior surface of the panel.
In another embodiment of the invention, an acoustical panel assembly comprises a core made of a synthetic material having a specific gravity in a range between about 0.1 and 1.4, and an acoustic device mounted to an exterior surface of the core.
In a method of the invention, the method comprises the steps of forming a panel comprising a core made of a synthetic material by one of a reaction injection molding (RIM) process, a reinforced reaction injection molding (RRIM) process, and a structural reaction molding (SRIM) process, and mounting an acoustic device to the panel.
In the drawings:
Referring to
As shown in
As illustrated in
It will be appreciated that the invention can be practiced without the use of the reinforcement material encapsulated in the core 13 of the panel 12. For example, as illustrated in
As illustrated in
It will be appreciated that the panel 12 may comprise any combination of the various layers of materials stated above. For example, the synthetic panel 12 may include a layer of scrim material 19 in the form of a “combo mat” on both the inner and outer surfaces 14, 16 and a cover material 20 bonded to the scrim material 19 on the outer surface 16 to provide a decorative appearance. The cover material 20 may have an embossed appearance, if desired. In another example, the synthetic panel 12 may include the cover material 20 bonded to the outer surface 16 of the core 13 having a fiberglass mat 15 encapsulated therein. Other combinations of layers of materials are within the scope of the invention.
Referring now to
In the illustrated embodiment, the attachment member 24 includes a pair of opposing, substantially identical mounting portions 28. Each mounting portion 28 is generally L-shaped in cross section having a lower mounting portion 30 and an upper mounting portion 32 that generally conform to shape of the outer surface of the acoustic device 26. To install the acoustic device 26 to the panel 12, the acoustic device 26 is aligned with the attachment member 24 such that the lower mounting portion 30 and the upper mounting portion 32 are aligned with the acoustic device 26. As the acoustic device 26 is moved toward the attachment member 24, the lower mounting portion 30 and the upper mounting portion 32 flex slightly outward to allow the acoustic device 26 to be inserted into the attachment member 24. Once the acoustic device 26 is fully inserted within the attachment member 24, the lower mounting portion 30 and the upper mounting portion 32 flex inwardly and press against the acoustic device 24 to positively secure the acoustic device 24 against the inner surface 14 of the panel 12.
It will be appreciated that the integrally formed attachment member 24 does not require a separate mounting plate for mounting the acoustic device 26 to the panel 12, unlike conventional mounting devices, thereby eliminating the need for holes in the panel 12 for attaching the separate mounting plate to the panel. Thus, the integrally formed attachment member 24 provides a more aesthetic Class “A” surface than conventional attachment members.
In addition, it will be appreciated that the invention is not limited by the type of attachment member that is integrally formed with the panel 12. For example, an attachment member 24′ may comprise a single piece of plastic material having a base portion 42 and an attachment portion 44 having a plurality of threads 46, as shown in
It will be appreciated that it is possible to mount the acoustic device 26 directly to the panel 12 without the need for the attachment member 24, 24′ by using an adhesive, or the like.
Referring to
At step S9.4, the synthetic material is prepared prior to injection into the mold tool at step S9.6. For example, the isocynate and polyol may be separately maintained in a holding tank at a temperature approximately equal to 80° F., and then mixed together at the mixing head or injection nozzle. At step S9.5, the attachment member 24 can be placed onto the opposite surface of the mold tool as the IMC or cover material 20. At step S9.6, the synthetic material is injected in the mold tool. A metered amount of synthetic material may be injected to yield a specific material density of the panel 12. For example, if a higher density of the panel 12 is desired, a relatively larger amount of synthetic material is metered to substantially fill 100% of the volume of the mold tool. According to an embodiment, the synthetic material is injected for 1.9 seconds at a metering rate approximately equal to 300 gram per second (a total of 570 grams of synthetic material) to yield a high density panel 12. As such, when foaming and expansion of the synthetic material occurs, a high density panel 12 may be yielded due to the compression of the synthetic material under tonnage of the closed mold tool. Preferably, a specific gravity of a high-density synthetic material is approximately equal to the range of about 0.60 to about 1.40. It will be appreciated that the invention is not limited by the metered amounts of synthetic material that is injected into the mold tool. For example, the synthetic material can be injected for 1.1 seconds at a metering rate approximately equal to 400 gram per second (a total of 440 grams of synthetic material) to fill a mold tool having dimensions of approximately 25″×25″× 3/16″.
Conversely, the synthetic material may be metered to yield a lower density panel 12 by injecting a relatively smaller amount of synthetic material that is less than 100% of the volume of the mold tool such that the synthetic material, upon injection, is permitted to expand into free space when the mold tool is closed. According to one embodiment of the invention, the synthetic material is injected for approximately 1.0 seconds at a metering rate approximately equal to 300 grams per second to yield a low density panel 12. In an alternative embodiment, a lesser amount of synthetic material may be metered at step S9.6 if a liquid, such as water, and the like, is introduced to the polyol component of the mixture. Upon introducing water to the polyol component, the cellular structure foams at a greater rate, which causes an even lower density of the panel 12. According to one aspect of the invention, a specific gravity of a low-density synthetic material is approximately equal to the range of 0.10 to 0.60.
Upon metering and injecting the synthetic material, the mold tool surface is preferably heated to a temperature in the range approximately equal to 130-190° F. It will be appreciated that the mold tool surface temperature range may include different temperatures depending on the material of the mold tool surface. For example, if the mold tool surface is made of aluminum and is heated to approximately 140° F., the cure time may be approximately 60 sec. to approximately 3 min. At steps S9.7 and S9.8, the mold tool is closed, and the synthetic material is cured to form the core 13 of the panel 12 made of synthetic material of unitary construction. Then, at step S9.9, the mold tool is opened and the panel 12 is removed from the mold tool.
A method for manufacturing the panel 12 by using a RRIM process is similar to the method for manufacturing the panel 12 using the RIM process, except that the reinforcing fibers 18 are introduced into the synthetic material prior to injecting the synthetic material into the mold tool at step S9.6.
Instead of forming the panel 12 using the RRIM process, a method for manufacturing the panel 12 by using a SRIM process is similar to the method for manufacturing the panel 12, except that the scrim material 21 is placed on one or both mold halves of the mold tool prior to injecting the synthetic material into the mold tool at step S9.6.
A method for manufacturing the panel 12 having the cover material 20 can be formed by using the RIM, RRIM or SRIM process described above, except that the decorative cover 20 is introduced onto the surface of the mold tool instead of the IMC at step S9.3, thereby providing a decorative surface finish to the panel 12.
The panel 12 may undergo additional, optional treatment operations once removed from the mold tool. For example, the panel may undergo a power washing step, a drying step, a clear coat application step, a clear coat baking step, and a package and shipping step. The clear coat may be applied in a single or multiple roll coating process steps. The clear coat improves weathering and UV resistance of the panel, especially when used as a floor or wall tile in residential or commercial applications.
It will be appreciated that these additional finishing steps may be omitted when making the final product. For example, if a low density synthetic material is prepared at step S9.4, the finishing procedure may only include an edge trimming operation after being removed from the mold tool. Then, the trimmed panel 12 may be packaged and shipped. In application, the panel 12 may be a ceiling tile applied to a drop ceiling grid (not shown) that is somewhat less rigidified and lighter in weight due to the low density composition of the synthetic material.
Several tests were conducted with the acoustical panel assembly 10 of the invention, as shown in
The test results indicated that the best performance of the two tests conducted above was provided by the acoustical panel assembly 10 comprising a covered RIM panel 12 of the invention having no reinforcement material and a cover material made of expanded PVC material with a layer of foam between the RRIM material and the cover material, but when the acoustic device 26 was mounted at a location offset from the center of the panel 12. This result was unexpected because it was believed that the conventional ROHACELL® panel should have provided the best performance based on the wide acceptance of the ROHACELL® panel material for it's acoustical properties when coupled with the acoustic device. However, the inventors have discovered, rather unexpectedly, that the material for the panel 12 produced by the SRIM process produced acceptable acoustical properties, and that the material for the panel 12 produced by the RIM process, and especially the panel 12 that was covered with expanded PVC and a layer of foam therebetween, produced exceptional acoustical performance. By discovering such an expected result, the inventors have discovered that the panel 12 produces superior acoustical properties, while providing the structural properties required for most automotive applications, such as for interior trim panels, and the like.
Another unexpected result discovered by the inventors is that better sound performance is achieved by mounting the acoustic device 26 not directly at the center of the panel 12, but slightly offset from the center location. Specifically, the location for the acoustic device 26 for a rectangular or square-shaped panel can be obtained according to the following equation:
Location=( 4/9)X, ( 3/7)Y
For example, the location for the acoustic device 26 for a panel 12 having an x-dimension of 18 cm and a y-dimension of 14 cm would be 8 cm along the x-dimension and 6 cm along the y-dimension. In other words, the optimum location would be 1 cm offset from the center location (9 cm along the x-direction and 7 cm along the y-direction) in both the x- and y-dimensions.
The inventors have also discovered that superior performance is also unexpectedly achieved when the panel 12 of the invention has a core 13 made of low density material that is disposed between two layers of relatively thin, high density material, for example, a thin sheet of aluminum, or the like. In fact, the lower the density of the core 13 and the higher the relative density of the outer surface layers, the better the acoustical performance of the panel 12. For example, it may be desirable that the core 13 be made of the synthetic material that includes voids, but still has the necessary structural properties for use in residential, commercial or automotive applications. For example, the panel 12 may comprise a core 13 having a honeycomb-shaped structure, an I-beam structure, and the like, disposed between layers of a metal, such as aluminum, and the like. The high density layers may be made of a variety of suitable materials, such as paper with or without resin material for bonding to the core, plastic material, glass veil composite skin material, and the like. The thickness of the high density layer may range between about 3 mm to about 5 mm. Other geometrically-shaped structures having the necessary structural properties and made of the synthetic material are within the scope of the invention.
While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.
This application claims the benefit of U.S. Provisional Application No. 60/588,872, filed Jul. 16, 2004, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60588872 | Jul 2004 | US |
