Fire escape – ladder – or scaffold – Horizontal traversing - actuation – control – or response – Holding means
Reexamination Certificate
2000-04-12
2001-09-04
Stodola, Daniel P. (Department: 3634)
Fire escape, ladder, or scaffold
Horizontal traversing - actuation, control, or response
Holding means
C182S012000, C187S255000
Reexamination Certificate
active
06283249
ABSTRACT:
FIELD OF THE INVENTION
This invention relates broadly to material handling, and more particularly, to a stepped structure, such as a mobile ladder, equipped with a lifting mechanism for raising and lowering materials along a vertical axis.
BACKGROUND OF THE INVENTION
Warehouse workers or the like regularly employ stepped structures such as mobile ladders, scaffolds and platforms to reach a particular work location. In the course of completing their tasks, it is common practice for a worker to carry various tools, supplies, accessories and other articles while climbing the stepped structure. For example, a retail worker may scale a ladder using one or both hands to transport inventory to a desired elevation. Such practice not only jeopardizes the safety of the worker, but may require multiple trips up and down the ladder which contributes to the inefficiency of the task.
In an effort to remedy these problems, the assignee of the present invention has previously produced a mobile ladder that is provided with a motorized lifting mechanism for selectively assisting the worker in raising and lifting a loaded tray thereby enabling the worker to use both hands to grasp handrails while climbing. This prior art design (See
FIG. 13
) includes a metal lifting tray that is slidably mounted upon a track assembly and connected to a cable which is engaged about a pulley at the top of the track assembly. The cable extends downwardly along the front side of the track assembly and is wound around a lower pulley fixed on a mounting plate on a movable base of the ladder. The free end of the cable is attached to a winch, which has a motor driven by a battery. Both the winch and battery are secured on the mounting plate.
While this combined ladder and lifting mechanism has generally been useful, it has been found that the winch motor is extremely noisy and also creates an unreasonable amount of vibration which is conducted to the surrounding framework. In addition, the cable between the lifting tray and the winch is susceptible to premature wear, thus limiting the maximum loads for the lifting mechanism. The engagement of the cable on the pulleys further adds to the noise problem of the winch. Another problem resides in the particular mounting of the lifting tray upon the track assembly which has occasionally led to binding and jamming during raising and lowering of the loaded tray. Also, the unprotected nature of the winch motor and the battery on the mounting plate exposes these elements to moisture, temperature and other environmental conditions which can affect their maintenance, operability and reliability.
For the above reason, the prior art design has not proved entirely effective and convenient to use. Accordingly, it has been found desirable to provide an improved ladder with a lifting tray that offers the following advantages over the prior art systems including a smoother and quieter lifting operation; a more efficient, reliable and better controlled drive system for the lifting tray; and, retrofit capability. Such a ladder and lifting tray should be easy to assemble and maintain, and more economical to produce.
SUMMARY OF THE INVENTION
The present invention advantageously resides in an enhanced, combination ladder and lifting mechanism having widespread utility for vertically moving articles between different heights. In particular, the invention uses a chain drive to overcome the problems associated with the prior art cable/winch system.
In accordance with one aspect of the invention, a combined stepped structure and lifting mechanism includes a base and a framework secured to the base.
The framework has a pair of spaced apart vertical tubes rising upwardly from the base. A ladder is incorporated in the framework. A vertical track assembly is disposed between the vertical tubes and includes a pair of tubular members connected together.
A trolley is rollably mounted for movement along one of the tubular members. A lifting tray assembly is connected for movement with the trolley. A drive system is operably connected to the trolley and driven by a DC motor and gearbox unit which are mounted to a bottom end of the vertical track assembly. The drive system selectively moves the lifting tray assembly upwardly and downwardly along the vertical track assembly. The tubular members of the vertical track assembly include a square tube and a box channel having a front wall and a rear wall provided with a slot running along the length of the rear wall. The trolley has an elongated vertical plate with an upper guide structure projecting through the slot and upper guide wheels engageable with the box channel rear wall, and lower guide structure projecting through the slot and including lower guide wheels engageable with the box channel front wall. The upper guide structure further includes an upper guide roller engageable with the surfaces forming the slot, and a lower guide structure further includes a lower guide roller engageable with the surfaces forming the slot. The upper and lower guide rollers are mounted on axes of rotation which are substantially perpendicular to the axes of rotation of the upper and lower guide wheels. This configuration helps to stabilize the lifting tray connected to the trolley. The top of the vertical track assembly includes an idler sprocket mounted for rotation, and the bottom of the vertical track assembly includes a drive sprocket mounted upon a driven shaft extending from the DC motor and gearbox. The drive system includes a first run of drive chain entrained about the idler sprocket, running entirely through the square tube and wrapping around the drive sprocket, and a second run of drive chain running partially through the box channel and being connected to the upper guide structure and the lower guide structure. The lifting tray assembly includes a generally rectangular tray having sides provided at forward ends with guide blocks constructed of low friction material slidably engageable with the framework vertical tubes. The lifting tray further includes a pair of spaced apart, right angled, tray mounting brackets depending from the forward end of the tray. Each tray mounting bracket has a laterally extending portion and a forwardly extending portion.
The vertical plate of the trolley is interposed between the forward extending portions of the tray mounting brackets and fixed thereto. The lifting tray also includes a face plate attached to the laterally extending portions of the tray mounting brackets and provided with a nut adapted to receive an adjusting screw which passes through the face plate and between the tray mounting brackets. An end of the adjusting screw is engageable with the vertical plate to adjust the level of the tray. The drive system includes a chain enclosed by the vertical track assembly and connected with the trolley, the chain being driven by the DC motor and gearbox unit. An adjustment assembly is mounted on the vertical track assembly for tensioning the chain.
In accordance with another aspect of the invention, the combined stepped structure and lifting mechanism has a movable base, a framework rising from the base, a ladder incorporated in the framework, a vertical track assembly secured to the framework and a lifting tray assembly mounted for movement along the vertical track assembly. A drive system is mounted adjacent the base for selectively moving the lifting tray assembly along the vertical track assembly. Preferably the vertical track assembly is formed by a tubular structure extending between top and bottom portions of the framework. The drive system includes a drive chain passing through the interior of the tubular structure and entrained about an idler sprocket rotatably mounted at the top of the vertical track assembly and a drive sprocket mounted on a driven shaft of an electromagnetic DC motor and gearbox unit secured to a bottom end of the framework. The tubular structure is defined by a pair of elongated tubular members connected together in side-by-side relationship. The vertical track assembly preferably includes a me
Kaczor Scott E.
Young David T.
Andrus Sceales Starke & Sawall LLP
EGA Products, Inc.
Stodola Daniel P.
Thompson Hugh B.
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