Land vehicles – Wheeled – Attachment
Reexamination Certificate
1999-03-17
2002-03-19
Vanaman, Frank (Department: 3611)
Land vehicles
Wheeled
Attachment
Reexamination Certificate
active
06357773
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to retractable steps for assisting in entering or exiting construction equipment cabs, vehicles or the like, and more particularly, to a locking step that is manually pulled to an extended, or operative position from a retracted position under a cab.
BACKGROUND OF THE INVENTION
Steps or ladders for assisting in entering and exiting vehicles are well-known in the art. In the past, these steps or ladders typically extended outwardly and depend downwardly from under the vehicle door. In some instances involving construction equipment without width restrictions, these steps are permanently fixed in an operative position. While such arrangements are also suitable for use on some other types of vehicles, such as passenger vans or truck cabs, construction vehicles with width restrictions require a different approach. For example, truck mounted cranes typically have operator cabs positioned on a rotating turntable or upper works that is mounted to the deck or lower works. To enter the cab, the crane operator must climb directly from the deck through the cab door. This climb is made difficult by the fact that the cab is substantially elevated above the deck and the cab door faces the side of vehicle. Since the entry side of the cab is often extending out only as far as the edge of the deck, which commonly is at or near the maximum width permitted for over-the-road vehicles under federal, state, and local regulations, this means that there is no deck space to step on when the operator is entering or exiting the cab with the boom extending directly forward or rearward. The use of a fixed step that extends outwardly from the cab is not permitted since it would increase the vehicle width beyond what is allowed by these regulations.
Lessening the width of the cab or the upper frame accommodate a fixed step is generally not an option. In most truck mounted cranes, the width of the carrier deck is made as wide as possible to provide greater crane stability. Also, all available space in and under the cab is needed for hydraulic plumbing, controls and other necessary operating mechanisms.
The comfort for the operator is also a concern. Thus, while the cab width is maximized to provide the necessary room for the mechanical equipment, it is imperative at the same time to provide the proper attention to operator ergonomics. All of this has to be accommodated without exceeding the width of the carrier deck.
The alternative of a fixed step that projects forwardly and outwardly is a ladder that depends directly down from the edge of the cab. Although such a ladder does not significantly add to the vehicle width, it is not suitable for use on a truck mounted crane. The fixed step or ladder may interfere with the deck, or structures on the deck, required for operation of the boom as the turntable and cab rotate. It is also difficult to access from the side, as indicated above.
Others in the past have proposed retractable steps that can be stored under the vehicle or cab and extended to an operative position. An example is found in U.S. Pat. No. 5,342,073 to Poole, which discloses a retractable step that is mounted on the underside of a passenger van. The step is provided with side support tubes that slide on horizontally extending cross guides. This arrangement permits the step to move horizontally between the retracted and extended positions. Plates at the inner ends of the support tubes trap the step adjacent the end of outward, extended travel to prevent inadvertent removal.
One disadvantage of the arrangement proposed in the '073 patent is that the step is held in the retracted position only by thin, spaced stops formed on the support tubes. If the vehicle carrying the retractable step is subjected to significant vertical jarring, such as is created when potholes, speed bumps, or the like are encountered, the step can inadvertently move into the extended position Of course, this lack of a positive locking arrangement suggests having to use stop gap measures, such as the use of a bungee cord or the like to hold the step in place.
Another disadvantage is that there is no lateral stability in the '073 design. Indeed, the step is intended for use by people entering only over the outer or front edge. Stepping on the side of the step would likely cause sudden sidewise shifting along the cross guides. This, in turn, could lead to a sudden loss of balance of the person using the step.
Other types of folding or retractable steps have also been proposed, but most of these have a large number of component parts, and are also actually restricted to use for entry over the outer or front edge. This is so since the part of the operating mechanism extends above the tread on the sides of the step providing direct foot interference; see, for example, U.S. Pat. No. 3,955,827 to Wonigar. Still others require relatively long and thin depending support arms and slotted levers that are also subject to sudden shifting or swinging, and thus also the risk of loss of balance when stepping onto the side of the tread of the step. Also, the arms and levers are subject to bending and over time becoming jammed rendering the step inoperative; see U.S. Pat. No. 5,284,349 to Bruns et al.
Accordingly, a need is identified for a retractable step that can be manually extended from under a vehicle, crane or excavator cab, or the like. In the operative position, the step would extend substantially in the horizontal plane, have a very low profile and be stable for side entry onto the tread, thus making it suitable for use with a cab mounted on a turntable supported on a truck chassis. To hold the step in both the extended and retracted positions, a manually operable mechanism would be provided to securely lock the step in place. The step would also be simple in design and inexpensive to manufacture. Ease of installation would allow the step to be retrofitted onto existing cabs or other desired locations without significant time or effort. Overall, the locking retractable step would result in an improvement in stability and reliability over those known in the art, and would be particularly adapted for use on crane/excavator cabs or the like.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to provide an improved step assembly. for mounting under a crane cab or other vehicle, and wherein the step can be manually pulled from a retracted position to an extended, operative position for assisting in climbing into or out of the cab from any direction.
Another object is to provide a pull out step assembly including a step that has a low profile and moves substantially horizontally to an extended position, such that during rotation of the crane cab, it does not interfere with existing structures required for operation of the crane.
Still another object of the present invention is to provide a pull out step assembly that includes a positive locking mechanism for holding the step securely in place in both the extended and retracted positions.
Still another object of the present invention is to provide a pull out step assembly that incorporates a step that is inherently stable to permit stepping on the side of the tread, as required by entry or exit of some cranes or the like.
Yet another object of the present invention is to provide a pull out step assembly that is inexpensive to manufacture, and sturdy and reliable in use.
A further object of the present invention is to provide a pull out step assembly that is simple to install and easily retrofitted onto locations where a retractable step is desired without extensive modification to the existing structure.
Additional objects, advantages and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combi
Griebel Francis J.
Yates Michael K.
King and Schickli PLLC
Link-Belt Construction Equipment Company, L.P., LLLP
Vanaman Frank
LandOfFree
Pull out locking cab step assembly does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pull out locking cab step assembly, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pull out locking cab step assembly will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2875205