FIELD OF THE INVENTION
This invention relates to Skirtboards and sealing system used on belt conveyors
in bulk material carrying industries, to arrest spillages in the form of Skirtboard
leakage and air suspended fugitive particles in the air during material loading on
the conveyor. This invention suggests a change in the design of the mounting
arrangement for rubber pad attached to the Skirtboard. More particularly, the
invention relates to an improved process of mounting Skirtboard rubber pads on
a conveyor belt carrying bulk materials. The present invention further relates to
an improved belt conveyor assembly with automatically adjustable rubber pads
to maintain desired clearance between a Skirtboard and the belt conveyor
assembly to present spillage of materials transported along the belt conveyor.
BACKGROUND OF THE INVENTION
The technique used for providing necessary barrier against loss of material from
conveyor belts is the provision of Skirtboards on each side of the belt, which is
attached to cover housing and extends beyond length of the housing called
chute. Bottom edges of both sides of the Skirtboard having rubberpads directly
contacting upper surface of the moving belt near outer edges of the belt, thus
providing a barrier against spillage of material over the edges of the belt. The
rubberpad attached with the Skirtboard should not be harder than the belt
otherwise it will abrade the belt. But the interaction of the belt rubbing against
the edge of the belt results in wear and erosion of the rubberpad edge attached
to the Skirtboard or chute mother plate, which creates a gap through which
spillage of material can happen. For adjustment of this gap it requires frequent
manual intervention and equipment downtime, which is costly for process
industries.

The present inventors noted that prior art fail to address the problems discussed
above, and this produces little guidance toward solving those problems. US
Patent 4,204,595 filed on May 27, 1980; discloses a method for adjustable
conveyor belt Skirtboard. It is a manual method for adjustment. A clamping bar
is provided which extend along the Skirtboard above the bottom edge of the
cover housing which is attached to several clamping means as shown in figure 1.
The clamping effect is obtained by force applied by the clamping means. A
flexible member as shown in figure 1 is turned by means of a handle or simply
be grasped and turned by hand or by wrench or pliers. When it is desired to
loosen the Skirtboard to adjust it downward into contact with belt, or to remove
the section completely, each clamping means is loosened manually in each case.
This technique has limitation of requiring human intervention and manual
surveillance for gap adjustment which is turn increases the maintenance and
requires equipment downtime.
Now, in each adjustment of the individual Skirtboard the clamp has to be
manually loosened and then the level of the rubberpad is adjusted. This is a very
tedious job and it requires constant surveillance so as to find out where the gap
exists so as to adjust the gap. Accordingly, the prior art need for continuous
maintenance which being impossible in every case, spillage from the conveyor
systems occurs in the form of Skirtboard leakage.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved belt conveyor
assembly with automatically adjustable rubber pads to maintain desired
clearance between a Skirtboard rubberpads and the belt conveyor assembly to
present spillage of materials transported along the belt conveyor.

Another object of the invention is to propose an improved process of mounting
Skirtboard rubber pads on a conveyor belt carrying bulk materials.
SUMMARY OF THE INVENTION
For avoiding human interface and huge downtime for maintenance of the
Skirtboard and adjustment of rubber pad gap is necessary. The present invention
teaches that the rubberpad are attached to the belt cover housing in a manner
to automatically permit the Skirtboard to be adjusted downward toward the belt,
so that a fresh bottom edge of the Skirtboard comes into contact with the belt.
Accordingly, a positive displacement reaction force of the compressed spring and
the clearance between the belt and the Skirtboard rubberpad even can be
moderated.
Thus, the present invention avoids the problems and difficulties present in prior
art techniques for example, providing a barrier for the spillage/loss of material
through the gap/clearance which is created above a conveyor belt and the
Skirtboard, because a precise manual adjustment of the clearance is not possible
according to known techniques. According to the invention, the Skirtboard
(which is continuous) is first clamped on the housing. Now at regular intervals of
say 45 cm, a slot is provided on it. The slot contains a compressed spring with
typical spring stiffness coefficient of 400 N/m. The spring is compressed by the
bolt of the rubberpad which is mounted in between the housing and the
Skirtboard such that no gap exists in between. The bolt of the mounted
rubberpad rests on the serrated clamps (equal in number in each of the slot).
These serrated clamps work like a claw. These are interlined and their retraction

is made synchronized. The gap stipulated to be maintained between the
rubberpad and the belt varies depending on the grit size of the material being
carried. In most cases when zero gap is required, (as in the case of most of the
materials) all the clamps are retracted inside. Then the bolt gets the reaction
force from the belt itself. If the spring is compressed by 5 cm then the maximum
distance the rubber pad automatically moves downwards is 5 cm. That is when
the bottom layer of the rubberpad wears, then the compressed spring push the
bolt interalia the rubberpad. downwards till the total gap is covered, After
wearing the bottom layer of rubberpad by 5 cm (as in this case), using a lever,
the height can be manually adjusted by loosening of the lever or the rubberpad
can be replaced.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
Figure 1 Shows a prior art arrangement for matching a clearance between
the Skirtboard and an adjustable conveyor belt.
Figure 2 is a perspective view of a conveyor belt having a cover housing
provided with a continuous Skirtboard and rubber pad interposed
between the housing and the Skirtboard.
Figure 3 an enlarged view showing mounting of individual rubber pad in
slots provided on the continuous length of the Skirtboard at regular
intervals.
FIG .4 it is a front view of the mounting arrangement proposed in this
invention.


DETAILED DESCRIPTION OF THE INVENTION:
Structure: With reference to FIG. 2, a conveyor belt 1 has been shown to move
in one direction. Belt 1 is supported by troughing idlers which may be angled to
each other to provide the desired troughing angle usually 25-45 degrees. A cover
housing 3 has a top portion .4 having vertical walls 5. In between the vertical
walls 5 and a Skirtboard 6, a rubber pad 7 is mounted such that the bottom edge
of the rubber pad (7) is in contact with an upper cover of the belt. The
overlapping surfaces of the wall 5 and the rubberpad (7) and the Skirtboard (6)
are in tight contact with each other to prevent spillage of material.
The Skirtboard section 6 is fixed against the housing wall 5 with at least one
clamping bar 12. Such clamping bars are provided at regular interval to hold the
continuous Skirtboard (6) in position. The clamping bars 12 only exert clamping
force on a top portion of the Skirtboard and thus imparting movement of the
rubberpad 7 mounted in between the vertical wall and the Skirtboard.
Now, the rubberpad is mounted in between the wall 5 and the Skirtboard 6 as
shown in the FIG. 3. The Skirtboard is provided with slots within regular intervals
throughout the length of the continuous Skirtboard 6. This slot may have
typically a length of 3 cm. A spring/coil 9 with required spring stiffness

coefficient is provided in the slot. In the slot, serrated clamps 8 are provided as
shown in the figure. Each one pair of these clamps 8 is retractable inside, The
rubber pad is bolted from behind the Skirtboard using a bolt 10. This bolt rests
on the top of the serrated clamps 8 and the spring/coil is compressed by it.
While installing, the length of the compressed spring (9) in each of the slot is
made sure to be same. Also the number of serrated clamps below the top one on
which the bolt is fixed is also same in each of the slots at the beginning if the
gap is required depending on material being carried. Usually no gap is desired in
between the belt and the rubberpad and in some cases a minute gap is required.
The bolt is constrained to move only in the vertical direction.
Installation: In the mounting process of the rubber pad on the Skirtboard for
the first time following procedures are to be followed. The rubberpad is
permanently fixed with the bolt of exact top flange length equal to the length of
the slot. The width of the top flange will also correspond to the width of the slot.
Thus the bolt will firmly fix the rubberpad to the Skirtboard. Now, the rubberpad
bottom layer rests on the belt deriving the required reaction force to balance the
spring compressive force. Both the rubber pad and along with the Skirtboard is
then mounted on the top vertical wall of the housing using clamping force
exerted on the Skirtboard.
Operation: The compressed spring is constantly exerting force on the bolt of
the rubberpad pushes it downwards towards the belt. After new arrangement of
the new rubberpad and Skirtboards as per this invention, after some time due to
the friction between the belt and the bottom layer of the rubberpad, bottom
layer wears and thus a gap exists.

The compressive force by the spring pushes the bolt down by a distance of the
width of the clamp. The clamp gets retracted inside the sidewalls of the slots
because of the horizontal component of the normal force between the bolt and
the clamp. The reason this happens because the rubberpad bottom layer wear
the bolt directly rests on the clamp and gets the reaction force to balance the
downward spring force by the vertical component of the normal reaction. The
total normal force acting will be perpendicular to the clamp inclined surface as
shown in FIG. 3. So the level of the rubber pad gets lowered by the same
distance and exposing a fresh layer of the rubber pad to the belt. So the gap
gets reduced/nullified and thus spillage occurring is curtailed. Now this procedure
is repeated till the final serrated clamp is retracted. The maximum distance
through which the rubberpad automatically adjust is limited to the compressed
length of the spring. After this the rubberpad can be adjusted in height by
loosening the clamping lever manually (which is rare as the rubberpad has to be
replaced at this point.) The procedure for replacement is as follows. First the
Skirtboard has to be loosened by loosening the clamp 12. So the clamping force
is reduced and thus the rubberpad between the Skirtboard 6 and the housing
may be replaced by slipping it in between. Since these operations are earned out
entirely outside housing cover 3 and they can be carried out in very small time,
the belt can remain in motion thus material flow is unhindered. This obviates the
necessity of shutting down operations connected with the passage of material on
belt 1 and thus saves large time and expense.
Some particular conveyor systems require (especially the ones carrying coarse
material) to maintain a gap of 2 mm in between the rubberpad and the top edge
of the conveyor belt. In this situation also the bottom layer of the rubber pad
gets eroded due to the material grits getting trapped in the clearance and

increasing the wear due to friction. So a fresh layer has to be exposed every time
wearing takes place.
With reference to FIG 2, the typical spacing between the successive clamping
means 12 is about 100 cm. The clamping part 12 is a piece of steel bar 1cm
thick, 4 cm wide and 20 cm long. The total flange length of the bolt will be 3 cm
for the dimensions of the slots discussed in this article. The bolt will be
hexagonal and the vertex to vertex distance be exactly equal to the length of the
slot. The width of the bolt is 3 cm that is equal to that of the slot. This will
constrain the bolt to only move in vertical direction. The typical length of the
interval in between the slots on the Skirtboard is 45 cm. The dimension of the
slot 3 x 15 cm. The width of the Skirtboard is typically 3 cm. The spring of the
material chrome silicon A401 if used then for the outer diameter of 3 cm, coil
diameter of 0.75 cm and free length of 10 cm with 10 active coils should have a
spring constant of 396 N/cm.


The equation governing to find out the spring constant pertinent to a typical application:
K = (G*d^4)/(8*N*D^3)
Where,
G = Shear modulus of the spring material
d = Coil diameter
D = Outer diameter of the coil
N = No. of active coils
K = Stiffness constant of the spring
Now, the force required to slide the rubber pad by the stipulated distance downward will
vary from situation to situation. And if the width of the slot is the constraint then there is
a limit to which the spring diameter can be increased. So in order to get the desired
stiffness constant more than one spring can be used such that the net stiffness constant
Keq will be the addition of individual stiffness constants of the springs attached.
Keq = K1 + K2 + + Kn
Even if using above arrangement the required K is elusive then instead of the spring a
compressed foil can be used which will serve the purpose.
It should be noted that the slot is sealed from outside so there is no question of material
escaping through the slot.
Although my invention has been described with considering two cases
considering a gap is stipulated to be maintained between the conveyor belt top
and rubber pad and no gap has to be present, the modification and variations of
above description may be practiced without digressing from the spirit and scope
of the invention.

WE CLAIM :
1. An improved belt conveyor assembly with automatically adjustable rubber
pads to maintain desired clearance between a Skirtboard and the belt
conveyor assembly to present spillage of materials transported along the
belt conveyor, comprising a conveyor belt supported by a plurality, of
troughing idlers moving unidirectional, the troughing idlers being angled in
respect of each other to provide a desired troughing angle; a cover
housing having vertical walls on a top portion of the housing in which
walls, a Skirtboard fixed through at least one clamping bar; at least; one
rubber pad to be in tight contact with an upper cover of the belt
interposed between the vertical wall and the Skirtboard, wherein a
plurality of clamping bars provided at regular intervals along the
continuous length of the Skirtboard having a corresponding number of
slots including each a spring member with predetermined spring constant,
the clamping bars exerting a clamping force on the Skirtboard to allow
movement of the mounted rubber pads, and wherein one each internally
retractable serrated clamp provided on said slots, wherein a bolt provided
to attach each rubber pad at backside of the Skirtboard, the bolt resting
on the serrated clamp to enable the spring to compress the bolt so as to
precisely seal a wear-related gap between the belt and the Skirtboard
rubber pads.
2. The assembly as claimed in claim 1, wherein a distance between each of
the clamping bar is about 100 cm.

3. The assembly as claimed in claim 1, wherein the bolt is preferably
hexagonal, and wherein a vertex to vertex distance of the bolt is equal to
a length of the slot.
4. The assembly as claimed in claim 1, wherein the intervals between the
slots along the Skirtboard is around 45 cm.
5. The assembly as claimed in any of the preceding claims, wherein the
spring material is preferably chrome silicon A 401, and wherein the spring
members have a spring constant of 396 N/Cm.
6. The assembly as claimed in claim 1 or 3, wherein the width of the bolt top
flange is equal to the width of the slot.

ABSTRACT

The invention relates to an improved belt conveyor assembly with
automatically adjustable rubber pads to maintain desired clearance
between a Skirtboard and the belt conveyor assembly to present spillage
of materials transported along the belt conveyor, comprising a conveyor
belt supported by a plurality, of troughing idlers moving unidirectional, the
troughing idlers being angled in respect of each other to provide a desired
troughing angle; a cover housing having vertical walls on a top portion of
the housing in which walls, a Skirtboard fixed through at least one
clamping bar; at least one rubber pad to be in tight contact with an upper
cover of the belt interposed between the vertical wall and the Skirtboard,
wherein a plurality of clamping bars provided at regular intervals along the
continuous length of the Skirtboard having a corresponding number of
slots including each a spring member with predetermined spring constant,
the clamping bars exerting a clamping force on the Skirtboard to allow
movement of the mounted rubber pads, and wherein one each internally
retractable serrated clamp provided on said slots, wherein a bolt provided
to attach each rubber pad at backside of the Skirtboard, the bolt resting
on the serrated clamp to enable the spring to compress the bolt so as to
precisely seal a wear-related gap between the belt and the Skirtboard
rubber pads.