Land vehicles – Wheeled – Running gear
Reexamination Certificate
2001-04-10
2001-08-28
Rice, Kenneth R. (Department: 2167)
Land vehicles
Wheeled
Running gear
C280S405100, C280S407100
Reexamination Certificate
active
06279933
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to semi-trailer subframes, and in particular to movable subframes for semi-trailers. More particularly, the invention is directed to a pin retraction mechanism of a semi-trailer movable subframe for locking the movable subframe in a selected position relative to the semi-trailer main frame, wherein each one of at least one pair of pins is individually retractable by a single mechanism to an unlocked position for moving the subframe to a selected position beneath the semi-trailer main frame, and further wherein each one of the pins is individually extendable to the locking position.
2. Background Art
Movable subframes, typically referred to as sliders, have been utilized on tractor-trailers or semi-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 main frame, 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, pins which conventionally are interconnected by a manual, electric, pneumatic, or hydraulic 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 a selected aligned one of a plurality of openings formed in the trailer main frame. The pins thereby lock the slider in a selected position relative to the trailer main frame.
However, these pins can become jammed. The mechanical advantage enjoyed by a manual operator of the pin mechanism is designed to overcome spring forces which bias the pins to the extended locked position, for retracting and unlocking the pins when it becomes necessary to reposition the slider. This mechanical advantage is not designed to free or retract jammed pins from their locked position. Since the mechanical advantage is sometimes inadequate, prior art slider pin mechanisms rely on either the brute force of the semi-trailer operator or add-on devices such as fluid, electric or stored-energy actuated systems designed to release jammed pins.
More specifically, the reason for jammed pins is that shear forces are imposed on the individual pins. The shear forces operate in the direction of the longitudinal axis of each cylindrical pin. More particularly, slight movement of the slider relative to the trailer main frame during operation of the semi-trailer can cause slight misalignment between the respective slider and trailer main frame openings through which each pin extends when in the locked position. This misalignment can in turn cause contact pressure points between each pin and its respective trailer main frame opening, aligned slider opening, and mounting bracket opening adjacent to the inboard end of the pin. These contact pressure points in turn cause the above-mentioned shear forces on the pins. Such whipsaw-like or jamming forces can become greater than the force that a semi-trailer operator can manually apply through a conventional crank mechanism to free the pins.
Thus, when prior art locking pin mechanisms become jammed, the operator of the semi-trailer risks personal injury due to overexertion in attempting to manually free jammed pins, and further risks damaging the retractable pin mechanism. Specifically, a typical method of attempting to release prior art jammed pin mechanisms is for the semi-trailer operator to rock the trailer fore and aft, while an assistant manually operates the retractable pin mechanism. The rocking motion briefly realigns the misaligned openings, so that the assistant can retract the pins during the period of realignment. The process has been simplified by various prior art assisted-release devices such as fluid, electric and stored-energy assisted-release devices, which generally allow the vehicle operator to maneuver the trailer while the quick release device automatically frees the jammed pins, thus effectively obviating the need for another person to manually operate the crank mechanism.
However, such devices, whether of the electric, fluid, stored-energy or typical manual type, usually are complicated assemblies which apply retraction force to the pins in an indirect or non-linear fashion through a usually complex assembly of parts such as shafts, levers, arms, and the like. For example, stored-energy type devices can include complicated spring assemblies, and electric devices can include components such as a solenoid. While such systems can operate satisfactorily for their intended purpose, they can suffer from several disadvantages. First, such complex assemblies utilize a relatively large number of parts which are more subject to wear and possible downtime than is a more simple retractable pin mechanism. In addition, increased complexity usually leads to increased weight, which is undesirable in the semi-trailer industry because it decreases the profit that the owner of a semi-trailer can realize by reducing the amount of cargo that can be hauled, as discussed hereinabove in relation to road and bridge laws. Also, such increased complexity also adds cost to the manufactured semi-trailer. Finally, during operation, and especially with respect to the locked or extended pin position, due to the complex interconnected nature of such mechanisms, which typically utilize a single actuator, if one pin fails to engage or lock, it follows that none of the pins can lock and the semi-trailer thus is inoperable until the condition is corrected. Moreover, if one pin accidentally disengages during operation of the semi-trailer, then all of the pins, usually four, must disengage, which can lead to dangerous consequences for the affected semi-trailer as well as for other vehicles operating in its vicinity. Another disadvantage of such assemblies is that various structural components of the slider must serve as a bearing surface for absorbing unbalanced reactive forces that occur during operation of such prior art locking pin mechanisms and for maintaining proper relative positioning of the various components of the mechanism for its reliable operation. Such positioning is important because the mechanism is sensitive to relatively small changes in timing or adjustment, and the entire assembly and supporting slider structure on which the mechanism is installed are tolerance sensitive. However, in order to make the slider structural components robust enough to withstand such reactive forces, additional structural components often must be added to the slider and/or existing structure must be made more sturdy. Unfortunately, such required changes to the slider structure typically result in unwanted added cost, weight and complexity.
Other prior art locking pin mechanisms solve certain ones of the above-described problems by implementing direct linear actuation of each pin by a separate, usually pneumatically, hydraulically or electrically operated actuator. While such a system solves the above-described problem of all or nothing locking and unlocking of the pin retraction mechanism, it fails to solve the problems of complexity, weight and cost, since such locking pin mechanisms require four, albeit independently operable, actuation mechanisms.
The present invention solves the above-described pro
Gibson Marc A.
Hess Timothy V.
Ross Joseph M.
Buckingham Doolittle & Burroughs LLP
Cuff Michael
Dureska, Esq. David P.
Rice Kenneth R.
The Boler Company.
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