Movable tipping frame for hoist trucks

A hoist vehicle of the semi-trailer type has a slide frame on which a tipping frame is pivotably mounted. The slide frame is adjustably movable between forward and rearward positions relative to the bed of the vehicle to locate the load carried by the tipping frame at positions where the weight bearing on the axles of the vehicle is optimized so that greater payloads may be carried without exceeding government imposed maximum axle loadings. A chain is trained about sprockets and connected to the slide frame to accurately adjust the position of the slide frame and the center of gravity of the payload.

BACKGROUND OF THE INVENTION 
This invention relates to hoist vehicles having apparatus for increasing 
the payload while limiting the load bearing on each axle, and more 
particularly to hoist vehicles having a tipping or tilting frame on to 
which a payload container or the like may be pulled, carried and pushed 
off and having means for moving the frame longitudinally to optimize the 
position of the load relative to the axles of the truck. 
Solid waste, for example, is collected in containers which when full are 
loaded onto a truck such as a semi-trailer and taken to a landfill where 
the container is emptied and returned by the truck to a waste collection 
point. A frame, called a tipping or tilting frame, is installed on the 
chassis of such a truck to facilitate the loading and unloading thereof. 
Conventionally, cables are utilized to pull the container onto the tilted 
tipping frame which is then lowered to its substantially horizontal 
position on the chassis, the frame being tilted by hydraulic cylinders. In 
U.S. application Ser. No. 921,597 filed Oct. 21, 1986, now U.S. Pat. No. 
4,737,063, issued Apr. 12, 1988, a tilting frame having a chain hoist 
system is utilized instead of a cable so as to afford more mechanical 
control over the load and also facilitate unloading by pushing the 
container from the frame. Most states limit the over-the-road weight of 
trucks to 80,000 pounds for semi-trailers, however in the typical load 
configuration the maximum weight is reduced somewhat since the tipping or 
tilting frame has a pivot point near the rear of the truck bed. This 
placement of the frame results in the center of gravity of the load being 
located toward the rear of the bed to thereby place most of the weight of 
the load on the rear axle. However, the maximum weight bearing on the 
axles is limited by Federal Bridge Law to approximately 35,000 pounds on a 
tandem axle truck. In actual practice in order to ensure compliance with 
the limitation on the axle bearing weight, typical tipping frame hoist 
trucks have limited the weight bearing on each axle to less than 30,000 
pounds taking into account the weight of the hoist system. Consequently, 
the maximum payload carried by such trucks is substantially less than that 
permitted. 
Although there are suggestions in the prior art for longitudinally moving 
the frame of a truck, no prior art is known which attempts to optimize the 
location of the load relative to the axles but merely permit the load to 
be moved between two positions, i.e., between a transport position, and a 
loading/unloading position. These mechanisms typically employ telescoping 
hydraulic cylinders to move the frame and are generally intended for 
application when neither the total truck weight nor axle bearing weight is 
a significant consideration. Thus, the prior art mechanisms are not 
directed toward allowing longitudinal adjustment of the frame in order to 
optimize the load bearing on the axles. For example, in Corompt U.S. Pat. 
No. 4,755,097 it is recognized that the location of the center of gravity 
of the load affects the weight on the axles, but no provision is made to 
allow for adjustment of the center of gravity except to the one fixed 
position where the frame is located during transport. The pivot point 
during loading operations is changed in order to increase the ability to 
lift the load onto the truck bed while at the same time moving some of the 
weight off the rear axle during transport. In Lisota U.S. Pat. No. 
2,621,814 a sliding bed is mounted on a tilting frame or the like for 
aiding in loading and unloading operations. Marlett U.S. Pat. No. 
4,702,662 is somewhat similar to Lisota in this regard. In Derain U.S. 
Pat. No. 4,009,791 an L-shaped pivot member is mounted on the tipping 
frame and may be moved between forward and rearward positions on the 
tipping frame. 
Since the load within a container or the like may not be equally 
distributed along the length of the container, and the lengths of 
containers may vary somewhat, it is important to adjust the transport 
position of the frame to where the weight bearing on the axles of the 
truck is optimized for each load transported. As aforesaid, the prior art 
has not proposed such a construction or attempted to offer a satisfactory 
solution to this problem. 
SUMMARY OF THE INVENTION 
Consequently, it is a primary object of the present invention to provide a 
vehicle having a bed including a pivotable tipping or tilting frame 
mounted for slidable movement in the direction of elongation of the bed 
for optimizing the position of a load carried by the tipping frame 
relative to the vehicle wheel axles so as to increase the payload carried 
by the vehicle while complying with mandated axle loading requirements. 
It is another object of the present invention to provide a vehicle having a 
tipping or tilting frame for hoisting a container thereon and transporting 
the container over a roadbed for depositing at a remote location, the 
tipping frame being mounted for permitting the load to be adjustably 
positioned relative to the bed and thus the wheel axles of the vehicle. 
It is a further object of the present invention to provide a vehicle having 
a tipping or tilting frame pivotably mounted on a slide frame, the slide 
frame being mounted in the bed of the vehicle for movement in the front to 
rear direction relative to the vehicle and driven in a manner permitting 
the tilting frame and the load carried thereon to be precisely located so 
that the load on the axles of the vehicle may be optimized. 
Accordingly, the present invention provides a hoist vehicle such as a 
semi-trailer having a slide frame on which a tipping frame is pivotably 
mounted, the slide frame being adjustably movable from forward to rearward 
positions relative to the vehicle to locate the load carried by the 
tipping frame at positions where the load bearing on the axles of the 
vehicle is optimized so that greater payloads may be carried while still 
complying with governmentally mandated maximum loadings. 
In carrying out the invention, a simple chain drive is utilized, the chain 
being trained about sprockets and connected to the slide frame for 
permitting adjustment of the center of gravity along the longitudinal axis 
of the truck bed thereby to spread the weight over the axles, including 
the additional axles of a semi-trailer. The chain drive arrangement 
permits accurate adjustment to the center of gravity of the load to 
optimize the loading on the vehicle axles so as to increase the payload 
that may be transported, and does so without adding materially to the 
weight of the vehicle which would have a negative effect on the load which 
could be transported.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, apparatus constructed in accordance with the 
principles of the present invention is illustrated in FIG. 1 in 
conjunction with a semi-trailer 10 which is conventionally connected by 
fifth wheel means to a truck 12 for conventionally driving the trailer. 
The trailer 10 includes a bed 14 having a pair of spaced apart elongated 
rails in the form of I-beams 16, 18 interconnected at spaced locations by 
a plurality of transversely extending plates 20, the rails and plates 
preferably being constructed from steel or similar high strength rigid 
material. 
In accordance with the present invention a slide frame 22 is slidably 
mounted in the bed 14. The slide frame 22, as best illustrated in FIG. 4, 
comprises a pair of longitudinally elongated rails 24, 26, preferably 
formed from tubular steel and connected together by spaced apart cross 
members 28 which may be heavy wall steel pipe. Disposed within each cross 
member 28 is a shaft 30. The shaft extends outwardly of the ends of the 
cross members and journally carries a cylindrical roller 32, 34 at the 
respective ends thereof. The rollers 32, 34 are respectively supported on 
wear bars 36, 38 preferably in the form of tubular steel box members or 
the like which function as trucks for the rollers and are securely 
supported on the upper walls 40 of a plurality of the cross members 20 
intermediate the ends of the bed 14. Thus, the slide frame 22 may slidably 
translate relative to the bed 14 of the trailer in the direction of 
elongation thereof. 
Pivotably mounted at the rear end of the slide frame 22 by journal means 
including a pivot shaft 42 is a tipping frame 44, the tipping frame 
forming the subject matter of patent application Ser. No. 921,597 filed 
Oct. 21, 1986 and assigned to the common assignee of the present 
invention. The tipping frame 44 as disclosed in the aforesaid patent 
application is pivotably driven about the pivot shaft 42 by one or more 
hydraulic cylinders 46, the housing of which is pivotably carried by the 
slide frame 22 with the extendible piston 48 pivotably connected to the 
tipping frame. The cylinders are powered by hydraulic fluid from pump 
means located in the bed 14 or carried by the truck 12. The tipping frame 
includes an endless chain 50 arranged to run around a motor driven 
sprocket and reducing means 51 as disclosed in the aforesaid patent 
application at one end thereof, the motor preferably being a hydraulic 
motor, and an idler sprocket. The chain 50 has a tail connected to the 
chain and to a hook for grasping a container 52 or the like which carries 
the payload therein. The container 52 may be loaded or unloaded from the 
tipping frame 44 by driving the chain 50 in a selected one of two 
directions as required after the tipping frame has been tilted by 
extension of the piston 48 from the hydraulic cylinder 46, as illustrated 
in FIG. 1. When the container has been loaded onto the tipping frame 44 
the tipping frame may then be pivoted back from the inclined position to a 
substantially horizontal position onto the slide frame 22. Spacer members 
54, 56 disposed on transversely projecting arms 58 extending from the 
tipping frame 44 are supported on the upper surfaces of the slide frame 
rails 24, 26 respectively when the tipping frame is in the horizontal 
position so that the tipping frame is supported on and may be secured to 
the slide frame with the container 52 thereon. 
In order to drive the slide frame 22 longitudinally relative to the bed 14 
so as to position the center of gravity of the load optiminally relative 
to the axles 58, 60 of the trailer 10 and at least the axles 62, 64 of the 
truck 12, an endless chain 66 having a plurality of articulated links is 
disposed within the bed and trained about a pair of sprockets 68, 70. The 
sprocket 68, which is the drive sprocket, is fastened on a shaft 72 of a 
rotary hydraulic motor 74, the assembly being supported by brackets 76 
secured to one of the cross members 20 preferably adjacent the forward end 
of the bed 14 for rigidly mounting the motor 74 and journally mounting the 
motor shaft. The motor 74 may be powered with hydraulic fluid by the same 
hydraulic pump means which supplies the hydraulic fluid to the cylinders 
46. The sprocket 70 is an idler sprocket and is mounted on a shaft carried 
intermediate a pair of bearing blocks 78 mounted on a shelf 80 secured to 
a cross member 20 adjacent the rear of the bed. A connecting and 
tensioning bracket 82 is fastened to one or more links of the chain 66 by 
means of the pins associated therewith and is secured to one of the cross 
members 28 of the slide frame 22. 
In order to provide clearance for the chain and bracket 82, the cross 
member plates 20 intermediate the transverse extremities thereof are 
formed with a trough 84 of sufficient width, the trough merely being a 
recess cut in the upper walls 40 of the plates. Additionally, to permit 
the chain to move freely between the cross member plates 20 of the bed 14, 
the plates intermediate the sprockets 68, 70 each have a cut-out formed 
beneath the trough 84 and a channel guide 86 in the form of tubing is 
inserted and secured therein, the guide channels either being separate 
tube members within each cross member as illustrated, or may be a single 
elongated tube extending between the bed cross member 20 and secured in 
the respective cut-outs. 
Accordingly, by means of a simply driven slide frame, the invention permits 
the load to be adjustably positioned backward and forward to the point 
where the weight of the load bearing on the axles of the trailer and truck 
is optimized for meeting the requirements of Federal Bridge Law while 
permitting a maximizing of the amount of weight carried by the trailer in 
compliance with the local legal weight limit for over-the-road 
semi-trailer trucks. By controlling the hydraulic motor 74, the chain 66 
may be positioned in fine increments to the optimum position for the 
center of gravity of the load being transported. 
Numerous alterations of the structure herein disclosed will suggest 
themselves to those skilled in the art. However, it is to be understood 
that the present disclosure relates to the preferred embodiment of the 
invention which is for purposes of illustration only and not to be 
construed as a limitation of the invention. All such modifications which 
do not depart from the spirit of the invention are intended to be included 
within the scope of the appended claims.