Conveyors: power-driven – Conveyor section – Endless conveyor
Reexamination Certificate
1998-04-23
2001-01-09
Bidwell, James R. (Department: 3651)
Conveyors: power-driven
Conveyor section
Endless conveyor
C198S860100
Reexamination Certificate
active
06170645
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a conveyor system, such as a conveyor belt system. The present invention is more particularly directed to a conveyor system with interchangeable bed modules and pulley sleeves.
BACKGROUND OF THE INVENTION
Conveyor belt systems are widely used to transport objects in various industrial, assembly and automation applications. For transporting relatively small objects, relatively small conveyor belt systems are used with dimensions on the order of several feet in the longitudinal (direction of conveyance) direction and two inches to several feet in the transverse direction.
A conventional conveyor belt system, shown in
FIG. 1
, includes a drive pulley
104
, a tail pulley
108
, a frame
106
, a bed
106
A and a conveyor belt
102
. The belt
102
is looped around the pulleys
104
,
108
and over the bed
106
A. The drive pulley
104
is driven to rotate in the direction R
1
by a driver (not shown) such as a conventional drive motor.
The rotating drive pulley
104
maintains rolling contact with the belt
102
, thereby driving the belt
102
to rotate in the direction R
2
around the frame
106
. The tail pulley
108
also maintains rolling contact with the belt
102
, and freely rotates in the direction R
3
in response to the rotation of belt
102
. In this way, the tail pulley
108
supports rotating belt
102
without significantly impeding its rotation.
Frame
106
supports the pulleys
104
,
108
so that they are appropriately spaced apart from each other. Frame
106
also includes an integral bed
106
A. The integral bed
106
A is generally constructed as a unitary piece with the rest of the, frame
106
, or is permanently fixed thereto.
The bed
106
A provides a relatively slick and relatively continuous surface to support the underside of the belt
102
. Because of the fairly continuous surface provided by the bed
106
A, objects placed on the top of the belt
102
will be substantially continuously supported by the underlying bed
106
A, thereby minimizing shear stress and strain on the belt
102
itself. Because the bed
106
A is relatively slick, the belt
102
will slide over the bed
106
A with relatively low friction, even when objects on top of the belt
102
weigh the belt
102
down onto the bed
106
A, thereby minimizing longitudinal forces in the belt
102
.
As shown in
FIG. 1
, the bed surface defines a line, herein called the bed height BH. The belt
102
travels over and along this bed height BH line. The tops of the drive pulley
104
and the tail pulley
108
are both co-linear with the bed height BH line. In other words the pulleys
104
,
108
have an outer radius of H
1
so that the tops of these pulleys reach the level of the bed. Thus, the height of the pulleys match the height of the bed.
This matching of pulley and bed heights is important for several reasons. First, if there is a disparity in heights between the pulley and the bed, then an object being transported on top of the belt
102
may be jolted as it travels over a portion of the system
100
where there is a transition in height between the bed
106
A and a pulley
104
or
108
. This kind of jolting caused by mismatched heights may be especially troublesome in application where two conveyor systems are placed end to end to effect a longer conveyor run.
Second, if bed
106
A is significantly lower than the height of the pulleys, then the belt
102
will not be supported by the bed
106
A. When heavy objects are placed on the belt
102
, the belt
102
may be (temporarily or permanently) deformed by objects pushing the unsupported belt
102
down to the level of the bed
106
A.
Third, if the bed
106
A is significantly higher than the pulleys
104
,
108
, then the belt
102
will be pulled tightly around the transverse edges of the bed. This increases wear on the belt
102
.
Fourth, if the bed
106
A is significantly higher than the pulleys
104
,
108
, then the contact area between the belt
102
and the drive pulley
104
will be reduced, thereby decreasing the load which the drive pulley
104
can effectively drive the belt
102
to convey. For at least these reasons, matching pulley and bed height is an important precept in the design of most conveyor belt systems.
In the embodiment of
FIG. 1
, the heights of the pulleys
104
,
108
and the bed
106
A are exactly the same (all heights are at the BH line). However, depending on factors such as the material of the belt, optimal performance may involve making the height of the bed either slightly higher or slightly lower than the height of the pulleys. In other words, the height of the pulleys may be slightly displaced from the bed line BH.
For example, if a conveyor belt is made of a stiff material, then the belt may not follow the outer surface of each pulley for a full 180° (even with an appropriate degree of tightening), and the belt may therefore come off the pulley at an angle relative to the tangent direction taken at the top of the pulley. This phenomenon is known as cupping. In this case, the frame may optimally be designed so that the bed is a bit higher than the top of the pulley, to appropriately account for the angle at which the belt comes off of the pulleys.
As used herein, the pulleys and bed are “matched” in height when the height of the pulleys and the height of the bed are close enough to each other to provide good performance and a low degree of belt stress, strain and wear, especially in view of the above-described problems caused by wide height disparities. As used herein, the pulleys and bed may be “matched” in height, even if their heights are not exactly the same, whether the slight disparity in heights is a result of design or random variations (such as manufacturing variations).
It is also noted that two pulleys and a bed may be matched in height even if the pulleys have different radii. In order to be matched in height, the top of each pulley should merely be sufficiently close to the height of the bed for optimal performance under the circumstances of the application.
Another embodiment of a conventional conveyor belt system
200
is shown in FIG.
2
. Conveyor belt system
200
includes a belt
202
, a drive pulley
204
, a frame
206
, a tail pulley
208
and a bed
210
. The conveyor belt system
200
is similar to conveyor belt system
100
, except that instead of an integral bed such as
106
A, the bed
210
is connected to frame
206
.
One advantage of such a detachable bed
210
, is that the bed
210
can easily be made from a different material than the frame
206
. For example the frame
206
may be made from metal, while the bed
210
might be made of ultra high molecular weight polymer (herein UHMW), which provides a smooth, slick supporting surface for the belt
202
. However, conveyor system
200
cannot be used without the detachable bed
210
for two reasons explained below.
First, if the system
200
is used without the detachable bed
210
, then the pulley height and the height of the frame
206
(without a bed) will be drastically mismatched. The pulleys
204
,
208
have an outer radius of H
4
and a resulting height of BH′. Likewise, the bed
210
also has a height of BH′. More specifically, as shown in
FIG. 2
, when the detachable bed
210
is in place, the aggregate height of the frame
206
(H
2
) and bed
210
(H
3
) adds up to H
4
, thereby matching the height of the pulleys
204
,
208
at the bed height BH′ line. If the bed
210
is removed, ther the height of the frame H
2
would fall short of the BH′ line defined by the tops of the pulleys
204
,
208
, and the heights would be problematically mismatched.
Second, the frame
206
(without the detachable bed
210
) does not provide a good bed surface for the belt
202
, because it is not continuous.
FIG. 3
shows the frame
206
from its underside. The frame
206
is actually a lattice of several elongated, aluminum members
212
,
214
,
216
,
217
,
218
,
220
,
222
.
More specifically, the frame
206
is assembled from two extruded sid
Bidwell James R.
Dinsmore & Shohl LLP
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