Truck cover having an improved telescopic arm assembly

A truck cover having an improved telescopic arm assembly for drawing a cover across an open topped truck body or other vessel or container. The assembly is powered by a pneumatic, hydraulic or other power source and comprises a pair of pivoting telescopic arms motivated by actuators The activators cause the telescopic arms to move pivotally from one end of the container to the opposite end and during the pivotal movement to cause the telescopic arms to retract as they move to a vertical position and to extend as they move from the vertical position to the opposite end of the container. The extension and retraction of the telescopic arms during pivotal movement from one end of the container to the opposite end causes a flexible cover carried by the upper ends of the telescopic arms to be drawn across the container in a low trajectory resulting in improved ease and safety of operation and reduced opportunity for damage to the flexible cover.

BACKGROUND OF THE INVENTION 
A variety of cover assemblies have been developed to prevent particulate 
matter escaping from open topped truck bodies. Generally, these assemblies 
comprise a pair of similar arms, pivotally attached to the approximate 
midpoint of the lower truck body sides. A cover is located between the 
upper ends of the arms, and means are provided for causing the arms to 
move pivotally and draw the cover lengthwise across and over the truck 
body. These cover assemblies are not entirely satisfactory due to the 
fixed length of the swinging arms once attached to the truck body. Some 
available assemblies incorporate arms which are axially adjustable to 
adjust the length of the arms to accomodate different length truck bodies, 
but do not provide for extension or retraction of the arms during 
operation of the assembly. U.S. Pat. Nos. 4,050,734 and 4,341,416 disclose 
such static adjustable arms. The result is a high clearance of the truck 
body by the cover as the cover is drawn arcuately lengthwise across the 
truck body. The highest clearance occurs when the swinging arms reach a 
vertical position. This high clearance is disadvantageous as the cover may 
be caught by the wind or other objects and be damaged or cause damage. In 
addition, the assembly may only be used where there is sufficient vertical 
clearance to permit operation of the similar swinging arms. Another 
disadvantage is that the assembly may be employed only where attachment of 
the swinging arms to the approximate midpoint of the side of the truck 
body is possible. 
SUMMARY OF THE INVENTION 
The present invention provides an improved truck cover having a telescopic 
arm assembly for drawing a cover across and over a truck body or other 
vessel or container having an upwardly open body. Two telescopic arms are 
pivotally attached to the container. Motive means cause pivotal movement 
of the telescopic arms from one end of the container to the opposite end. 
In one embodiment, the motive means comprise hydraulically powered 
cylinders attached to the container and linked to the telescopic arms. The 
telescopic arms retract during pivotal movement from one end of the 
container to a vertical position and extend during pivotal movement from 
the vertical to the opposite end of the container. Thus, minimal clearance 
of the container is ensured as the cover or cover mechanism is drawn 
across the container.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to the drawings and particularly to FIGS. 1A-1C and FIG. 2 an 
upwardly open truck body or trailer 10 having an upper edge 11 is 
illustrated. A cover mechanism 12 houses a flexible cover 14 of sufficient 
size to cover the trailer. The cover mechanism 12 may be mounted on an end 
of the trailer, with the free end of the cover 14 affixed to the upper 
free ends of a pair of telescopic arms 16. Alternatively, the cover 
mechanism may be mounted to the upper ends of the arms, and the free end 
of the cover attached to an end of the trailer. The cover maintains loose 
articles in the trailer. The telescopic arms 16 have a lower stage 18 and 
a narrower axially extendable upper stage 20. The telescopic arms 16 are 
pivotally mounted respectively, to the approximate lower midpoint 22 of 
each side of the trailer. The arms 16 may be mounted away from the 
approximate lower midpoint, as the assembly of the present invention will 
compensate for the off-center pivot point. A hydraulic actuator 24 is 
mounted on each side of the trailer and is linked to a respective one of 
the telescopic arms 16. In an alternative embodiment, the telescopic arms 
are slaved together and are operated by a single actuator. 
As the actuators 24 extend and pivotally move said telescopic arms 16 from 
one end 26 of the trailer to the opposite end 28, the cover is drawn 
lengthwise across the trailer. During pivotal movement, the telescopic 
arms 16 retract as they swing from one end 26 of the trailer, as shown in 
FIG. 1A, to a vertical position 30, as shown in FIG. 1B. At the vertical 
position 30, the telescopic arms 16 are more fully retracted. As the 
telescopic arms 16 move pivotally from the vertical position 30, as shown 
in FIG. 1B, to the opposite end 28 of the trailer, as shown in FIG. 1C, 
the telescopic arms 16 extend until the opposite end 28 of the trailer is 
reached. When the telescopic arm assembly is operated in reverse, the 
actuators 24 retract and pivotally move the telescopic arms 16 in the 
opposite direction. The telescopic arms 16 retract as they move pivotally 
from one end of the trailer 28 to the vertical position 30 and extend as 
they move pivotally from the vertical position 30 to the opposite end of 
the trailer 26. During pivotal movement, a minor portion of telescopic arm 
16 extends above upper edge 11 of trailer 10. 
In FIG. 1C, it will be noted that the arc 32 traced by the movement of the 
upper ends of the telescopic arms 16 is very shallow in relation to the 
upper edge 34 of the side wall of the trailer. 
Referring now to FIG. 2, an embodiment of one of the telescopic arms is 
illustrated. The telescopic arm 16 comprises a multi-stage hydraulic 
cylinder 36 encased in a lower stage 18 shown in cross section and linked 
to an upper stage 20. The lower stage 18 is attached to a truck body, or 
other vessel or container. As the telescopic arm pivots about its fixed 
point from a starting position at one end of the container towards a 
vertical position, the upper arm 38 of the multi-stage hydraulic cylinder 
36 retracts into the lower arm 40, drawing the upper stage 20 of the 
telescopic arm 16 into the lower stage 18. When the telscopic arms 16 
moves pivotally from the vertical to the opposite end of the container, 
the upper arm 38 of the multi-stage hydraulic cylinder 36 extends from the 
lower arm 40 pushing the upper stage 20 of the telescopic arms 16 in an 
outwardly direction relative to the lower stage 18. The telescopic arm 
illustrated in FIG. 3 may be powered by means comprising a hydraulic 
system, a servo motor, a pneumatic system or any other suitable system 
known to one of ordinary skill in the art. 
A hydraulic system for powering the cover assembly is illustrated in FIG. 
3. A tank 42 of suitable size stores hydraulic fluid for use by a motor 
driven pump 44. A first three-position four-way valve 46 regulates the 
flow of hydraulic fluid through a first flow divider 48 such as a 50/50 
flow divider to the two actuators 24. Moving a first lever 50 into a first 
position causes the hydraulic fluid to flow through the first flow divider 
48 to the lower chambers 52 of the actuators 24 urging the actuators to 
extend. A first check valve 54 prohibits undesired backflow of the 
hydraulic fluid and prevents unwanted or premature retraction of the 
actuators. Moving the first lever 50 into a second position causes the 
hydraulic fluid to flow through a second flow divider 56 to the upper 
chambers 58 of the actuators 24, urging them to retract. A second 
three-position four-way valve 60 regulates the flow of hydraulic fluid 
through a third flow divider 62 to the two telescopic arms 16. Moving a 
second lever 64 into a first position causes the hydraulic fluid to flow 
through the third flow divider 62 to the lower chambers 66 of the 
telescopic arms 16, urging the telescopic arms 16 to extend. A second 
check valve 68 prohibits undesired backflow of the hydraulic fluid and 
prevents unwanted premature retraction of the telescopic arms. Moving the 
second lever 64 into a second position causes the hydraulic fluid to flow 
through a fourth flow divider 70 to the upper chambers 72 of the 
telescopic arms 16, urging the telescopic arms 16 to retract. An 
adjustable relief valve 74 prevents overpressurization of the hydraulic 
system. 
An alternative system for powering the cover assembly is illustrated in 
FIG. 4. This embodiment provides for the automatic concurrent operation of 
the actuators 24 and telescopic arms 16. A programmable controller 76 is 
connected to four solenoids 81, 82, 83 and 84 which in effect replace the 
first and second levers 50, 64 of FIG. 3 and are tied to the first and 
second three-position four-way valves 46 and 60 respectively. Operation of 
the programmable controller 76 activates the solenoids 81, 82, 83 and 84 
and causes the two three-position four-way valves 46 and 60 to operate in 
a preset sequence to cause the actuators 24 and telescopic arms 16 to 
extend and retract in cooperation. The cover is thereby motivated to cover 
or uncover the truck body in a very low trajectory relative to the upper 
edge of the side of the container. The programmable controller is 
activated by a "cover" switch 78 and an "uncover" switch 80. 
Alternatively, the programmable controller may be activated by a lever or 
any other suitable mechanism known to one of ordinary skill in the art. 
Referring now to FIG. 5, a second embodiment of one of the telescopic arms 
is illustrated. The telescopic arm 86 of FIG. 5 comprises a lead screw 88 
a threaded nut 90 and a servo motor 92. The servo motor 92 is housed at 
the lower end of the lower arm 94 of the telescopic arm 86. The lead screw 
88 is connected to the servo motor 92 and extends from the lower arm 94 
into the upper arm 96 of the telescopic arm 86. The threaded nut 90 is 
fixed to the inner wall of the upper arm 96. Operation of the servo motor 
92 causes the lead screw 88 to rotate along its longitudinal axis. 
Rotation of the lead screw 88 in one direction urges the threaded nut 90 
along the lead screw 88 towards the servo motor 92 causing the upper arm 
96 to retract into the lower arm 94. Activating the servo motor 92 to 
cause rotation of the lead screw 88 in the opposite direction causes the 
lead screw 88 and threaded nut 90 to cooperate to cause the upper arm 96 
to extend from the lower arm 94. In a typical installation, the servo 
motor 92 is connected to and controlled by a programmable controller 76. 
Referring now to FIG. 6, a third system for powering the cover assembly is 
illustrated. A programmable controller 76 as shown in FIG. 4 is connected 
to two of the telescopic arms 98 of FIG. 5 and to first and second 
solenoids 100 and 102. The first and second solenoids are tied to the 
first three-position four-way valve 46 of FIG. 4. The first three-position 
four-way valve 46 is connected to a hydraulic actuating system comprising 
a tank 42, adjustable relief valve 74, pump 44, first check valve 54, 
first and second flow dividers 48, 56, and actuators 24. The programmable 
controller 76 is activated by a "cover" switch 78 and an "uncover" switch 
80. 
Depressing the "cover" 78 and "uncover" 80 switches activates the 
programmable controller 76 which instructs the telescopic arms 98 , the 
first three-position four-way valve 46 and the first and second solenoids 
100 and 102 to cooperate with the hydraulic actuating system to 
automatically draw the cover 14 across or over to cover or uncover 
respectively the truck body at a very low trajectory. 
Numerous modifications and variations of the present invention are possible 
in light of the above teachings. It is, therefore, to be understood that 
within the scope of the appended claims, the present invention may be 
practiced otherwise than as specifically described hereinabove.