Patent Publication Number: US-9896884-B2

Title: Telescopic ladder for firefighting vehicle

Description:
RELATED APPLICATIONS 
     This non-provisional patent application claims priority to U.S. Provisional Patent Application Ser. No. 62/150,060 filed on Apr. 20, 2015, and entitled “EXTENSION LADDER FOR AERIAL FIREFIGHTING VEHICLE,” the disclosure of which is herein incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a telescopic ladder for a firefighting vehicle. More specifically, the invention relates to a multiple-section telescopic ladder with an extension support system for facilitating extension and retraction of the ladder&#39;s multiple sections. 
     BACKGROUND 
     Firefighting vehicles, such as ladder trucks, are often equipped with aerial ladders configured to be rotated, raised, lowered, and extended. Certain aerial ladders may be extended in excess of one hundred feet, such as may be required to aid firefighters in fighting fires in multiple story buildings and/or in conducting rescues therefrom. Generally, aerial ladders are hydraulically operated, such that the ladders may be raised, rotated, and/or extended to an operative position and lowered and retracted to a stowed position. 
     Aerial ladders often comprise a plurality of individual ladder sections, which are configured to telescopically extend and retract with respect to each other. Specifically, the individual ladder sections of an aerial ladder are configured to telescopically extend from a retracted position so as to extend the entire reach of the ladder. 
     The individual ladder sections are often formed from high-strength material, such as steel or aluminum. As such, each of the individual ladder sections can weigh a significant amount, such that the individual ladder sections may undergo significant frictional forces (i.e., static and dynamic friction) during extension and retraction. Furthermore, when the ladders are extended and/or at least partially raised in an operational configuration, significant forces are applied to the individual ladder sections due to the weight of the individual ladder sections and due to any personnel or equipment supported thereon. 
     Accordingly there exists a need for an aerial ladder with an extension support system for supporting the significant weight of individual ladder sections of the aerial ladder and for minimizing the frictional forces experienced by the individual ladder sections during extension and retraction. 
     SUMMARY OF THE INVENTION 
     In one embodiment of the present invention, there is provided a firefighting vehicle comprising a vehicle body, a telescopic ladder attached to the vehicle body, and an extension support for facilitating the extension of the second ladder section with respect to the first ladder section. The telescopic ladder includes a first ladder section and a second ladder section, with the second ladder section being configured to telescopically extend from the first ladder section. The extension support provides for the second ladder section to extend from the first ladder section while experiencing a coefficient of friction of less than 0.10. 
     In another embodiment of the present invention, there is provided a telescopic ladder for a vehicle. The telescopic ladder comprises a first ladder section and a second ladder section, with the second ladder section being configured to telescopically extend from the first ladder section, and an extension support for facilitating the extension of the second ladder section from the first ladder section. The extension support provides for the second ladder section to extend from the first ladder section while experiencing a coefficient of friction of less than 0.075. Furthermore, the extension support does not require the use of lubrication. 
     In still another embodiment of the present invention, there is provided a method of operating a telescopic ladder for a vehicle, with the telescopic ladder including at least a first ladder section and a second ladder section, and with the second ladder section being configured to telescopically extend and retract from the first ladder section. The method comprises the initial step of extending the second ladder section with respect to the first ladder section. During the extending step, the second ladder section is at least partially vertically supported by a front roller assembly located on a front portion of the first ladder section and at least partially vertically supported by a cam-follower assembly located on a rear portion of the second ladder section. The method comprises the additional step of retracting the second ladder section with respect to the first ladder section. 
     In yet another embodiment of the present invention, there is provided a telescopic ladder for a vehicle. The telescopic ladder comprises a first ladder section and a second ladder section, with each ladder section comprising a front portion and a rear portion and each including opposing sides extending from the front portion to the rear portion. The second ladder section is configured to telescopically extend from the first ladder section. The telescopic ladder further includes an extension support for facilitating the extension of the second ladder section from the first ladder section. The extension support includes at least one front roller assembly positioned adjacent to the front portion of the first ladder section, at least one pair of side roller assemblies positioned on the sides of the first ladder section, with side roller assemblies from each pair laterally aligned with respect to the first ladder section, and at least one pair of cam-follower assemblies positioned on the sides of the second ladder section adjacent to the rear portion of the second ladder section. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Other aspects and advantages of the invention will be apparent from the following detailed description of the embodiments and the accompanying drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Embodiments of the present invention are described herein with reference to the following drawing figures, wherein: 
         FIG. 1  is side elevation view of a firefighting vehicle with a telescopic ladder according to embodiments of the present invention, with the telescopic ladder in a retracted position; 
         FIG. 2  is side elevation view of the firefighting vehicle from  FIG. 1 , with the vehicle shown in a smaller scale to illustrate the telescopic ladder in an extended position; 
         FIG. 3  is a top partial plan view of the telescopic ladder from  FIG. 1 ; 
         FIG. 4  is a bottom partial perspective view of the telescopic ladder from  FIG. 3 ; 
         FIG. 5  is a cross-section of the telescopic ladder of  FIG. 3  taken along the line  5 - 5 ; 
         FIG. 6  is a front perspective view of a first bottom section of the telescopic ladder of  FIG. 3 ; 
         FIG. 7  is a perspective exploded view of a front roller assembly from a third bottom section of the telescopic ladder of  FIG. 3 ; 
         FIG. 8  is a front left perspective view of the first bottom section of  FIG. 6 ; 
         FIG. 9  is a perspective exploded view of a side roller assembly from the third bottom section of  FIG. 7 ; 
         FIG. 10  is a cross-section of the telescopic ladder of  FIG. 3  taken along the line  10 - 10 ; 
         FIG. 10 a    is an enlarged partial view of the circled area labeled “a” of  FIG. 10 , with a portion of the telescopic ladder removed to shown side roller assemblies and cam-follower assemblies of the present invention; 
         FIG. 11  is a cross-section of the telescopic ladder of  FIG. 3  taken along the line  11 - 11 , particularly showing cam-follower assemblies in phantom line; 
         FIG. 12  is a rear perspective partial view of a first ladder section, a second ladder section, and a third ladder section, particularly showing cam-follower assemblies attached to the second and third sections; 
         FIG. 13  is a front perspective view of a cam-follower assembly according to embodiments of the present invention; 
         FIG. 14  is a rear perspective exploded view of the cam-follower assembly of  FIG. 13 ; 
         FIG. 15  is a front perspective view of a cam-follower assembly according to an additional embodiment of the present invention; and 
         FIG. 16  is a rear perspective exploded view of the cam-follower assembly of  FIG. 15 . 
     
    
    
     The drawing figures do not limit the invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. 
     DETAILED DESCRIPTION 
     The following detailed description of the invention references the accompanying drawings that illustrate specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense. The scope of the invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled. 
     In this description, references to “one embodiment,” “an embodiment,” or “embodiments” mean that the feature or features being referred to are included in at least one embodiment of the technology. Separate references to “one embodiment,” “an embodiment,” or “embodiments” in this description do not necessarily refer to the same embodiment and are also not mutually exclusive unless so stated and/or except as will be readily apparent to those skilled in the art from the description. For example, a feature, structure, act, etc. described in one embodiment may also be included in other embodiments, but is not necessarily included. Thus, the technology can include a variety of combinations and/or integrations of the embodiments described herein. 
     Embodiments of the present invention generally relate to multiple-section aerial ladders for firefighting vehicles, and particularly to an extension support system for supporting each of the sections of the aerial ladder and for improving the function of such sections during extension and retraction. The present invention can be employed in emergency vehicles, such as firefighting vehicles and/or trucks similar to those described and illustrated in U.S. Pat. Nos. 4,570,973 and 5,368,315, the entire disclosures of which are incorporated herein by reference.  FIGS. 1-2 , depict an exemplary aerial firefighting vehicle  10  on which a ladder  12  of the present invention can be integrated. The ladder  12  may be configured to rotate and pivot with respect to the vehicle  10 , via a ladder connection  11  from which the ladder  12  is rotatably secured (in both horizontal and vertical directions) to the vehicle  10 . 
       FIG. 1  is illustrative of the ladder  12  in a retracted position, while  FIG. 2  is illustrative of the ladder  12  in an extended position. As perhaps best shown by  FIGS. 2 and 3 , the ladder  12  includes multiple ladder sections  14 ,  15 ,  16 , and  17 , which are configured to actuate so as to extend and retract the ladder  12 . Although the figures illustrate a ladder  12  with four ladder sections, it should be understood that the ladder  12  may have more or less than four ladder sections. As shown, each of the ladder sections  15 ,  16 , and  17  may telescopically extend with respect to ladder sections  14 ,  15 , and  16 , respectively, such that the ladder  12  will transition from the retracted position (i.e.,  FIG. 1 ) to the extended position (i.e.,  FIG. 2 ). As such, ladder sections  14 ,  15 , and  16  may be referred to as lower ladder sections when referenced in relation to ladder sections  15 ,  16 , and  17 , respectively. Likewise ladder sections  15 ,  16 , and  17  may be referred to as upper ladder sections when referenced in relation to ladder sections  14 ,  15 , and  16 , respectively. For instance, ladder section  14  may be a lower ladder section with respect to section  15 , and section  15  may be an upper ladder section with respect to section  14 . Similarly, section  15  may be a lower ladder section with respect to section  16 , and section  16  may be an upper ladder section with respect to section  15 . Similarly, section  16  may be a lower ladder section with respect to section  17 , and section  17  may be an upper ladder section with respect to section  16 . As such, each of the upper ladder sections (i.e., sections  15 ,  16 , and  17 ) is configured to telescopically extend with respect to its adjacent lower ladder section (i.e., sections  14 ,  15 , and  16 ). 
     With reference to  FIG. 4 , each of the ladder sections  14 ,  15 ,  16 , and  17  of the ladder  12  may include a pair of base rails  18  and a pair of top rails  19  (only one of each of the pairs of top rails  19  are in view in  FIG. 4 ). The base rails  18  of each of the ladder sections  14 ,  15 ,  16 , and  17  may be interconnected via support members extending therebetween. Similarly, each of the top rails  19  may be interconnected to one of the base rails  18  via support members extending therebetween. The base rails  18 , top rails  19 , and the support members may be formed from material with high strength and durability, such as steel, aluminum, or the like. In some embodiments portions of the ladder  12 , such as the base rails  18 , will be coated with a corrosion-resistant material, such as zinc, to reduce the amount of corrosion that can affect the ladder  12  over time. For instance, ladders can deteriorate due to corrosion that results from the rollers repeatedly and/or continuously contacting the surfaces of the ladders during use. Embodiments of the present invention reduce such deterioration by incorporating a corrosion-resistant material, such as zinc, on the surface of the ladders. 
     The upper ladder sections  15 ,  16 ,  17  may be caused to extend via one or more actuating mechanisms. In some embodiments, section  15  can be extended from within section  14  via hydraulic actuation. Specifically, a hydraulic actuator can act on a rear portion of section  15 , thereby causing section  15  to extend from section  14 . As used herein with respect to the ladder sections  14 ,  15 ,  16 ,  17 , the term “rear” means a position or direction proximally directed towards the ladder connection  11 , which as described above, connects the ladder  12  with the vehicle  10 . Alternatively, the term “front” means a position or direction distally directed away from the ladder connection  11 . The term “right” means a right-side direction when viewing from the ladder connection  11  distally along a length of the ladder  12 , and the term “left” means a left-side direction when viewing from the ladder connection  11  distally along the length of the ladder  12 . Returning to the description of the actuating mechanisms, in some embodiments, the hydraulic actuator may be used to extend the remaining upper ladder sections  16 ,  17 . In other embodiments, however, other types of actuating mechanisms may be used to cause the upper ladder sections  15 ,  16 ,  17  to extend and retract. For example, a cylinder and cable system, a winch and pulley system (e.g., a cable system), a chain system, a gear system, pneumatic system, or the like, or combinations thereof may be used. 
     To facilitate the extension and retraction of the upper ladder sections  15 ,  16 ,  17 , embodiments of the present invention may include an extension support system for supporting each of the upper ladder sections  15 ,  16 ,  17 . As will be discussed in more detail below, the extension support system may broadly comprise front roller assemblies, side roller assemblies, and cam-follower assemblies, each of which will be described below with reference to the drawings. 
     With reference to  FIGS. 4-7 , the extension support system may include front roller assemblies  20  located a front portion of each of the lower ladder sections  14 ,  15 ,  16 . As perhaps best shown by  FIG. 6 , some embodiments of the ladder  12  may include two front roller assemblies  20  on each of the ladder sections  14 ,  15 ,  16  (only ladder section  14  is shown in  FIG. 6 ), with one roller assembly  20  positioned on each of the left and ride sides of the front portions of the lower ladder sections  14 ,  15 ,  16 . As perhaps best shown by  FIG. 7 , in some embodiments, each of the roller assemblies  20  may comprise two or more front rollers  22  rotatably secured within a front bracket  24  coupled with the lower ladder sections  14 ,  15 ,  16  (only lower ladder section  16  shown in  FIG. 7 ). 
     In such a configuration, and with reference to  FIG. 4 , the upper ladder sections  15 ,  16 ,  17  are configured to telescopically extend from the lower ladder sections  14 ,  15 ,  16  by rolling on the front roller assemblies  20 . Specifically, a bottom surface of the base rails  18  of the upper ladder sections  15 ,  16 ,  17  are positioned on and are configured to roll across the front rollers  22  of the roller assemblies  20 . The ability of the upper ladder sections  15 ,  16 ,  17  to roll on the front roller assemblies  20  significantly reduces the friction experienced between the upper and lower ladder sections during extension and retraction. Furthermore, the front rollers  22  may allow for more uniform frictional forces to be applied to the base rails  18  of the upper ladder sections  15 ,  16 ,  17 , thereby allowing for smoother operation than previously-used pad systems. Although configured to reduce friction, the mechanical strength of the front roller assemblies  20  is sufficient to support the upper ladder sections  15 ,  16 ,  17  during extension and retraction, as well as while the upper ladder sections  15 ,  16 , and  17  are in static positions. 
     Remaining with  FIG. 4 , the front roller assemblies  20  may be secured to the lower ladder sections  14 ,  15 ,  16 , such that the front rollers  22  are orientated along a horizontal axis of rotation extending perpendicularly between the base rails  18  of the ladder  12 . As used herein with reference to the rollers described throughout this description, the term horizontal means horizontal with respect to the ladder section  14 ,  15 ,  16 ,  17  with which the rollers are associated, and the term vertical means vertical with respect to the ladder section  14 ,  15 ,  16 ,  17  with which the rollers are associated. As shown in  FIG. 7 , the front rollers  22  are supported within the front bracket  24  by way of pins  26  that are secured to the front bracket  24  and that extend along the axis of rotation of their associated front roller  22 . The front roller assemblies  20  may additionally include roller bearings, washers, end-caps, and the like, which allow the pins  26  and the front rollers  22  to be secured in position, while facilitating the ability of the front rollers  22  to freely rotate about their axes of rotation. 
     Given the above, the front roller assemblies  20  positioned on lower ladder section  14 ,  15 , and/or  16  are configured to facilitate extension and retraction of upper ladder sections  15 ,  16 , and/or  17  respectively, by allowing the upper ladder sections  15 ,  16 , and/or  17  to extend or retract by rolling on top of the front roller assemblies  20 . The front rollers  22  may be formed from various materials that provide sufficient strength, durability, and reduced friction. For instance, in some embodiments, the front rollers  22  may be formed from a polymer, such as from polyurethane. Embodiments of the present invention may provide for the front rollers  22  to have an outer diameter of at least 3 inches, at least 3.25 inches, at least 3.5 inches, at least 3.75 inches, or at least 4 inches, and/or no more than 6 inches, no more than 5.75 inches, no more than 5.5 inches, no more than 5.25 inches, or no more than 5 inches. 
     With particular reference to  FIGS. 6-7 , the front brackets  24  may be formed as C-channel brackets secured to and supported on the front portions of lower ladder sections  14 ,  15 ,  16  (only lower ladder section  14  shown in  FIGS. 6-7 ). In particular, the front brackets  24  may be secured to the base rails  18  and/or to the support members connected between the base rails  18 . In some embodiments, the front brackets  24  may be secured to the base rails  18  or to the support members via weldments that are secured to the base rails  18  or to the support members. The front brackets  24  may be secured to the lower ladder sections  14 ,  15 ,  16  (e.g., to the weldments) via one or more elastic devices  28 , such as elastomeric materials, springs, or the like. In some embodiments, such as illustrated in the figures, the elastic devices  28  may comprise Belleville springs. In certain embodiments, each front bracket  24  will include at least two elastic devices  28  positioned generally under each of the front rollers  22  (i.e., for a total of four elastic devices  28 ). As such, the elastic devices  28  are configured to permit the front bracket  24  to pivot about two axes of rotation, such that each of the front rollers  22  will maintain consistent and simultaneous contact with the base rails  18  of the upper ladder section  15 ,  16 ,  17 , which are being supported by the front roller assemblies  20  during extension and/or retraction. 
     Turning to  FIGS. 8-10   a , the extension support system may additionally include a plurality of side roller assemblies  30  positioned on each of the lower ladder sections  14 ,  15 ,  16  (only the lower section  14  is shown in  FIG. 8  and the lower section  16  is shown in  FIG. 9 ). As illustrated by  FIG. 8 , each lower ladder section  14 ,  15 ,  16  may include four or more side roller assemblies  30  located on the left and right sides of the lower ladder sections  14 ,  15 ,  16  and positioned towards a front half of the lower ladder sections  14 ,  15 ,  16 . Specifically, the side roller assemblies  30  may be positioned on a top surface of the base rails  18  of the lower ladder sections  14 ,  15 ,  16 . As shown in the drawings, the side roller assemblies  30  may be incorporated on the lower ladder sections  14 ,  15 ,  16  in pairs, such that each side roller assembly  30  on one of the base rails  18  is positioned directly across from an opposing side roller assembly  30  on the other of the base rails  18 . Although  FIG. 8  illustrates a lower ladder section (e.g., lower ladder section  14 ,  15 ,  16 ) having four side roller assemblies  30  (i.e., two on each base rail  14 ), it is understood that embodiments of the present invention may provide for more or less than four side roller assemblies on each lower ladder section  14 ,  15 ,  16 . 
     As shown in  FIGS. 8-9 , the side roller assemblies  30  may each comprise a side roller  32 , a side support bracket  34 , a position adjustment mechanism  36 , a base section  38 , and an overturning restraint component  40 . The side rollers  32  may be rotatably secured, along a vertical axis of rotation, within the side support bracket  34 . With reference to  FIG. 9 , each of the side rollers  32  may be supported within its associated side support bracket  34  by way of a pin  41  that is configured to be received within the side support bracket  34 . The pin  41  may comprise an axle about which the side roller  32  rotates, such that the pin  41  extends along the axis of rotation of the side roller  32 . In some embodiments, the side roller assemblies  30  may additionally include roller bearings positioned between the side rollers  32  and their associated pins  41  to facilitate rotation of the side rollers  32 . Furthermore, the side roller assemblies  30  may include end-caps, nuts, washers, and the like, which allow the pins  41  and the side rollers  32  to be secured in position with respect to the side support bracket  34 , while facilitating the ability of the side rollers  32  to rotate about their axes of rotation. The side rollers  32  may be formed from various materials, such as metal (e.g., steel, stainless steel, etc.), polymers, or the like. 
     The side support bracket  34  may be adjustably secured to the base section  38 , via the position adjustment mechanism  36 . In more detail, as shown in  FIG. 9 , the base section  38  can be rigidly secured to the top surface of the base rail  18 , such as via a mechanical fastener, welding, or the like. With the base section  38  rigidly secured to the base rail  18 , the side support bracket  34  and the side roller  32  can be horizontally shifted with respect to the base section  38  via the position adjustment mechanism  36 . The position adjustment mechanism  36  may comprise an adjustable bolt, or a nut/bolt combination, or other component that extends from the base section  38  and into the side support bracket  34 . As such, the side support bracket  34  (and the roller  32  supported therein) may have their horizontal positions adjusted by actuating the position adjustment mechanism  36 . For example, the positions of the side support bracket  34  and the roller  32  can be adjusted inwardly (i.e., toward a longitudinal centerline of the ladder section  14 ,  15 ,  16 ) by actuating the position adjustment mechanism  36  in a first direction (e.g., rotating the nut of the nut/bolt combination in a first direction). Alternatively, the positions of the side support bracket  34  and the rollers  32  can be adjusted outwardly (i.e., away from the longitudinal centerline of the ladder  12 ) by actuating the position adjustment mechanism  36  in a second direction (e.g., rotating the nut of the nut/bolt combination in an opposite second direction). 
     As perhaps best shown in  FIGS. 8-9 , the overturning restraint  40  may be secured to the base section  38  and may extend over a top of the side support bracket  34  and the side roller  32 . The overturning restraint  40  may be secured to the base section  38  via mechanical fasteners, welding, or the like. At least a portion of the overturning restraint may be formed from metal (e.g., steel, stainless steel, etc.), nylatron, or combinations thereof. 
     As will be discussed in more detail below, the side roller assemblies  30  are configured to facilitate extension and retraction of the upper ladder sections  15 ,  16 ,  17 , while maintaining proper positioning and alignment of the upper ladder sections  15 ,  16 ,  17  during extension and retraction and/or during operation of the telescopic ladder  12 . For example, with a given upper ladder section  15 ,  16 , or  17  nested within its adjacent lower ladder section  14 ,  15 , or  16 , the upper ladder section  15 ,  16 , or  17  will be held centered within the lower ladder section  14 ,  15 , or  16  via the side roller assemblies  30 . Specifically, with reference to  FIGS. 10 and 10   a , exterior surfaces of the upper ladder section&#39;s  15 ,  16 , or  17  base rails  18  will be in contact with the side rollers  32  of the side roller assemblies  30  of adjacent lower ladder sections  14 ,  15 , or  16 , respectively, such that the side roller assemblies  30  keep the upper ladder section  15 ,  16 , or  17  generally centered. Beneficially, the ability for the side roller  32  and the side support bracket  34  to be horizontally shifted ensures that the upper ladder section  15 ,  16 , or  17  can be properly centered. Furthermore, as perhaps best shown by  FIGS. 10 and 10   a , the upper ladder sections  15 ,  16 , or  17  are positioned such that the overturning restraints  40  at least partially overhang the top surface of each of the base rails  18 . As such, the overturning restraint  40  is operable to restrict the upper ladder sections  15 ,  16 ,  17  from rotating or overturning out of position with respect to adjacent lower ladder sections  14 ,  15 ,  16 . 
     With reference to  FIGS. 11-15 , the extension support system further includes one or more cam-follower assemblies  50  located at a rear portion of each of the upper ladder sections  15 ,  16 ,  17 . As partially illustrated in  FIG. 12 , each of the upper ladder sections  15 ,  16 ,  17  may include two cam-follower assemblies  50 , with one cam-follower assembly  50  positioned on each side of the rear portion of the upper ladder sections  15 ,  16 ,  17  (only the cam-follower assemblies  50  of upper ladder sections  15  and  16  are shown in  FIG. 12 ). In particular, the cam-follower assemblies  50  may be positioned on outer surfaces of the base rails  18  of their associated upper ladder section  15 ,  16 ,  17 , such that the cam-follower assemblies  50  can engage with the adjacent lower ladder sections  14 ,  15 ,  16 , as will be described in more detail below. 
     With reference to  FIGS. 12-14 , the cam-follower assemblies  50  may each comprise a mounting housing  52  rotatably secured, via a rotation shaft  54 , to the outer surface of the base rail  18  (base rail  18  not shown in  FIGS. 13-14 ). The mounting housing  52  and the rotation shaft  54  may be formed from materials with high strength and durability, such as steel, stainless steel, or the like. The cam-follower assemblies  50  may each further comprise a pair of cam-followers  56  rotatably secured on each opposing end of the mounting housing  52 . The cam-followers  56  may be formed from metal (e.g., steel, stainless steel, etc.), polymer, or the like. 
     With the cam-follower assemblies  50  positioned on the upper ladder sections  15 ,  16 ,  17 , the cam-followers  56  are configured to be received within cam-follower tracks  58  (See  FIGS. 6, 8, 10   a , and  11 - 12 ) formed within the base rails  18  of adjacent lower ladder sections  14 ,  15 ,  16 . In more detail, the cam-follower tracks  58  may comprise longitudinal openings, grooves, and/or channels formed on the interior surfaces of the base rails  18 . As will be described in more detail below, the cam-follower assemblies  50  support the rear portions of the upper ladder sections  15 ,  16 ,  17  during extension and retraction, as well as while the upper ladder sections  15 ,  16 , and  17  are in static positions. Furthermore, the cam-follower assemblies  50  provide such support while facilitating the ability of the upper ladder sections  15 ,  16 ,  17  to extend and retract from within the lower ladder sections in reduced-frictional manner. Specifically, such reduced-frictional manner of extension and retraction is facilitated by the cam-followers  56 , which roll along and/or within the cam-follower tracks  58  during such extension or retraction. As such, the cam-followers  56  support the upper ladder sections  15 ,  16 ,  17  with respect to the lower ladder section  14 ,  15 ,  16 , while facilitating extension and retraction of the upper ladder sections  15 ,  16 ,  17  during extension and retraction. 
     With particular reference to  FIGS. 15-16 , certain embodiments of the present invention provide for the cam-follower assemblies  50  to include a support pad elements  60  secured to the mounting housing  52  between the cam-followers  56 . The support pad elements  60  may be secured to the mounting housing  52  via a base element  62 , as illustrated in  FIG. 17 . Specifically, the base element  62  may be rigidly secured to the mounting housing  52  via mechanical fastener, welding, or the like, while the support pad element  60  may be removably secured to the base element  62  via mechanical fasteners or the like. The support pad element  60  may be formed from various materials, such as polymers, nylatron, or the like. The support pad element  60  is configured to provide additional support for the upper ladder sections  15 ,  16 ,  17  during extension and retraction from within the lower ladder sections  15 ,  15 ,  16 , respectively. In particular, the top and/or sides portions of the support pad elements  60  are configured to contact the interior portions of the cam-follower track  58  so as to further support the upper ladder sections  15 ,  16 ,  17  during extension and retraction, as well as during operational use of the ladder  12 . In certain embodiments, the support pad elements  60  may only be used on the cam-follower assemblies  50  of certain of the upper ladder sections (e.g., sections  15  and  16 ), which may be required to support the total overall weight of multiple upper ladder sections (e.g., sections  15 ,  16 , and/or  17 ), as well as any personnel and firefighting equipment (e.g., ladder pipes and discharge monitors). 
     In operation, the extension support system described above facilitates and enhances the ability of individual sections  14 ,  15 ,  16 ,  17  of the ladder  12  to telescopically extend and retract with respect to each other. Although for brevity the following description of the operation of the ladder  12  is described with reference to a single lower ladder section (i.e., lower ladder section  14 ) and a single upper ladder section (i.e., upper ladder section  15 ), it should be understood that the components of the extension support system can similarly be used on other lower ladder sections (e.g.,  15  and  16 ) to facilitate extension and retraction of the other upper ladder sections (e.g.,  16  and  17 ). 
     To begin operation of the ladder  12 , the ladder  12  will generally be in the retracted position, such as shown in  FIG. 1 , with the upper ladder section  15  retracted within (i.e., nested within) the lower ladder section  14 . In such a configuration, the upper ladder section  15  has generally all of its weight (and any weight from other upper ladder sections, e.g., sections  16  and  17 ) supported by the lower ladder section  14 . To accomplish such support, a front portion of the upper ladder section  15  is supported by the front roller assemblies  20  positioned on each of the left and right sides of the front portion of the lower ladder section  14 . A rear portion of the upper ladder section  15  is supported by the cam-follower assemblies  50  on the left and right sides of the rear portion of the upper ladder section  15 . Specifically, the cam-followers  56  on each of the left and right sides of the rear portion of the upper ladder section  15  are received within the cam-follower tracks  58  formed through the interior surfaces of the base rails  18  of the lower ladder section  14 . Furthermore, the upper ladder section  15  is supported in a generally centered position within the lower ladder section  14  via the side roller assemblies  30 . 
     The upper ladder section  15  can be extended out from the front portion of the bottom section  14  via an actuation mechanism, such as a hydraulic actuator, that acts on the rear portion of the upper ladder section  15 . It should be understood that in some embodiments, other types of actuating mechanisms may be used to cause the individual ladder sections to extend and/or retract, as was previously described. Once the upper ladder section  15  begins to extend our from the front of the lower ladder section  14 , the bottom surface of the base rails  18  of the upper ladder section  15  will begin to roll along the front roller assemblies  20  of the lower ladder section  14 . Simultaneously, the cam-followers  56  of the upper ladder section  15  will begin to roll along the cam-follower tracks  58  of the lower ladder section  14 . 
     Beneficially, the elastic devices  28  of the front roller assemblies  20  allow each of the front rollers  22  of the front roller assemblies  20  to remain in constant contact with the base rails  18  of the upper ladder section  15  so as to provide enhanced support and to reduce frictional forces experienced between the lower and upper ladder sections  14 ,  15  during extraction and retraction. Similarly, the ability for the cam-followers  56  to pivot about their rotation shaft  54  allows each of the cam-followers  56  of the cam-follower assemblies  50  to remain in constant contact with the cam-follower tracks  58  of the lower ladder section  14  so as to provide enhanced support and to reduce frictional forces experienced between the lower and upper ladder sections  14 ,  15  during extraction and retraction. In embodiments in which the cam-follower assemblies  50  include support pad elements  60 , such support pad elements  60  will further enhance the ability of the cam-follower assemblies to provide support between the between the lower and upper ladder sections  14 ,  15 . 
     Furthermore, it should be understood that when the upper ladder section  15  has at least half of its length positioned over the lower ladder section  14 , the cam-followers  56  of the cam-follower assemblies  50  will impart a downward force on the lower ladder section  14  via the cam-follower tracks  58 . Alternatively, once the upper ladder section  15  has extended to a point that at least half of its length is extended beyond (i.e., overhangs) the front of the lower ladder section  14 , the cam-followers  56  and/or the support pad elements  60  (if included) will impart an upward force on the lower ladder section  14  via the cam-follower tracks  58 . Regardless, the receipt of the cam-followers  56  within the cam-follower tracks  58  will provide support to maintain the upper ladder section  15  firmly in place with respect to the lower ladder section  14  during extension and retraction. 
     Finally, during the extension and retraction of the upper ladder section  15 , the upper section  15  is further maintained in a generally centered position with respect to the lower ladder section  14  via the side roller assemblies  30 . In particular, the exterior side surface of the base rails  18  of the upper ladder section  15  will roll along the plurality of side rollers  32  of the side roller assemblies  30  of the lower ladder section  14 . Beneficially, the position adjustment mechanisms  36  of the side roller assemblies  30  allow the side  32  rollers to be precisely positioned so as to accurately support the upper ladder section  15  in a centralized manner with respect to the lower ladder section  14 . Furthermore, the side roller assemblies  30  are configured to provide lateral support to the ladder  12  during operation of the vehicle  10 , such as during use of ladder pipes or discharge monitors that are operated from the end of the ladder  12 . Furthermore still, the overturning restraint  40  restricts vertical movement of the base rails  18  of the upper ladder section  15  so as prevent the upper ladder section  15  from overturning or tipping during extension or retraction or during operation of the ladder  12  and the vehicle  10 . 
     Embodiments of the present invention are configured to minimize the frictional forces experienced between the individual sections  14 ,  15 ,  16 ,  17  during extension and retraction. For instance, embodiments of the present invention provide for a dynamic coefficient of friction experienced by the upper ladder sections  15 ,  16 ,  17  with respect to the lower ladder sections  14 ,  15 ,  16  during extension and retraction to be less than 0.15, less than 0.125, less than 0.10, less than 0.075, or less than 0.0305, or alternatively, between 0.0305 and 0.15, between 0.075 and 0.125, or between 0.8 and 0.10, as measured according to ASTM D1784 or PTM55008. Such a minimized coefficient of friction being due, at least in part, to the each of the following: front roller assemblies  20  of the lower ladder section  14 ,  15 ,  16 , the side roller assemblies  30  of the lower ladder sections  14 ,  15 ,  16 , the cam-follower assemblies  50  of the upper ladder sections  15 ,  16 ,  17 , or combinations thereof. Beneficially, the extension support system of embodiments of the present invention provides for such reduced coefficient of friction without the use of lubricants, such as grease-type or liquid-type lubricants that are often used with nylatron products. Such reduced friction enhances the longevity of the ladder  12  and its components, such as the individual ladder sections  14 ,  15 ,  16 ,  17 , the actuating mechanisms (e.g., hydraulic systems, cable systems, etc.), and the extension support systems. Furthermore, the extension support system as described above is configured to provide for extension and retraction of the individual ladder sections in a smooth, continuous manner. 
     Furthermore, as noted above, the extension support system of the present invention facilitates the generation of more uniform frictional forces between the extending and/or retracting ladder sections  14 ,  15 ,  16 ,  17 . The generation of uniform frictional forces allows for a smoother operation of the ladder  12 , particularly with respect to previously-used ladders, such as previously-used ladders that incorporate pad-based systems. Specifically, in some previously-used ladders, frictional forces are often high enough to cause a “slip-stick” effect, whereby during extension and/or retraction of the ladders sections, the ladder sections will intermittently be overcome by frictional forces and will entirely stop moving. It is generally understood that it requires a stronger force to overcome a frictional force between two objects if the objects are not moving with respect to each other than if the objects are moving with respect to each other. As such, in previously-used telescopic ladders that experienced “slip-stick,” the force required to overcome the “stick” would impart an impulsive, jerky movement to the ladder sections. Embodiments of the present invention provide for a reduced, uniform frictional force between the ladders sections, thereby providing a smoother operation that avoids such “slip-stick” effects often experienced by previously-used ladders. 
     Although the invention has been described with reference to the preferred embodiment(s), it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention. Thus, the invention described herein is entitled to those equivalents and substitutions that perform substantially the same function in substantially the same way.