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BACKGROUND 
     Many people are reluctant to work on ladders, especially when it is more than a few rungs up. They feel insecure. Also, the available space atop a ladder for the tools and materials to do a job is limited. Even the step ladders with a fold down trays have only a small space available. I personally do not like to work on ladders. There is a lot of climbing up and down to get the right tool or the sealant or retrieving the screw that fell down or whatever. I cling to the ladder and worry, for example, that when I pull out a nail I will fall backward when it releases. 
     Accidents and deaths from falling off of ladders are more prevalent than one might imagine. The Center for Disease Control reported in their weekly Morbidity and Mortality Report (MMWR) of Apr. 25, 2011 (titled “Occupational Ladder Fall Injuries-United States, 2011) that “falls remain a leading cause of unintentional injury/mortality nationwide, and 43% of fatal falls in the last decade have involved a ladder. Among construction workers, an estimated 81% of fall injuries treated in U.S. emergency departments (EDs) involve a ladder.” There is clearly the need for a safer way to access work areas that are too high to reach normally. One day when I was studying the rust stain on an outside wall that was caused by rust in a second story window, I thought to myself, “Never in a million years will I climb up there on a ladder and clean that up”. That&#39;s when I realized that I could invent/build an electric ladder with a platform that would carry me and my tools up there where I could work comfortably and with a feeling of security. The current technology in small high power motors, new improved batteries with higher capacities, and improved high strength composite materials now make it feasible to construct an extremely practical battery powered electric ladder for home or professional use. 
     SUMMARY 
     The Electric Ladder described in this specification is both safe and user friendly. It allows one to work comfortably and securely at moderate to extreme heights. Fabricated from high strength graphite composites and utilizing the latest technology in batteries and small high output motors, the ladder is lightweight and easily portable for home or field use. A platform, riding on wheels which are supported on either side by structural tubes, moves up or down based on input from the operator. Safety items include a restraining tube around the operator and switches and brakes to limit the travel of the platform. Margins of safety on the structural elements far exceed basic requirements. The platform is sized to accommodate both the operator and his hand tools. 
    
    
     
       FIGURES 
         FIG. 1  is a view of the entire Electric Ladder. 
         FIG. 2  shows the major sub assemblies of the ladder. 
         FIG. 3A  depicts the cover of the base assembly. 
         FIG. 3B  shows a majority of the items making up the base assembly. 
         FIG. 4  is a sectional view of the base assembly, looking to the left, from a plane between the motor and the worm gear. 
         FIG. 5  is an exploded view showing the various elements making up the spool sub assembly and its mounting to the base plate. 
         FIG. 6  provides further details of the worm and the worm gear and the winding of the cable on the spools. 
         FIG. 7A  depicts the left middle sub assembly. 
         FIG. 7 b    depicts the right middle sub assembly. 
         FIG. 8  is an exploded view of the right middle sub assembly. 
         FIG. 9  shows how the wheels ride on top of the support tube. 
         FIG. 10  is a cut-away view showing how the tang rides inside of the support tube and also provides details of the attachment of the cable. 
         FIG. 11  is an overall view of the platform assembly. 
         FIG. 12  is the same view of the platform assembly—but with the gate open. 
         FIG. 13  is an exploded view of the brake assembly. 
         FIG. 14A  provides the details of the left support tube. 
         FIG. 14B  provides the details of the right support tube. 
         FIG. 15  shows assembly details of the top of the right support tube. 
         FIG. 16  is an overall view of the rear support assembly. 
         FIG. 17A  is an assembled arm. 
         FIG. 17B  provides details of one arm of the rear support assembly. 
         FIG. 17C  shows the arm attached to the rear support tube. 
         FIG. 18  is a ladder view with platform in extreme lower forward position. 
         FIG. 19  is a ladder view with platform in extreme upper forward position. 
         FIG. 20  is a ladder view with platform in extreme upper rearward position. 
         FIG. 21  shows the ladder folded. 
     
    
    
     DESCRIPTION 
     General Description 
     The Electric Ladder described in this specification is vastly different from the ladders that one would see in a typical hardware store. Instead of rungs or steps that are a normal part of a conventional ladder, the Electric Ladder has a platform which moves up or down at the operator&#39;s discretion. The platform provides a secure and spacious work area at heights that would be uncomfortable for the operator using a conventional ladder. The platform can be moved forward or backward to get closer to or further from the work area and also can be tilted to accommodate a non level ground surface or an other than normal tilt of the ladder. A restraining tube is mounted to the platform. It provides security for the operator and also provides a means for supporting tools and supplies. The Electric Ladder is powered with a compact and efficient DC motor in combination with a high efficiency state of the art battery. The motor drives a reduction gear comprising a worm/worm gear combination. The resultant output rotates a spool assembly to which are spooled the steel cables that move the platform up and down. The steel cables are guided by pulleys which allow the cable to move through the structural support tubes and ultimately attach to the platform. Rotation of the motor in one direction will raise the platform and in the other direction the platform will be lowered. Control of the motor is accomplished through the control electronics where either manual or remote control is available to operate the platform. Safety features include the use of micro switches on the structural support tubes. Activation of these micro switches signals the control electronics to stop the motion of the platform, thereby preventing ove-travel of the platform in either the up or down direction. A low battery cutoff is also incorporated in the control electronics. This feature prevents motion of the platform if there is insufficient charge in the battery to complete a full up and down cycle. Margins of safety on the structural elements and on the rigging elements, the cable and associated pulleys, are more than adequate for any anticipated loads. 
     DETAILED DESCRIPTION 
     An overall view of the Electric Ladder  1  is depicted in  FIG. 1 . It comprises eight principal subsystems. These are, as shown in  FIG. 2 ; a Top Bar  2 , a Rear Support Assembly  3 , the Right Middle Sub Assembly  4 , the Right Structural Tube Assy  5 , the Base Assembly  6 , the Platform Assembly  7 , the Left Middle Sub Assembly  8 , and the Left Structural Tube Assy  9 . Each of these subsystems is discussed in detail in what follows. 
     Base Assembly 
     The heart of the Electric Ladder  1 , the area which provides the motive power and the control functions to operate the ladder, is within the Base Assembly  6 , details of which are shown in  FIGS. 3A and 3B .  FIG. 3A  depicts the Base Cover  10  which is removable to allow for servicing of the items shown in  FIG. 3B . The Base Cover  10  is made of plastic composite and acts to protect the enclosed components. The items depicted in  FIG. 3B  consist of a Base Plate  15  made of metal or high strength composite to which is welded or bonded the Left Support Plate  14  and the Right Support Plate  24  both made of metal or composite as required to match the base plate. The Battery  16 , the Dc Motor  19  and the Control Electronics  20  are all mounted to the Base Plate  15  as are the Front Spool Support  17  and the Rear Spool Support  27 . On the left side is the Left Lower Pulley Mount  12  which is held in place with the Left Pulley Mount Retainer  13  to the Left Support Plate  14 . The Left Pulley Mount Retainer  13  is a steel pin screwed to the back of the Left Support Plate  14  and acts as a bearing surface to allow for rotational motion of the Left Lower Pulley Mount  12 . The rotation is necessary to accommodate an other-than-normal angular attitude of the ladder. On the right hand side a similar configuration exists: the Right Lower Pulley Mount  25  held in place with the Right Pulley Mount Retainer  23 . Also on the right we see the Right Lower Pulley  22 . It is held in place with the Right Lower Pulley Retainer  21 . The Left Cable  11  and the Right Cable  26 , guided by their respective pulleys, are spooled onto the Spool Sub Assembly  28 . 
     A view to the left from the view point at the left side of the Dc Motor  19 , as indicated on  FIG. 3B , is shown in  FIG. 4 . Among the new items not previously described are the Left Lower Pulley Retainer  30  and the Left Lower Pulley  29  which guides the Left Cable  11  up through the Left Lower Pulley Mount  12 . The Rear Spool Support Nut  31  and the Front Spool Support Nut  18  hold the spool supports in place. There are two spools: the Rear Spool  33  and the Front Spool  36 . The steel cables wind and unwind on these spools depending on the rotational direction of the Dc Motor  19 . The Front Spool Support Nut  18  and the Rear Spool Support Nut  31  screw onto the Front Stud  35  and the Rear Stud  32 , as depicted in  FIG. 5 , to hold the spool supports in place. Finally the Worm  34  and the Worm Gear  37  are located as shown.  FIG. 5  shows how the pieces of the Spool Sub Assembly  28  all fit together. 
     New items in  FIG. 5  not previously identified are the Front Bearing  38 , the Rear Bearing  40 , the Square Drive Shaft  39 , the Rear Base Stud  32  and the Front Base Stud  35 . The unit is assembled by inserting the bearings into the bottom drilled holes in the two mounts, then slipping the spools and the worm gear over the square shaft and then inserting it into the bearings, setting the unit over the studs and finally installing the nuts. Square holes through the centers of the spools and gear prevent rotation of any individual element with regard to the whole unit. This configuration provides a near frictionless assembly for spooling the cables. Further insight into the spooling is obtained by viewing the top view of  FIG. 6 . Here we see the Right Cable  26  winding or unwinding on the top of the Front Spool  36  and the Left Cable  11  winding or unwinding on the bottom of the Rear Spool  33 . Rotation of the Spool Sub Assembly  28  plays out cable when rotating in one direction and takes in cable when rotating in the opposite direction, thereby lowering or raising the Platform Assembly  7 . There are two very beneficial reasons for using worm/worm gear gearing for this application. The first is size and weight. For a given gear ratio this type of gearing is considerably smaller and lighter than conventional spur gear arrangements. The second, and perhaps more important reason, is that worm/worm gear gearing is self locking. That is to say the output cannot drive the input. In the case of the electric ladder, when power is applied to the drive motor the platform raises or lowers, but when power is removed, the platform remains locked in place. 
     Middle Sub Assemblys 
       FIG. 7A  and  FIG. 7B  are drawings of the left and right middle sub assemblies. Wheels, depicted by the identifying numerals  41 ,  43 ,  52  and  56  ride on the left and right structural tubes shown in  FIG. 2 , whose identifying numerals are  9  and  5  respectively.  FIG. 9  shows the arrangement. The two sub assemblies are held together and move as one when the Platform Assembly  7 , shown in  FIG. 2  is installed between them. Starting with  FIG. 7A  the parts making up the Left Middle Sub Assembly  8  are the Lower Left Wheel  41 , the Left Wheel Mounting Plate  42 , the Upper Left Wheel  43 , the Left Adjuster Knob  44 , the Left Spring  45 , the Left Adjuster Plate  46 , the Left Slide Rollers  47 , and the Left Roller Pins  48 . On the right side we have the parts as shown in  FIG. 7B  comprising the Right Spring  49 , the Right Adjuster Knob  50 , Right Wheel Mounting Plate  51 , the Upper Right Wheel  52 , the Upper Wheel Mounting Bolt  53 , the Tang  54 , the Lower Wheel Mounting Bolt  55 , the Lower Right Wheel  56 , the Right Roller Pins  57 , the Right Side Rollers  58 , and the Right Adjuster Plate  59 . The exploded view of  FIG. 8  shows more details of the parts and assembly of the Right Middle Sub Assembly  4 . The Left Middle Sub Assembly  8  is just a mirror image; and, therefore, the following discussion applies equally to it. With the exception of the Right Threaded Stud  60  and the Right Nut  61  all of the other parts in this figure have been previously identified. A description of the assembly of the unit and the function of the parts begins with the Right Adjuster Plate  59 . It holds the Right Roller Pins  57  which retain the Right Side Rollers  58 . The guides in the lower portion of the Platform Assembly  7  slide over the rollers, thereby allowing the platform to move forward and backward easily. A series of holes in the top of the Right Adjuster Plate  59  provide the capability to vary the angle of the plate and thereby vary the angle of the Platform Assembly  7 . This capability allows one to level the platform when the base of the ladder is slanted. The Right Spring  49  is welded to the Right Adjuster Knob  50  on one end and on the other end to the Right Wheel Mounting Plate  51 . When the unit is assembled, the end of the Right Adjuster Knob  50  protrudes through the Right Wheel Mounting Plate  51  and into one of the top holes. 
     This then fixes the angle of the platform. The Right Wheel Mounting Plate  51  is affixed to the Right Adjuster Plate  59  by slipping it over the Threaded Stud  60  and installing the Right Nut  61 . The wheels are held in place by inserting the two threaded bolts, the Upper Wheel Mounting Bolt  53  and the Lower Wheel Mounting Bolt  55 , through the wheels and screwing them into the threaded bosses on the Right Wheel Mounting Plate  51 . That completes the assembly of the unit. The Tang  54  plays a key role in the operation of the ladder. It is welded to the mounting plate as shown in  FIG. 8  and rides within the Right Structural Tube  62 . A slot running the full length of the tube allows the Tang  54  to travel the full length of the tube. It is here at the Tang  54  that the cable is attached that moves the platform up or down. A cut-away view showing the Tang  54  inside the Right Structural Tube  62  is depicted in  FIG. 10 . The Crimp Fitting  63  is crimped to the end of the Right Cable  26  to secure it and to prevent the cable from passing through the Tang  54 . As the cable is drawn up the entire Right Middle Sub Assembly  4  is raised and, conversely, a downward movement of the cable allows the Right Middle Sub Assembly  4  to descend. A complete discussion of the rigging, e.g. the movement of the cable within the entire ladder is discussed later on in this document. 
     Platform Assembly 
     The Platform Assembly  7  is shown in  FIG. 11 . It comprises the Latch Pin  64 , the Gate  65 , the Latch  66 , the Brake Unit  67 , the Right Roller Guide  68 , the Right Tube Mount  69 , the Platform  70  the Left Roller Guide  71 , the Left Tube Mount  72 , the Gate Hinge Pin  73 , the Gate Hinge  74  and the Security Tube  75 . The Security Tube  75  is mounted to the Platform  70  by inserting its ends into the Left Tube Mount  72  and the Right Tube Mount  69 . The mounts are bonded to the top of the platform. The Gate  65  can be raised to allow access to the platform and lowered to provide security.  FIG. 12  depicts the gate in the open position. The final item to discuss as related to the platform assembly is the brake. 
     The Brake 
     The function of the brake is to lock the platform in position to prevent it from moving during normal operation of the ladder. The brake is unlocked when the operator wants to move the platform forward or backward. It is placed on the floor of the platform to allow the operator to move it with his foot.  FIG. 13 , an exploded view of the Brake Unit  67 , has the following components: the Brake Pedal  117 , the Brake Mount  76 , the Brake Nut  77 , the Brake Pad  78  and the Elastomeric Pad  79 . The Brake Unit  67  resides in a cutout on the right side of the Platform  70  as can be seen in  FIG. 11 . To assemble the unit the Elastomeric Pad  79  is first bonded to the Brake Pad  78  then the Brake Mount  76  is bonded to the underside of the Platform  70 . The Brake Pedal  117  and the Brake Pad  78  are then slid over the shaft on the Brake Mount  76  and retained with the Brake Nut  77 . The cam on the end of the Brake Pedal  117  is inserted between the two triangular elements during the assembly. As the pedal is rotated about the shaft the cam presses down, more or less, on the top of the Brake Pad  78 . Slotted holes in the triangular elements of the pad allow it to follow the cam position. When locked the pedal is basically in the position shown in  FIG. 13 . The cam position is such as to put maximum downward pressure on the brake and elastomeric pads and then onto the roller assembly, thereby preventing it from moving. When the operator wants to release the brake he puts his toe under the pedal and flips it up. Pushing down with the foot resets the brake and over rotates the cam slightly, thereby holding the brake in place. 
     The Structural Support Tubes 
       FIG. 14A  and  FIG. 14B  are external views of the Right Structural Tube Assy  5  and the Left Structural Tube Assy  9  respectively. On the right hand side the parts are: the Right Structural Tube  62 , the Right Upper Pulley  80 , the Right Upper Pulley Retainer  81 , the Right Sleeve  82 , the Right Upper Threaded Boss  83 , the Right Lower Threaded Boss  84 , the Micro Switch  2   85 , the Micro Switch  1   86 , the Right Middle Threaded Boss  115  and the Right Upper Pulley Mount  87 . The parts for the left hand side are: the Left Upper Pulley  88 , the Left Pulley Retainer  89 , the Left Sleeve  90 , the Left Structural Tube  91 , the Left Lower Threaded Boss  92 , the Micro Switch  4   93 , the Micro Switch  3   94 , the Left Upper Threaded Boss  95 , the Left Upper Pulley Mount  96  and the Left Middle Threaded Boss  116 . The upper portion of the Right Structural Tube Assy  5  is shown as an exploded view in  FIG. 15 . Item  26  is the Right Cable  26 . The other items have already been identified above. Assembly is simple enough. The Right Sleeve  82  is bonded to the tube at the halfway point of the sleeve. The Right Upper Pulley  80  with its Right Upper Pulley Retainer  81  is inserted into the Right Sleeve  82 . The Right Upper Threaded Boss  83  is bonded to the tube. It accommodates the Upper Right Bolt  98  of the Rear Support Assembly  3 . The Micro Switch  3   94  is snapped into its opening and the electrical wires from the switch are routed inside the tube. During the rigging operation, which is discussed later, the Right Cable  26  is inserted as shown. 
     Rear Support Assembly 
     The Rear Support Assembly  3  supports the ladder in an upright posture. Elements of the unit as portrayed in  FIG. 16  are the Rear Support Tube  97 , the Upper Right Bolt  98 , the Middle Right Threaded Boss  99 , the Right Rear Bolt  100 , the Right Rear Arm  101 , the Right Middle Bolt  102 , the Right Front Arm  103 , the Right Front Bolt  104 , the Left Rear Bolt  105 , the Left Rear Arm  106 , the Left Middle Bolt  107 , the Left Front Arm  108 , the Left Front Bolt  109 , the Upper Left Bolt  110  and the Middle Left Threaded Boss  111 .  FIG. 17A  is a drawing of the Cross Arm Assembly  114 , and  FIG. 17B  is an exploded view of that assembly. Items shown in this view not previously identified are the Middle Bolt Nut  112  and the Spring Washer  113 . The Spring Washer  113  when properly compressed by turning the Middle Bolt Nut  112  produces sufficient friction between the two arms to hold them in place.  FIG. 17C  provides insight about the connection of the Cross Arm Assembly  114  to the Rear Support Tube  97  and the subsequent connections to the Right Structural Tube Assy  5 . The Rear Support Tube  97  attaches to the Right Upper Threaded Boss  83  of the Right Structural Tube Assy  5  using the Upper Right Bolt  98 . The Right Front Bolt  104  screws into the Right Middle Threaded Boss  115  of the Right Structural Tube Assy  5 . 
     Top Bar 
     The Top Bar  2  provides a fixed separator for the top of the Right Structural Tube Assy  5  and the Left Structural Tube Assy  9  (reference  FIG. 2 ). It slips into place but is removable to allow adjustment and maintenance of the pulleys and the related rigging. 
     Rigging 
     Rigging of the ladder with the cable is best understood by starting with  FIG. 10  which is a drawing showing a view on the right side of the ladder. The discussion that follows applies equally well to the left side. We start by attaching the Crimp Fitting  63  to the end of the Right Cable  26 . This is accomplished by using a crimping tool and results in a strong and secure termination for the cable. The Right Cable  26  is then fed up thru the Tang  54  and then looped over the top of the Right Upper Pulley  80  as depicted in FIG.  15  and then down and around the Right Lower Pulley  22  as depicted in  FIG. 3B  and finally attaching to the Front Spool  36  shown in  FIG. 5 . As mentioned above the rigging on the left is the same. 
     Position Extremes 
     The Platform Assembly  7  can be moved by the operator through a wide range of positions. Some representative extremes are shown in  FIG. 18 ,  FIG. 19  and  FIG. 20 .  FIG. 21  shows the ladder with the Rear Support Assembly  3  folded.

Summary:
This invention is an electric ladder. It is like no other ladder you have ever seen. It has no rungs or steps but instead has a spacious work platform which traverses up or down at the command of the operator. It is powered by a rechargeable battery feeding an electric motor. The direction of rotation of the motor acting through a series of pulleys and cables moves the platform up or down. Fabricated from high strength graphite composites and utilizing the latest technology in batteries and small high output motors it is lightweight and easily portable for home or professional use.