A bi-directional accumulation roller conveyor includes a plurality of upper load carrying rollers longitudinally coextensive with and superimposed over a plurality of lower load carrying rollers, a drive for driving the upper and lower load carrying rollers for counter rotation with respect to each other, a first clutch for drivingly engaging the upper load carrying rollers, a second clutch for drivingly engaging the lower load carrying rollers, a actuator for disengaging the clutches respectively in response to the presence of a pallet on each terminal end of the upper or lower plurality of load carrying rollers and a lifting device for transferring pallets between the upper and lower load carrying rollers thereby providing a continuous loop of conveyable pallets and managing pallet flow.

TECHNICAL FIELD 
This invention relates generally to accumulation roller conveyor systems 
and more particularly to a slave pallet system including a bi-directional 
over-and-under accumulation roller conveyor adapted to handle palletized 
loads and function as a pallet dispenser and collector. 
BACKGROUND ART 
Accumulation roller conveyors have been available in various forms in which 
conveyor sections stop as loads come to the end of the conveyor and 
accumulate before being removed. One known prior system of this type has 
included successive sections, each with a set of load supporting rolls and 
each section provided with an actuating roller adapted to respond to the 
presence of a load. The actuating roller, when depressed by the presence 
of the load, declutches the drive to that set of rollers and 
simultaneously conditions the mechanism for a preceding section to 
declutch its drive mechanism when a load passes thereon. If no load is 
present on the first mentioned section, the drive mechanism will continue 
to provide positive driving action and the preceding drive system will 
also continue even though a load passes over it. 
In connection with known accumulation roller conveyors used in slave pallet 
systems wherein loads are palletized on reusable pallets, it has been 
necessary to employ separate mechanisms for dispensing slave pallets to 
the accumulation roller conveyor and also for collecting slave pallets 
from the accumulation roller conveyor. Empty slave pallets are stacked in 
a separate device and returned to the input point where they are dispensed 
as needed. Such systems require a surplus of pallets and often times there 
is either a glut of pallets at one of the mechanisms or one of the 
mechanisms is starved for pallets. 
DISCLOSURE OF INVENTION 
An object of the present invention is to provide a bi-directional 
accumulation roller conveyor that improves the conveyability of pallet 
loads. 
Another object of the present invention is to provide a bi-directional 
accumulation roller conveyor that manages pallet flow. 
A further object of the present invention is to provide a bi-directional 
accumulation roller conveyor that functions as a pallet dispenser and 
pallet collector. 
Still another object of the present invention is to provide a 
bi-directional accumulation roller conveyor having over and under conveyor 
rollers driven by a single conveyor drive for the recirculating conveyance 
of pallets in two directions. 
In carrying out the above objects and other objects of the invention, a 
bi-directional accumulation roller conveyor includes a frame structure 
including a pair of longitudinally extending transversely connected side 
frames. A first plurality of parallel upper load carrying rollers is 
supported between the side frames and are arranged in a series of 
successive upper groups. Each of the upper groups has a driving connection 
between the rollers. A second plurality of parallel lower load carrying 
rollers is supported between the side frames below the upper load carrying 
rollers. The lower load carrying rollers are arranged in a series of 
successive lower groups and each group has a driving connection between 
the rollers of that group. 
A single drive unit supported by the frame structure is drivingly connected 
through a drive transmission to each of the upper groups of rollers and to 
each of the lower groups of rollers for driving the rollers of the upper 
groups in one direction of rotation and for driving the rollers of the 
lower groups in the opposite direction of rotation whereby articles 
supported on the upper load carrying rollers are conveyable by successive 
upper groups to a terminal upper group at one end of the conveyor and 
articles supported on the lower load carrying rollers are conveyable by 
successive lower groups to a terminal lower group at the opposite end of 
the conveyor. The drive transmission includes, for each of the series of 
upper and lower groups, a respective series of upper and lower drive 
trains. Each drive train includes a clutch for selective engagement and 
disengagement of the drive transmission. 
Upper and lower accumulation members disengage the clutch of the respective 
drive trains of the upper groups and the lower groups of rollers in 
response to the presence of an article on each of the terminal upper and 
terminal lower groups of rollers and on successive groups upstream from 
each of the terminal upper and lower groups. 
The above objects and other objects, features, and advantages of the 
present invention are readily apparent from the following detailed 
description of the best mode for carrying out the invention when taken in 
connection with the accompanying drawings.

BEST MODE FOR CARRYING OUT THE INVENTION 
With reference to FIGS. 1--5, an accumulation roller conveyor is generally 
referred to by reference numeral 10 and is used to convey pelletized loads 
between combination loading and unloading stations 12 and 14. As is 
hereinafter more fully described accumulation roller conveyor 10 is a 
bi-directional over and under accumulation roller conveyor that improves 
the conveyability of pelletized loads, managing pallet dispensing and 
collecting, by conveying pallets in an endless loop thereby eliminating 
the need for independent pallet dispensing and collecting mechanisms. 
Referring to FIGS. 1 and 2, the accumulation roller conveyor 10 illustrated 
is comprised of four consecutive conveyor sections 16 connected in 
end-to-end relation and positioned between combination loading and 
unloading stations 12 and 14. It will become apparent that as many 
sections as necessary for a particular installation may be positioned 
together in end-to-end relation. Each section 16 includes a frame 
structure 20 including a pair of longitudinally extending transversely 
connected side frames 22,22'. 
Parallel upper load carrying rollers 24, illustrated by groups of eight 
rollers each although the number may be varied, are supported at their 
ends between side frames 22,22'. The upper load carrying rollers 24 are 
arranged in a series of successive groups and are adapted to support 
pallets on which articles are mounted. Each group has a length sufficient 
to accommodate one pallet. Adjacent pairs of upper load carrying rollers 
24 are drivingly connected to one another by means of a sprocket gear 26 
mounted to the end of each roller and in mesh with a driving chain belt 28 
looped over each sprocket gear. The upper load carrying rollers 24 in each 
section 16 are driven by power transmitted through drive rollers 30. Each 
conveyor section 16 includes a load sensing photoelectric element 31 (FIG. 
5) preferably located at the downstream end of each conveyor section next 
to the last upper load carrying roller so that a load coming onto a 
particular group will move up to the end of that group before coming to a 
stop if that group has been conditioned or set to stop. 
Parallel lower load carrying rollers 32, illustrated by groups of five 
rollers each although the number may be varied, are also supported at 
their ends between side frames 22,22'. The lower load carrying rollers 32 
are arranged in a series of successive lower groups each arranged in 
substantially vertically aligned relation and longitudinally coextensive 
with a superimposed upper group. The vertical distance between upper load 
carrying rollers 24 and lower load carrying rollers 32 need only be 
sufficient to convey an empty pallet on the lower load carrying rollers. 
Adjacent pairs of lower load carrying rollers 32 are drivingly connected 
to one another by means of a sprocket gear 34 mounted to the end of each 
roller and in mesh with a driving chain belt 36 looped over each sprocket 
gear. The lower load carrying rollers 32 in each section 16 are driven by 
power transmitted through drive rollers 38. Each lower conveyor section 16 
also includes a load sensing roller 40 (FIG. 5) preferably located between 
the last and next to last load supporting rollers in each group so that a 
pallet coming onto a particular group of lower load carrying rollers will 
move up to the end of that group before coming to a stop if that group has 
been conditioned or set to stop. 
With further reference to FIGS. 1 and 2, the rollers 24,32 are driven by 
power supplied from a single drive unit 42 supported by the frame 
structure 20. Drive unit 42 includes a motor and reduction gear unit 
extending longitudinally of the conveyor 10 providing continuous drive 
through a chain belt 44 looped over sprocket 46. Sprocket 46 is fixed to 
an input shaft 48 which also has fixed thereto sprocket gears 50,52. The 
sprocket gear 50 meshes with chain belt 54' looped over a similar sprocket 
gear 50' mounted on a similar input shaft 58' thereby transferring power 
to the adjacent conveyor section 16. Sprocket gear 52 is in mesh with a 
similar chain belt 54 looped over a similar sprocket gear mounted on a 
similar input shaft thereby transferring power to the next adjacent 
conveyor station 16 as is readily apparent from FIG. 3. 
With reference to FIGS. 2, 4 and 5, each conveyor section includes a first 
on-off type clutch 56 drivingly connected to input shaft 48. The output 
hub of first clutch 56 includes a sprocket gear 58 that drives a chain 
belt 60 looped over sprocket gears 26 on drive rollers 30 which in turn 
drive an upper group of load carrying rollers 24 in one direction of 
rotation whereby articles supported on the upper load carrying rollers are 
conveyable by successive upper groups of rollers to a terminal upper group 
at one end of the conveyor 10. 
Referring again to FIGS. 1 and 2, each conveyor section 16 includes an 
idler shaft 62 including a sprocket 64 drivingly connected to chain belt 
54. A second on-off type clutch 66 is drivingly connected to idler shaft 
62. The output hub of second clutch 66 includes a sprocket gear 68 that 
drives a chain belt 70 looped over sprocket gears 34 on drive rollers 38 
which in turn drive a lower group of load carrying rollers 32 in the 
opposite direction of rotation to the upper load carrying rollers 24. 
Thereby pallets supported on the lower load carrying rollers 32 are 
conveyable by successive lower groups of rollers to a terminal lower group 
at the opposite end of the conveyor 10. 
First and second on-off type clutches 56,66 are commercially available and 
operable for engaging and disengaging the upper load carrying rollers 24 
and lower load carrying rollers 32 respectively. 
Each first on-off type clutch 56 includes an electrical solenoid actuator 
72 (FIG. 5) electrically activated by a photoelectric element 31 mounted 
at each conveyor section 16 adjacent upper load carrying rollers 24. With 
photoelectric element 31 clear the solenoid 72 is extended, raising the 
clutch actuator 74, and the clutch 56 engaged, is transmitting power to 
the upper load carrying rollers 24. 
First on-off type clutches 56 are engaged when a load moves onto the upper 
group of load carrying rollers 24. The load is conveyed until it blocks 
the photoelectric element 31 of the roller group at the discharge end of 
the conveyor. Photoelectric element 31 will send a signal to a controller 
C in communication therewith and with the solenoid actuator 72 on clutch 
56, disengaging the clutch to stop power transmission to the upper load 
carrying rollers for that group. When a load is to be conveyed from the 
upper load carrying rollers of a particular conveyor section 16, the 
controller energizes the solenoid 72, causing clutch 56 to engage and 
again drive that group of upper load carrying rollers. 
Second on-off type clutch 66 includes a counterweighted, pivoting actuator 
76 that engages the clutch release sleeve on the clutch and is 
mechanically actuated in response to actuating rods 78 and 80 in 
communication with the load sensing rollers 40. Actuating rod 80 extends 
from the actuator 76 of one clutch 66 to the actuator 76 of the next 
upstream clutch 66 and conditions that upstream clutch for disengagement 
in response to operation of a load sensing roller 40 associated therewith. 
Second on-off clutch 66 is actuated to disengage by actuating rod 76 
extending from one end of the load sensing roller 40. A pallet is carried 
along a group of lower load carrying rollers until it passes over the load 
sensing roller 40. The pallet causes the load sensing roller 40 to depress 
to a position where the actuating rod 76 is extended, allowing the clutch 
actuator 76 to fall into contact with the clutch release sleeve, 
disengaging the second on-off type clutch 66 to stop power transmission to 
that group of lower load carrying rollers. 
Each time the photoelectric element 31 at the end of conveyor 10 signals 
the controller C to disengage that group of upper load carrying rollers 24 
in response to the presence of a load on the rollers the controller sets 
the preceding group of upper load carrying rollers to be declutched when a 
load on the preceding stage moves into view of the associated 
photoelectric element. Similarly, the presence of a load on sensor roll 40 
on the end conveyor section 16 group of lower load carrying rolls will 
extend actuator rod 78 set the actuator 80 for declutching when a pallet 
moves onto the load sensing roller 40 for the respective preceding 
conveyor section 16. 
The combination loading and unloading stations 12 and 14 mounted at each 
end of conveyor 10 are lifting devices that include a plurality of load 
carrying rollers 82 (FIG. 3) extending between side frame members 84,84' 
(FIG. 1) mounting the rollers. A pivotable linkage assembly 86 connected 
to frame members 84,84' is movable through the actuation of a pneumatic 
actuator 88. Stations 12 and 14 transfer pallets between the upper and 
lower groups of load carrying rollers 24,32, respectively providing 
automated pallet management as hereafter more fully described. Sensing 
elements associated with these stations provide signals through 
connections 92 and 94 to the controller C to indicate their position and 
their loaded or unloaded condition. 
OPERATION OF THE INVENTION 
Referring to FIGS. 1 and 3, a load moves without interruption, from right 
to left on the upper groups of load carrying rollers 24 as pallets move 
from left to right on the lower groups of load carrying rollers 32. At 
each end of the conveyor 10, combination loading and unloading stations 12 
and 14 are available and operable for lifting and lowering pallets so they 
can be exchanged between the upper and lower groups of load carrying 
rollers 24,32. When the combination loading and unloading station 12 at 
the loading end of the conveyor 10 is in a raised position, a pallet on 
the station is available to receive a load. A fork lift (not shown) 
typically deposits a load on the pallet and leaves the area of the 
combination loading and unloading station 12. Combination loading and 
unloading station 12 conveys the loaded pallet onto the group of upper 
load carrying rollers 24 of the first conveyor section 16 adjacent the 
combination loading and unloading station and the loaded pallet is 
conveyed toward the combination loading and unloading station 14 at the 
opposite unloading end of the conveyor. 
At the unloading end of the conveyor 10, the combination loading and 
unloading station 14 includes a detection element in communication with 
the controller for the preceding conveyor section 16. The detection 
element signals the preceding conveyor section 16 to cause the clutch 56 
to disengage the group of upper load carrying rollers 24 for that conveyor 
section and brake the rollers to stop the associated load so that the load 
on the combination loading and unloading station 14 can be removed from 
the conveyor. Concurrently, the group of lower load carrying rollers 32 
for the end conveyor section 16 and the upper and lower groups of load 
carrying rollers 24,32 for the preceding conveyor section are set to stop 
when the corresponding photoelectric element 31 or load detecting roller 
detects a corresponding load or pallet respectively. 
When the load is removed from the combination loading and unloading station 
14 the last conveyor section 16 and its associated first on-off type 
clutch 56 is engaged to convey the next load onto the combination loading 
and unloading station. In the same operation, the last conveyor section 16 
receives the next load from the preceding conveyor section as becomes 
readily apparent. The combination loading and unloading station 14 at the 
unloading end of conveyor 10 lowers the empty pallet through vertical 
displacement initiated by the pivotable linkage assembly and pneumatic 
actuator to the horizontal level of the groups of lower load carrying 
rollers 32 so the empty pallet can be conveyed back to the combination 
loading and unloading station at the beginning of the conveyor. The system 
manages pallet flow by establishing a continuous loop of conveyable 
pallets utilizing a fixed number of pallets for any accumulation conveyor 
sections and pallet spacing setting, thereby improving the conveyability 
of pallet loads. 
While the above invention has been described in terms of bi-directional 
over and under accumulation roller including conveyor sections 16 in 
end-to-end relation with a combination loading and unloading station 12 
and 14 at either end, it will be appreciated by on skilled in the art that 
in alternative embodiments a transfer car or carousel can be included in 
the system to take advantage of the improved conveyability provided by the 
invention. 
While the best mode for carrying out the invention has been described in 
detail, those familiar with the art to which this invention relates will 
recognize various alternative embodiments for practicing the invention as 
defined by the following claims.