Abstract:
A handrail for a gangway and a method for manufacturing the same where the handrail comprises a single, continuous piece of plastic.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to fall restraint equipment components. More particularly, the present invention relates to handrails for gangways. 
     BACKGROUND OF THE INVENTION 
       FIG. 1  illustrates an example of fall restraint equipment  100  comprising a stairwell  102 , a platform  104 , handrails  106 , and a gangway  108 . Stairwell  102  ascends to platform  104 , where gangway  108  is connected. An optional cage  110  may be connected to gangway  108  if desired. Handrails  106  are located on the sides of platform  104  that are not connected to either gangway  108  or stairwell  102  in order to prevent a user from proceeding in a direction from the platform that does not lead to the gangway or the stairwell. In this example, the fall restraint equipment provides a user with access to a top  112  of a container  114  (such as a railway car). 
       FIG. 2  illustrates a gangway  200  that may be used as gangway  108  of  FIG. 1 . Gangway  200  comprises a base tread  202 , which includes two posts or “uprights”  204  connected to base tread support  206 . Uprights  204  are typically welded to base tread support  206  but may be connected to the support by other suitable means, such as by bolting. Base tread  202  is conventionally connected to a fixed structure, such as platform  18  ( FIG. 1 ). A support structure or “underbody”  208  is pivotally connected to base tread support  206  at one end and is pivotally connected to another tread  210 , such as a seatainer tread, at the other end. Seatainer tread  210  is comprised of uprights  212  and  214  connected to each side of a tread support  216 . Each set of uprights  212  and  214  are interconnected by lateral posts  218  and  220 . Lateral posts  218  and  220  may be referred to as “joiners,” “connectors,” or “spacer tubes.” In this example, gangway  200  additionally comprises a pair of self-leveling supports  222  pivotally connected to underbody  208 . Uprights  212  include top portions  226  that are configured to pivotally receive respective portions of a pair of handrails  224 . Likewise, uprights  204  are configured to pivotally receive opposite ends of handrails  224 . Gangway  200  may comprise additional components, such as a pair of supports, handrails, or “blocking rails”  228 , as desired or needed. 
       FIG. 3  is a side view of a handrail  300  that may be used as handrail  224  of  FIG. 2 . Handrail  300  comprises a main body portion  302 , a handle portion  304 , a pair of end caps  306 , a pair of lugs  308 , and a pair of bronze bushings  310 . Main body portion  302  is a metal tube that is sawed to a specific size from larger metal tubing stock material. As should be understood by those of ordinary skill in the art, the length of main body portion  302  depends on the size of the gangway to which it is attached. Similarly, handle portion  304  is manufactured from a metal tube exhibiting a diameter relatively smaller than that exhibited by the metal tubing used to manufacture main body portion  302 . The metal tube is sawed to a specific size from larger stock material and is then bent near both ends at approximately 45° angles. The ends of handle portion  304  are then welded to main body portion  302 . 
     Lugs  308  are also manufactured from larger pieces of stock metal. The stock metal is typically rectangular by nature and must therefore be plasma cut to form lugs  308 . Each of lugs  308  is additionally plasma cut in order to define an aperture within the lug. Bronze bushings  310  are then pushed into the aperture, and lugs  308  are welded to main body portion  302 . Ends caps  306  are specifically manufactured to fit the distal ends of main body portion  302 . After caps  306  have been applied to the ends of main body portion  302 , they are welded to the main body portion. Handrail  300  is then powder coated, which also requires heating the handrail. Lugs  308  and bronze bushings  310  are designed to allow handrail  300  to be connected to a gangway. Referring to  FIGS. 2 and 3 , for instance, the top portions of uprights  204  and  212 , such as portions  226 , are configured to receive lugs  308 . For example, a connecting mechanism such as a carriage bolt or rod is inserted through apertures defined in one side of top portions  226 , through bronze bushings  310 , and through apertures defined in the other side of the top portions. Handrail  300  is connected to gangway  200  in this manner. 
     Manufacturing handrail  300  in this manner is both time-consuming and costly. Additionally, the drilling and cutting of the stock materials must be accomplished with precision in order to create a stable end product. Variances greater than an acceptable level render the smaller pieces unusable, which are typically discarded as it is often unfeasible to use them in another product once they have been drilled or cut. Moreover, if other parts cannot be cut or drilled from the remaining portions of the stock materials, they too are discarded. Further, different types and sizes of the metal stock material must be kept on hand in order to form the components of handrail  300  to be welded together. The inefficient yet inescapable use of stock material also increases the costs associated with manufacturing handrail  300 . 
       FIG. 4  illustrates an exemplary rotational molding process for creating a product comprised primarily of plastic. The rotational molding process consists of four separate steps. First, a hollow mold is made of the desired end product. Next, the mold is filled with a predetermined amount of polymer powder or resin. The powder can be pre-compounded to the desired color of the end product. Typically, the powdered resin is polyethylene, polyvinyl chloride (“PVC”), or nylons. An oven is preheated by convection, conduction, radiation, or any other suitable means to a temperature ranging between 500 and 700° F. (260 to 370° C.) depending on the polymer used. Once the powder is loaded into the mold, the mold is closed, locked, and loaded into the oven. 
     Inside the oven, the mold is rotated about two axes so that the polymer melts and coats the inside of the mold. The rotation speed is relatively slow, such as less than 20 rotations per minute. Those of ordinary skill in the art should understand that the process does not involve centrifugal rotation. Alternatively, the polymer may be melted before rotation of the mold begins. It should be further understood that if the mold is heated for too long a period of time, the polymer will degrade, thereby reducing its impact strength. In contrast, if the mold is heated for too short of a period of time, the polymer will not melt completely and will not fully coalesce on the mold&#39;s walls. As a result, large bubbles may be created within the end product. Those of ordinary skill in the art should understand that the amount of time the mold should be heated depends on certain variables including the shape, size, and configuration of the mold, as well as the polymer used. Heat transfer causes the plastic charge inside the mold to melt and uniformly coat or fill the interior of the mold. Additionally, applying a small amount of pressure internally to the mold during the heating process accelerates coalescence of the polymer. As a result, the end product is produced with fewer bubbles and in less time. 
     Once the heating process is complete, the mold is removed from the oven and cooled, which is typically accomplished though the use of fans. However, water cooling or a combination of the two may be used. Cooling allows the polymer to solidify to the desired shape, as well as shrink slightly so that it may then be handled and removed from the mold. As should be understood, the amount of time required to cool the polymer varies depending on the shape, size, and configuration of the mold, as well as the type of polymer used and the temperature to which it has been heated. It should be further understood that cooling the polymer at a pace too rapid may cause the polymer to shrink too fast and warp the end product. 
     Once the polymer has cooled sufficiently to be handled so that it can retain the end product&#39;s shape, the mold is opened and the product is removed. The process may then be repeated by adding the polymer powder to the mold and repeating. 
     SUMMARY OF THE INVENTION 
     The present invention recognizes and addresses the foregoing considerations, and others, of prior art construction and methods. 
     In this regard, one aspect of the invention provides a method for manufacturing a handrail for a gangway. The method comprises the steps of providing a mold comprising a cavity, where the cavity corresponds to a shape of the handrail, filling the mold with a polymer, heating the mold, rotating the mold, cooling the mold, and removing the handrail from the mold. 
     According to another aspect, the present invention provides a gangway comprising an underbody support structure, a first support surface connected to an end of the underbody support structure, a second support surface connected to another end of the underbody support structure, a left handrail, and a right handrail. A first support surface first upright extends from one side of the first support surface and a first support surface second upright extends from another side of the first support surface. A second support surface first upright extends from one side of the second support surface and a second support surface second upright extends from another side of the second support surface. One end of the left handrail is connected to the first support surface first upright and another end of the left handrail is connected to the second support surface first upright. One end of the right handrail is connected to the first support surface second upright and another end of the right handrail is connected to the second support surface second upright. The right handrail is a single, continuous piece of plastic. 
     Yet another aspect of the present invention provides a handrail for a gangway. The gangway comprises a single, continuous piece of plastic. The single, continuous piece of plastic comprises an elongated, generally cylindrical main body portion and a first tab extending from the elongated, generally cylindrical main body portion. The first tab is adapted to be received by a first portion of the gangway and defines a first aperture through which a first connecting mechanism is passed in order to connect the handrail to the gangway. 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended drawings, in which: 
         FIG. 1  is a perspective view of an exemplary fall restraint system; 
         FIG. 2  is a perspective view of an exemplary gangway that may be used in the system of  FIG. 1 ; 
         FIG. 3  is a side view of an exemplary handrail that may be used in the gangway of  FIG. 2 ; 
         FIG. 4  is a schematic illustrating an exemplary process for a rotational molding process; 
         FIG. 5  is a flowchart illustrating an exemplary process for manufacturing a handrail in accordance with an embodiment of the present invention; 
         FIG. 6  is a perspective view of a gangway handrail in accordance with an embodiment of the present invention; 
         FIG. 7  is a side elevation view of the gangway handrail of  FIG. 6 ; 
         FIG. 8  is a top plan view of the gangway handrail of  FIG. 6 ; 
         FIG. 9  is a front plan view of the gangway handrail of  FIG. 6 ; 
         FIG. 10  is a rear plan view of the gangway handrail of  FIG. 6 ; 
         FIG. 11  is a bottom plan view of the gangway handrail of  FIG. 6 ; 
         FIG. 12  is a perspective view of a gangway handrail in accordance with an embodiment of the present invention; 
         FIG. 13  is a side elevation view of the gangway handrail of  FIG. 12 ; 
         FIG. 14  is a top plan view of the gangway handrail of  FIG. 12 ; 
         FIG. 15  is a front plan view of the gangway handrail of  FIG. 12 ; 
         FIG. 16  is a rear plan view of the gangway handrail of  FIG. 12 ; 
         FIG. 17  is a bottom plan view of the gangway handrail of  FIG. 12 ; 
         FIG. 18  is a perspective view of a gangway handrail in accordance with an embodiment of the present invention; 
         FIG. 19  is a side elevation view of the gangway handrail of  FIG. 18 ; 
         FIG. 20  is a top plan view of the gangway handrail of  FIG. 18 ; 
         FIG. 21  is a front plan view of the gangway handrail of  FIG. 18 ; 
         FIG. 22  is a rear plan view of the gangway handrail of  FIG. 18 ; 
         FIG. 23  is a bottom plan view of the gangway handrail of  FIG. 18 ; 
         FIG. 24  is a perspective view of a gangway handrail in accordance with an embodiment of the present invention; 
         FIG. 25  is a side elevation view of the gangway handrail of  FIG. 24 ; 
         FIG. 26  is a top plan view of the gangway handrail of  FIG. 24 ; 
         FIG. 27  is a front plan view of the gangway handrail of  FIG. 24 ; 
         FIG. 28  is a rear plan view of the gangway handrail of  FIG. 24 ; 
         FIG. 29  is a bottom plan view of the gangway handrail of  FIG. 24 ; 
         FIG. 30  is a perspective view of a gangway handrail in accordance with an embodiment of the present invention; 
         FIG. 31  is a side elevation view of the gangway handrail of  FIG. 30 ; 
         FIG. 32  is a top plan view of the gangway handrail of  FIG. 30 ; 
         FIG. 33  is a front plan view of the gangway handrail of  FIG. 30 ; 
         FIG. 34  is a rear plan view of the gangway handrail of  FIG. 30 ; and 
         FIG. 35  is a bottom plan view of the gangway handrail of  FIG. 30 . 
     
    
    
     Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference will now be made in detail to presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
       FIG. 5  is a flowchart illustrating an exemplary process for manufacturing a handrail for a gangway in accordance with an embodiment of the present invention. At step  500 , stock metal is manipulated to form a mold comprising a cavity representative of a handrail. For instance, the mold comprises a cavity that can hold one of the gangway handrails illustrated in  FIGS. 6 through 35  and described below with reference to  FIG. 18 . 
     At step  502 , the cavity of the mold is filled with a polymer, such as polyethylene, polyvinyl chloride (“PVC”), or nylons. In a preferred embodiment, the mold is filled with cross-linked polyethylene. Although it should be understood by those of ordinary skill in the relevant art that any cross-linked polyethylene resin may be used, in this embodiment, the PAXON 7004 crosslinkable rotational molding powder resin offered by EXXONMOBIL CHEMICAL of Houston, Tex. is used. The powder resin is dry-blended with a pigment so that the handrail exhibits a noticeable color, such as bright orange, once created. It should be understood by those of ordinary skill in the art, however, that other colors may be used as desired. 
     At step  504 , the mold is placed in an oven and heated to approximately 500 to 700° F. Preferably, the molds of the present invention are heated to approximately a range of 510 to 550° F. Once the polymer has melted, the mold is rotated biaxially about both its lateral and medial axes at step  506 . In the presently-described embodiment, the molds are heated for approximately 30 to 35 minutes, but those of ordinary skill in the art should understand that this time may be altered depending on the shape and size of the mold, as well as external factors, such as the time of the year and the temperature of the ambient air. After the mold has been heated a sufficient amount of time, rotation terminates, and the mold is removed from the oven at step  508 . The mold is then cooled at step  510  in order to allow the polymer to solidify and harden. In the presently-described embodiment, the molds are cooled by air and water spray for approximately 30 to 35 minutes. At step  512 , the handrail is then removed from the mold and is one single, integral, continuous piece of plastic as a result of the rotational molding process. Process flow returns to step  502  in order to repeat the process described above so that additional handrails may be manufactured. 
       FIGS. 6 through 35  are exemplary views of handrails created from a rotational molding process in accordance with various embodiments of the present invention. As illustrated in  FIGS. 6 through 35 , handrails may exhibit different sizes, shapes, and configurations depending on the size, shape, and configuration of the gangway to which the handrail is to be connected. It should therefore be understood by those of ordinary skill in the art that the cavity of each mold corresponding to each respective handrail may exhibit the specific shape, size, and configuration of the respective handrail. It is preferable to create a mold for each handrail configuration so that the process described above may be repeated as needed. The handrails illustrated in  FIGS. 6 through 35  vary with respect to size, shape, and configuration, and exhibit different embodiments of the present invention. Accordingly, while the following description is made with reference to  FIG. 18 , those of ordinary skill in the art should understand that the ensuing description is applicable to handrails of varying shapes, sizes, and configurations, including those illustrated in  FIGS. 6 through 35 . 
       FIG. 18  is a perspective view of an exemplary handrail  1800  in accordance with an embodiment of the present invention. Handrail  1800  is created from the rotational molding process described above with respect to  FIG. 5 , and is therefore comprised of a single, continuous piece of plastic. Handrail  1800  comprises a main body portion  1802 , an upper handle portion  1804 , connections  1806  and  1808  between the two, and a pair of tabs  1810 . A front end of main body portion  1802  defines a flat area  1812 , while the opposite end defines a half spherical end  1814 . Each of tabs  1810  defines a respective aperture  1816 . 
     The mold used to create handrail  1800  using the rotational molding process forms connections  1806  and  1808  between upper handle portion  1804  and main body portion  1802 . It should be understood by those of ordinary skill in the art, however, that middle connection  1808  may be unnecessary depending on the size and shape of the handrail. The mold also forms tabs  1810  and defines apertures  1816 , into which bushings are pressed. Tabs  1810 , apertures  1816 , and the bushings are used to connect handrail  1800  to a gangway. That is, portions of the gangway are designed to receive or engage tabs  1810 . Tabs  1810  are inserted into these portions and a connecting mechanism, such as a carriage bolt, rod, or pole, is inserted through one side of these portions, through apertures  1816 , and through the other side of these portions. In this manner, handrail  1800  is connected to the respective gangway. Flat area  1812  is configured to provide clearance between handrail  1800  and portions of the gangway to which the handrail is connected that may have come into contact with main body portion  1802  had the entire main body portion exhibited a cylindrical shape. 
     The bushings inserted into apertures  1816  engage the connecting mechanisms in order to minimize any friction created between the handrail and the portions of the gangway to which they are connected. It is unnecessary to powder coat handrail  1800  at this point because it is plastic and the polymer used to create the handrail is preferably pre-compounded with the handrail&#39;s desired color. Moreover, because handrail  1800  is created from the rotational molding process, the portions of the handrail do not need to be sawed or cut from stock materials and welded together. 
     Those of ordinary skill in the art should understand that the above description discloses a handrail for a gangway manufactured by a rotational molding process. The handrail comprises a single, continuous piece of plastic. As a result, the materials, costs, and time associated with manufacturing a handrail for a gangway are reduced. 
     While one or more preferred embodiments of the invention have been described above, it should be understood that any and all equivalent realizations of the present invention are included within the scope and spirit thereof. The embodiments depicted are presented by way of example only and are not intended as limitations upon the present invention. Thus, it should be understood by those of ordinary skill in this art that the present invention is not limited to these embodiments since modifications can be made. Therefore, it is contemplated that any and all such embodiments are included in the present invention as may fall within the scope and spirit thereof.