Conveyor roller

A roller of the slip-type is comprised of a sleeve with an insert press fitted therein. The other end of the insert houses a bearing assembly, the inner and outer race of which are respectively keyed to a stationary support axle and to the insert. A driven element is loosely mounted about the insert but is pressed against the insert by a belt under tension which also engages one or more driven elements of adjacent rollers. The driven element is driven by an endless driving devices. When a counter-torque is experienced by the roller due to an impediment which is greater than the driving torque, slippage will occur between the driven element and the insert, and the article being carried by the conveyor will come to rest.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
This invention relates to a slip roller for use in powered roller conveyors 
and more particularly to an improved slip roller which provides an 
accumulating function to a powered roller conveyor assembly. 
(2) Description of the Prior Art 
There are a number of slip type rollers which are described in the patent 
literature. Examples may be found in U.S. Pat. Nos. 4,006,815, 4,096,942 
and 2,976,981. Additionally, co-pending application Ser. No. 912,676, 
assigned to the same assignee as the instant invention, describes a 
slip-type roller. U.S. Pat. Nos. 2,976,981 and 4,006,815 and application 
Ser. No. 912,676 have slipping characteristics which occur when the 
"counter-torque" (caused by an impediment to further movement of articles 
carried by the conveyor) becomes greater than the driving torque of the 
roller. Actual slippage occurs between the roller sleeve and a hub member 
contacting the sleeve. This prevents damage to the articles due to the 
pressure which otherwise would result from the driving torque. A 
disadvantage to this type of slip-roller assembly may occur with heavy 
loads. The frictional force between sleeve and hub becomes greater with 
increasing loads, thus increasing the driving torque. Slippage will occur 
with heavy loads only with greater counter-torque. This may be a serious 
problem, particularly with fragile but heavy articles since the pressures 
on the articles caused by their weight may be directly responsible for 
damage. 
A variation of the slip-roller is described in U.S. Pat. No. 4,096,942. The 
drive which is an endless drive means engages a slip collar about a 
roller. The roller itself is supported for rotation by means independent 
of the slip collar. Thus, the slip collar is not affected by increasing 
loads and the driving torque remains essentially constant. There is, 
however, relative movement between the roller sleeve and slip collar which 
inevitably results in some wear to the sleeve. 
It is, therefore, a paramount object of the present invention to provide 
for an improved slip-type roller which provides a constant driving torque 
to articles being carried by a powered roller conveyor assembly. 
It is another important object of the present invention to provide a 
slip-type function to a roller without concurrent wear to the roller 
itself. 
Still another important object of the present invention is to provide an 
improved slip-type roller which permits a conveyor assembly to have zones 
for accumulating articles. 
SUMMARY OF THE INVENTION 
Each roller of the improved apparatus is supported at one end in a manner 
similar to conventional rollers of the prior art. That is, conventional 
rollers are in the form of a cylindrical sleeve. A hub bearing assembly is 
housed within the sleeve and caps one end thereof, providing rotational 
support at that point to the sleeve about a stationary axle. Disposed at 
the other end are various elements which collectively provide an 
accumulating function to the conveyor. First, a cylindrical shaped insert 
has a portion press fitted within the sleeve. A second portion of the 
insert extends away from the sleeve and encloses a bearing assembly, the 
outer race of which is in a press fit relationship with the internal 
diameter. The inner race of the bearing assembly is keyed to be supported 
by an axle extending between a pair of side rails. The sleeve, insert, and 
outer race of the bearing assembly all rotate together. Mounted on the 
second portion of each insert is a driven element engaging an endless 
driving means. The driven element has an inner diameter slightly larger 
than the outer diameter of the second portion. Additionally, a plurality 
of belts, each under a predetermined tension, engage selected pairs of 
driven elements at a postion adjacent the positions of engagement of said 
driving means. The belts, being under tension, produce reactionary or 
normal forces between the surfaces of the driven elements and insets. 
In ordinary situations, the rollers of the assembly carry various loads 
along the surface of the assembly. Each roller is rotated by an endless 
driving means engaging each driven element. The frictional or driving 
force between surfaces of each element and its insert caused by the 
tension belt engaging paired driven elements is sufficient to transmit 
rotation to the insert, bearing assembly, and sleeve. As the various loads 
encounter one another at a point on the assembly, stoppage occurs and line 
pressure begins to build, causing a countervailing torque to act upon each 
roller. When the countervailing torque reaches a level equal to or greater 
than the torque of the roller imposed by the driving force on the rollers, 
i.e. the driving torque, the paired rollers will cease to rotate. This 
occurs irrespective of the total weight of the load. In other words, the 
frictional force between the driven element and insert is independent of 
the load on the rollers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The roller conveyor apparatus of FIG. 1 is comprised of three major parts: 
a frame structure consisting of two parallel rails 10, 12; a plurality of 
rollers 14 mounted on axles 16 supported by rails 10, 12; and a roller 
drive which is here illustrated as sprockets 20 and chain 18. It should be 
understood that other drives may be used also such as pulleys and v-shaped 
drive belts. The power may be supplied by any motor (not shown) typically 
used to drive chain or other endless driving devices. 
Rollers 14 and axles 16 are generally positioned horizontally between rails 
10, 12 with rollers 14 providing a conveyig surface to articles placed on 
the rollers. To prevent materials from contacting sprockets 20 and chain 
18, both are positioned within a safety enclosure 22. Enclosure 22 serves 
both as a safety guard and lateral guide for articles being moved along 
the conveyor. As graphically illustrated in FIG. 2 by conventional drawing 
symbol 1, rails 10 and 12 can be mounted on any conventinal support for 
roller conveyor apparatus. 
Each roller 14 is an elongated cylinder, usually made of metal sheet 
material. As seen in FIG. 2, the right end of roller 14 houses a typical 
bearing assembly 24 mounted on axle 16. The inner race 26 of such as 
assembly is typically secured or keyed to axle 16 while the outer race is 
keyed to roller 14. Axle 16 which may be of hexagonal cross-section is 
held stationary in this instance by rails 10, 12. Thus, inner race 26 of 
the assembly 24 is also held stationary while outer race 28 and roller 14 
are free to rotate about axle 16. 
Viewing the left end of roller 14, an insert 30, in general cylindrical 
form, has a portion 32 with a diameter slightly greater than the internal 
diameter of roller 14 press fitted into roller 14. Extension 34 of insert 
30 with a reduced diameter extends about the bearing assembly 24 and is 
keyed to outer race 28. The keying may be accomplished in a number of 
ways, but in this instance is obtained through a press fit relationship 
between the inner diameter of extension 34 and outer race 28. Inner race 
26 is keyed to axles 16 by virtue of the hexagonal shape of axles 16. 
Sprocket 20 is journaled about the extended portion and is shown being 
engaged by chain 18 along teeth 20a. A belt 42 is shown engaging the 
extended barrel 44 of sprocket 20 near the base of teeth 20a. 
As best seen in the side sectional view of FIG. 3, depicting two adjacent 
slip sprocket assemblies, the inner diameter of barrels 44 are slightly 
larger than the outer diameter of insert extensions 34. Belt 42 engages 
both barrels and is under a predetermined tension which can be set through 
appropriate selection of a belt or which can be adjusted through up or 
down movement of adjustable snub roller 46. 
Belt 42, being under tension, pulls adjacent sprockets 20 toward one 
another as depicted by the gaps appearing between the inner surfaces of 
barrel 44 and outer surface of insert extension 34. The dimensions of the 
gap are exaggerated for purposes of explanation. 
It should be noted that the force exerted by sprocket 20 on extension 34 is 
independent of the load on roller 14. It is, however, directly 
proportional to the tensional force exerted by belt 42. Thus, the greater 
the tensional force, the greater the force exerted by sprocket 20 on 
extension 34. Under normal conditions, the rotative force of sprocket 20 
being pressed by belt 42 against extension 34 is sufficient to transmit 
the continuous rotation of sprocket 20 to roller 14. 
When the articles carried by rollers 14 encounter resistance to forward 
movement, it is desirable to stop the rotation of the rollers to prevent 
damaging the articles. The line force exerted on the stopped lead articles 
from articles collecting toward the rear rapidly mounts unless the 
conveyor assembly is of the accumulator type such as the invention 
described herein. When the resistance to the forward movement of the 
articles reaches a predetermined level, rollers 14 supporting the article 
will cease to rotate. This occurs as the counter-torque on the surface of 
roller 14 caused by the increasing resistance against forward motion 
equals the driving torque generated by sprocket 20. Since the force needed 
to turn extension 34 is now greater than .mu.T where .mu. is the 
coefficient of sliding friction between sprocket 20 and extension 34 and T 
is the force exerted by belt 42, sprocket 20 slides across the surface of 
extension 34. Roller 14 then ceaes to rotate. 
The importance of the independence of the sprocket force of load now 
becomes apparent. Increasing the weight of the articles, i.e., the load as 
would be experienced in ordinary material handling situations has little 
affect since the rolling coefficient of friction in the bearing assembly 
is so small. Sprocket 20 easily rotates roller 14, outer race 28, and 
extension 34. Slippage then occurs only in response to the resistance 
encountered by the movement of articles. 
The ability to vary the tension of belt 42 is extremely important since it 
may be desirable to accomodate various levels of load resistance. For 
fragile articles, the tension of belts 42 would ordinarily be less so that 
slippage occurs for small counter-torques. The converse would be true 
where gentle line pressure is not as important. Different tension settings 
for various regions of the conveyor assembly may also be desirable in some 
situations. For example, to offset gravitatinal counter-torques generated 
by moving articles up or down an incline, one needs to change the tension 
of the belt in such a region. 
The present invention is readily adaptable to the automatic zoning of 
conveyor assemblies. Automatic zoning is extremely advantageous in that 
line pressure build up is avoided almost completely. Most slip drive 
arrangements do not eliminate but merely minimize line pressure. For 
example, in the instant invenion, line pressure exerted on an article 
stopped due to an obstacle is proportional to the sum of the forces 
exerted by all upstream articles pressing against the stopped article. 
Even where the individual force is small, the total can be large. 
Automatic zoning, however, permits reduction of the upstream forces 
whenever an article stops or articles become a certain minimum distance 
apart. 
The schematic of FIG. 4 illustrates such an automatic zoning device. For 
descriptive purposes, only two zones depicted as A and B, respectively, 
are shown. All elements are duplicated in each zone for clarity and denote 
their proper zones by "a" or "b" following the character numbers. An 
actual assembly would have a plurality of zones in which a blocking event 
at a downstream zone would cause the rollers of upstream zones perhaps 
several zones away to cease rotation. For the sake of clarity, however, 
FIG. 4 depicts an event in zone A which affects zone B. 
Photoelectric cell 48a is positioned above rollers 14 for detecting the 
presence of articles 84a such as shown in dashed lines. Snubbing rollers 
46a are shown engaging belt 42a and applyig tension thereto. Positioned 
beneath rollers 46a is a channel 50a enclosing an inflatable tube 52a 
having an inlet 54a, which is connected to a source of fluid pressure 56a 
via electromechanical valve 58a. Channel 50a is provied with a plurality 
of cylindrical openings 60a which receive piston member 62a which engages 
a plate 64a resting on inflatable tube 52a. Piston member 62a has 
bifurcated upper portions which support axles of the snub rollers 46a. 
In operation, if the path of light to photoelectric cell 48a is blocked by 
an article 84a as shown in dashed lines in FIG. 4, a signal generated by 
cell 48a is sent to AND gate 66a and time delay relay 68b. Relay 68b may 
have a delay time of any predetermined amount but is generally set for a 
period of time sufficient in ordinary circumstances for an article to 
completely pass through the light path focussed upon cell 48a. When set, 
relay 68b provides a signal directly to AND gate 66b. If at the same time 
another article is also blocking cell 48b, a second signal goes to AND 
gate 66b which signals valve 58b to open and vent the pressurized fluid to 
the atmosphere. Tube 52b deflates, lowering snub rollers 46b and thereby 
permitting belt 42b to slide freely over sprocket extension 44. Any 
articles being carried by rollers 14a in zone B would immediately stop, 
preventing line pressure buildup. It should be noted that valve 58b 
operates only when both cells 48a and 48b are blocked. When only cell 48a 
is blocked, the rollers in zone B will continue to rotate. Whether this 
function is performed, however, depends on the need of the operator. 
Once the article clears cell 48a, both relay 68b and valve 58b are rest. 
The latter in its reset mode permits fluid under pressure to flow back 
into tube 52b, forcing snub rollers 46b again to contact belt 42b. Rollers 
14b in zone B again being coupled to driving chain 18 start to rotate and 
the belt moves. 
It should be understood that the sensing means embodied herein as cell 48a 
could be employed to control rollers of zones several groups removed from 
zone A if desired. Similarly, various other mechanical and 
electro-mechanical means could be employed to vary the tension of belts 
42. 
The foregoing is believed sufficient for those skilled in the art to 
understand the invention. Modifications and variations will be readily 
apparent in light of this disclosure. The actual inventive scope, however, 
is defined by the following claims.