US 3738447 A
A barrier for attenuating sound in accordance with this invention comprises a rigid frame member having a plurality of channel members, which may be made of dispersion strengthened lead, mounted on it to form a plurality of sub-frames. Sheets of free-standing, dispersion strengthened, creep-resistant lead are carried in the subframes by the channel members and may be embossed to add to their rigidity. One face of the sheets may be roughened in order to disperse reflected sound waves. According to another preferred embodiment of the invention, the channel members may be secured to the frame member by lead bolts in order to reduce the leakage of sound across the barrier.
Claims available in
Description (OCR text may contain errors)
United States Patent 1 Rose [ June 12, 1973 FREE-STANDING LEAD SOUND BARRIERS  References Cited UNITED STATES PATENTS 3,134,020 5/1964 Shoenfeld 250/108 3,299,270 1/1967 DAvella 250/108 391,295 10/1888 Brooks 85/37 1,193,013 8/1916 Grant 181/33.1 2,152,297 3/1939 Wilson 52/630 3,234,702 2/1966 Zibell .1 52/506 FOREIGN PATENTS OR APPLICATIONS 9/1953 Canada 52/194 Primary Examiner-John E. Murtagh Assistant Examiner-James L. Ridgill, Jr. Attorney-Brumbaugh, Graves, Donohue & Raymond 57 ABSTRACT A barrier for attenuating sound in accordance with this invention comprises a rigid frame member having a plurality of channel members, which may be made of dispersion strengthened lead, mounted on it to form a plurality of sub-frames. Sheets of free-standing, dispersion strengthened, creep-resistant lead are carried in the subframes by the channel members and may be embossed to add to their rigidity. One face of the sheets may be roughened in order to disperse reflected sound waves. According to another preferred embodiment of the invention, the channel members may be secured to the frame member by lead bolts in order to reduce the leakage of sound across the barrier.
12 Claims, 5 Drawing Figures PATENTED 3.738.447
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MICHAEL v. ROSE ATTORNEYS 1 FREE-STANDING LEAD SOUND BARRIERS Transformers, engines, turbines, and other electrical and mechanical machinery generally produce an unwanted hum or noise during their operation. These sounds may reach a critical level where they must be isolated from the environment in which the machine operates. For example, transformers located in residential areas should be enclosed so as not to disturb the area residents. Also, it is not unusual in factories to shield the operator of noisy equipment by providing a sound-proof control booth.
For good sound attenuation, it is necessary to make the barrier of a relatively dense but limp material. If the barrier is located outside, it must be impervious to weather, and in general, it must be strong enough to withstand rough handling.
Lead has a high density and a low modulus of elasticity (is relatively flexible or limp) and is, therefore, an excellent sound attenuator. However, pure lead is weak and has a poor resistance to creep when subjected to relatively light loads and, therefore, cannot be satisfactorily used as a structural material in sound barriers.
In an effort to overcome the above-mentioned strength and creep problems, lead has been laminated or welded to wood or metal to form a composite barrier in which the wood or metal provides a structural support for the lead. This method increases the cost of the barrier and also, by adding to the rigidity of the lead, reduces its efficiency as a sound barrier.
Another approach to the above-mentioned problems has been to strengthen the lead by alloying it with an other material; This approach has not been satisfactory because the degree of strengthening in conventional alloys is slight and the resultant sheets require closely spaced structural supports to prevent creep. Accordingly, because of the supports, the sheets cannot be considered to be free-standing. Alloying the lead and installing the supports greatly increases the cost of the barrier and, also, since the free span of the lead is reduced, the flexibility of the barrier is decreased, thus reducing the barriers sound attenuating efficiency.
Both of the above approaches result in leak paths across the barrier that must be eliminated in order to improve its effectiveness. Heretofore, this was accomplished by overlapping the lead sheets, or by butting the sheets together and welding them at the seams, each of which not only detracts from the appearance of the barrier, but also, adds to its cost.
This invention seeks to overcome the above problems by using a dispersion-strengthened lead that is of a high density and as flexible as pure lead. In addition, this lead has a structural strength and creep resistance previously unattainable. By using this material, a freestanding lead sound barrier can be provided that overcomes all of the problems mentioned above and which is less costly and easier to assemble than lead barriers heretofore known. By the term free-standing is meant that the lead sheets are neither laminated to a sub-support, nor structurally braced along their face in any way. In effect, except for edge support, they stand by themselves, and in such condition are stressed to at least 200 p.s.i. under their own weight. Any stress above about 2,000 p.s.i. is avoided however because it would provide a tendency for the lead to creep and would create the problems previously outlined.
Although reference has been made to dispersion strengthened lead, it is to be understood that any lead or lead alloy having a tensile strength of at least 3,200 p.s.i. can be used.
Briefly described, this invention comprises at least one sheet of free-standing, high' strength, creepresistant, lead bounded on its edges by connector elements, which may also be made of the same type of material in order to reduce leakage across the barrier. These connector elements may frictionally engage the sheet and include lead bolts for securing them to a rigid frame or support. According to another preferred embodiment of the invention, the sheet may be embossed to add rigidity and/or further sound attenuating properties thereto, and may also have one face thereof roughened, or scratched, so as to disperse reflected sound waves.
For a better understanding of the present invention, reference is made to the following specification and the accompanying drawings, in which:
FIG. 1 is a front view of a barrier constructed in accordance with this invention with the length and width thereof broken to reduce its size;
FIG. 2 is a rear view of the barrier shown in FIG. 1;
FIG. 3 is a view in section taken along the line 3-3 of FIG. 1 and looking generally in the direction of the arrows;
FIG. 4 is an enlarged view of a portion of one of the lead sheets taken along the outline shown in FIG. 1; and
FIG. 5 is a perspective view of a connector element that can be used in carrying out this invention.
Referring to FIG. 1, a plurality of free-standing, high strength, creep-resistant lead sheets 10 are surrounded on their edges by a plurality of horizontal connectors 12 and vertical connectors 14 to form a sound attenuating barrier. This barrier may be attached to a suitable frame member 16, as can best be seen in FIG. 2.
The frame member 16 comprises a pair of horizontal beam members 18 and vertical beam members 20 forming a rectangular outer frame. For adding rigidity to the frame, a plurality of horizontal brace members 22 extend parallel to the beam members 18, and a plurality of vertical brace members 24 extend parallel to the beam members 20. The brace members 22 and 24 not only add rigidity to the frame 16, but also, provide a support to which the connectors 12 and 14 may be secured. In order to secure the barrier and frame to a support element, brackets 26 with suitable fastening members may be provided on the frame. In this embodiment, the bracket members 26 extend from the vertical brace members 24, but it is to be understood, that they could be located elsewhere.
The lead sheets 10 could be held in place by any suitable connector element, but in this embodiment, H- shaped elements are used for both the vertical and horizontal connectors. Referring specifically to FIG. 5, the vertical connector 14 is shown and comprises a central web 28 having a pair of spaced-apart flange members 30 and 31 extending from its opposite edges to engage the edges of the sheets 10. It is to be understood that the connector 12 is the same. The distance between each pair of flanges is substantially equal to the thickness of the sheets 10 so that the flanges frictionally engage .the sheets. In order to prevent any tendency for the web 28 to crack due to the weight of the sheets, the intersection of the flanges and the edge of the web is arcuately formed as shown at R to remove all corners or sharp edges. This construction provides a knockdown assembly that is easy to install.
As can best be seen in FIG. 3, the connectors 12 and 14 are fastened to the frame member 116 by bolts 32 that extend through openings in the web 28. Placed between the connectors 12 and 14 and the brace 22 is a suitable sleeve 34 that spaces the barrier from the frame.
In order to reduce sound leakage across the barrier, it is preferable to extrude the connectors 12 and 14 from a high strength, creep-resistant lead and to use lead bolts 32 as the fastener elements. Obviously, in many applications, leakage of sound would not be as critical as in others, and in these applications it would not be necessary to use lead connectors or bolts.
Still referring to FIG. 3, it can be seen that along the horizontal span, two connector elements 12 are placed side by side so that one pair of flanges 31 of each element are not in use. One of the connector elements 14 can be done away with and the upper sheet, for example, could be carried by the upper flanges 31 of the lower connector 14. However, in order to enhance the ornamental appearance of the barrier by breaking up its solid appearance, two connectors are shown.
As pointed out previously, the lead sheets can be made of any high strength, creep-resistant lead or lead alloy, but a preferred embodiment disclosed herein uses a dispersion strengthened lead as described in the U.S. Pat. to Krantz, et al., No. 3,320,664, in which there is disclosed the coating of fine particles of lead with lead oxide in the range of 0.7 to 16.0 percent by weight of PhD, and thereafter breaking the lead oxide film into finely divided particles and dispersing them in a lead matrix. The particles of PbO may be 1 micron diameter and below. It is not necessary to use this process or type of lead, and any lead or lead alloy that has tensile strength in the range of 3,200 to 8,500 p.s.i. may be used. The preferred range is from 5,000 to 7,000 p.s.i. and the preferred PbO content is about I 2 percent.
Furthermore, in the free-standing condition the lead is internally stressed by its own weight in the range of 200 to 2,000 p.s.i. to provide the rigidity and creep resistance desired. Any stress greater than 2,000 p.s.i. may cause the lead to creep, that is, flow due to the imposed stress, so that it elongates, buckles, or fails. The preferred range forthe internal stress is from 500 to 1,000 psi.
In order to add rigidity to the sheets 10, and also, to improve their ornamental appearance and/or sound attenuating properties, they may be embossed as best seen in FIG. 4. It is also possible to disperse reflected sound waves by roughening one surface of the sheet.
An example of a barrier made in accordance with this invention provides for a 12-inch horizontal spacing between the connectors 14 and a 40-inch spacing between the connectors 12. The lead sheets may, for example, be of a thickness of 0.062 inches. Significant sound attenuation may be obtained with sheet thicknesses of at least about 0.010 in., although for mechanical strength, thicknesses above 0.016 in. are preferred. A practical maximum for thickness of the sheet is about 0.25 inch. The flanges 30 of the extruded connectors project about 0.50 inches from the edge of the web 28 and from a slot therebetween. Obviously, these dimensions are not by way of limitation, but can be varied according to the requirements of a particular installation.
While in the foregoing there has been disclosed an illustrative embodiment of this invention, various modifications will occur to those skilled in the art to which this invention pertains. Accordingly, it is not desired to limit the invention to the exact features disclosed, but to encompass all modifications that fall within the scope of the appended claims.
1. A sound barrier for apparatus that generates undesirable sound, comprising a main frame for the barrier, said frame having a plurality of spaced members, an auxiliary frame comprising a grid of support members, the support members being secured to said main frame, and a plurality of relatively thin panels of lead, said support members providing means for supporting the lead panels in edge-to-edge relationship, said support members holding marginal portions of the lead panels whereby the lead panels are mounted within said auxiliary frame by their edges.
2. A sound barrier as set forth in claim 1 wherein the lead has a tensile strength of at least 3,200 p.s.i.
3. A sound barrier as set forth in claim 1 wherein the lead has a tensile strength in the range of 5,000 to 7,000 p.s.i.
4. A sound barrier as set forth in claim 1 wherein the panel is stressed under its own weight to between 200 to 2,000 p.s.i.
5. A sound barrier as set forth in claim 1 wherein the panel is stressed under its own weight to between 500 to 1,000 p.s.i.
6. A sound barrier as set forth in claim 1 wherein one face of at least one of the panels is roughened so as to disperse reflected sound waves.
7.. A sound barrier as set forth in claim 1 wherein said panels are embossed.
8. A sound barrier as set forth in claim 1 wherein said main frame forms a grid substantially in registry with the grid constituted by said support members.
9. A sound barrier as set forth in claim 8 wherein said main frame includes means for mounting the barrier to said apparatus.
110. A sound barrier as set forth in claim 1 wherein said panels comprise strengthened lead.
Ill. A sound barrier as set forth in claim 10 wherein said panels comprise dispersion-strengthened lead containing lead oxide in the range of 0.7 to 16.0 percent.
12. A sound barrier as set forth in claim 11 wherein said support members comprise dispersionstrengthened lead containing lead oxide in the range of 0.7 to 16.0 percent.
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