Conveyor system with frictionally driven conveyor belt

A conveyor system comprises an endless belt and means for carrying and driving the belt along a path comprising a plurality of vertically spaced apart loops by frictionally engaging the underside of the belt at the curved portions of the loops. The belt is supported at the straight portions of the loop. The belt is driven by friction between the carrying means and the underside of the belt.

BACKGROUND 
This invention relates to endless conveyor belt systems, and more 
particularly, to such systems utilizing metallic belts capable of 
negotiating edgewise horizontal curves. 
In many situations, particularly in the food processing industry, it is 
desirable to provide a long length of conveyor belt in a relatively small 
space. For example, such belts find application in the freezing, cooling 
and heating of foods. In addition, in industries like the baking industry, 
cakes and other products to be decorated are placed on such belts to 
permit decorating and other processing steps to be conducted in an 
assembly line. 
A conveyor system for these types of applications is described in U.S. Pat. 
No. 3,348,659 issued to Roinestad. According to the Roinestad system, the 
belt is driven and supported by a pair of horizontally spaced apart drums. 
Support means engage the underside of the belt to support the belt for 
helical movement upwardly around one of the drums and downwardly around 
the other of the drums. The helical movement occurs in a plurality of 
vertically spaced apart loops contiguous to the drums throughout their 
length, the loops being curved edgewise with the radially inner edge of 
the belt being in sliding frictional engagement with the drum driving 
surface. The belt is maintained in tension by engagement with the drum. 
The frictional engagement between the drum and belt causes the continuous 
movement of the belt. 
Such drive systems suffer from significant disadvantages. For example, the 
length of the belt is limited because the horsepower required for moving 
the belt and the tension on the belt are proportional to the length of the 
belt. About 50 horsepower can be required to pull a belt only 1200 feet, 
and the high tension on the belt can result in its premature failure. 
Further, the prior art systems tend to be bulky, requiring large-diameter 
drums. 
A further disadvantage of some prior systems is that only one type of 
product can be carried on the belt at a time. If products of different 
weight are carried on the belt, there is a tendency for the belt to tip 
edgewise with the result that the products slide onto the floor. 
In view of these problems, it is apparent that there is a need for a 
conveyor system utilizing endless belts which permits use of belts of 
substantially unlimited length, requires low power consumption, is 
compact, and produces low tension and low wear on the belts. 
SUMMARY 
The present invention is directed to a conveyor system with these features. 
The conveyor system comprises an endless flat belt capable of bending in an 
edgewise direction and a belt driving and supporting assembly. The belt 
driving and supporting assembly comprises two horizontally spaced apart, 
rotatable, upright drums which preferably are tubular in shape. Carrying 
means project outwardly from each drum for frictionally engaging the 
underside of the belt for carrying the belt through a plurality of 
vertically spaced apart loops as the drums rotate. The loops comprise a 
first portion contiguous to the peripheral surface of the first drum, a 
second portion contiguous to the peripheral surface of the second drum, a 
third portion along which the belt passes from the first drum to the 
second drum, and a fourth portion along which the belt passes from the 
second drum to the first drum, thereby completing a loop. The belt is 
driven by, and preferably substantially only by, frictional engagement 
between the carrying means and the underside of the belt. The belt driving 
and supporting assembly also comprise support means for supporting the 
belt along the third or fourth portions of each loop. 
The carrying means project radially from each drum substantially horizontal 
to the ground so that the first and second portions of each loop are 
substantially horizontal. The belt moves upwardly or downwardly only along 
the third and fourth portions of each loop, the direction depending upon 
the direction of rotation of the drums. 
Unlike prior art conveyor systems where the belt is driven principally by 
frictional engagement between the inside edge of the belt and the 
peripheral surface of the drum, in the conveyor system of the present 
invention the belt is driven substantially only by frictional engagement 
between carrying means and the underside of the belt. This has many 
significant advantages, including substantially less tension on the belt 
and less power consumption. For example, belt lengths in excess of 1,000 
feet can be carried using a motor that produces less than about 10 
horsepower. Further, small diameter drums can be used because the tension 
on the belt and power required for carrying the belt are substantially 
independent of the diameter of the drum. With prior art systems, as the 
diameter of the drum decreases, the tension on the belt and the horsepower 
required for pulling the belt greatly increase. Thus, with the present 
invention, small diameter drums, with a large number of vertical loops, in 
excess of sixteen vertically spaced apart loops, can be used, thereby 
minimizing the floor space required for a conveyor system. 
To enable the carrying means to frictionally engage the belt, preferably 
the carrying means comprises a belt-engaging surface of a material that is 
prone to gall against the underside of the belt. To minimize the 
frictional drag on the belt as the belt moves between drums along the 
third and fourth portions of each loop, preferably the support means 
comprises a belt engaging surface of a smooth, synthetic polymeric 
material. 
It is necessary that the pulling force on the belt resulting from the 
frictional engagement between the belt and the carrying means be 
sufficiently large to overcome the friction between the belt and the 
stationary support means, as well as provide the force required for moving 
the belt upwardly between loops. To achieve this, preferably the combined 
length of the first and second portions of each loop is greater than the 
combined length of the third and fourth portions.

DESCRIPTION 
With reference to FIGS. 1 and 2, a conveyor system 10 according to the 
present invention comprises an endless flat belt 12 capable of bending in 
an edgewise direction. The belt is driven and supported by first and 
second drum assemblies 14 and 16 horizontally spaced apart (not shown in 
FIG. 1). Each drum assembly 14 and 16 comprises an identical rotatable 
upright drum 18 and 19, respectively. Each drum 18 and 19 has a circular 
cross-section, a peripheral surface, and a vertical axis. As described in 
detail below, as the drums rotate, they cause the endless belt to move 
through a plurality of vertically spaced apart loops. 
The path the belt travels is shown in FIG. 1. The path includes a straight 
horizontal feed portion 20 that can be as long as required. The feed 
portion ends at the bottom portion of the first drum assembly 14. In the 
version of the invention shown in FIGS. 1 and 2, the belt travels along a 
path that includes seven vertically spaced apart loops 22. Each loop 
includes a first portion 24 contiguous to the peripheral surface of the 
first drum 18, a second portion 25 contiguous to the peripheral surface of 
the second drum 19, a third portion along which the belt 12 passes from 
the first drum 18 to the second drum 19, and a fourth portion 27 along 
which the belt 12 passes from the second drum 19 to the first drum 18. 
The first portion 24 and second portion 25 of each loop 22 are 
substantially horizontal, while the third portion 26 and fourth portion 27 
of each loop are inclined to the horizontal. Thus, the belt 12 moves 
upwardly (or downwardly if the direction of rotation of the drums is 
reversed) only along the third 26 and fourth 27 portions of each loop. 
This provides a generally helical upward movement for the belt. 
The vertical distance between the loops 22 depends upon the size of the 
product to be carried by the belt. For example, the loops can be 
vertically spaced apart by as little as 21/2 inches. This change in 
elevation can be accomplished by spacing the drum assemblies apart so that 
the third 26 and fourth 27 portions of the loops 22 are from about 3 to 
about 6 feet long. The fourth portion 27 of the top loop continues to a 
discharge portion 28 that can lead to a separate room or facility for 
removal of products from the belt 12. The discharge portion 28 can be as 
long as required. 
The belt with products removed passes from the discharge portion 28 of its 
path along an upper return path 30 that is below the discharge portion 28. 
The belt passes over a first pulley 32 and then passes downwardly through 
a vertical section 34 to a lower elevation than the elevation of the feed 
portion 20. The belt then passes over a second pulley 36 to resume 
substantially horizontal travel along a lower return section 38. At the 
feed end of the path, the belt passes over a third pulley 40, then moves 
upwardly along a short vertical section 42, and then over a fourth pulley 
44 to resume its travel along the feed portion 20 of the path. 
In the event that there is excessive slack in the belt 12, a belt takeup 
assembly 46 can be used along the lower return portion 38 of the belt 
path. The takeup assembly includes a Browning torque clutch 48 over which 
the belt 12 reverses direction and a reversing pulley 50 over which the 
belt reverses direction to resume its original direction of travel. The 
Browning torque clutch 48 provides from about 4 to about 6 pounds of 
torque and is driven by a chain 52 mounted on a sprocket 54 attached to an 
angle gear box 56. 
The drive mechanism for rotating the drums 18 and 19 and the chain takeup 
assembly 46 comprises a motor 58 that is connected by a belt 60 to a 
variable speed drive 62 that is used for controlling the speed at which 
the belt moves. A vertical shaft 64 extends from the variable speed drive 
62 and has mounted thereon a lower sprocket 66 and an upper sprocket 68. A 
belt 70 on the upper sprocket 68 turns a sprocket 72 attached to a shaft 
74 of the angle gear box 56. Thus, as the drums 18 and 19 are rotated by 
the motor 58, the takeup assembly 46 is also driven. 
A primary drive shaft 76 is used to drive the two drums 18 and 19. The 
primary drive shaft 76 has a follower sprocket 78 on which is mounted a 
drive chain 80 that is also mounted on the lower sprocket 66 of the 
variable speed drive shaft 64. The primary drive shaft also has mounted 
thereon two vertically spaced apart sprockets, a first drive sprocket 82 
and a second drive sprocket 84. The first drive sprocket 82 is connected 
via chain 86 to a sprocket 88 mounted on the first rotatable drum 18. 
Likewise, the second drive sprocket 84 is connected via a chain 92 to a 
sprocket 94 mounted on a the second rotatable drum 19. 
The primary drive shaft 76 is used to insure that both drums 18 and 19 
rotate at the same speed. The drums rotate in a counterclockwise direction 
as viewed from overhead for raising the belt along the third and fourth 
portions of a loop. Alternatively, the drums can rotate in a clockwise 
direction for lowering the belt along the third and fourth portions of a 
loop. 
Other drive mechanisms for the drums can be used. For example, instead of 
using chain and sprockets, direct drives utilizing jack shafts can be 
used. If desired, hydraulic drives can be used. 
As best shown in FIGS. 2 and 8, the belt 12 is supported along the feed 
portion 20 of the path by an elongated pan 102 having vertically extending 
sidewalls 104 for guiding the belt. On the upper surface of the pan 102 
are three spaced apart, elongated, stainless steel rods 106. The belt 
actually rides on and is slidably engaged by the three spaced apart 
elongated round rod or bars 106, the rods can be made of stainless steel, 
and are typically of about 3/8 inch outer diameter. The rods 106 extend 
along the path of the belt and are spaced apart so that there is one rod 
proximate to each end of the belt and a rod at about the middle of the 
belt. Preferably the rods are clad in a material that minimizes the 
frictional drag of the belts against the rod. A suitable material can be a 
low coefficient of resistant synthetic polymer such as nylon or 
polyethylene. A suitable polyethylene is an ultra high density 
polyethylene distributed by Plastic Sales of Los Angeles, Calif. 
The belt 12 is supported along the discharge portion 28 of the path by a 
similar pan structure comprising an elongated piece of sheet metal having 
sidewalls with three rods clad with a low coefficient of resistance 
material. 
As the belt passes along the third 26 and fourth 27 portions of each loop 
it is supported in a similar pan 120 comprising a horizontally oriented, 
elongated flat section of sheet metal 122 with upstanding sidewalls 124 
for retaining the belt along the path. The pans 120 have the same three 
spaced apart polymer clad rods 106 for actually supporting the belt 12. 
The pan structures 102 and 120 can be removed from the belt path along the 
feed and discharge sections and/or the third or fourth portions of the 
loops. One disadvantage of using the pans is their tendency to block air 
flow. The sidewalls or their equivalent are required for guiding the belt. 
With reference to FIGS. 6 and 7, the belt 12 can be made of a plurality of 
metallic rods or links 132 collapsibly connected together at their ends 
and also at a location between the ends so that the belt can negotiate 
straight runs or edgewise curves. The links are connected by means of 
"U-shaped" connectors 134 having coaligned holes 136 through the end 
portion of each arm of the connector and a coaligned slot 138 through the 
portion of each arm adjacent to the base of each connector. 
Each rod 132 at its ends and at a location between the ends is mounted on 
two connectors, extending through the holes 136 of one connector and 
through the slots 138 of the next adjacent connector. The ends of the rods 
132 are peened or welded to maintain them mounted in the connectors. The 
connectors are sized so that the arms 140 extend outwardly slightly from 
the base 142 so that the slots 138 of one connector can be aligned with 
the holes 136 of the next adjacent connector. The rods can collapse 
together on the inside portion of a curve and become more spaced apart on 
the outside portion of a curve due to the play in the slots. The slots 138 
of the middle connectors 134 are smaller than the slots of the end 
connectors because little, if any, collapsing occurs in the center portion 
of the belt as the belt goes around curves. 
An advantage of using the center connectors for collapsing the belt is that 
they allow use of compact, relatively small diameter drums 18 and 19 in 
the conveyor system 10. This is because the minimum radius of curvature of 
the curve around which the belt 12 can go is directly proportional to the 
distance between the inner connector and the center connector. If there is 
no center connector, then the minimum radius of curvature of the curve 
around which the belt can go is proportional to the length of the rods. By 
using a center connector, drums of a smaller diameter can be used than if 
no center connector were used. 
This type of belt is available from Ashworth Bros., Inc. of Salinas, Calif. 
With reference to FIGS. 3 and 4, the first drum assembly 14 and second drum 
assembly 16 each comprises a drum 18 and 19, respectively, mounted to 
rotate about a shaft 90 or 96, respectively. Only the second drum assembly 
16 will now be described because the first drum assembly 14 and the second 
drum assembly 16 are substantially identical. 
The shaft 96 of the second drum assembly 19 is mounted on a base 204 that 
is supported by feet 208. The shaft 96 is held vertically oriented by 
round, seamless mechanical tubing 210 of larger diameter than the solid 
shaft 96. The tubing 210 is also mounted on the base 204 and is vertically 
oriented. The shaft 96 fits into the tubing 210 and is held secured in 
position by Allen fasteners 212. 
The drum 19 that rotates about the shaft 96 comprises an upper flange 
bearing 214 and a lower flange bearing 216 vertically spaced apart from 
each other and mounted to rotate about the shaft 96. A horizontally 
oriented upper circular plate 218 is mounted to the bottom of the upper 
flange bearing 214 and a horizontally oriented lower circular plate 220 is 
mounted to the bottom of the lower flange bearing 216. Both plates have 
holes through the middle through which the shaft 96 extends so that the 
plates can rotate about the shaft without contacting the shaft. Both 
plates have spaced apart segments 222 cut out to reduce the mass of the 
plates, giving the plates the appearance of a wheel with spokes and an 
exterior rim. The lower plate 220 rests on a Torrington thrust bearing 224 
which is mounted on top of a horizontally oriented plate 226 mounted 
around the shaft 96. The drum 19 is supported in position by fins 228 
secured to a plate 230 mounted on top of the base 204. 
A reinforcing bar 233 extends between the top of the shafts 90 and 96 to 
help maintain the shafts vertically oriented. 
As described above, rotation of the drum 19 about the shaft 96 results from 
the primary drive shaft 76 pulling chain 92, the chain 92 being connected 
to the sprocket 94 that is attached to the second drum 19. The sprocket 94 
is secured to the bottom of the lower plate 220 and spaced apart 
vertically therefrom by spacers 232. 
Rigidity to the drum assembly is provided by a gridwork structure 
comprising tubing 234 extending between the upper 218 and lower 220 
plates. In addition, a plurality of circumferentially spaced apart, 
vertically-oriented bars 236 extend between the bottom of the upper plate 
218 and the top of the lower plate 220 at the peripheral edges thereof. In 
the version of the invention shown in the figures, there are sixteen such 
vertical bars defining the periphery of the drum 19. A plurality of 
vertically spaced apart arms 238 extend radially outwardly from each of 
the vertical bars 236 in a direction substantially perpendicular to the 
axis of the drum. There is one arm 238 from each bar 236 for each loop of 
the chain path. In the version of the invention shown in the figures, 
seven arms 238 extend from each bar. 
The drums 18 and 19 are reinforced where the end of the belt 12 rubs. As 
shown in FIG. 5, a reinforcing angle iron 240 is mounted at the junction 
between each arm 238 and its vertical bar 236. The reinforcing angle iron 
240 is provided with a reinforcing stainless steel wear plate 242 on its 
vertical surface facing the chain against where the inside edge of the 
rods 132 rub. 
As shown best in FIG. 4, the arms 238 are vertically spaced apart from each 
other so as to form seven loop segments that are substantially horizontal. 
The belt does not ride on top of the arms 238, but rather on top of the 
same type of stainless steel rods used in the feed and discharge sections 
and along the third and fourth segments of a loop. Two stainless steel 
rods 250 of about 3/8 inch diameter are provided on top of each arm. The 
rods 250 form horizontally oriented circles that are radially spaced apart 
from each other. One rod 250 is at the radially outward end of the arms 
238 and another rod is toward the center of the arms 238. The inward edge 
of the chain is supported on the angle iron 240. The rods frictionally 
engage the underside of the belt, and thus are not covered with a low 
coefficient of friction material. Preferably the rods 250 are formed of a 
galling material. One advantage of using a stainless steel for the rods 
250 is that it is prone to gall against the underside of the belt, thereby 
aiding in the frictional engagement between the belt 12 and the rods 250. 
The rotating drums 18 and 19 carry the belt by frictionally engaging the 
underside of the belt. Preferably the belt 12 is driven substantially only 
by frictional engagement between the drums 18 and 19 and the belt. Thus, 
unlike prior art systems where the belt is pulled to cause it to move, in 
the conveyor system 10, the belt is carried along its path by frictional 
engagement with the rotating drums. 
It is easy to determine if the belt is being driven "substantially only" by 
frictional engagement between the belt and the drum rods 250. All that is 
necessary is to loosen the belt sufficiently so that the inside edge of 
the belt does not rub against the wear plates 242. If the belt continues 
to be driven, then the belt is being driven substantially only by 
frictional engagement between the belt and the rods 250. 
The frictional engagement between the belt 12 and the drums 18 and 19 is 
sufficient to cause the belt to move upwardly along the third and fourth 
portions of each loop. To insure that this occurs, preferably the combined 
length of the first and second portions of each loop greater than the 
combined length of the third and fourth portions of the respective loop. 
As shown in the figures, preferably the length of the first portion of 
each loop is greater than the length of the third portion and the fourth 
portion of the respective loop, and preferably the length of the second 
portion of each loop is also greater than the length of the third portion 
and the fourth portion of the respective loop. When comparing the 
distances of different portions of a loop, the distances are measured 
along the center connectors 134 of the belt. For a belt that does not have 
a center connector 134, the distances are measured along the center line 
of the belt. 
A conveyor system according to the present invention has many significant 
advantages. For example, a substantially unlimited length of belt can be 
used because each loop is supported. Further, the pulling force is not 
proportional to the length of the belt. Thus, it is possible to extend the 
drum assemblies very high and have a very large number of loops stacked 
one on top of the other. Although the drawings show the conveyor system 10 
having only seven loops, systems having in excess of 15 loops are 
possible. 
Another advantage of the conveyor system is that compact, small diameter 
drums are possible, i.e. less than 10 feet in diameter. The drum diameter 
is shown as line 302 in FIG. 4. One factor contributing to this ability to 
use compact drums is the use of the center link on the belt. Another 
contributing factor is the low force required to move the belt. Normally, 
the frictional resistance on a belt being pulled around a curve is 
inversely proportional to the square of the radius of curvature of the 
curve. In the present invention, the chain is not pulled around the curve, 
but rather supported by the drum assembly arms. Thus curves having a small 
radius of curvature can be negotiated without excessively high frictional 
resistance. 
Another advantage of the present invention is that substantially less 
horsepower is required for moving the belt. For example, a belt in excess 
of 1,000 feet long can be moved with drive means producing less than 10 
horsepower. It has been demonstrated that a fully loaded belt 1,400 feet 
long can be moved with a 71/2 horsepower motor, and most likely, with a 
motor as small as 21/2 horsepower. Prior art conveyor systems have 
required about 50 horsepower for only 1,200 feet of belt. 
A further advantage of the conveyor system 10 is that products of different 
weight can be carried simultaneously. With prior art conveyor systems 
where the chain was pulled and products of different weight were used, 
there was a tendency for the belt to tilt. This is not a problem with the 
conveyor system 10. 
The conveyor system 10 can be used in a wide variety of applications. It is 
particularly adapted to cooling food products because the long length of 
belt can be placed in a compact space, thereby minimizing the volume that 
needs to be cooled or refrigerated. 
Although the present invention has been described in considerable detail 
with reference to certain preferred versions thereof, other versions are 
possible. For example, belts other than the belt 12 shown in the drawings 
can be used. Therefore the spirit and scope of the appended claims. should 
not be limited to the description of the preferred versions contained 
herein.