WEIGHT REDISTRIBUTION IN FREIGHT TRUCKS

Cross Reference to Related Applications

[0001] This application claims the benefit of U.S. Provisional Application Serial

No. 60/636,564, titled "Weight Distribution in Freight Trucks", filed on December 16,

2004, the disclosure of which is fully incorporated by reference herein.

Field of the Invention

[0002] The present application relates to moving tandem axles to properly distribute

weight in a freight trailer.

Background of the Invention

[0003] The distribution of the weight in a tractor trailer is a serious consideration in

today's tracking industry. With a high percentage of tracks reaching the allowable gross

vehicle weight of 40 tons, it is important for the weight to be distributed properly to avoid

fines and increased road damage, and to maintain proper stability. At the same time,

however, necessary repetitions of weighing and redistributions can be timely and

expensive.

[0004] A significant problem with the current method of weight distribution is in the

movement of the rear tandem axles. This solution, however, is riddled with problems that

greatly decrease efficiency. The first step, the removal of the locking pins, is a time

intensive procedure typically requiring more than one person if the locking pins are stuck

or corroded in place. The second step, the movement of the trailer over the tandems,

involves repeated iterations and trips to and from the trailer to get the locking pins lined up

properly in the correct locations. This cycle, in addition to frequent trips to a certified

scale, can cost valuable time.

[0005] In view of the deficiencies in the prior methods of weight redistribution, a

need exists for automating the movement of the tandem trailer and actuation of the locking

pins in a more efficient manner.

Summary of the Invention

[0006] The present invention resolves the above described deficiencies in the prior

art by a system that achieves uniform payload distribution without manual relocation of the

rear trailer tandems (axles) or manual activation of the locking pins. The inventive system

by reducing the manual labor of the prior art process of weigh redistribution allows for

maximized road time. Broadly, the inventive means of relocating the rear trailer tandems

(axles) is provided by a weight redistribution apparatus comprising:

an axle carrier slideably engaged along a length of a trailer frame, wherein

said axle carrier comprises a threaded fixture; and

an axle carrier positioning means comprising a motor mounted at a first end

of said trailer frame and a bearing mounted at an opposing end of said trailer frame,

said motor and said bearing being connected by a shaft in threaded engagement with

said threaded fixture, wherein rotating said shaft in a first directed traverses said

axle carrier along a first longitudinal direction of said trailer frame and rotating said

shaft in a second direction traverses said axle carrier along a second longitudinal

direction of said trailer frame.

[0007] In another aspect of the present invention, a system is provided that allows

for weight redistribution though an operator controlled interface between a slideably

positioned axle carrier, a weight monitoring means, and a means for locking the slideable

mounted tandem axle trailer in secure engagement with the trailer frame. Broadly, the

inventive system comprises:

an axle carrier slideably engaged along a length of a trailer frame, wherein

said axle carrier comprises a threaded fixture and said trailer frame comprises a

plurality of axle carrier lock sites;

an axle carrier positioning means comprising a motor means and a threaded

shaft mounted to said trailer frame, said threaded shaft being in rotational

engagement with said threaded fixture of said axle carrier.

a weight monitoring system integrated in said axle carrier, said weight

monitoring system comprising at least one sensor mounted in said axle carrier to

correspond to each axle;

an axle carrier locking means comprising at least one extendable pin

mounted on said axle carrier, wherein said at least one extendable pin when in an

extended position engages one of said plurality of axle carrier lock sites; and

a control interface for displaying data from said at least one sensor of said

weight monitoring system, actuating said axle carrier positioning means, and

actuating said axle carrier locking means.

Brief Description of the Drawings

[0008] Figure 1 (top view) depicts one embodiment of a tandem axle carrier that is

slideably engaged along the length of a trailer frame having a controllable axle positioning

means.

[0009] Figure 2 (prospective view) further illustrates the axle carrier depicted in

Figure 1.

[0010] Figure 3 (top view) depicts one embodiment of a weight monitoring pad for

use with the weight monitoring system of the present invention.

[0011] Figure 4 (prospective view) illustrates an axle carrier having a plurality of

pneumatically actuated locking pins.

[0012] Figure 5 (prospective view) depicts one embodiment of an operator interface

for use with the axle carrier positioning means, the locking pins and the weight monitoring

system of the present invention.

[0013] Figure 6 (prospective view) illustrates the axle carrier and trailer frame

depicted in Figures 1 and 2 having a trailer freight body mounted to the trailer frame and

an operator interface mounted to the trailer freight body.

Detailed Description of Preferred Embodiments

[0014] The present invention provides a weight redistribution system that achieves

uniform payload distribution without manual relocation of the rear trailer tandems or

manual activation of the locking pins. The present invention is now discussed in more

detail referring to the drawings that accompany the present application. It is noted that in

the accompanied drawings, like and/or corresponding elements are referred to by like

reference numbers.

[0015] Referring to Figure 1, trailer frame 10 is depicted having an axle carrier

positioning means 11, 12, 13, 14 mounted under the bed of the trailer body (also referred to

as box trailer). The trailer frame 10 comprises of longitudinal beams and cross beams

running laterally for the entire length of the trailer. Guide rails 11 are mounted to the

crossbeams, on which the axle carrier 15 is traversed along for weight redistribution.

[0016] A threaded shaft 12 is one component of the axle carrier positioning means.

In a preferred embodiment, the threaded shaft 12 comprises a worm gear. The threaded

shaft 12 preferably comprises aluminum, which provides a weight savings and corrosion

resistance advantage over alternative metals, such as steel. The axle carrier positioning

means may further comprise a motor 14 mounted to one end of the trailer frame 10, which

is in rotational engagement with the threaded shaft 12. The motor 14 may be mounted to

one of the frames crossbeams. In a preferred embodiment, the motor 14 is electrically

powered. In one example, the motor 14 is capable of producing a torque on the order of

approximately 500 to 600 lbs-ft.

[0017] It is preferred that the axle carrier positioning means further comprises a

bearing 13, such as a thrust bearing, mounted to the portion of the frame 10 opposing the

motor 14 mount, wherein the bearing 13 is in rotational engagement with the threaded

shaft 12. The bearing 12 attachment of the threaded shaft 12 opposite the motor 14

strengthens the system in both a lateral and longitudinal direction. In one embodiment, at

least portions of the axle positioning means 12, 13, 14, 16 are encased in a protective

structure. Preferably, the protective structure obstructs operator contact to all components

of the axle carrier position means, with the exception of access points for maintenance.

Although the protective structure preferably comprises aluminum, other metals have also

been contemplated and are within the scope of the present invention.

[0018] Referring to Figure 2, the axle carrier 15 is slideably traversed along the

guide rails 11 of the trailer frame 10 and is actuated by the axle carrier positioning means

12, 13,14, 16. The axle carrier 15 and the axle carrier positioning means are threadably

engaged between the threaded shaft 12 and a threaded fixture 16 that is mounted on the

axle carrier 15. Since several teeth of the threaded shaft 12 (worm gear) and the threaded

fixture 16 are engaged simultaneously, the gear system provides greater shear strength than

would be possible using rack and pinion gears systems. The axle carrier 15 includes

mounting points for at least two axles 17, each of which may include four tires 18 (two on

each side for a total of eight). Preferable, the axle carrier 15 comprises aluminum.

[0019] Rollers 19 may be integrated into the surfaces of the axle carrier 15 that are

in contact with the guide rails 11 and/or trailer frame 10 to decrease the frictional

resistance to the movement of the axle carrier 15. In a one embodiment, the rollers 19 may

comprise nylon. As opposed to the rollers 19, a low friction strip may be positioned

between the surfaces of the axle carrier 15 and the guide rails 11 and/or trailer frame 10

that are in contact. The low friction strips may comprise Teflon, Nylon or any other like

low friction material. Brakes may be attached to either end or both ends of each axle. In

one example, there are four sets of leaf springs for support (one per side, per axle), and

four air shocks. An on-board air compressor (not shown) operates the braking and

suspension system.

[0020] Referring to Figure 3, a weight monitoring system may also be integrated

into the axle carrier. In one embodiment, strain gauges 20 may be mounted to a portion of

the axle carrier 15 corresponding to each axle 17. In another embodiment, strain gauges

20 are mounted to measure the strain on the axles 17 supported by the axle carrier 15 and

additional strain gauges 20 are mounted to the trucks suspension (not shown) to measure

the strain on the front and drive axels of the truck that transports the trailer.

[0021] In one embodiment, the strain gauge 20 provides a voltage across a very fine

wire or metallic foil arranged in a grid pattern. The grid pattern 25 maximizes the amount

of metallic wire or foil subject to strain in the parallel direction. The cross sectional area of

the grid 25 is minimized to reduce the effect of shear strain and Poisson Strain. The grid 25

is bonded to a thin backing 26, called the carrier, which is attached directly to the test

specimen; such as the portions of the axle carrier 17 or track corresponding to the axles.

The strain experienced by the axles is transferred directly to the strain gauge 20, which

responds with a linear change in electrical resistance. This change in resistance can be

extrapolated to determine the strain in the axles 17. By determining the strain of the axle

17, the weight placed on the axle can be extrapolated.

[0022] In a preferred embodiment, the strain gauge 20 consists of a load cell, which

is the actual wire or foil 25 that accepts the loads, as depicted in Figure 3. Preferably, the

load cell is protected by an enclosure. The information measured by the strain gauge 20 is

processed by software and transferred to a readout station, which will be a part of the

operator interface that provides controllability of the axle positioning means, as well as,

the axle carrier locking means.

[0023] Referring to Figure 4, in one embodiment, the inventive weight redistribution

system may further comprise an axle carrier locking means. In one embodiment, the axle

carrier locking means comprises pneumatically actuated pins 50 that lock the axle carrier

into place by engagement of the pins 50 into openings 51 in the trailer frame. For

example, equally spaced openings 51, also referred to as locking sites, for the locking pins

50 may be formed along the longitudinal beams of the trailer frame or the guide rails. The

axle carrier locking means may draw air pressure from the air brake 53 or air suspension

system 52 already on the trailer, and may have a fail-safe system similar to that of the

brakes 53.

[0024] In one example, the pins 50 are naturally engaged by spring engagement, and

need air pressure to disengage and release the axle carrier 15. In this example, should the

air system fail, leak, etc., the pins 50 will remain or become engaged, substantially

reducing the possibility for the system to release while the truck is in motion. In another

embodiment, the pins 50 are naturally disengaged by spring pressure, and need air pressure

to engage and lock the axle carrier 15. In one embodiment, a plurality of locking pins may

be utilized, such as four locking pins, wherein each locking pin is separately actuated by an

individual air piston. Although a pneumatically actuated locking system 54 is preferred,

the locking pins 50 may alternatively be actuated by mechanical, hydraulic or electric

means.

[0025] Referring to Figures 5 and 6, each of the above described elements may be

integrated by an operator interface 40 facilitating the interaction of the driver with the

system. The operator interface 40 could be mounted on the trailer body 45, as depicted in

Figure 6, or be mounted within cab of the truck, as depicted in Figure 5, or accessible from

both. The operator interface 40 may be radio controlled allowing for wireless operation of

the system from both inside and outside the truck cab. Regardless of the mounting point,

the operator interface 40 preferably provides the operator with the ability to directly

monitor and control the axle movement.

[0026] Having described the presently preferred embodiments, it is to be understood

that the invention may be otherwise embodied within the scope of the appended claims.