Abstract:
An adjustable platform for a stepladder can be raised by simply lifting the platform manually, and the platform automatically stays there after being released. For safety, strength and stability, the platform is supported by two extendable rods. Even though there are two rods and two clamps for holding them, a single worker can still release and lower the platform at a controlled rate of descent. To do this, the clamps are of a particular design and are strategically positioned relative to the rods.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The subject invention generally pertains to stepladders and more specifically to an extendable tool for such a ladder.  
         [0003]     2. Description of Related Art  
         [0004]     There are a variety of lift platforms that can be attached to a stepladder. A drawback of many of them is that the user needs to use one hand to raise the platform and another one to lock it in place. This may be fine when the platform is lightweight and unloaded; however, a heavier platform or one carrying a load may be difficult to lift with just one hand. Moreover, if the platform needs to be raised to a significant height, the user may need to stretch in an awkward manner between the platform and the locking mechanism.  
         [0005]     U.S. Pat. No. 3,208,555 discloses a hoisting attachment for a ladder where a user operates a crank to raise and lower the platform. With a hoist, a user could conceivably raise the platform by simply turning the crank and not bother with stretching between the platform and the crank. If the user, however, does not manually hold the platform or steady the load as it rises, there is a risk that the load may accidentally slip off the platform, which could damage the load or injure the user.  
         [0006]     Consequently, a need exists for a ladder-mounted lift platform that overcomes the drawbacks of current lift platforms.  
       SUMMARY OF THE INVENTION  
       [0007]     An object of some embodiments of the invention is to provide a ladder-mounted platform where the platform can be readily raised by simply pushing the platform up, and the platform automatically stays at the elevated position without having to manually actuate a locking mechanism.  
         [0008]     Another object of some embodiments is to support the platform with two extendable rods for stability and strength, and position each rod sufficiently close to a locking mechanism so that each hand of the user can simultaneously release the locking mechanism and grip one of the rods so that the platform can be lowered in a controlled manner.  
         [0009]     Another object of the invention is to enable a user to simultaneously stand upon a lower step of a stepladder (thereby adding stability to the ladder), using one hand to grasp the side of the ladder (thereby stabilizing the user), and using the other hand to simultaneously 1) raise the platform 2) steady the load on the platform, and 3) lock the platform at the desired elevation.  
         [0010]     Another object of the invention is to install a platform just above an uppermost step a stepladder so that the platform creates an obstruction that deters a user from stepping upon that uppermost step.  
         [0011]     Another object of some embodiments is to support a raisable platform using square or rectangular tubes (as opposed to round ones) to ensure that grippers solidly engage discrete points on a facet of the tube.  
         [0012]     Another object of some embodiments is to provide the platform or ladder-mounted tool with a stop member that ensures at least minimum hand clearance between the platform and the top step of the ladder to avoid creating a hand-pinching hazard therebetween.  
         [0013]     Another object of some embodiments is to provide the ladder tool with clamp assembly that includes a spring for urging the clamp to a hold-position so that the clamp assembly automatically holds the platform at a raised position upon simply releasing the platform and clamp assembly.  
         [0014]     Another object of some embodiments is to support the platform with two extendable rods that include an evenly distributed series of gripping points so that the clamp assembly can selectively engage the points to solidly hold the platform at a series of discrete elevations.  
         [0015]     Another object of some embodiments is to provide a plastic platform with a raised outer rim to help contain a wooden top, wherein the wooden top can be readily replaced, cut, drilled, nailed into, or otherwise modified to meet the needs of the user.  
         [0016]     Another object of some embodiments is to support the platform with two extendable rods and use a rod-locking mechanism with a lever that can unlock the rod-locking mechanism by pushing the lever down or towards an adjacent rod so that the user can readily and simultaneously grip a rod and move the lever to its unlock position with one hand.  
         [0017]     Another object of some embodiments is to provide a ladder-mountable lift platform with a clamping mechanism that includes a rod-gripper and an actuating lever that extend integrally from each other to comprise a unitary piece, which can reduce product cost and increase reliability.  
         [0018]     Another object of some embodiments is to place the platform-supporting rods between the locking levers so that a user can readily grip the rods and actuate the levers at the same time.  
         [0019]     One or more of these and/or other objects of the invention are provided by a tool or method that enables a user to raise a ladder-mounted platform and automatically lock it into position by simply releasing the platform 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0020]      FIG. 1  is a front view of a stepladder with a platform tool being manually raised.  
         [0021]      FIG. 2  is a front view of the stepladder of  FIG. 1  but showing the platform held at a raised position.  
         [0022]      FIG. 3  is a front view of the stepladder of  FIG. 1  but showing the platform being lowered.  
         [0023]      FIG. 4  is a left side view of an upper portion of the stepladder of  FIG. 1 .  
         [0024]      FIG. 5  is a cross-sectional front view of a RH side of the platform tool with the clamp assembly in a hold-position.  
         [0025]      FIG. 6  is a cross-sectional view similar to  FIG. 5  but showing the platform being lifted while the clamp assembly is in a hold-position.  
         [0026]      FIG. 7  is a cross-sectional view similar to  FIGS. 5 and 6  but showing the clamp assembly in a release-position that allows the platform to be freely raised or lowered. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]      FIGS. 1-7  shows a tool  10  that can be attached to an uppermost step  12 , which is above a second highest step  14 , of a self-supporting stepladder  16 . The term, “stepladder” refers to a self-standing generally triangular structure with a series of steps. Tool  10  includes a work platform  18  supported by two substantially parallel rods  20  (a RH rod  22  and a LH rod  24 ) that can be manually raised and lowered. Platform  18  can be used for holding tools, light fixtures, planks, boards, conduit, pipes, drywall, paint cans, a vise or clamp, and other parts. Tool  10  also includes a clamp assembly  26  that works in conjunction with rods  20  in such a way as to make it easy and safe to raise and lower platform  18 . Clamp assembly  26  is movable between a hold-position ( FIGS. 1, 2 , and  4 - 6 ) and a release-position ( FIGS. 3 and 7 ).  
         [0028]      FIG. 1  shows a user  28  manually lifting platform  18  from a lowered position ( FIG. 5 ) to a raised position ( FIG. 2 ). While user  28  is lifting platform  18 , clamp assembly  26  (which comprises a RH clamp assembly  30  and a LH clamp assembly  32 ) is in the hold-position. Even with clamp assembly  26  in the hold-position, platform  18  can be readily raised without significant resistance.  
         [0029]      FIG. 2  shows that upon manually releasing platform  18 , the platform generally stays at its raised position (or settles to a discrete point slightly below that) and does so automatically because clamp assembly  26  is in its hold-position even while platform  18  is rising. The term, “automatically” means that a clamp does not have to be manually manipulated in order for the platform to be held in place.  
         [0030]      FIG. 3  shows how platform  18  can be lowered at a controlled rate of descent. With a right-hand  34 , user  24  simultaneously grips RH rod  22  and pushes a RH lever  36  of RH clamp assembly  30  down to an unlock-position (RH unlock position), which moves RH clamp assembly  30  to its release position (RH release position, see also  FIG. 7 ). Likewise, user  28  uses a left-hand  38 , to simultaneously grip LH rod  24  and push a LH lever  40  of LH clamp assembly  32  down to an unlock-position (LH unlock position), which moves LH clamp assembly  32  to its release position (LH release position). Friction between the user&#39;s hands and rods  22  and  24  slow the decent of platform  18 .  
         [0031]     Although such operation can be achieved by various structural designs, details of one example of the invention are shown in  FIGS. 4-7 . The following description will be primarily with reference to the right-hand side of tool  10  ( FIGS. 5-7 ), since the left-hand side ( FIG. 4 ) has basically the same structure as the right side.  
         [0032]     In this example of the invention, tool  10  comprises a base  42  that can be removably attached to uppermost step  12  by way of a fastener  44 . A ring nut  46  fastens a RH sleeve  48  to base  42 . A coupling  50  connects a tube  52  to RH sleeve  48 , and a cap  54  can be fitted to the bottom end of sleeve  52 . RH rod  22 , in this example, is square tubing that slides within the generally cylinder pieces of sleeve  48 , coupling  50  and tube  52 . A bracket  56  connects an upper end of rod  22  to the underside of platform  18 .  
         [0033]     To hold RH rod  22  at various elevations, RH clamp assembly  30  includes a RH clamp housing  58 , a RH gripper  60 , a RH spring  62 , and RH lever  36 . RH lever  36  and RH gripper  60  can be integral extensions of each other, whereby RH lever  36  and RH gripper  60  comprise a unitary piece. A pin  64  allows RH lever  36  and RH gripper  60  to pivot relative to RH clamp housing  58 . Spring  62  urges RH lever  36  in a RH lock direction (such as upward) to the RH lock-position and urges RH gripper  60  to a RH hold-position where RH gripper  60  engages RH rod  22  ( FIGS. 5 and 6 ).  
         [0034]     Manually pushing RH lever  36  in a RH unlock direction (such as downward) against the urging of RH spring  62  moves RH gripper  60  to the RH release position where RH gripper  60  disengages RH rod  22  as shown in  FIG. 7 .  
         [0035]     To positively hold RH rod  22  at various discrete elevations, RH rod  22  includes a series of discrete gripping points  66  that can be solidly engaged by RH gripper  60 . Gripping points  66  can be in the form of recesses or protrusions.  
         [0036]     Cap  54  at the bottom of tube  52  provides a stop member that can limit the downward movement of tube  22 , thereby ensuring that at least a minimum hand clearance exists between the underside of platform  18  and the top surface of uppermost step  12  to avoid creating a hand-pinching hazard therebetween. It should appreciated by those of ordinary skill in the art that a various other structures could provide a functionally equivalent stop member.  
         [0037]     It should be noted that all of the named RH elements have an equivalent LH corresponding element. For instance, RH sleeve  48  corresponds to LH sleeve  48 ′, RH rod  22  corresponds to LH rod  24 , RH gripper  60  corresponds to LH gripper  60 ′, the RH hold-position corresponds to the LH hold-position, the RH release-position corresponds to the LH release-position, the RH lock position corresponds to the LH lock position, the RH unlock-position corresponds to the LH unlock-position, the RH lock direction (e.g., upward) corresponds to the LH unlock direction (e.g., also upward), the RH unlock direction (e.g., downward) corresponds to the LH unlock direction (e.g., also downward), etc.  
         [0038]     In some embodiments platform  18  comprises a plastic base  68  with a raised outer rim  72  and a wooden top  70  overlaying plastic base  68 , wherein the raised outer rim  72  helps align wooden top  70  to plastic base  68 . Wooden top  70  provides a convenient work surface that can be readily replaced, cut, drilled, nailed into, or otherwise modified to meet the needs of the user. Rim  72  is preferably less than 1.5-inches tall (inside vertical dimension) so that standard lumber having a 2-inch nominal thickness (1.5-inch actual thickness) can protrude above rim  72 . Platform  18  can also be provided with various openings and cavities for holding an assortment of tools and parts.  
         [0039]     Although the invention is described with reference to a preferred embodiment, it should be appreciated by those of ordinary skill in the art that various modifications are well within the scope of the invention. Therefore, the scope of the invention is to be determined by reference to the following claims.