Interface for discharging hopper contents onto feeder

The interface is an apparatus that is attached to the outlet of a hopper to assist and control the discharge of particulate material onto the loading surface of a feeder, such as a moving belt. The interface results in a saving of 50 to 75 percent in the power required to drive the feeder. Three structural innovations contribute to this saving in power. First, a plate that extends vertically and in the direction of movement of the feeder is introduced into the stream of material within the interface to reduce downward pressure on the loading surface of the feeder. Second, the lower edge of the strike-off plate is arched upwardly, which reduces the power required for maintaining the shearing action. Third, the interface is provided with vertical skirts that prevent lateral spreading of the material so that a narrower feeder can be used.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is in the field of particulate material handling, and 
specifically relates an apparatus that is attached to the outlet of a 
hopper to assist and control the discharge of particulate material onto 
the loading surface of a feeder, such as a moving belt, so that an 
uninterrupted controlled flow will be obtained with a considerable 
reduction in the power required to drive the feeder, compared to the prior 
art. 
2. The Prior Art 
In a hypothetical and impractical situation, no interface would be used. 
The particulate material would stream from the outlet of the hopper, would 
become airborne, and would land on a moving belt which would transport it 
to a truck, a railroad car, or a pile. Such a technique would require an 
oversized feeder which would be only lightly loaded and hence operating at 
very low efficiency. Also, there would be no control over the discharge 
rate. 
To improve the efficiency and controllability of the system, workers in the 
art discovered that it was advantageous to provide an interface between 
the outlet of the hopper and the feeder. Such an interface could serve to 
control the lateral dispersion of the particulate material and to reduce 
the effect of cross winds. With reduced lateral dispersion, narrower 
feeders were used and these were more heavily loaded and hence more 
efficient. 
Normally when an interface is used, the body of particulate material 
extends without interruption from inside the hopper, downward through the 
hopper outlet and through the interface to the loading surface of the 
feeder. 
Since the particles within the hopper outlet have no velocity in the 
direction of travel of the feeder, while the particles bearing against the 
loading surface of the feeder necessarily have a moderate velocity, it 
follows that the feeder produces a shearing effect in the body of 
particulate material. In fact, typically, the power supplied to the feeder 
is largely used to overcome the shearing resistance, and a smaller 
component of the power is used to overcome friction and to accelerate the 
particulate material. The frictional component is related to the downward 
pressure on the feeder loading surface. 
Until the present invention, it was believed that little could be done to 
reduce the shear component or the frictional component of the power 
required to operate the feeder. Progress in reducing the required feeder 
power was at a standstill until, in the mind of the present inventor, 
there arose some remarkable insights that will now be described. 
SUMMARY OF THE INVENTION 
The present inventor attacked the problem of how to reduce the power 
required to operate the feeder in three distinct ways. First, he 
discovered how to reduce the vertical pressure on the feeder loading 
surface, thereby reducing the frictional component. Secondly, he 
discovered how to reduce the power required to shear the stream of 
particulate material. Thirdly, he discovered how to enable the use of 
narrower-width feeders. Each of these three improvements is derived from 
structural innovations in the interface, as will now be described. 
The knowledgeable reader is no doubt familiar with the phenomenon of 
arching that occurs under certain circumstances in hoppers, wherein the 
material forms a bridge at the outlet preventing further discharge. 
Clearly the mechanics of particulate flow are strikingly different from 
those of liquid flow. Keeping in mind this distinction, workers in the 
field will recall that the downward pressure at the outlet of a hopper is 
proportional to the width of the outlet. When an interface is used, this 
pressure is related to the downward pressure on the loading surface of the 
feeder. 
The insight of the present inventor was that the downward pressure on the 
loading surface of the feeder can be reduced by introducing a plate that 
extends vertically and in the direction of movement of the feeder in the 
stream of material directly below the outlet of the hopper, thereby, in 
effect producing two outlets side by side, each having only half of the 
total width and hence exerting only half as much downward pressure. This 
reduces the downward pressure on the loading surface of the feeder and 
results in reduced friction and a corresponding lower power requirement. 
In the following Description this plate is referred to as the "vertical 
center plate." 
Next, the present inventor noted that in any hopper undergoing discharge, 
there must be a preferred imaginary three-dimensional surface on which the 
shear force imparted by the belt is imposed on the flowing mass of solids. 
Generally, this imaginary three-dimensional surface has a convex upward 
curvature that results from the interaction between the motion of the 
loading surface of the feeder and the friction exerted by the converging 
side plates and the vertical center plate. 
It was an insight of the present inventor that the shearing forces could be 
greatly reduced if the shearing action could be made to take place along 
this preferred imaginary three-dimensional surface. It became clear that 
prior art interfaces required unnecessarily high amounts of power to 
continually shear the material because in the prior art designs the 
strike-off plate had a straight horizontal lower edge which did not even 
come close to approximating the preferred three-dimensional imaginary 
surface. The present inventor acted upon this insight by changing the 
shape of the lower edge of the strike-off plate from a straight horizontal 
lower edge to an upwardly arched lower edge. Because this more closely 
approximates the shape of the preferred surface, the power required to 
produce the shearing action is dramatically reduced. 
The present inventor further reduced the power required to operate the 
feeder by reducing the width of the loading surface of the feeder. This he 
accomplished by providing the interface with vertical skirts on either 
side, which limited the tendency of the material to spread laterally 
across the loading surface of the feeder. As a result, narrower feeders 
that require less power can be used. In the following Description these 
skirts are referred to as "vertical side plates." 
The present inventor combined the above described improvements into a 
single practical interface in which the power required to operate the 
feeder is reduced in all three ways described above. 
Last, but not least, the present inventor discovered that the discharge 
rate of the hopper could be controlled advantageously by simply raising or 
lowering the height of the strike-off plates above the loading surface of 
the feeder. 
As a result of the above improvements, the size of the feeder can be 
reduced approximately 50 percent and the power required is reduced 
typically between 50 percent and 75 percent when the interface of the 
present invention is used. 
The novel features which are believed to be characteristic of the new 
interface, together with further objects and advantages thereof, will be 
better understood from the following description considered in connection 
with the accompanying drawings in which two preferred embodiments of the 
invention are illustrated by way of example. It is to be expressly 
understood, however, that the drawings are for the purpose of illustration 
and description only and are not intended as a definition of the limits of 
the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 is a side elevational medial cross sectional view showing an 
interface of the prior art interposed between a hopper 12 and a feeder 14. 
Typically, the hopper 12 has the form of a hollow inverted 4-sided pyramid 
truncated by a horizontal plane so that the outlet 16 of the hopper is a 
rectangular slot lying in the truncating plane. Because it is rectangular, 
the outlet of the hopper 12 includes two spaced parallel longer edges and 
two spaced parallel shorter edges. 
Typically, the feeder includes a belt 18 having a loading surface 20 on 
which the discharged material lies while it is transported by the belt in 
the direction indicated by the arrow in FIG. 1. Ordinarily this direction 
is parallel to the longer edges of the outlet of the hopper. 
In the interest of clarity, the upper edge 22 of the interface is shown 
slightly separated from the lower edge 24 of the hopper in FIG. 1, but in 
actual use, the upper edge 22 of the interface is attached to the lower 
edge 24 of the hopper. FIG. 1 is a cross sectional view taken at a 
vertical plane that passes through the centerline of the belt 18. 
The prior art interface of FIG. 1 consists of four plates, which are: two 
converging side plates 26 (visible in FIG. 1 ) and 28 (best seen in FIG. 
2), a laterally-extending vertical plate 30, and a strike-off plate 32. 
The converging side plates 26 and 28 slope downwardly and inwardly as if 
they were swung about the lower edge 24 of the hopper. The converging side 
plates are truncated by an imaginary plane 34 that is inclined in the 
direction of travel of the loading surface 20, and that is seen edge-on in 
FIG. 1. The inclined imaginary plane 34 intersects the converging side 
plates 26 and 28 in two edges 36 and 38 that are the lower edges of the 
converging side plates. These edges 36 and 38 not only are inclined in the 
direction of travel of the loading surface 20, but also diverge laterally 
in the direction of travel of the loading surface, as best seen in FIG. 2. 
The four plates that make up the prior art interface are also visible in 
FIG. 2, and they are among the components of the present invention. The 
geometric relationship of these four plates must be clearly understood if 
one is to understand the present invention. 
In addition to showing the four plates of the prior art interface, FIG. 2 
shows the vertical side plates 40 and 42 that are not found in the prior 
art interfaces and that are unique to the present invention. The vertical 
side plates 40 and 42 lie in vertical planes that pass through the lower 
edges 36 and 38 of the converging side plates 26 and 28 respectively. 
Accordingly, the average lateral distance between the vertical side plates 
40 and 42 is equal to the average lateral distance between the lower edges 
36 and 38 of the converging side plates 26 and 28, respectively. The 
vertical side plates 40 and 42 extend downwardly to horizontal lower edges 
44 and 46 that are adjacent to but spaced from and parallel to the loading 
surface 20 of the feeder. 
The vertical side plates 40 and 42 are unique to the present invention, but 
the present invention also includes other structures, shown in FIGS. 3, 4 
and 5. In particular, the present invention includes the vertical center 
plate 48 which is inclined upwardly in the direction of travel of the 
loading surface of the belt and which is located mid-way between the 
converging side plates 26 and 28. The vertical center plate 48 has a lower 
edge 50 that lies in the imaginary plane 34 and has an upper edge 52 that 
is parallel to the lower edge. In a preferred embodiment of the present 
invention, the height of a vertical cross section through the vertical 
center plate 48 is approximately equal to W/6, where W is the average 
lateral distance between the vertical side plates 40 and 42. 
It is generally known in the art that the downward pressure at the outlet 
of a converging hopper is proportional to the width of the outlet. The 
vertical center plate 48 divides the width of the outlet in half, and 
thereby also reduces the downward pressure to half of what it would be if 
the vertical center plate 48 were not present. 
It is a reasonable concern that the downward pressure might be reduced too 
much, in which case flow might not occur. Fortunately, it can be shown 
mathematically that flow will always occur so long as the height of a 
vertical cross section through the vertical center plate 48 does not 
exceed W/6, as best seen in FIG. 5, where W is the average lateral 
distance between the vertical side plates 40 and 42. Lowering the outlet 
pressure reduces the force required to shear the particulate material from 
the hopper, thereby reducing drag on the loading surface 20, and also 
reduces the downward force on the loading surface 20. Both of these 
reductions act to reduce the power required to drive the feeder. 
The vertical side plates 40 and 42 serve to prevent the particulate 
material from spilling laterally over the side of the belt, thereby 
reducing the required belt width. This also reduces the power required to 
operate the feeder. 
As best seen in FIG. 3, the strike-off plate 54 of the present invention is 
connected to the vertical center plate 48. In the first preferred 
embodiment shown in FIGS. 3, 4 and 5, the strike-off plate 54 extends 
laterally on both sides from the vertical center plate to lateral edges 
that are attached to the converging side plates 26 and 28. 
Unlike the strike-off plate 32 of the prior art, shown in FIG. 1, in 
accordance with the present invention, the lower edge 56 of the strike-off 
plate 54 is arched upwardly between each lateral edge and the vertical 
center plate 48. The arched shape of the lower edge 56 more closely 
conforms to the preferred imaginary three-dimensional surface on which the 
shear force imparted by the belt is imposed on the flowing mass of a 
particulate material thereby facilitating the shearing action. Also, the 
arched lower edge 56 of the strike-off plate 54 relieves the tendency of 
the material to build up in front of the strike-off plate, where the 
build-up would oppose the shearing action. Thus, the upwardly arched lower 
edge 56 further reduces the power required to operate the feeder. 
In the first preferred embodiment shown in FIG. 3, the lower edge of the 
strike-off plate is arched upwardly an amount approximately equal to W/8, 
where W is the average lateral distance between the vertical side plates 
40 and 42. 
In the first preferred embodiment of FIG. 3, the vertical center plate 48 
is connected to the converging side plates 26 and 28 by one or more 
lateral support plates, of which the lateral support plates 58 and 60 are 
typical. The lower edges 62 and 64 respectively of the lateral support 
plates 58 and 60 are arched upward an amount approximately equal to W/8, 
where W is the average lateral distance between the vertical side plates 
40 and 42. 
FIGS. 6, 7 and 8 show a second preferred embodiment of the present 
invention. The second preferred embodiment differs from the first 
preferred embodiment of FIGS. 3, 4 and 5 in that a center converging 
member 66 is used in place of the vertical center plate 48; the strike-off 
plate 68 and the lateral plates (of which the lateral plate 70 is typical) 
are attached to the center converging member 66, but the strike-off plate 
68 and the lateral plate 70 extend to lateral edges 76 and 78 respectively 
that are adjacent to, but spaced from the vertical side plates 40 and 42. 
Further, in the second preferred embodiment of FIGS. 6, 7 and 8, the 
center converging member 66 is pivotally connected by the pin 88 of FIG. 7 
to the laterally-extending vertical plate 30 to permit limited pivotal 
motion of the center converging member 66 in a vertical plane. A metal 
strap 90 is attached to and extends upward from the end of the center 
converging member 66 nearest the strike-off plate 68. The strap 90 
includes a number of vertically-spaced holes, of which the hole 92 is 
typical. The plate 80 includes a laterally-centered hole. A bolt 94 passed 
through the hole in the plate 80 and through one of the holes in the strap 
90 secures the center converging member 66 at a selected inclination with 
respect to the belt loading surface 20. The purpose of being able to pivot 
the center converging member 66 in a vertical plane is to permit 
alteration of the rate at which the particulate material is removed from 
the hopper. 
As in the first preferred embodiment, the lower edge 72 of the strike-off 
plate 68 is arched upwardly between the lateral edge 76 and the center 
converging member 66. In the preferred embodiment, the amount of this 
arching is approximately equal to W/8, where W is the average lateral 
distance between the vertical side plates 40 and 42. 
Likewise, the lower edge 74 of the lateral plate 70 is arched upwardly 
between the lateral edge 78 and the center converging member 66. In the 
preferred embodiment, the amount of arching is approximately equal to W/8 
where W is the average lateral distance between the vertical side plates 
40 and 42. 
As best seen in FIG. 8, the height of a vertical cross section through the 
center converging member 66 is approximately equal to W/6, where W is the 
average lateral distance between the vertical side plates 40 and 42. 
When the angle of inclination of the center converging member 66 is 
adjusted to smaller angles, the center converging member 66 lies between 
the vertical side plates 40 and 42. If the center converging member 66 
were a simple vertical plate as in the first preferred embodiment, there 
would be no downward convergence between the center member and the 
vertical side members, and this would not reduce the pressure on the 
particulate material at the shear interface, since the material would be 
confined between non-converging surfaces. Therefore, in order to provide a 
downwardly-converging-surface situation for the particulate material, in 
the second preferred embodiment, the sides 82 and 84 of the center 
converging member 66 must converge downwardly toward the vertical side 
plates 40 and 42 respectively. 
The adjustability of the second preferred embodiment allows a very large 
feed depth adjustment with only minor negative effects. This feed depth 
adjustment permits the feed rate to be varied without having to use a 
variable speed drive on the feeder. 
When the teachings of the present invention have been applied to practical 
situations, it has been found that feeders of smaller size can be used. 
Generally, the feeder can be reduced 25 percent to 50 percent in width. 
Also, it has been found that the teachings of the present invention permit 
the power required to operate the feeder to be in the range of 25 percent 
to 50 percent of the power required in prior art designs. In addition to 
this noteworthy reduction in the power requirement, the interface of the 
present invention results in less feeder pressure and consequently less 
wear, lower feeder loads, less support structure, lower starting torque, 
and longer feeder life. 
It has also been found in practice that the design of the present invention 
can be used, not only for belt-type feeders, but can also be used with 
apron feeders, screw feeders, and drag chain feeders. 
Thus, there have been described two embodiments of an interface used in 
controlling the flow of particulate materials from a hopper to a feeder. 
Both embodiments result in a significant reduction of the power required 
to drive the feeder, and permit the use of smaller sized feeders. 
The foregoing detailed description is illustrative of several embodiments 
of the invention, and it is to be understood that additional embodiments 
thereof will be obvious to those skilled in the art. The embodiments 
described herein together with those additional embodiments are considered 
to be within the scope of the invention.