Sweeper bristle and method of making
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a bristle for a broom and method of making the bristle. More specifically, this invention relates to a bristle for use in a railroad bed or track. 
     2. Description of the Prior Art 
     The use of bristles for a broom machine adapted for cleaning a railway road bed or track is well known to the art. Generally, such bristles are mounted on a rotary sweeping element and are commonly used for sweeping ballast and other debris along the railway track. 
     The ballast is usually a thick layer of crushed limestone which is placed between and along side of the rails. Preferably, the top service of the ballast should be level with or slightly below the railway ties. Unfortunately, when new ballast is dumped onto a railway roadbed, the ballast is not properly and evenly distributed. There may be spaces between rails which are not properly filled in with ballast. Additionally, the rails, which should be free of loose ballast, may be at least partially covered by ballast. 
     In order to evenly distribute the ballast and clear ballast from the tops of the railway ties, it is known to use rotary sweeping cores. However, because of the extremely harsh wear on the bristles commonly mounted. to such cores, the bristles are subject to breakage if they do not yeild properly. Additionally, as will be readily appreciated, the limestone or similar ballast will cause an extreme amount of wear on the bristle elements. 
     Among prior art Patents, my previous U.S. Pat. No. 3,237,232, issued on Mar. 1, 1966, discloses the use of hollow, resilent tube-like bristles on a rotary sweeper core. The generally hollow bristle element is mounted to a rotary sweeping core by an elongate stiffner element extending into the interior of the bristle. 
     The patent to Kershaw et al., U.S. Pat. No. 3,649,984, issued on Mar. 21, 1972, discloses a bristle element having a core made of a bundle of parallel straight spring-steel spines or wires incased in a resilent sheath. 
     The Price U.S. Pat. No. 4,184,223, issued on Jan. 22, 1980, discloses a sweeper bristle element having a knob at one end. Additionally, a nylon or similar reinforcing material reinforces the solid elastomeric stem to which the knob is attached. 
     Although the prior art bristles have been generally useful, they have been subject to a number of significant disadvantages. Specifically, the longer lasting of the prior art bristles have often been complex in construction and expensive to manufacture. Those prior art bristles which may be made inexpensively and efficiently are generally prone to wearing out and/or breaking, 
     Accordingly, it is an object of the present invention to provide a railway roadbed bristle which is simple in construction. 
     A further object of the present invention is to provide a railway roadbed bristle of elastomeric material and configured to minimize the risk of breakage. 
     Yet another object of the present invention is to provide a railway roadbed bristle designed to accomodate a great deal of use before wearing out. 
     Yet another object of the present invention is to provide a method for making railway roadbed bristles which is inexpensive, and efficient. 
     SUMMARY OF THE INVENTION 
     These and other objects of the present invention which will be apparent as the description proceeds are accomplished by providing an elongate bristle having at least a first elongate elastomeric member, a second elongate elastomeric member distinct from the first elongate elastomeric member and a first piece of reinforcing strand material. The first elongate member and second elongate member are bonded together with the first piece of reinforcing stranded material there between. The first piece of reinforcing stranded material is further from a bristle center of gravity axis than from the nearest external surface of the bristle. The bristle further includes a third elongate elastomeric member bonded to the second elongate elastomeric member with a second piece of reinforcing stranded material there between. Preferably, the first elongate elastomeric member is U shaped in cross section and the second elongate elastomeric member fills the inside of the U. Preferably, the cylindrically curved external surface corresponding to the base of the U serves as a sweeping surface when the bristles are mounted on a rotary sweeping core. 
     The present invention further includes a process for making sweeper bristles wherein an elongate cavity of a mold is first lined with an elastomeric lining having a concave portion. A first piece of reinforcing stranded material is installed into the concave portion of the elastomeric lining. An elongate elastomeric core member in inserted into the concave portion of the elastomeric lining. Next, a second piece of reinforcing stranded material is installed on top of the elongate elastomeric core member. Following the placement of an elastomeric layer on top of the second piece of reinforcing material, the mold contents are subjected to heat and pressure, thereby forming a bristle by the bonding of the elastomeric lining to the elongate elastomeric core member with the first piece of reinforcing stranded material there between and the bonding of the elongate elastomeric core member to the elastomeric layer with the second piece of reinforcing material there between. Preferably, the mold has a plurality of parallel elongate cavities separated by walls each of which is lined with a separate piece of elastomeric lining whereas the first and second pieces of reinforcing stranded material are installed to extend into a plurality of the mold cavities and the elastomeric layer is placed to extend on the top of a plurality of the mold cavities such that the heating of the mold contents will result in a mold product with a plurality of elongate portions joined by relatively thin portions. Upon the cutting of the mold product at each of the thin portions, the mold product yields a plurality of sweeper bristles. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a broom bristle of the present invention. 
     FIG. 2 is a cross sectional view of the present bristle taken along lines 2--2 of FIG. 3. 
     FIG. 3 is a simplified side view showing the operation of a broom according to the present invention. 
     FIG. 4 is an end view of a mold and parts used to make bristles according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning now to FIG. 1, a railway roadbed bristle according to the present invention has been shown. The bristle 10 includes a first elongate elastomeric member 18 which is generally U shaped in cross section having a concave portion extending along its length between two noncontiguous boundary portions (e.g. the points on the U). Filling the interior of the U shape and bonding to the inside of the first elongate elastomeric member is as second elongate elastomeric member 16, a first piece of reinforcing stranded material 17 being bonded there between. A third elongate elastomeric member 12 is bonded to the second elastomeric member 16 with a second piece of reinforcing stranded material bond 14 being bonded there between. The first or U shaped elongate elastomeric member 18 has a cylindrically curved surface 18B on the external portion of the base of the U. As will be discussed presently, this external cylindrically curved surface 18B is used as the sweeping or leading surface when the bristle 10 is mounted on a rotary sweeping core. 
     Referring now to FIG. 3 of the drawings, there is shown a simplified drawing to illustrate the operation of the bristles 10 of the invention. Specifically, a series of bristles 10 would be mounted around a rotary core 30. The bristles 10 may be mounted by clamps (not shown) or any other manner commonly used and well known in the prior art. The rotary core 30 may be mounted on a railway car (not shown) as is well known in the prior art. As the rotary core moves along the railway track 32, the ballast 34 will be redistributed into the gaps between the ties 36 and generally swept off the ties 36. Curved surface 18B will be the sweeping or leading surface on each bristle. Specifically the ballast will be thrown generally forward in the direction of movement of rotary core 30 as is indicated by ballast 34 T in the drawing. The ballast 34 will be generally re-distributed in an even manner along the surface of the track as is desirable. 
     Turning now to FIG. 2, for viewing in conjunction with both FIG. 1 and FIG. 3, there is shown a cross sectional view taken along lines 2--2 of FIG. 3. Specifically, the cross section of a bristle 10 is shown. Note that the cross section could be taken anywhere along the length of the bristle 10 in as much as the cross section is the same any place on its length or axis. As is shown in FIG. 2, the second elongate elastomeric member 16 constitutes a core surrounded, except on its ends, by the first elastomeric member 18 and the third elastomeric member 14. It will be readily appreciated that the first elongate elastomeric member 18 and the third elongate elastomeric member 12 together constitute a skin covering the elongate elastomeric core member 16 at any place along its length. Moreover, the first and second pieces of reinforcing stranded material 17 and 14 are bonded co-extensively with the interface between the core member 18 and the skin members 14 and 18. As previous mentioned, the cylindrically curved external surface 18 B is used as a sweeping surface. The third elongate elastomeric or skin member 12 has an external generally flat surface 12F which will be the trailing surface when the bristle is in operation on a rotary sweeping core. As clearly shown in FIG. 2 the first, second, and third elastomeric members are distinct from each other. Further, FIG. 2 shows that the bristle is solid, not hollow, in construction. 
     An important aspect of the present invention is the use of reinforcing stranded material which is near the external surfaces of the bristle 10. More specifically, as shown in FIG. 2, the pieces of reinforcing stranded material 14 and 17 are further from the center of gravity axis (labeled C. G.) than from the nearest external surface of the bristle. By installing the reinforcing stranded material near the surface of the bristle, the strength of the reinforcing stranded material in tension will prevent premature cracking and breaking of the bristle at the point of maximum bending stress. Additionally, this reinforcing stranded material installed near the surface will provide greater stiffness of the bristles leading to better sweeping action. 
     In addition to the placement of reinforcing stranded material near the surface of the bristle, the present invention is especially advantageous in the shape and contours of the individual pieces making up the bristle element 10. More specifically, the U shaped interior surface of skin or first elongate elastomeric 18 is especially advantageous in cooperating with the reinforcing stranded material 17 to distribute any stresses caused by the bristle hitting a piece of ballast or similar debris. The contours at the interface between core member 16 and skin member 18 causes any such stresses to be distributed throughout a wide area thereof. The third elongate elastomeric or skin member 12 is bonded to the curved skin member 18, thereby allowing some of the stress on curved skin member 18 to be transmitted to the backside of core member 16 by way of flat skin member 12 and reinforcing material 14 disposed in between flat skin member 12 and the core member 16. Further, the use of a curved leading or sweeping surface 18B is advantageous in providing a sideways (into or out of the plain of FIG. 3) component to the velocity imparted to the ballast material 34T. This will tend to evenly distribute the ballast throughout the width of the roadway track, instead of merely throwing it along the length of the track. The cylindrically curved sweeping surface 18B is especially adapted to hold up for a long period of use under harsh conditions. 
     Turning now to FIG. 4, a method of making a bristle will presently be discussed. A mold 50 having a series of elongate cavities 52 separated by walls 54 is initially lined with a elastomeric lining 28. Preferably, a separate piece of elastomeric lining 28 is placed in each of the series of generally parallel elongate cavities. Each piece of elastomeric lining 28 is U-shaped with a concave portion. Note that those numbers in FIG. 4 in the 20 series generally correspond by a difference of 10 to the numbers of FIG. 1 and FIG. 2 in the 10 series. For example, the elastomeric lining 28 will correspond to the first elongate elastomeric member 18 in the bristle 10 produced by the process of molding illustrated in FIG. 4. 
     Following the lining of the mold cavity with elastomeric lining, a first piece of reinforcing stranded material 27 is distributed throughout a plurality of the mold cavities 52 as shown. An elongate elastomeric core member 26 is inserted into the concave portion of the elastomeric lining 28. A second piece of reinforcing stranded material 24 is then installed on top of the elongate elastomeric core member, the reinforcing stranded material 24 extending over a number of the similarly situated core members 26. Next, an elastomeric layer is placed on top of the second piece reinforcing stranded material, the elastomeric layer also extending throughout or over several of the mold cavities 52. The loaded mold should now be placed in a molding machine which consists of upper and lower heated plates arranged to provide a clamping force on the mold of about 120 pounds per square inch which presses the raw rubber or similar elastomeric material and the nylon or similar reinforcing stranded material into a solid mass in the mold and heat cures the raw rubber into a solid section securely bonding the rubber and reinforcing material in about one hour of curing time. Upon completion of the curing period the mold pressure is released and the mold is removed. As will be readily appreciated, the mold product will be a plurality of elongate portions joined by relatively thin portions, the relatively thin portions corresponding to the walls 54 in between the mold cavities 52. Next, the mold product may be cut at each thin portion, thereby dividing the mold product into a plurality of separate elongate pieces. Although each elongate piece may constitute a sweeper bristle, it is preferred to practice the present inventive process with twelve feet along elongate pieces which may then be cut into twelve or eighteen inch lengths before use as bristles. Preferably, the machine used to make these bristles is a truck tread molding machine which will accept a mold twelve feet long by two feet wide by three inches thick and heat to various temperature ranges well-known in the art. After cutting the mold product along the thin portions, one will obtain twelve elongate pieces, each being twelve feet long and suitable for cutting into a plurality of bristles, the number of bristles being dependent upon the desired length. 
     Although the various elastomeric members and pieces of the present invention are preferably made of rubber and the reinforcing stranded material is preferably a fabric such as nylon, it will be readily appreciated that the present invention is not so limited except where otherwise noted in the appended claims. More geneally, although specific constructions, steps and features have been discussed in detail, it is to be readily appreciated that these are for illustrative purposes only. Various changes and modifications will readily occur to those of ordinary skill in the art and, accordingly, the scope of the present inventin should be determined by reference to the appended claims.