Fire escape – ladder – or scaffold – Convertible
Reexamination Certificate
2002-02-19
2003-11-25
Chin-Shue, Alvin (Department: 3634)
Fire escape, ladder, or scaffold
Convertible
C182S129000, C182S161000, C280S047160, C280S047280
Reexamination Certificate
active
06651774
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a stepladder.
More particularly, the invention relates to a stepladder that has multiple functions useful for every day use.
There are many prior art stepladders that have additional functions such as hand truck, and tool tray, etc.
U.S. Pat. No. 4,235,449 shows a combined hand truck and step stool. Usually, it is used as a hand truck. To use it as a step stool, the steps of pivoting side rails, reversing the entire device, and locking a support are required. Also, the device is quite bulky even in its storage state since many parts such as wheels, steps, and a bed are fixed.
U.S. Pat. No. 4,448,282 shows a ladder formed as a multiple-purpose device. To convert the ladder between a step ladder, a leaning type ladder, and a hand truck, the steps of disassembling the beams forming the ladder and reassembling them are required. The conversion is not achieved in a simple step like unfolding a parallel link. A disadvantage of the prior art multi-function stepladders is that they are bulky in size compared to a simple stepladder. Another disadvantage is that it is cumbersome to convert the stepladder between the multiple functions.
Accordingly, there has been a demand for an improved multi-function stepladder having a compact size and easy to convert between the multiple functions.
SUMMARY OF THE INVENTION
The present invention is contrived to overcome the conventional disadvantages. Therefore, an object of the invention is to provide an enhanced stepladder having multiple functions.
Another object of the invention is to provide a combined stepladder and hand truck assembly having the functions as a stepladder, a tool tray, and a hand truck.
Still another object of the invention is to provide a combined stepladder and hand truck assembly which is easy to convert between its functions.
Still another object of the invention is to provide a combined stepladder and hand truck assembly which is compact in its size.
To achieve the above-described objects, in accordance with an embodiment thereof, the invention provides a combined stepladder and hand truck assembly that comprises a first frame having two side rails, each of the side rails having a lower end, a second frame pivotally attached to the back side of the first frame and having two side rails, each of which having an upper end and pivotally attached to the side rail of the first frame at the upper end, a third frame pivotally attached to the front side of the first frame and having two side rails, each of which having an upper end and a lower end and pivotally attached to the side rail of the first frame at the upper end, two bars, a plurality of steps pivotally attached to the side rails of the first frame and the bars so that the steps, the side rails of the first frame, and the bars form a parallel link, a lock securing the second frame with the first frame at an acute angle between the second frame and the first frame, two casters attached at the lower end of the side rail of the first frame, a fastener securing the third frame to the first frame, a tray rotatably attached to the third frame at the lower ends of the side rails of the third frame, and a stop limiting the rotation of the tray.
The assembly has a folded position, a hand truck position, a stepladder position, and a tool tray position.
In the folded position, the second frame and the third frame abut on the first frame, the lock is released, the fastener is released, the link is folded between the side rails of the first frame and the second frame, and the tray is folded between the side rails of the third frame.
In the hand truck position, the second frame and the third frame abut on the first frame, the lock is released, the fastener is released, the link is folded between the side rails of the first frame and the second frame, the tray is rotated downward until the tray abuts on the stop so that the tray is substantially vertical to the third frame.
In the stepladder position, the second frame is pivoted so that it makes the acute angle with the first frame, the lock is engaged, the third frame abuts on the first frame, the fastener is released, the link is unfolded so that the steps are substantially horizontal, and the tray is folded between the side rails of the third frame.
In the tool tray position, the second frame is pivoted so that it makes the acute angle with the first frame, the lock is engaged, the third frame is rotated upward, the fastener is engaged, the link is unfolded so that the steps are substantially horizontal, and the tray is rotated until the tray abuts on the stop so that the tray is substantially horizontal.
When the link is folded, the steps are pivoted downward so that the height of the entire assembly is just the sum of the heights of the first frame and the castors.
The stop comprises two brackets rotatably attached to the side rails of the third frame near the lower ends of the side rails, and a bar fixed between the brackets. The bar has a first wall and a second wall, and each of the bracket has a projection, and the first wall and the second wall makes an angle of approximately 90 degrees. When the assembly is in the hand truck position, the first wall abuts on the side rails of the third frame to block downward pivoting of the brackets, and the second wall abuts on the tray to block downward rotation of the tray. When the assembly is in the tool tray position, the projections abuts on the side rails of the third frame to block downward pivoting of the brackets, and the first wall abuts on the tray to block downward rotation of the tray.
The fastener includes a hook pivotally attached to the side rail of the third frame, a handle, and a spring. The hook engages a pin provided at the side rail of the first frame and the spring presses the hook so that the hook is kept engaged with the pin. The handle is used to pivot the fastener against the force of the spring to disengage the hook from the pin.
Each of the casters has a wheel bracket attached at the lower end of the side rail of the first frame, and a wheel rotatably attached to the wheel bracket. The wheel bracket is rotatable around the side rail and lockable on a first position, a second position, or a third position.
In the first position, the castors are positioned between the side rails of the first frame, and in the second position, the castors are rotated 90 degrees from the first position and backward from the first frame, and in the third position, the casters are rotated 180 degrees from the first position.
The castors are locked in the first position when the assembly is in the folded position to minimize the folded size of the assembly.
The castors are locked in the second position when the assembly is in the hand truck position.
The castors are locked in the third position when the assembly is in the stepladder position or in the tool tray position.
The side rails of the first frame are hollow, and the wheel bracket of the caster includes a wheel cover, a shaft, a pin, a first block, a second block, and a spring. The wheel is rotatably attached to the wheel cover and the shaft is fixed to the wheel cover. The first block is secured at the lower end of the side rail of the first frame and has a hole receiving the shaft. The second block is slidably received inside the side rail of the first frame and has a hole receiving the shaft. The pin is inserted into a bore provided at an end of the shaft and contacts with the second block to limit the sliding movement of the second block. The spring surrounds the shaft between the first block and the second block. The first block has a circular recess having four grooves spaced by 90 degrees with one another and the wheel cover has a circular boss received in the recess of the first block and having four projections spaced by 90 degrees with one another to engage with the recesses of the first block.
In accordance with another embodiment thereof, the invention provides a combined stepladder and hand truck assembly that comprises a first frame having two side rail
Chin-Shue Alvin
Park John K.
Park & Sutton LLP
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