A dual side-dumping truck and trailer combination utilizing a dolly-type trailer and a frameless material hauling bed. The bed is suspended on bunk assemblies mounted rotatably on bolsters on the truck frame and the trailer frame. Hinge mounting arrangements on the ends of the bunk assemblies enable selective tilting of the bed to one side or the other. The dolly-type trailer provides increased maneuverability and improved safety factor by enabling jackknifing while dumping.

This invention relates, in general, to material-hauling conveyances and, in 
particular, to material-hauling conveyances having a side-dumping 
capability. 
The trucking industry standard for large payload hauling of heavy materials 
such as rock, rip rap, and aggregates of all sizes has been the frameless 
end dump trailer first introduced by Bailey Engineering and Manufacturing 
Company over ten years ago. A variation of the Bailey frameless end dump 
trailer is shown in U.S. Pat. No. 3,844,616. The frameless construction of 
this type of trailer greatly reduced the tare weight of the trailer, and 
thus enabled the hauling of a larger payload within the forty-ton legal 
limit on gross vehicle weight. Generally, these frameless trailers are 
about twenty-four feet long, eight feet wide overall, and have a payload 
capacity of about twenty-two and one-half tons. 
While the frameless end dump trailer performs in a generally satisfactory 
manner for hauling heavy material useful in building roads, dams, levees 
and the like, it is sometimes disadvantageous to be required to dump the 
payload to the rear of the trailer when the material then has to be spread 
or relocated to another place such as the side of an earthen dam or levee 
or into a trench beside the roadway. Under such conditions, it would be 
preferable to have a hauling conveyance with a large payload capacity 
which is capable of dumping the load to the side of the vehicle. 
Another somewhat frequently encountered disadvantage of the frameless end 
dump trailer is the inability of the trailer to be used in work on narrow 
curving road beds because the wheels on the trailer do not track the truck 
wheels. Thus, it is often necessary to dump the payload out of the truck 
and use a more maneuverable conveyance to cart the material to its 
ultimate destination. This often wastes material, adds substantial cost to 
the project, and delays the completion of the project. 
The trucking industry has recognized to some extent the need for a 
side-dumping, material-hauling conveyance. Some of the equipment which has 
heretofore been designed carries the load between the rear truck tires and 
trailer tires to provide stability while dumping, i.e., to prevent 
overturning the tractor and trailer while dumping to the side. This 
approach is exemplified in Gustafson U.S. Pat. No. 2,693,531 and Armington 
U.S. Pat. No. 2,848,275. The trailers illustrated in these patents are 
capable of dumping selectively to either side, but are intended for 
offroad use only and for carrying small payloads over short distances. 
Other side-dumping trailers have been designed with over-the-wheels bed 
positions, but they employ heavy chassis and bed construction, and use 
side doors on the bed to enable the bed to reach a sufficient angle to the 
horizontal to dump all the load without having the center of gravity of 
the loaded trailer go over and beyond the pivot point of the bed. This 
type of equipment is exemplified in Flowers U.S. Pat. Nos. 3,240,164 and 
3,316,019. While this equipment is capable of selectively dumping the load 
to either side, the weight of the hauling bed and chassis reduces the 
gross payload capacity. Furthermore, the side door mechanisms add 
substantially to the complexity and cost of the equipment. 
Trucco et al. U.S. Pat. No. 3,323,838 also discloses a side dump vehicle 
having the hauling beds mounted on a chassis over the wheels, but uses two 
separate beds simultaneously dumping to opposite sides to prevent 
overturning. Furthermore, the beds each have one shallow side in order to 
achieve a sufficient dumping angle without taking the center of gravity of 
the loaded bed over the pivot point. This bed profile, along with the 
construction of the bed and the weight of the chassis, limits the payload 
capacity of the vehicle. The requirement to dump simultaneously to both 
sides could be highly disadvantageous in some projects where the payload 
needs to be located only on one side of the vehicle, such as when a trench 
on one side of the vehicle is to be filled. 
None of this prior art side-dumping equipment provides a trailer-truck 
arrangement having improved tracking ability, and none of the equipment is 
capable of achieving the payload capacity of the frameless end dump 
previously described, much less a larger payload capacity. 
It is an object of this invention to provide an improved material-hauling 
conveyance with a dual side-dumping capability. 
It is a further object of this invention to provide a material-hauling 
conveyance having both a larger payload capacity than the frameless end 
dump trailer and a dual side-dumping capability. 
It is a further object of this invention to provide a material-hauling 
trailer having a side-dumping capability and improved tracking capability. 
In accordance with one aspect of this invention, an improved 
material-hauling conveyance with dual side-dumping capability employs a 
frameless material-containing bed comprising a floor portion, a pair of 
side wall portions each meeting the respective edge of the floor portion 
at a break line and angling away from the floor portion to form a 
preselected angle to the vertical, and a pair of end wall portions. A 
conveyance means is provided for transporting the bed and includes a 
chassis adapted to be carried above at least a pair of rear wheels and a 
pair of front wheels. At least a pair of hinge-mounting means is located 
on opposite sides of the bed for normally retaining the bed on the chassis 
and for enabling the bed to be tilted selectively to one of the sides 
around a rotation axis. A hoisting means is mounted to the chassis and to 
the bed at the center line of the bed for raising the bed to tilt it on a 
selected one of the hinge-mounting means. The profile of the bed and the 
position of the rotation axis provided by the hinge-mounting means are 
constructed and arranged such that the bed, when loaded with material, may 
be tilted by the hoisting means until the center of gravity of the bed and 
the load passes over and beyond the rotation axis to a position such that 
one of the side wall portions of the bed is at an angle to the horizontal 
sufficient to completely dump the material from the bed without bumping 
into the wheels or turning over the conveyance means. 
In a preferred embodiment of the invention, the conveyance means is a 
dolly-type trailer having a chassis comprising separate front and rear 
bunk assemblies adapted to be mounted in a horizontally rotatable fashion 
on the frame of a truck tractor and the bolster assembly on the frame of 
the trailer, respectively. The dolly-type trailer further includes a reach 
extending forward from the trailer frame and having a sliding pole 
compensator mounted therein which is adapted to be hitched to the rear of 
the frame of the truck tractor. In this embodiment, the bed has a pair of 
top hats, each mounted on the bottom one of the end wall portions thereof, 
and the front and rear bunk assemblies each have a bottom hat shaped to 
engage in mating fashion with one of the top hats. Furthermore, the 
hinge-mounting means is positioned on each end of each of the bunk 
assemblies, whereby the bed is suspended between the front and rear bunk 
assemblies on the top hats, and the trailer is pulled by the bed and 
steered by the reach and compensator assembly to provide a 
tracking-cornering action between the truck tractor wheels and the trailer 
wheels. This type of conveyance means further enables the truck tractor 
and trailer combination to be jackknifed to the side opposite the side to 
be dumped toward to increase the safety factor of dumping. 
In accordance with another aspect of this invention, a material-hauling 
conveyance having a side-dumping capability and improved maneuverability 
is provided by utilizing a dolly-type trailer having a frame, at least a 
pair of wheels mounted on the frame, a bolster assembly mounted on the 
frame over the wheels, and a reach extending forward from the frame with a 
sliding pole compensator mounted therein and adapted to be hitched to the 
rear of the frame of the truck tractor. A pair of bunk assemblies are 
employed, and these bunk assemblies are adapted to be mounted in 
horizontally rotatable fashion on a bolster assembly on the trailer and on 
a bolster assembly provided on the frame of the truck tractor. A material 
container bed is provided, together with means for mounting the bed in a 
suspended fashion on the bunk assemblies. Hinge-mounting means are 
provided for normally retaining the bed on the bunk assemblies and for 
enabling the bed to be tilted to at least one side to dump the contents 
thereof. Hoisting means are mounted to each of the bunk assemblies and the 
bed for raising the bed to tilt it on the hinge-mounting means. Via this 
combination, the trailer is pulled by the bed and steered by the reach and 
compensator assembly to provide a tracking-cornering action of the truck 
and trailer and to enable the truck and trailer combination to be 
jackknifed to the side opposite the dumping side of the bed to increase 
the safety factor of dumping. 
The dual side-dumping conveyance of this invention has a number of 
advantages over both the frameless rear end dump vehicle previously 
described and the prior art side-dumping conveyances discussed above. The 
special design of the profile of the bed enables the center of gravity of 
the loaded bed to be carried over the pivot point such that the load can 
be completely dumped without requiring side gates which add to the 
complexity and cost of the prior art equipment. Because of this 
side-dumping capability, the conveyance is capable of dumping to either 
side while stationary or while travelling slowly in order to distribute 
the load along the side of the truck. This is particularly advantageous 
when dumping into a trench and avoids the wasting of material either by 
dumping too much material in one location or dumping part of the material 
on the ground. It is especially advantageous when dumping into a trench 
where traffic would be blocked by a rear dump vehicle. 
The use of a frameless bed mounted on the dolly-type trailer enables the 
attainment of both a larger, legal payload due to the increased wheel base 
made possible by the side-dumping capability and improved maneuverability 
of the trailer and truck combination due to the improved tracking. This 
enables the side-dumping conveyance of this invention to be utilized in 
areas which would be otherwise inaccessible to the end-dumping equipment. 
When utilized in a jackknifed dump position, the contents of the bed may 
be dumped to the side on level ground and thereafter the truck and trailer 
can back-up and then pull around the pile. This avoids driving the tires 
over the dumped material and thus precludes damaging the tires, getting 
the tires dirty or stuck in the material, or contaminating the material 
itself.

FIG. 1 is a partly exploded view of the major elements of a side-dumping, 
material-hauling conveyance in accordance with a preferred embodiment of 
this invention. As illustrated, the main components are a material-hauling 
bed 10, front and rear bunk assemblies 20 and 30, and truck and trailer 
bolster assemblies 70 and 80 which together form part of a chassis means 
on which the front and rear bunk assemblies 20 and 30 are mounted. The 
truck bolster assembly 70 is mounted on the frame 110 of a tractor truck 
100 and extends over the truck wheels 105. 
The trailer bolster assembly 80 is mounted on the frame 140 of a dolly-type 
trailer 130 and is mounted over the trailer wheels 135. As shown, a 
stinger section 110A on the truck frame 110 extends beyond the rear truck 
wheels. Reach 150 extends forward from trailer frame 140 toward the 
stinger 110A on the truck and contains a sliding pole compensator 155 
which is hitched in a normal fashion via a hitch 160 to the rear of 
stinger 110A. 
The major features of bed 10 can best be seen by considering the side view 
in FIG. 1 together with the end profile shown in dotted lines in FIG. 4. 
As illustrated, bed 10 consists essentially of a floor portion 11, a pair 
of side wall portions 12 and 13, a pair of top rails 14, a front headboard 
15, and a rear headboard 16. As can best be seen in FIG. 4, the floor 
portion 11 of bed 10 comprises a section of an ellipse which meets the 
side wall portions 12 and 13 at the break lines 12A and 13A. The top rails 
14 consist of box-like structures which are fastened in any suitable 
fashion, such as welding, to the tops of side wall portions 12 and 13. 
Front headboard 15 and rear headboard 16 form end wall portions of bed 10 
and are mounted on the ends of the floor and side wall portions of bed 10 
in an appropriate manner such as by welding. Preferably, the floor portion 
11 and the two side wall portions 12 and 13 of bed 10 are formed of a 
continuous sheet of "T-1" steel or its equivalent, with the total length 
of the bed 10 being made up of separate sections of steel plates which are 
first formed to the bed profile and then welded together. 
As can be seen, bed 10 is a frameless bed, that is, there are no supporting 
structural elements for the floor and side walls. The elliptical floor 
portion 11 together with the break lines 12A and 13A where the side wall 
portions 12 and 13 meet the elliptical floor provide a bed which has a 
high degree of strength, such that it will not buckle under loading, yet 
is able to twist and flex sufficiently to prevent cracking of the bed. The 
specific profile and dimensions of the bed 10 will be discussed later in 
connection with the side-dumping feature where it will be explained how 
the bed profile, together with other aspects of the design, enables the 
frameless bed to be completely dumped without overturning the truck and 
trailer combination. 
As shown in FIGS. 1 and 4, front headboard braces 17 and rear headboard 
braces 18 are provided to brace the top of front headboard 15 and rear 
headboard 16, where the hoisting means 60A and 60B are rotatably mounted 
via hoist mounting bracket and pin assemblies 65A and 65B. Hoisting means 
60A and 60B are rotatably mounted to bunk assemblies 20 and 30 via 
mounting bracket and pin assemblies 66A and 66B. 
As shown in FIG. 1, a front top hat 19A is mounted on bed 10 at the bottom 
of front headboard 15 and a rear top hat 19B is mounted at the bottom of 
rear headboard 16. These two top hats 19A and 19B are utilized to suspend 
bed 10 between the front bunk assembly 20 and the rear bunk assembly 30. 
Referring momentarily to FIG. 8, it is seen how the top hats 19A and 19B 
rest on mating bottom hats which form part of the front and rear bunk 
assemblies 20 and 30. Since the front and rear bunk assemblies are 
identical, only one need be considered in connection with FIG. 8. As shown 
in FIG. 8, the front bunk assembly 20 consists essentially of a bottom hat 
21 and a bunk plate 22 on which the bottom hat 21 is supported and 
fastened by any appropriate means such as welding. Top hat 19A is fastened 
(e.g., by welding) to the front headboard 15 of bed 10 and the floor 
portion 11 of bed 10. Both top hat 19A and bottom hat 21 have a generally 
inverted V shape with a rounded top portion. It can thus be seen that the 
mating top hat 19A and bottom hat 21A provide for the suspension of bed 10 
between the bunk assemblies 20 and 30. FIG. 8 also shows the saucer and 
hub mounting arrangement whereby front bunk assembly 20 is mounted in a 
rotatable fashion on truck bolster assembly 70. An identical saucer and 
hub arrangement is provided for mounting rear bunk assembly 30 on trailer 
bolster assembly 80, as shown in FIG. 1. This mounting arrangement, as 
shown in FIG. 8, includes a hub 71 which is mounted on truck bolster 
assembly 70 and a saucer 23 which is mounted on the bottom of bunk plate 
22. A bolt and nut arrangement 72 is provided to retain saucer 23 and hub 
71 together. Saucer 23 and hub 71 have complementary circumferential 
grooves which enable the hub 71 to pull the saucer 23 and the bunk 
assembly affixed thereto while maintaining a rotatable mounting 
arrangement between bunk assembly 20 and bolster assembly 70. As will 
later be seen, this rotatable mounting arrangement is an important aspect 
of the overall preferred embodiment of this invention employing a 
dolly-type trailer such that tracking-type cornering action of the truck 
and trailer is achieved. 
Referring back to FIG. 1 again, it can be seen that releasable 
hinge-mounting means comprises a hinge saddle assembly 40A, a hinge pin 
assembly 40B, and a latch assembly 40C, are provided on both ends of each 
of the front and rear bunk assemblies 20 and 30. These releasable 
hinge-mounting means enable the bed 10 to be selectively tilted to either 
side in order to dump its contents next to the truck and trailer 
combination. The releasable hinge-mounting means cooperate with the 
hoisting means 60A and 60B in order to accomplish this selective dual 
side-dumping capability. 
The detailed structure of the releasable hinge-mounting means is depicted 
in FIG. 2. As shown in FIG. 2, hinge pin assembly 40B preferably consists 
of a hinge pin bracket 401 and a hinge pin 402. The hinge pin bracket 401 
mounts the hinge pin 402 parallel to the floor portion 11 of bed 10. The 
axis of hinge pin 402 is substantially intersected by the plane of the 
side wall portion 11 of bed 10 and is otherwise located near the break 
line 11A. This places the axis of rotation at a point of strength and 
reduces the tendency to work the metal structure in this area which might 
ultimately produce cracks and structural failure. 
In addition, it will be noted that the axis or center line of hinge pin 402 
coincides precisely with the point where the upper portion of the bottom 
surface of top hat 19A mates with the top portion of the top surface of 
bottom hat 21. This location is important because as the bed 10 starts to 
rotate on hinge pin 402, it is desirable that the weight of bed 10 be 
rapidly transferred to the hinge saddle assembly rather than tending 
initially to rest on the edge of the top and bottom hat. 
Hinge pin bracket 401 consists of a base member 403 which is mounted in 
appropriate fashion to the floor portion 11 of bed 10. This mounting can 
be accomplished by welding or other appropriate means. One half of the 
base 403 extends beyond the floor portion of the bed and the front 
headboard 15 and provides a bottom support for the headboard brace 17. A 
pair of arms 404 are mounted on base 403 and extend vertically downward. 
Arms 404 have bushings 405 mounted in apertures (not shown) formed in arms 
404. Hinge pin 402 is actually received in the bushings 405 such that 
hinge bracket 401 rotates with respect to hinge pin 402 when the bed 10 is 
tilting around the hinge pin. 
Hinge saddle assembly 40A essentially consists of a pair of saddle arms 410 
which are fastened in appropriate fashion such as by welding to the top of 
bunk plate 22. Each of the hinge saddle arms 410 has a cradle portion 411 
which receives the hinge pin 402. A pair of hinge saddle gussets 412 
extend between the inner surfaces of the saddle arms 410 and the latch 
mounting bracket 430. These gussets are fastened to the hinge saddle arms 
410 and the latch bracket 430 by an appropriate means, such as welding, 
and are also fastened by appropriate means, such as welding, to the end of 
bottom hat 21. In this manner, the hinge saddle arms are well supported on 
the bunk plate 22 and can readily withstand one-half of the weight of bed 
10 and a load therein when the bed is rotating on hinge pin 402. 
Latch assembly 40C consists essentially of a latch bracket 430, a latch 
hook 431, and an air-operated spring brake 432. More specifically, latch 
bracket 430 consists of two support arms 433 which are mounted in an 
appropriate fashion, such as welding on the top of bunk plate 22. Latch 
hook 431 is rotatably mounted on latch bracket 430 via latch pin 434. The 
air-operated spring brake 432 is rotatably mounted to latch bracket 430 
via any suitable mounting arrangement designated 435 in FIG. 2. The arm 
436 of spring brake 432 is fastened to the bottom of latch hook 431 via a 
mounting bracket 437 and is operative to move the latch hook 431 between a 
latched position shown in solid lines in FIG. 3 and an unlatched position 
shown in dotted lines in FIG. 3. A stop pin 438 is mounted behind the 
latch hook to limit the backward travel of the latch hook. As can be seen, 
the rotational mounting of spring brake 432 enables it to rotate slightly 
as it operates to rotate the latch hook 431. The latched position of latch 
hook 431 is such that the hook on the upper end thereof surrounds the 
hinge pin 402 and prevents bed 10 from raising vertically. On the other 
hand, when latch hook 431 is in the unlatched (dotted line) position shown 
in FIG. 3, the illustrated corner of bed 10 can raise up vertically. It is 
this selective latching feature which enables the bed 10 to be selectively 
tilted by the hoist means shown in FIG. 1 to one side or the other. 
As shown in FIG. 2, a hook 450 is mounted on one side of saddle arm 410 in 
order to attach a loop on a cable 451 to the bunk assembly 20. The hinge 
saddle arm on the rear bunk assembly would have a similar hook to attach 
the other end of the cable 451. These cables may be utilized when the dual 
side-dumping trailer is dumping to the other side, while the truck and 
trailer are moving in a straight line so that the bunk assemblies will 
remain substantially in alignment and the top hats mounted on the bottom 
of the headboards of the bed will come down in a substantially mating 
fashion with the bottom hats on the bunk assemblies. If such a cable 
arrangement were not utilized to keep the bunk assemblies lined up, the 
jostling of the bunk assemblies while dumping might produce a substantial 
misalignment which might, in turn, cause one of the top hats to come down 
substantially misaligned with the corresponding bottom hat. This might 
damage either the top hat or the bottom hat since these two elements are 
capable of providing self-alignment only within a certain range of 
tolerance in the bunk positions. 
Having described the releasable hinge mounting means which are provided on 
the four corners of the floor of bed 10 and the ends of the bunk 
assemblies 20 and 30, it will be readily apparent how the selective dual 
side-dumping capability is achieved with the apparatus of this invention. 
FIG. 4 shows bed 10 with the top hat 19A resting on the bottom hat in a 
normal load carrying position. This is the position that the bed would be 
in while the truck and trailer are going down the highway. At this time, 
all of the latches on the releasable hinge-mounting arrangements 40 are in 
a latched position such that the bed 10 is mechanically restrained from 
lifting off of the bunk assemblies 20 and 30. It will be noted that there 
is a slight amount of clearance between the bottom surface of the top rub 
plates 24 which are fastened to the underside of the bunk plate 22 and the 
top surface of the bottom rub plate 71 which is part of the bolster 
assembly. While going straight down the highway, the weight of the load is 
carried on the saucer 23 and the hub 72. However, when the truck and 
trailer combination is cornering and the bed and bunk assemblies lean to 
one side, one of the combinations of upper rub plates and lower rub plates 
will be in contact with each other and part of the weight of the load will 
be transferred to the bolster assembly through the rub plates. 
Consider now the operation of the apparatus to dump the bed selectively to 
one side. To dump the bed to the left, as shown in FIG. 5, the latch hooks 
431 in the hinge-mounting assemblies 40 on the right side of the bed would 
be shifted to the unlatched position by supplying air to the spring brake 
devices associated with these latch hooks. Once this has been 
accomplished, hydraulic fluid is supplied to the lower input port 62 of 
the double-acting hydraulic hoist 60A and to the corresponding lower port 
on the hydraulic hoist 60B on the other end of the bed. Since the weight 
of the load in the bed may be unevenly distributed between the front 
section and the rear section of the bed, it is necessary to utilize a flow 
divider (not shown) in the hydraulic lines (not shown) to the lower input 
ports 62 of the hoists 60A and 60B so that the amount of hydraulic fluid 
going to each hoist will be the same and both ends of the bed will be 
lifted the same distance regardless of the weight distribution. If this 
were not done, an uneven weight distribution in the bed could cause the 
bed to twist severely as one side is raised further than the other due to 
the differential pressure on the pistons of the two hoists. 
As hydraulic fluid is supplied to the lower ports 62, the pistons 61 
gradually push out. Initially, this tends to raise both sides of the bed 
10. However, since the left-hand side is latched and the right-hand side 
is unlatched, the right side of the bed will go up and the left side of 
the bed will remain in the hinge-mounting means. As shown in FIGS. 2 and 
4, the hinge pin 402 is not normally in contact with the bottom of the 
cradle portion of the hinge saddle arms. However, when the right-hand side 
of bed 10 is lifted up by the hoist, the pins associated with the 
left-hand hinge means drop into the cradle portion of the saddle arms, and 
at this point, the hinge bracket with the bushings attached thereto begins 
to rotate along with the bed on hinge pin 402. At this point as the bed 
gradually rotates around the left rotation axis, most of the weight of the 
bed comes to rest on the hinge saddle brackets and is transferred through 
the bunk plate 22 and the upper rub plate 24 to the bolster assembly 70. 
As the hoist tilts the bed 10 further and further over the pivot axis on 
the left-hand side, the initial center of gravity of the bed and load 
(labeled CG) passes vertically over the pivot axis, and at some point, a 
portion of the load will begin to dump out of bed 10. To completely dump 
the load, the center of gravity CG which is approximately seventeen inches 
above the bottom of the bed at the start for a full load, passes beyond 
the pivot axis of the hinge-mounting means. Tilting of the bed around the 
axis of rotation of the hinge-mounting means continues until the left side 
portion 13 of the bed makes an angle of approximately forty-five degrees 
to the horizontal. At this angle, virtually all types of material will 
completely slide out of the bed and the contents of the bed may be 
completely dumped. At this point, however, the center of gravity of the 
partially dumped bed has passed well over the pivot axis of the 
hinge-mounting means. It will be appreciated that without careful design 
of the bed profile and optimized location of the pivoting axis of the bed 
on the hinge-mounting means, the tilting of the bed with the center of 
gravity of the bed and load passing well beyond the pivot point would be 
expected to overturn the truck and trailer together with the bed. It has 
been discovered, however, that by utilizing a low profile frameless bed of 
the type shown and by properly locating the pivot point of the bed, i.e., 
by properly locating the hinge-mounting means, the bed can be completely 
dumped with the dumping side wall portion of the bed achieving a 
forty-five degree dump angle without running into the tires on the truck 
or trailer, and without overturning with the truck and trailer on level 
ground. 
Because the center of gravity of the bed after the load has been dumped is 
still past the pivot point of the hinge-mounting means, the hoist 60A must 
be a double-acting hoist in order to be able to pull bed 10 back to its 
normal hauling position. To do this, hydraulic fluid is pumped into the 
upper port 63 on the hoists and forced out of the lower port 62 such that 
the piston 61 is forced back into the hoist and the bed 10 rotates back 
toward the normal hauling position shown in FIG. 4. The inverted V-shaped 
design of the top hat and bottom hat provides a self-aligning feature for 
the bed on the bunk assembly. Thus, under normal conditions, the top hat 
19A will come down to rest in an aligned position on bottom hat 21. Under 
certain circumstances, the alignment may not be sufficient for the hinge 
pin on the nondumping side of the bed to come to rest in the hinge saddle. 
When this occurs, the trailer brakes may be utilized to jostle the bed 
back and forth slightly to seat the hinge pin in the saddle. After the 
hinge pin is completely seated in the saddle, the operator can remove the 
air to the air-operated spring brakes on the right-hand side of the front 
and rear bunk assemblies, and the latch hooks will again engage the hinge 
pin and retain the bed securely on the bunk assemblies. To dump the bed 10 
in the other direction the sequence would be just the opposite of that 
given above. 
FIGS. 6 and 7 show the tracking-cornering action of the dual side-dumping 
conveyance of this invention when a dolly-type trailer is utilized. FIG. 6 
shows the truck and trailer combination going in a straight line such that 
the truck wheels 105 and the trailer wheels 135 are lined up and the reach 
150 extending forward from the trailer frame 140 is substantially lined up 
with the center line of the truck 100. FIG. 6 shows the stinger 110A on 
the rear of the truck as an A-frame structure, which is preferable to 
minimize the overall road width occupied by the truck and trailer 
combination when cornering. The stinger 110A may be mounted to the frame 
110 of the truck in a removable fashion if it is desired that the truck be 
available to be used for other hauling purposes. 
FIG. 7 shows the truck and trailer combination when the truck 100 is either 
cornering or backing in a jackknifing position to maneuver the trailer. As 
can be seen in FIG. 7, the bed 10 which is shown in dotted outline may 
remain in a horizontal position while both the truck 100 and the trailer 
130 are at a substantial angle. This is achieved by having the rotatable 
bunk assemblies mounted on the bolster assemblies of the truck and 
trailer. As the truck 100 turns, either for cornering or a backing type 
maneuver, the distance between the center pins of the saucer and hub 
arrangements on the bunk assemblies and bolster assemblies of the truck 
and trailer, respectively, remains the same. However, the stinger 110A of 
the truck pulls the reach 150 and sliding pole compensator 155 around to a 
location such that the truck frame and the reach and compensator make a 
triangle with the center line of the bed so that the wheels 135 on the 
dolly-type trailer 130 will tend to track the wheels 105 of the truck as 
the truck and trailer combination are cornering. Since the total length of 
the two sides of the triangle is greater than the hypotenuse which is the 
bed length, the sliding pole compensator 155 is pulled out of reach 150 as 
the truck 100 goes around a corner. It will thus be seen that it is 
actually the bed, suspended on the front and rear bunk assemblies which is 
pulling the trailer and the stinger 110A and the reach 150 with the 
sliding pole compensator 155 are merely steering the trailer 130 in a 
tracking fashion. The extent to which the trailer wheels follow in 
precisely the same track as the truck wheels can be adjusted by the 
relative distance between the front of the bed and the end of the stinger 
and the distance between the rear of the bed and the end of the reach. 
Generally, for purposes of stability, it is preferable for the trailer 
wheels not to track exactly but to track slightly inside the truck wheels. 
Because of the tracking-cornering action between the truck and the 
trailer, the overall conveyance utilizing the dolly-type trailer is 
considerably more maneuverable than a similar length truck and trailer 
combination utilizing a fixed set of trailer wheels and having only a 
pivot point on the bolster of the truck as in the normal kind of fifth 
wheel arrangement. This additional maneuverability can be highly 
significant in terms of permitting a longer bed and thus achieving a 
higher payload without sacrificing maneuverability and actually achieving 
a greater maneuverability of the overall conveyance at the higher payload. 
FIGS. 9 and 10 depict some of the details of an alternate fifth wheel type 
mounting arrangement for the rotational mounting of the front bunk 
assembly. Basically, the mounting arrangement shown is the standard fifth 
wheel type mounting arrangement involving an upper fifth wheel plate 200 
and a lower fifth wheel plate 210. For purposes of use with this 
invention, the lower fifth wheel plate 210 is blocked with a blocking 
means 220 in order to retain it in a horizontal position on the truck 
frame 110. The bunk assembly 20A and the portion of the releasable hinge 
mounting means 40 provided thereon are mounted to the upper fifth wheel 
plate 200. The center line of the front bunk assembly 20 coincides with 
the center line of the kingpin 205. As is well known, the kingpin 205 is 
adapted to be received in a latching aperture mechanism 215 on the lower 
fifth wheel so that the kingpin and upper fifth wheel plate can rotate 
with respect to the lower fifth wheel plate 210. The bunk assembly 20A has 
a slightly different skid plate arrangement with the skid plates 24A being 
mounted on extending legs 24B. This arrangement is necessary since the top 
of the lower fifth wheel plate is typically higher off of the truck frame 
than the bolster assembly on the arrangement depicted in FIG. 1 and FIG. 
8. Accordingly, the upper skid plate 24A must be extended substantially 
below the bunk plate 22 in order to be in a proper position with respect 
to the lower skid plate 71A. 
For the fifth wheel mounting arrangement, the lower skid plate 71A 
preferably comprises the configuration shown in FIG. 10. The skid plates 
71 shown on the bolster assemblies 70 and 80, respectively, in FIG. 6 and 
the skid plate configuration 71A shown in FIG. 10 are designed such that 
the upper and lower skid plates will have a substantially complete mating 
surface regardless of the angle of the respective bolster assemblies on 
the truck and trailer with respect to the bunk assemblies. As discussed in 
connection with FIG. 4, the weight of the bed is transferred via the skid 
plates to the bolster assembly or the truck frame while dumping to a 
particular side. Since the truck may be jackknifed while dumping, it is 
important that the upper skid plate rest completely on the lower skid 
plate to avoid loading just a portion of the upper skid plate. 
FIG. 11 is a dimensioned drawing of the contour of the bed 10, showing the 
actual location of the hinge pin and the dimensions with respect to the 
top and bottom hat and the distance from the bunk plate 22 to the ground. 
As can be seen, the overall height of the top of the bed above the ground 
is approximately ninety-six inches. The depth of the bed at the center 
line is slightly over three feet and the total width of the bed at the top 
is slightly under eight feet. 
This bed profile or contour together with the hinge mounting arrangement 
was designed to meet the following requirements: 
1. A bed capacity of twenty cubic yards minimum. 
2. A legal highway/bridge gross weight of forty tons maximum. 
3. A legal highway width of eight feet maximum. 
4. A dump angle of the bed side of forty-five degrees minimum. 
5. Dumping to either side with a center hoist. 
6. A bed height of ninety-six inches maximum to accommodate most front 
loader devices. 
7. A maximum safety factor of two against overturn of the truck and trailer 
under worst case conditions of attempting to dump a full bed of hardened 
concrete which will not leave the bed. 
In order to minimize the tare weight of the bed, a frameless type cross 
section was selected for the bed. A curved elliptical floor section with 
an angle break of approximately sixty-six degrees between the floor 
section and the flat sides was selected to provide good structural 
strength for both lateral loading and longitudinal twisting. The bed 
length was essentially dictated by highway weight and bridge laws, which 
in California, for example, require thirty-six feet between outer axle 
groups. Taking into account the trunion-to-axle dimensions, a minimum bed 
length of thirty-three feet was established. 
Having established a general bed profile for optimum loading strength, the 
optimum location of the axis of the hinge pin must be determined. To 
achieve such an optimum location, several factors must be taken into 
account: 
1. As the hinge pin axis position is moved towards the center line of the 
vehicle, the bed must be raised higher above the wheels in order to be 
able to achieve the forty-five degee dump angle without interfering with 
the tires. This greatly increases the overturn torque on the truck and 
trailer while dumping a load and will reduce or eliminate the safety 
factor in dumping. 
2. As the hinge pin position is moved outward from the center line of the 
vehicle, the pin can be in a lower position, but if the hinge axis is 
positioned too far out from the center line, the overturn torque again 
increases to an unsafe amount. In addition, the ninety-six inch legal 
width limit is a limiting factor on the movement of the hinge pin axis 
outwardly. 
3. Another factor is the angle of the flat upper side of the bed. As the 
side angle approaches the vertical, the bed center of gravity must rotate 
further beyond the hinge pin axis to achieve the required dump angle for 
the side. Conversely, as the flat side angle becomes more horizontal, the 
capacity of the bed is severely reduced due to the ninety-six inch legal 
width constraint. 
4. The best structural design from a strength standpoint is achieved by 
locating the dump pin center line very close to the break line between the 
elliptical floor section and the flat side section of the bed. 
Taking all of these factors into consideration, the optimum bed profile and 
optimum hinge pin location can be determined by a careful trial and error 
approach utilizing calculations and scale modeling of the bed profile and 
pin location. It should, of course, be apparent that the difficulty of 
providing a sufficient safety factor in side dumping is reduced as the 
weight of the truck and trailer increases with respect to the weight of 
the bed and load. Utilizing the principles of this invention, it has been 
discovered that it is possible to design a high payload side-dumping 
vehicle which is capable of completely dumping the load by taking the 
center of gravity of the worst possible load over the pivoting axis of the 
hinge-mounting means without overturning the tractor and trailer. In the 
specific case of the preferred embodiment of this invention, the bed is 
designed to carry a payload of twenty-five tons with a weight of the empty 
bed itself being about three tons. This leaves twelve tons for the weight 
of the truck and trailer itself. As can be seen, the total weight of the 
bed and load is two-and-one-half times that of the truck and trailer. In 
spite of this, it has been possible to design a bed profile and hinge pin 
axis location which enables complete dumping of the bed with a safety 
factor of two under the worst load conditions. It should also be 
understood that the use of the dolly-type trailer with reach and sliding 
pole compensator arrangement enables the truck and trailer to be 
jackknifed to the side opposite the dumping side in order to further 
increase the safety factor in dumping a load from the bed. This is 
particularly useful where the material in the bed is to be dumped on 
ground which is not level and slopes down on the side of the truck and 
trailer on which the load is to be dumped. Consequently, the dolly-type 
trailer and truck combination enables the safe dumping of a load under 
virtually all conditions. 
While the basic principles of this invention have been discussed above in 
connection with a dual side-dumping bed and mounting arrangement and a 
dolly-type trailer and truck combination, it should be understood that 
various alternative utilizations of the principles of this invention are 
possible. For example, as shown in FIG. 12, the bed 310 could be mounted 
on a flat bed truck chassis 300 instead of on a dolly-type trailer and 
truck combination. The chassis 300 could be either a flat bed truck 
chassis, a flat bed trailer chassis or a railroad car chassis. While the 
dual hoist arrangement shown in FIG. 1 could be utilized on a flat bed 
chassis, it would be preferable, as shown in FIG. 12, to utilize a single 
telescoping hoist 360 mounted between the chassis 300 and the bed 310 
within the center baffle 370 of the bed. This can be accomplished by way 
of a lower hoist mounting bracket 366 which rotatably mounts the hoist to 
the chassis and a upper hoist bracket 365 which rotatably mounts the 
piston of the hoist to the bed 310. A stress plate 375 may be utilized on 
each of the two side portions of bed 310 in order to aid in distributing 
the stress of the loaded bed along the side walls thereof. The hoist 360 
would extend through an appropriately sized slot 380 cut into the floor of 
the bed at the center portion thereof in order to enable the hoist to 
pivot freely to the required position during dumping. In all other 
respects, the bunk assemblies and the releasable hinge mounting means 
could be identical to those shown in FIGS. 1 through 3. 
It should also be understood that, in the flat bed mounting arrangement 
shown in FIG. 12, it would further be possible to utilize a hoist which is 
positioned within a well in the chassis of the flat bed trailer or 
railroad car and has the piston attached to the bottom of the 
material-hauling bed. 
It should also be apparent that the combination of the dolly-type trailer 
and truck arrangement could be utilized with any type of side dumping bed 
and hinge mounting arrangement, including any type of single or dual 
side-dumping arrangement and any type of bed design. It should also be 
understood that a variety of releasable hinge-mounting means could be 
employed and the particular means shown in FIGS. 2 and 3 is only one 
preferred way of providing a releasable hinge-mounting means for the dual 
side-dumping feature of the invention. An alternative would be to use, for 
example, a normal door-type hinge arrangement with a hinge pin which could 
be removed from the hinge means on one side to dump to the other side. 
Removal of the pin would be either manual or automatic. 
It should also be understood that various configurations could be utilized 
for the top and bottom hat arrangement. For example, the top and bottom 
hats could both be essentially semicircular in profile or could have a 
parabolic or hyperbolic shape. 
It will thus be seen that this invention is not limted to the embodiments 
disclosed, in that numerous modifications could be made without departing 
from the spirit and scope of the invention as claimed in the following 
claims.