Pin box assembly for trailer

A pin box assembly is provided for a trailer. The pin box assembly includes a first section having a trailer attachment point, a second section carrying a king pin and a pivot connecting the first and second sections together. In addition the pin box assembly includes a shock absorber having a first end connected to the first section and a second end connected to the second section. Still further, the pin box assembly includes an air spring connected between the first and second sections.

TECHNICAL FIELD

The present invention relates generally to the towing equipment field and, more particularly, to a new and improved pin box assembly for a trailer.

BACKGROUND OF THE INVENTION

The present invention relates to a new pin box assembly for a trailer that provides both softening in the vertical direction and anti-chucking in the longitudinal or horizontal direction so as to provide enhanced performance and a smoother ride. In effect the pin box assembly acts as a buffer between the tow vehicle and the trailer, significantly reducing the negative impact of vertical shock and longitudinal chucking to provide an improved ride. The assembly relieves stress on the towing vehicle, trailer frame, cabinets, mechanicals and support mechanisms. The smoother ride also reduces fatigue for drivers and passengers in the towing vehicle.

SUMMARY OF THE INVENTION

In accordance with the purposes of the present invention as described herein, a pin box assembly is provided for a trailer. The pin box assembly comprises a first section including a trailer attachment point, a second section carrying a king pin, a pivot connecting the first section and the second section together, a shock absorber having a first end connected to the first section and a second end connected to the second section and an air spring connected between the first section and the second section. More specifically, the shock absorber is provided between the air spring and the trailer attachment point. The air spring is provided between the shock absorber and the pivot. Still further, the pivot is provided at a front end of the assembly. In addition the trailer attachment point is provided adjacent a rear end of the assembly.

More specifically describing the invention, the air spring and the shock absorber are provided between the trailer attachment point and the king pin. The air spring and the shock absorber are both offset from the king pin and the trailer attachment point. In addition the first section includes a top wall and two downwardly depending side walls. The second section includes a skid plate and two upwardly depending side skirts. The margins of the two downwardly depending side walls and two upwardly depending side skirts overlap so as to form an enclosure with the top wall and the skid plate. The enclosure receives and protects the air spring. Still further, in one embodiment the air spring is a rubber air bladder.

In the following description there is shown and described one possible embodiment of this invention, simply by way of illustration of one of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.

DETAILED DESCRIPTION OF THE INVENTION

Reference is now made toFIGS. 1-4illustrating the pin box assembly10of the present invention. The pin box assembly10includes a first section12having a top wall14and two downwardly depending sidewalls16. A cross member18extends between the sidewalls and provides additional strength and rigidity to the structure. A shock absorber mounting bracket20also extends between the sidewalls. The mounting bracket20includes a pair of ears22that cooperate to form a trunnion mounting for one end of a shock absorber24in a manner that will be described in greater detail below. The top wall14, sidewalls16, cross member18, mounting bracket20and ears22may all be constructed from steel for high strength and may all be connected together by welding if desired. The sidewalls16may also include rounded edges or return flanges25in order to provide added strength while minimizing weight.

The pin box assembly10also includes a second section26incorporating a skid plate28, an upper king pin support plate30and two upwardly depending side skirts32. A king pin34includes a mounting end that is received and welded into cooperating, aligned apertures36provided in the skid plate and the upper king pin support plate30. This two point mounting of the king pin34enhances the low transfer characteristics of the assembly10. A pair of ears38are welded adjacent a rear end of the upper support plate30and function as a trunnion to receive one end of the shock absorber24. A pivot tube40is received and welded in cooperating slots42provided in the front end of the side skirts32. Like the sidewalls16, the side skirts32include return flanges44for added strength. The skid plate28, upper king pin support plate30, side skirts32, king pin34, ears38and pivot tube40may all be constructed from high strength steel and, for example, may all be secured together by welding if desired.

An air spring, generally designated by reference numeral46includes an air bladder48, a bottom or base plate50and a top plate52. The upper king pin support plate30includes two series of aligned apertures54and an elongated slot56therebetween. The base plate50of the air spring46is secured to the support plate30by fasteners such as a pair of cooperating bolts58. The point of attachment of the air spring46to the support plate30may be adjusted fore and aft to optimize the performance of the assembly10for differing trailer weights by aligning the two mounting apertures in the base plate50with different sets of the cooperating mounting apertures54provided in the support plate. The air bladder48of the air spring46is connected by a line60that passes through the slot56and connects through a valve62with an air source64. The lower end of the shock absorber is connected to the ears38by means of the cooperating nut and bolt66.

The first section12and second section26are pivotally connected together at the front end thereof by means of pivot shaft68that passes through the aperture70in one of the side walls16, the pivot tube40of the second section26and the aperture70of the other sidewall16. Bushings72provided between the pivot shaft68and the pivot tube40insure free pivoting action between the two sections12,26. Outer retainer washers74and a cooperating nut and bolt76complete the pivotal connection. A cooperating nut and bolt78completes the connection of the upper end of the shock absorber24to the ears22on the first section20. Aligned apertures80in the sidewalls16function as the trailer attachment point for the pin box assembly10in a manner that will be described in greater detail below.

As should be appreciated from reviewing the drawing figures, the margins of the sidewalls16and side skirts32overlap so that the sidewalls, side skirts, top wall14and skid plate28define an enclosure82. In the illustrated embodiment, the shock absorber24is provided at the opening of the enclosure82between the mounting apertures or trailer attachment point80and the air spring46(see particularlyFIG. 3). The air spring46is provided in the enclosure28between the shock absorber24and the forward pivot tube40. In this position, deep in the enclosure82, the air spring46is well protected from UV exposure, malicious tampering and road hazards thereby substantially increasing its service life. The rear mounted shock absorber24is also shielded from road hazards and together the first and second sections12,26provide a clean, aesthetically pleasing streamlined design.

The pin box assembly10of the present invention may be secured by bolts, cooperating nuts and washers to the frame of a trailer. More specifically, the mounting apertures or trailer attachment point80are aligned with cooperating apertures in the frame of the trailer. The bolts are then inserted through the aligned apertures, lock washers are then positioned over the bolts and the cooperating nuts are tightened to complete the connection. Of course, any other appropriate attachment method known in the art could be utilized including, for example, welding. The king pin34of the pin box assembly10is then positioned in the jaw assembly of a fifth wheel trailer hitch mounted to the bed of a towing vehicle. The jaw assembly of the fifth wheel trailer hitch is then locked in a manner known in the art. The pin box assembly10functions with the pivoting head of the fifth wheel trailer hitch to provide two separate pivot points to reduce fore and aft movement on the tow vehicle and up and down movement on the trailer.

The expandable and compressible air spring46regulates the compression and expansion rates of the pin box assembly10. Where an air source64such as an air compressor is contained within the trailer, the driver may adjust the air pressure in the air spring30and accordingly, the compression and expansion rates in order to provide more ideal ride characteristics. More specifically, this allows the operator to tune the performance of the pin box assembly10so as to avoid operating at the natural harmonic/Hz frequency of the tow vehicle. The valve62is used to control the air flow from the source64to the bladder48of the air spring46or from the air spring to the environment to release pressure. When inflated for use, the top plate52engages the bearing surface90of the cross member18.

The shock absorber24functions to provide conventional dampening during the towing of the trailer. By moving the pivot shaft or pivot point40forward of the king pin34center line, the pivot now works in better harmony with the fifth wheel hitch to which the pin box assembly10and trailer are connected thereby significantly reducing longitudinal chucking during trailer towing. More specifically, the pin box assembly10of the present invention successfully combines the best performance characteristics of the leading air-ride and anti-chucking couplers to provide better softening in the vertical direction and anti-chucking in the longitudinal direction so as to provide better overall performance than devices of the prior art.