US3772993A

US3772993A - Noise abating barrier

Info

Publication number: US3772993A
Application number: US00228505A
Authority: US
Inventors: P Noble; J Carey
Original assignee: Westinghouse Air Brake Co
Current assignee: Hitachi Rail STS USA Inc
Priority date: 1972-02-23
Filing date: 1972-02-23
Publication date: 1973-11-20
Anticipated expiration: 1990-11-20
Also published as: AU4362172A; CA970698A

Abstract

This disclosure relates to a noise barrier structure for reducing the level of wheel squeal produced by a railroad car retarder. The barrier structure includes a row of supporting ties disposed on each side of the car retarder. An L-shaped steel column is secured to each of the supporting ties. A rectangular wooden mounting frame has a top section which is secured to the upper ends of the columns and has a bottom section which is secured to the top surfaces of the supporting ties. A canted solid wall structure including a plurality of corrugated panels are disposed in side-by-side relationship. The panels are securely fastened to the frame so that the sound of the wheel squeal is partially absorbed by the wall and is reflected by its surface into the surrounding ballast.

Description

[ Nov. 20, 1973 NOISE ABATING BARRIER [75] Inventors: Peter M. Noble, Valencia; John H. Carey, Churchill Borough, both of Pa.

[73] Assignee: Westinghouse Air Brake Company,

Swissvale, Pa.

22 Filed: Feb. 23, 1972 21 Appl. No.1 228,505

[52] U.S. Cl. 104/1 R, 104/26 R, 181/33 E, 256/12.5, 256/24 [51] Int. Cl B611: 13/00 [58] Field of Search 181/33 E, 33 HE; 104/1 R, 26 R, 26 A; 246/182 A; 2515 24, 256/12.5;244/118 B [56] References Cited UNITED STATES PATENTS 3,226,063 12/1965 Wagner 244/114 B 1,820,874 8/1931 White 105/452 2,974,910 3/1961 Lynn 244/114 B Primary Examiner-Gerald M. Forlenza Assistant Examiner-George H. Libman Attorney-H. A. Williamson et al.

[5 7 ABSTRACT This disclosure relates to a noise barrier structure for reducing the level of wheel squeal produced by a railroad car retarder. The barrier structure includes a row of supporting ties disposed on each side of the car retarder. An L-shaped steel column is secured to each of the supporting ties. A rectangular wooden mounting frame has a top section which is secured to the upper ends of the columns and has a bottom section which is secured to the top surfaces of the supporting ties. A canted solid wall structure including a plurality of corrugated panels are disposed in side-by-side relationship. The panels are securely fastened to the frame so that the sound of the wheel squeal is partially absorbed by the wall and is reflected by its surface into the surrounding ballast.

10 Claims, 3 Drawing Figures PAIENTEU um 20 ms SHEET 3 BF 3 NOISE ABATING BARRIER Our invention relates to a car retarder sound suppressing barrier and, more particularly, to a combination of a car retarder and a canted noise barrier structure which reduces the level of the wheel squeal produced by a car retarder by absorbing and reflecting the sound waves into the track ballast surrounding the car retarder.

' In railroad classification yards, car retarders at both the master and group locations which brake the wheels of moving railway vehicles generate an extremely severe audible noise which is irritating, painful, and, in some cases, results in hearing loss to individuals, such as, railroad personnel who work in the area. This high pitched sound is produced by the grating and rubbing action which takes place between the sides of the wheels of the passing cars and the engaging surfaces of the brake shoes of the car retarder. Tests have conclusively proven that the troublesome pitch and frequency range of the generated noise is between 2,000 and 4,000 Hz and that the loudness of the noise reaches a level of I20 decibels (db) or more at a distance of feet or less. Otolaryngologists and other acoustics experts have found that humans experience pain at noise levels of a ldb or more and that repeated exposure to such high levels of noise can eventually result in hearing losses. Previous attempts, such as replacing steel brake shoes with ductile iron or providing a lubricant on the surfaces of the brake shoes, have not proven totally effective in abating wheel squeal. The use of ductile iron shoes in place of the present steel shoes is one of economics since ductile iron wears four (4) times as fast as steel. Thus a car retarder equipped with ductile iron shoes requires four (4) times as many shoe replacements and maintenance periods as an all steel car retarder. The alternative method of preventing wheel squeal by lubricating the brake shoes is also possessed of several disadvantages. The use of lubricants on the brake shoes not only dramatically reduces the amount of effective braking that may be exerted by the car retarder but also materially increases the initial purchase and subsequent maintenance costs ofithe car retarder. Another approach to resolving the noise problem has been the erection of barriers along the sides of the car retarder. Previous noise barriers were generally unacceptable for various reasons. Porous types of absorption noise barriers become relatively ineffective in abating the retarder noise soon after installation. The main reason for this loss of effectiveness resides in the fact that the low density of the barrier material quickly causes it to become clogged and filled with dirt, oil, grease, sludge, water, and other foreign matter which is ever present in a yard millieu. Also, the absorption barrier material is susceptible to rapid deterioration by elements of the weather. In addition, many municipal authorities have or have recently enacted noise abatement ordinances so that it has become mandatory upon the railroads to solve the noise problem in their classification yards. Even at great distances, such as two (2) miles from the location of the retarder, the level of wheel squeal exceeds the noise level of these abatement ordinances.

Accordingly, it is an object of our invention to provide a new and improved noise barrier for abating the wheel squeal produced in a railway car retarder.

Another object of our invention is to provide a unique elongated canted wall structure on both-sides of a car retarder for absorbing and reflecting wheel squealing noises.

A further object of our invention is to provide an absorption and reflection type of noise barrier for reducing the level of wheel squeal produced by railroad car retarders in classification yards.

Yet another object of our invention is to provide in combination a canted wall structure along the entire length of a railway vehicle car retarder for reducing the level of wheel squeal to a point which is not harmful to human beings.

Yet'a further object of our invention is to provide a unique sound barrier including a pair of canted walls each constructed of high density material and each supported by a frame structure located on each side of a railroad car retarder.

Still another object of our invention is to provide an acoustical barrier structure for absorbing and reflecting wheel squeals produced by railroad car retarders.

Still a further object of our invention is to provide a noise control barrier which reduces the level of wheel squeal generated by car retarders by absorbing a portion of the sound waves and by reflecting the remaining portion of the sound waves into the ballast surrounding the car retarder.

Still yet another object of our invention is to provide an improved noise abating arrangement which includes a pair of canted wall structures which straddle the length of a railway car retarder.

Still yet a further object of our invention is to provide a new and improved noise reducing wall type barrier which is economical in cost, simple in construction, easy to install, durable to use, and reliable in operation.

In the attainment of the foregoing objects, a noise barrier wall structure is disposed on each side of a wheel gripping type of railroad car retarder. Each wall structure includes a row of wooden supporting ties, a plurality of steel columns, a box-like wooden frame and a plurality of wall panels. The supporting ties are disposed in line with the rail mounting cross ties, and ballast is tamped around the ties. Each barrier supporting tie carries the horizontal leg of an L-shaped steel column.'A wooden box-like frame rests on the top of the barrier supporting ties and is secured to the tops of the vertical legs of the L-shaped steel columns. Panel members are disposed in side-by-side relationship and are secured to the box-like wooden frame. The panel members are corrugated and are fabricated from a high density material having a sound absorbing capacity over a wide range of retarder noise frequencies and for sounds of varying levels of intensities. Of course, since a perfect sound absorbing material is not available, some of the sound waves produced by the retarder are absorbed by the material and some of the sound waves are reflected by the surface of the panel members in the ballast around the retarder area.

Other objects, features and advantages of our invention will become more apparent from the following description of a preferred embodiment described with reference 'to the accompanying drawings forming a part of this specification, in which:

FIG. 1 is a fragmentary top plan view of a track section in, for example, a railroad freight car classification yard, utilizing a car retarder for controlling the speed of moving cars and a noise barrier for reducing wheel squeal in accordance with our invention.

FIG. 2 is a sectional view taken along the lines II--ll of FIG. 1.

FIG. 3 is a fragmentary elevational view of the noise barrier as viewed from the retarder side of the yard installation.

In hump-type railroad classification yards, it is desirable to classify the railway vehicles or cars of an incoming train into other trains in accordance with their next destination. The cars of the incoming train are pushed over an incline or hump so that the force of gravity moves the cars to their final destination. However, various parameters, such as weight, rolling resistance, and the like, cause each of the rolling cars to travel down the track at a different speed. In order to control the speed of the moving cars in accordance with their weight and the distance-to-go, suitable braking apparatus is situated at certain locations in the trackway. Generally, the braking apparatus takes the form of a railway car retarder which has braking bars that move into and out of engagement with the wheels of a railway car for controlling the speed thereof.

Referring now to FIG. 1 of the drawings, it will be noted that a railroad car retarder is generally shown and characterized by numeral 1. In group and hump applications, it is common practice to employ a dual track car retarder to ensure that sufficient braking effort is exerted on the wheels of the cars as they pass through the retarder. As shown in FIG. 1, a pair of running

rails

2a and 2b form the trackway leading to the various class tracks. In viewing FIG. 2, it will be noted that the

rails

2a and 2b (not shown) are mounted on supporting stands 3 which, in turn, are secured to cross ties in the usual and well known manner. The car retarder includes a pair of braking bars 4 disposed on opposite sides of the

track rails

2a and 2b. The braking bars extend parallel to the track rails and consist of a plurality of brake beams 5 and replaceable brake shoes 6. As previously mentioned, the brake bars 4 are adapted to be moved relative to the track rails into braking and nonbraking positions. A plurality of independent operating units 8 are preselectively spaced at regular intervals along the parallel extending brake bars 4. Each of the operating units 8 is alike and, therefore, a description of one will suffice for all. As best shown in FIG. 2, the operating unit 8 consists of an upper lever 9 and a lower lever 10. The levers are operated by a fluid actuated motor which causes pivotal movement about a common fulcrum point 1 1. That is, the free end of lever 9 is pivotally connected to the pneumatic cylinder 12 while the free end of lever is pivotally connected to the reciprocal piston 13. The pivotal movement about the common fulcrum point causes the braking bars 4 carried by the other ends of levers 9 and 10 to move toward and away from each other as the fluid actuated motor is energized and deenergized. That is, upon application of fluid pressure to the fluid actuating motor the braking bars 4 undergo an elevating and closing movement for frictionally engaging a wheel 14 of a railway car, as shown in FIG. 2. Upon venting of the air of the actuating motor to the atmosphere, the force of gravity acts to lower and open the braking bars 4 to their normal retracted nonbraking position. Accordingly, as the vehicle moves through the retarder, the closing and opening of the retarder allows for the speed of the vehicle to be controlled in accordance with its ultimate destination.

It has been found that when a squeeze type of car retarder is closed for a long period of time, high pitched and large amplitude vibrations are set up in the wheel and the brake bars. These vibrations cause a squealing sound or noise which is annoying to residents and in some cases injurious and painful to persons in the area. Tests have shown that the most detrimental frequency range lies between 2,000 to 4,000 hertz and that the noise level of the wheel screech lines between 1 l0 and db. at the retarder site. The principal noise waves are radiated in a lateral and horizontal direction away from the trackway, as shown by the thickest lines 15 in FIG. 2. While the elevational and depressional noise waves are less intense, as shown by the lighter lines 15a and 15b in FIG. 2, it is beneficial to suppress them to some extent. Tests have shown that the noise waves which are tangential to the track rails have markedly decreased levels so that these waves present little, if any, problem. Similarly, upwardly propogated vertical sound waves present little, if any, problem since they are dissipated in outer space. In order to abate this noise problem, it has been found to be advantageous to construct a unique sound barrier which both absorbs and reflects the sound waves in order to minimize the level of the noise produced in a railroad car retarder. The noise reduction is accomplished by constructing a barrier wall on opposite sides of the car retarder 1.

In viewing FIG. 1, it is assumed that the trackway runs east to west so that a northern barrier 20 is located on one side of the retarder and a southern barrier 21 is located on the other side of the car retarder. Each of the barriers is identical in construction and, for the purpose of convenience, only the barrier 20 will be described in detail. As shown in FIGS. 2 and 3, the barrier is constructed of readily available material and basically includes supporting members, a frame structure, and a wall structure.

The supporting members include a plurality of precut railroad tie members 24 which are approximately onehalf the length of the retarder supporting ties. The ties 24 are disposed along each side of the retarder and form a row which is parallel to the supporting ties of the car retarder. An L-shaped steel angle member 26 is carried by each of the barrier ties 24. The horizontal leg 27 of the L-shaped steel angle member 26 is securely fastened to the tops of the tie members 24 by lag screws 28. An angle iron 29 spans the ties, and a lag screw 28a secures the ends of the angle irons 29 and the knee of the L-shaped members 26 in place. The angle irons 29 stabilize the structure and ensure that the inner ends of the ties will not be displaced.

A box-like wooden frame 30 is disposed against the upper end of a vertical leg of the support member 26 and rests on the upper surface of the barrier ties 24. The wooden frame 30 is fabricated from commercially available lumber, such as, 2 X 6's. The frame includes upper horizontal boards 31 and lower horizontal boards 32 which extent the length of the car retarder. The boards 31 and 32 form joists or support beams to which are nailed a plurality of canted board members 33. The canted board members 33 are spaced substantially on center with the barrier supporting ties 25. In order to increase the strength of the wooden frame, a pair of horizontal reinforcing boards 34 are interposed between the upper and lower board members 31 and 32, respectively. The lower board members are predrilled and a series of lag screws (one of which is shown at 35) are fastened to the tops of the respective ties 24. The upper ends of the side members 33 are secured by bolts 36 to the upper end of the vertical leg member of 5 the L-shaped member 26. After the frame is secured in place, the next step in the noise barrier construction involves the wall structure 40. This simple yet rigid form of construction allows the barrier to withstand wind velocities as high as 85 mph without detrimentally deforming the structure.

The noise reducing wall 40 is made up of a plurality of large wall panels, such as, corrugated sheets 41 which are disposed in side-by-side relationship on the wooden frame 30. The panels are constructed of a high density material, such as, an asbestos-concrete composition which is readily available on the open market. The asbestos-concrete panels are virtually indestructible and durable and require practically no maintenance or upkeep. The average thickness of the corrugated panels is generally three-eights of an inch with an optimum mass or average weight of four (4) lbs. per square foot. The length of each panel generally extends to a length of twelve (12) feet and has a standard width of approximately forty-two (42) inches. The panels are situated against the wooden frame and are securely fastened to the wooden members by suitable fasteners, such as, lead head drive screws. The corrugated panels may be erected in straight or butt joint construction. The straight joint method simply requires that the panels be overlapped so that no gap exists between adjacent panels. In the illustrated embodiment, the butt joint method of erection is used so that vertical batten strips 42 are placed behind the juncture lines of adjacent panels. Thus, no opening will exist between the panels. Each method maximizes noise reduction in that no leakage losses result. The canted barrier structure not only reduces the wheel squeal noises but also effectively protects the retarder against the adverse elements of the weather. That is, the barrier also operates as an effective snow fence to prevent drifting snow from accumulating in the retarder area. In addition, the barrier structure reduces the effects of high winds and gusting rains and snow on the operation of the retarder.

It has been found that the asbestos-concrete composition is practically impervious to rain or snow. In addition, oils, grease, chemicals, and the like which are ever present in a railroad environment do not materially-affect the physical characteristics of the corrugated panels so that the noise reducing qualities are not diminished with time.

In viewing FIG. 2, it will be noted that the sound waves of the wheel squeal noise waves emanating from the car retarder not only are effectively absorbed by the high density panel members 41 but also are reflected by the canted panels into the ballast surrounding the retarder area. The asbestos-concrete wall 40 is highly effective in absorbing the higher frequency noise waves which are the most annoying and harmful to individuals. The lower frequency noise waves are also absorbed to some extent but they are not much of a problem since they are less detrimental and have a relatively short range of travel. The dual function of absorbing some of the sound waves and reflecting the remaining sound waves results in a more efficient method of reducing the noise level of the wheel squeal. Further, it will be noted that the ballast operates in a dual function, namely, that of supporting the cross ties as well as absorbing the noise squeal, as shown in FIG. 2. In actual field testing, it has been observed that the presently described barrier had an attenuation of approximately 23 db. on the retarder noise which is theoretically the maximum attenuating level for a barrier of this type.

It is apparent that numerous changes may be made in the above described construction without departing from the spirit and scope of the invention, and therefore it is intended that all the subject matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having thus described our invention, what we claim 1. In a combination, comprising a car retarder located in the railroad track of a classification yard, said car retarder acts on the wheels of railroad vehicles passing through said retarder for controlling the speed of said vehicles, and an elongated canted noise abating barrier structure located on either side of said track and extending along the length of said car retarder so that wheel squeal produced by said retarder is abated by being absorbed by said barrier and by being reflected by the surface of said barrier into the ballast in the area of said car retarder.

2. The combination as defined in claim 1, wherein each of said canted barrier structures includes a solid wall constructed of a high density material which is impervious to liquids.

3. The combination as defined in claim 2, wherein said' solid wall is formed by a plurality of corrugated sheets which are disposed in side-by-side relationship with each other and which are securely fastened to frame structures.

4. The combination as defined in claim 2, wherein said high density material is a cement and asbestos composition.

5. The combination as defined in claim 1, wherein a plurality of vertical steel columns, each of which is secured one of a row to supporting ties, are located adjacent the cross-ties supporting said car retarder.

6. The combination as defined in claim 5, wherein said canted barrier structure includes frame members to which are secured solid wall panels.

7. The combination as defined in claim 6, wherein said frame members are secured to said supporting ties and to the tops of said vertical steel columns.

8. The combination as defined in claim 6, wherein said steel columns are L-shaped members which have one leg secured to the tops of said supporting ties and have the other leg secured to said frame members.

9. The combination as defined in claim 3, wherein batten strips cover the abutting edges of said corrugated sheets.

10. The combination as defined in claim 6, wherein said wall panels are corrugated members which have their adjacent edges overlapped and securely fastened by batten strips.

Claims

1. In a combination, comprising a car retarder located in the railroad track of a classification yard, said car retarder acts on the wheels of railroad vehicles passing through said retarder for controlling the speed of said vehicles, and an elongated canted noise abating barrier structure located on either side of said track and extending along the length of said car retarder so that wheel squeal produced by said retarder is abated by being absorbed by said barrier and by being reflected by the surface of said barrier into the ballast in the area of said car retarder.

3. The combination as defined in claim 2, wherein said solid wall is formed by a plurality of corrugated sheets which are disposed in side-by-side relationship with each other and which are securely fastened to frame structures.