Ramp-accommodating movable subframe for a semi-trailer

Land vehicles – Wheeled – Running gear

Reexamination Certificate

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Details

C014S069500, C414S558000

Reexamination Certificate

active

06244608

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to semi-trailer subframes, and in particular to movable subframes for a semi-trailer. More particularly, the invention is directed to a movable subframe for a semi-trailer which accommodates storage of a walk ramp beneath the semi-trailer.
2. Background Art
Movable subframes, typically referred to as sliders, have been utilized on semi-trailers or tractor-trailers for many years. One or more axle/suspension systems usually are suspended from a single slider structure. The slider in turn is mounted on the underside of the trailer body, and is movable longitudinally therealong to provide a means of variable load distribution. More specifically, the amount of cargo that a trailer may carry is governed by local, state and/or national road and bridge laws, and is dependent on proper load distribution. The basic principle behind most road and bridge laws is to limit the maximum load that a vehicle may carry, as well as to limit the maximum load that can be supported by individual axles. A trailer having a slider gains an advantage with respect to laws governing maximum axle loads. More particularly, proper placement of the slider varies individual axle loads or redistributes the trailer load so that it is within legal limits.
Once properly positioned, the slider is locked in place on the underside of the trailer by a retractable pin mechanism. The retractable pin mechanism generally includes two or more, and typically four, retractable pins which may be interconnected by a usually manually or pneumatically actuated crank mechanism. When the pins are in their extended or outboardmost position, they each extend through a respective opening formed in the slider and into a selected aligned one of a plurality of openings formed in rails depending from the trailer body. The pins thereby lock the slider in a selected position relative to the trailer body.
However, known prior art sliders fail to provide for incorporation of a storable walk ramp beneath the trailer. Such walk ramps typically are required on trailers used in food service and appliance delivery applications, as well as in other applications. Since known prior art sliders are not made to accommodate storage of a walk ramp, if a ramp must be installed on a trailer having a prior art slider, a pair of large steel spacers usually is attached to the bottom of the trailer and extends the full length of the body rails, which is typically about 200 to 300 inches. The spacers are needed to provide clearance for the walk ramp carrier, which has a cross-section of approximately 6 inches high by 28 inches wide and is mounted on the underside of the trailer. The trailer body rails then can be attached to the bottom of the spacers, instead of the bottom of the trailer, and the slider in turn is mounted on the rails in the usual manner. Unfortunately, while such an arrangement of parts accommodates storage of the walk ramp when not in use and its carrier, the prior art spacer system adds significant unwanted weight to the semi-trailer.
The present invention solves the above-described weight problem in the following manner. Rather than attaching spacers the entire length of the trailer body rails, a spacer cap is attached directly to each main member of the slider and measures only about 96 inches in length, thus saving significant weight over the above-described prior art arrangement of parts. The slider locking pins are relocated into the spacer caps to allow standard trailer body rails to be utilized. The present invention can be utilized in new trailer manufacturing, as well as on existing trailers of semi-trailers using prior art sliders, to easily convert such existing trailers to accommodate walk ramp storage merely by replacing the prior art slider with the slider of the present invention. This ease of conversion should be compared to the case where it is desired to utilize the prior art walk ramp storage spacer system, which would require that the rails be cut off the trailer body, the spacers installed, and the rails reattached.
SUMMARY OF INVENTION
Objectives of the present invention include providing a ramp-accommodating movable subframe for a semi-trailer, which provides for incorporating a storable walk ramp beneath the trailer, and also limits the addition of weight to the semi-trailer from incorporation of the walk ramp.
Another objective of the present invention is to provide such a ramp-accommodating movable subframe for a semi-trailer, which can be quickly and easily retrofit on existing semi-trailers.
A still further objective of the present invention is to provide such a ramp-accommodating slider for a semi-trailer, which is economical to install, durable in use and easy to maintain.
These objectives and advantages are obtained by a subframe structure for a vehicle trailer, the subframe structure being movably mountable on spaced-apart, parallel and longitudinally extending elongated rails mounted on the bottom of said trailer, the trailer rails each being formed with a plurality of openings, the subframe structure including a pair of spaced-apart, parallel and longitudinally extending elongated main members, and at least one cross-member structure extending between and being connected to the main members to maintain the spaced-apart parallel relationship between the main members, wherein the improvement comprises spacer means including, an elongated spacer member mounted on each of the main members and extending substantially the entire length of the main members, the spacer members each including means for movably engaging a respective one of the trailer rails, the spacer members each further being formed with at least one locking pin opening, the spacer member opening being selectively alignable with its respective trailer rail openings, and at least one locking pin mounted on each of the spacer members adjacent to its respective locking pin opening, the locking pin further being generally complementary-sized and shaped for passage through the respective aligned openings, the locking pin being operatively connected to a locking pin retraction mechanism, the retraction mechanism and the locking pin being operable for locking the subframe structure in one selected position relative to the vehicle trailer when the locking pin extends through the aligned openings, and for unlocking the subframe structure for moving the subframe structure to another selected position beneath the trailer when the locking pin is retracted from the aligned openings, the spacer means providing a bay generally defined by the bottom of the trailer, the subframe cross-member structure and the spacer members, so that a walk ramp is mountable in the bay.


REFERENCES:
patent: 4958845 (1990-09-01), Parks
patent: 5720489 (1998-02-01), Pierce et al.

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