Lift conveyor with single belt having criss-cross return segments

A single endless belt lift conveyor has lower criss-cross return segments that are guided by vertically spaced guide rollers that rotate about vertical axes. The vertical guide rollers are mounted to adjacent towers spaced along a telescoping boom of the conveyor. This arrangement ensures that load carrying cleats on the belt clear each other and allows the boom to be leaned against a roof, gutter, or other supporting structure without the cleats striking the same.

BACKGROUND OF THE INVENTION 
The present invention relates to material handling apparatus and more 
particularly, to a lightweight portable conveyor having parallel endless 
belt segments with upstanding cleats for lifting loads of shingles, tiles 
tar paper and other building materials to rooftops. 
Residential construction frequently requires the lifting of substantial 
amounts of building materials to rooftops under construction or repair. It 
is inefficient and dangerous to accomplish such lifting with manual labor. 
The high cost of operating forklifts, cranes and other heavy lifting 
equipment is prohibitive is such applications. Skilled labor is required 
to operate such machinery and the hourly rental cost of the heavy lifting 
equipment can be very substantial. 
Conveyors have long been available for lifting materials from the ground to 
higher elevations. If one single wide belt is utilized, the conveyor must 
have a very substantial supporting framework due to the substantial weight 
of the belt. Such single wide belt conveyors are thus quite heavy and not 
adapted for portability between job sites. In order to lessen the weight 
of lift conveyors various models have been developed that employ a long 
extensible boom with a pair of pulleys mounted at the rearward or lower 
end of the boom and another pair of pulleys mounted at the forward or 
upper end of the boom. A pair of endless belts, each having upstanding 
longitudinally spaced load supporting metal cleats, are then entrained 
around each set of forward and rearward pulleys so that they can be driven 
around the pulleys in parallel. An electric motor drives the rear pulleys 
through a gear reduction mechanism. Each belt is made of a light weight 
but very strong woven fabric material. Individual loads of building 
materials can be stacked on top of the upper forward moving segments of 
the belts, one load in advance of each set of transversely aligned cleats. 
Due to tolerance variations, the pulleys do not have identical diameters 
and the belts do not have identical lengths. Therefore, even though the 
cleats are initially aligned in the transverse direction, over time the 
cleats on one belt gradually lag further and further behind the 
corresponding cleats on the opposing belt. When the misalignment of 
corresponding opposite cleats becomes too great loads cannot be properly 
retained by the cleats and they fall off of the conveyor. 
It is not practical to use chains instead of belts to ensure that the 
opposing pairs of cleats stay aligned. This is because such conveyors 
typically extend over thirty feet in length and the weight of such long 
endless chains would be prohibitive, not to mention the problems with rust 
and breakage of the chains that would be expected in harsh construction 
site environments. One solution to the aforementioned problem is disclosed 
in U.S. Pat. No. 4,366,900 granted in 1983 to Johansson. It discloses a 
lightweight twin belt lift conveyor which includes a belt synchronizing 
mechanism to maintain the load supporting cleats in opposing transverse 
alignment. Magnetic position indicators on the belts are sensed by a 
control circuit which selectively actuates clutch mechanisms to briefly 
stop either rearward drive pulley so that the other belt can catch up. 
However, the clutch mechanisms are complex, expensive, and subject to 
failure from excessive loading and wear. Also, the momentary stoppage of 
the drive pulleys can be abrupt and dislodge the loads. 
U.S. Pat. No. 4,582,192 granted in 1986 to Rojlar, assigned to the inventor 
of the subject application, discloses another lightweight lift conveyor 
with a less complex belt synchronizing mechanism. Reed switches sense 
magnetic position indicators on the belts A control circuit connected to 
the reed switches momentarily moves spacer arms into and out of engagement 
with the drive pulleys to vary their circumference and thereby momentarily 
vary the speed of advancement of the corresponding belt. Again this 
system, while serviceable, was too expensive, too complex and subject to 
failure in the harsh construction site environment. A variation on this 
conveyor was successfully commercialized for many years by the assignee of 
the present application in which the operator manually moved a spacer into 
engagement with one of the drive pulleys as needed. However the operators 
tended to forget to engage or disengage the spacer. In addition, some 
operators actually used the spacers as brake mechanisms, causing damage 
and/or interfering with the proper operation of the lift conveyor. 
U.S. Pat. No. 4,854,447 granted in 1989 to Johansson discloses a 
light-weight lift conveyor system having a single endless belt that is 
entrained about a pair of rearward pulleys and a pair of forward pulleys 
to define a pair of parallel upper forward run segments and a pair of 
lower rearward running return segments that criss-cross. With this 
arrangement, the load-supporting cleats remain transversely synchronized, 
i.e., side-by-side. This eliminates the need to use side-by-side, separate 
parallel belts and complex speed controls, clutching arrangements and/or 
pulley enlargers in order to transversely synchronize the cleats. In the 
design of the aforementioned U.S. Pat. No. 4,854,447 of Johansson, the 
lower return run segments of the belt criss-cross underneath the 
longitudinal frame spar or boom. This results in several problems. First 
of all, the cleats can tangle with each other as they cross each other. 
This can bend or even tear off the cleats, sever the belt, or damage the 
belt drive mechanism. Secondly, the underside of the conveyor cannot be 
leaned against, and supported by, a structure such as a roof or a gutter. 
Some sort of support stand must be attached to the remote outer end of the 
boom that will extend below the boom and the return segments of the belt. 
This type of stand adds weight, and also results in the load carried by 
the forward upper segments of the belt being delivered to a greater height 
than is necessary or convenient. Thirdly, it has proven to be extremely 
difficult for a construction worker to properly mount the endless belt at 
the job site. 
SUMMARY OF THE INVENTION 
The present invention provides a single endless belt lift conveyor with 
parallel upper forward run segments and lower criss-cross rearward run 
segments. The lower rearward running return segments of the endless belt 
are guided by vertically spaced guide rollers that rotate about vertical 
axes. The vertical guide rollers are mounted to adjacent towers spaced 
longitudinally along a boom of the conveyor. This ensures that the load 
bearing cleats on the belt clear each other. In addition, the boom of the 
lift conveyor can be leaned against a roof, gutter, or other supporting 
structure without the cleats striking the same.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 2, a lightweight portable lift conveyor 10 includes a 
central boom 12 that extends in a longitudinal direction. A pair of 
transversely spaced drive pulleys 14 and 16 (FIG. 1) are rotatably mounted 
on opposite ends of a common drive axle 18 supported at a rearward end of 
the boom 12. A motor drive 20 (FIG. 2) is mounted to a rear end of the 
boom 12 and includes an electric motor, the drive pulleys 14 and 16, and a 
gear reduction for coupling the high speed motor shaft and the axle 18 to 
spin the axle at a relatively slow RPM. The drive axle 18 is journaled in 
bearings (not illustrated) forming a part of the motor drive 20. A pair of 
upper and lower horizontal guide rollers 25 (FIG. 2) are mounted adjacent 
each of the drive pulleys 14 and 16. A pair of transversely spaced return 
pulleys 22 and 24 (FIG. 1) are rotatably mounted on opposite ends of a 
return axle 26 journaled in bearings (not illustrated) mounted at the 
forward end of the boom 12. 
The central boom 12 (FIG. 2) is comprised of a plurality of telescoping 
sections 12a. 12b. 12c and 12d preferably made of lightweight hollow 
Aluminum box beams of progressively smaller dimensions. In transit, the 
boom sections 12a-12d are collapsed into each other so that the lift 
conveyor 10 can be conveniently stowed in a pickup truck. Upon arrival at 
the construction site, the boom sections 12a-12d are extended or 
telescoped and locked into position relative to each other by locking 
means (not illustrated) such as aligned holes and pins brakes or other 
suitable mechanisms heretofore utilized in commercial lightweight 
telescoping lift conveyors of this general type. 
The rear end of the boom 12 is provided with a pair of legs 28 (FIG. 2) 
each having a wheel 30 mounted at its lower end so that the lift conveyor 
10 can easily be maneuvered by a single construction worker A handle bar 
assembly 32 is also mounted to the rear end of the boom 12 to allow the 
worker to grip the same to facilitate maneuvering of the rear end of the 
lift conveyor 10. Another handle bar assembly 34 is mounted to the forward 
end of the boom 12 to allow another worker to grip the same and easily 
maneuver the forward end of the lift conveyor 10. A vertical leg 35 
extends downwardly from the forward end of the forwardmost boom section 
12d. The leg 35 supports the forward end of the lift conveyor 10 after the 
boom sections have been fully extended and during the time that an endless 
belt 36 is installed. 
The endless belt 36 (FIG. 1) is entrained around the pulleys 14, 16, 22 and 
24 to define a pair of upper forward run segments 36a and 36b and a pair 
of lower rearward run segments 36c and 36d that cross-over each other. The 
upper forward run segments are generally parallel and substantially 
co-planar with each other. The endless belt 36 has a plurality of load 
engaging cleats 38 connected thereto at equal intervals, such as 
thirty-six inches apart for example. These cleats are typically L-shaped 
pieces of metal riveted to the belt 36. 
The endless belt 36 (FIG. 1) is preferably made of a long length of strap 
with a full twist put into the same before its terminal ends are 
connected. The full twist is necessary for the belt to be able to navigate 
around the pulleys 14, 16, 22 and 24 in the geometry illustrated in FIG. 1 
with the cleats 38 always on the outside of the pulleys. The strap 
material for the endless belt 36 is preferably lightweight fabric woven 
from a strong synthetic fiber such as that sold under the trademark NYLON. 
Of course the length of the strap needed depends upon the longitudinal 
dimension between the drive pulleys 14 and 16 and the return pulleys 22 
and 24 and the transverse dimension between tile pulleys of each adjacent 
pair, By way of example, for a thirty-five foot long lift conveyor, the 
endless belt 36 may be made from a one-hundred and thirty-two foot long 
strap approximately three inches in width. 
An adjustment mechanism is provided for moving the return pulleys 22 and 24 
in and out to adjust tension of the endless belt 36. It is very important 
to have high tension on the endless belt 36 in order for the upper forward 
run segments 36a and 36b to carry substantial loads without undue sagging. 
A hand crank 40 (FIG. 2) at the forward end of the forwardmost boom 
section 12d turns a threaded shaft 42 inside the boom section 12d. The 
rearward end of the threaded shaft 42 screws into a threaded hole in a 
stationary collar 44 secured inside the boom section 12c. It will thus be 
understood that the crank 40 can be manually turned to extend or retract 
the boom section 12d relative to the boom section 12c. This varies the 
longitudinal distance between the rearward drive pulleys 14 and 16 and the 
forward return pulleys 22 and 24 thus applying or releasing tension on the 
endless belt 36. When the endless belt 36 is tensioned, the criss-cross 
segments 36c and 36d act like cross-braces adding to the sturdiness of the 
lift conveyor 10. 
A plurality of vertically extending Aluminum towers 46, 47, 48 and 49 (FIG. 
2) are mounted to the boom 12 at longitudinally spaced apart locations. 
The towers extend in an upward direction away from the boom 12. The towers 
46 and 47 are bolted to the top portion of the boom section 12a, the tower 
48 is bolted to the top portion of the boom section 12b and the tower 49 
is bolted to the top portion of the boom section 12c. The construction of 
all the towers is identical so only one need be described in detail. Each 
tower such as 48 (FIG. 6) has a pair of substantially horizontally 
extending arms 50 and 52 that extend in the transverse direction from 
opposite sides of the upper end of the tower. In the preferred embodiment 
the arms 50 and 52 are formed from a single U-shaped piece of Aluminum 
screwed intermediate its length to the upper end of the tower 48. 
Referring still to FIG. 6, a plurality of pairs of substantially horizontal 
guide rollers such as 54, 55, 56 and 57 are rotatably mounted on the arms 
50 and 52 for carrying and guiding the parallel upper forward run segments 
36a and 36b. Each of the horizontal guide rollers 54-57 rotates about an 
axis extending in a direction transverse to the longitudinal extension of 
the central boom 12. Each of the horizontal guide rollers 54-57 preferably 
comprises a long cylindrical body made of a highly wear resistant plastic 
such as that sold under the trademark DELRIN. These cylindrical rollers 
are formed with a central bore through which support rods such as 58 
extend. The ends of the support rods are secured in holes in upstanding 
brackets such as 60, 61 and 62 secured to the arms such as 52 of each 
tower such as 48. The rods supporting adjacent horizontal guide rollers 
such as 54 and 55 extend at a slight angle relative to each other so that 
the upper forward run segments such as 36a of the endless belt 36 will 
stay centered in the slight valley created between the two adjacent 
substantially horizontal rollers 54 and 55. 
Four vertical guide rollers 64, 65, 66 and 67 (FIG. 1) are provided for 
guiding the lower rearward run segments 36c and 36d of the endless belt 36 
so that the cross-over each other. One pair 64 and 65 of the vertical 
guide rollers are mounted to opposite sides of the tower 48 as shown in 
FIGS. 3 and 6. Another pair 66 and 67 of the vertical guide rollers are 
mounted to opposite sides of the tower 47 as shown in FIG. 3. The vertical 
positioning of the guide rollers 64-67 is carefully selected to ensure 
that the lower rearward run segments 36c and 36d of the endless belt 36 
criss-cross without their cleats 38 interfering with each other. The 
mounting of the vertical guide rollers 64-67 on the towers 47 and 48 at 
different vertical heights also ensures that the lower rearward run 
segments 36c and 36d of the endless belt 36 and the terminal outer ends of 
the cleats 38 carried thereby arc above the underside of the central boom 
12. This permits the forward portion of the boom to be leaned against and 
supported on an edge of a roof during construction or repair thereof. This 
was not possible with the lift conveyor of U.S. Pat. No, 4,854,447 of 
Johansson in which the lower criss-cross rearward run segments of the 
single endless belt extended beneath the underside of the boom. A roof 
stand (not illustrated) may be attached to the forward end of the boom 12 
to prevent damage to gutters. The endless belt segments 36a, 36b, 36c and 
36d run synchronously around the pulleys and guide rollers with the cleats 
38 on the upper run segments 36a and 36b in transverse alignment. 
As best seen in FIG. 3, the vertical guide rollers 64 and 66 are mounted to 
the towers 48 and 47, respectively at a first height, and on opposite 
sides of the boom 12. The vertical guide rollers 65 and 67 are mounted to 
the towers 48 and 47, respectively at a second height below the first 
height, and on opposite sides of the boom 12. The vertical guide rollers 
for each tower are thus mounted at different heights on opposite sides of 
the same tower. The vertical guide rollers 64-67 are configured like 
spools in that they have retaining flanges on opposite ends thereof to 
ensure that the endless belt 36 stays entrained about them and does not 
slip off. 
A pair of parallel auxiliary load supporting straps 70 (FIG. 5) may be 
threaded through brackets 72 connected to the outer ends of the arms such 
as 50 and 52. Where wide loads of building materials are to be carried by 
the lift conveyor 10 that extend transversely well beyond the upper belt 
segments 36a and 36b, the auxiliary straps 70 may be installed to 
stabilize the loads. 
It will also be understood that my invention provides a useful and novel 
method of lifting loads of building materials from ground level to roof 
level. The first step of my method is to provide a longitudinally 
extending boom having sufficient length to extend between a ground 
location and an edge of a roof of a building under construction or repair. 
Next, an endless belt with equally spaced load engaging cleats is 
entrained around transversely spaced pairs of drive and return pulleys 
rotatably mounted to the rearward and forward ends of the boom and around 
a plurality of guide rollers mounted along the length of the boom. The 
guide rollers are positioned: 1) to define parallel upper forward run 
segments and lower rearward run segments that criss-cross over each other; 
2) the cleats do not interfere with each other; and 3) the cleats and belt 
do not extend below an underside of the boom. The next step of my method 
is to erect the boom so that its rearward end rests on the ground location 
and a forward portion of the boom rests on the edge of the roof. The drive 
pulleys arc then propelled to cause the endless belt to continuously wind 
around the pulleys and guide rollers with the upper segments moving 
forwardly and the lower segments moving rearwardly. In accordance with the 
final steps of my method, individual loads of building material are 
manually stacked on top of the upper forward run segments of the endless 
belt in advance of pairs of transversely aligned cleats so that the loads 
are carried up to the roof. These loads of building material are manually 
removed from the upper segments of the belt when they reach the edge of 
the roof. The use of a tensioned single endless belt to form all of the 
forward and rearward load supporting segments ensures against any 
slippage. 
The endless belt 36 is best installed by first installing it over the right 
front return pulley 24, laying it over the horizontal guide rollers 54 and 
55, and wrapping it around the right rear drive pulley 16. The belt 36 is 
then threaded around the vertical guide rollers 66 and 64 and around the 
left front return pulley 22. From there, the belt 36 is threaded over the 
horizontal guide rollers 56 and 57 on the left side of the lift conveyor, 
and around the left drive pulley 14. The remainder of the belt 36 is then 
threaded around the vertical guide rollers 67 and 65. The foregoing 
installation procedure is simple enough for the average construction 
worker to accomplish at the job site. 
The lift conveyor 10 is often collapsed and extended several times per day. 
It is not necessary to remove the endless belt 36 each time this is done. 
Instead, when the boom 12 is collapsed, the endless belt 36 is wrapped 
around the towers 46, 47, 48 and 49 in a figure eight fashion. When it is 
time to extend the lift conveyor 10, the belt 36 is unwrapped, the boom 12 
is extended, and the two lower belt segments 36c and 36b are moved to the 
cross-over point. The upper segments 36a and 36b are threaded over the 
horizontal guide rollers 54 and 55 from the front return pulleys 22 and 24 
back to the drive pulleys 14 and 16. The cross-over point on the boom 12 
is preferably marked such as by an adhesive label. The tension on the belt 
36 is then increased to a suitable point via hand crank 40. The belt 
segments 36c and 36d then wrap around the vertical guide rollers 64, 65, 
66 and 67. The foregoing procedure can be accomplished by the average 
construction worker in about two minutes. 
Having described a preferred embodiment of my single belt lift conveyor 
having criss-cross return segments, modifications and adaptations thereof 
will occur to those skilled in the art. Therefore, the protection afforded 
my invention should only be limited in accordance with the following 
claims.