 |
Description  |
|
|
BACKGROUND OF THE INVENTION
This invention relates generally to apparatus for mixing materials and,
more particularly, to apparatus for mixing water with a concentrated
liquid slurry in order to dilute the slurry.
During an intermediate stage in the manufacture of tires, rubber is formed
either into slabs or pellets which are temporarily stored. To keep the
material from sticking together, the slabs and pellets must be coated with
an anti-stick substance, the slabs being dipped and the pellets being
sprayed. Initially, the tire manufacturer creates the anti-stick material
by dumping bags of powdered chemical into water in a large tank to create
a concentrated slurry having a solids content ranging from 40-70 percent
by weight. Subsequently, the slurry is diluted and is applied to the
rubber slabs or pellets. In the case of slabs, the solids content of the
diluted slurry may be as low as 3-5 percent by weight. Pellets, however,
must be coated with a more concentrated slurry, for example, a slurry
having a solids content of 13-15 percent by weight.
In typical tire manufacturing operations, the diluted slurry is created
under manual control with a human operator being responsible for mixing
the proper weight of highly concentrated slurry with the proper weight of
water. Due to human error, diluted slurries of inaccurate proportions are
inherently produced from time-to-time. Also, the mixing and diluting
process is labor-intensive.
SUMMARY OF THE INVENTION
The general aim of the present invention is to provide new and relatively
simple and inexpensive programmable mixing/diluting apparatus in which
precisely proper weights of constituent materials are automatically
introduced into a mixing tank at proper intervals.
A more detailed object of the invention is to achieve the foregoing by
providing mixing apparatus having a programmable controller which
automatically operates to cut off the flow of one material to the tank
after a predetermined weight of that material has been introduced into the
tank, to thereafter initiate the flow of the second material into the
tank, and to cut off that flow when a predetermined weight of the second
material has been introduced into the tank.
The invention also resides in the ability of the controller to initiate
another mixing cycle after a predetermined weight of the previously mixed
mixture has been discharged from the mixing tank.
These and other objects and advantages of the invention will become more
apparent from the following detailed description when taken in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of new and improved mixing and diluting
apparatus incorporating the unique features of the present invention.
FIGS. 2 and 3 are front elevation and top plan views, respectively, of the
apparatus shown in FIG. 1.
FIG. 4 is a diagrammatic view of the apparatus in a typical operating
environment.
FIG. 5 is a flow chart which shows the operational sequence of the
apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
For purposes of illustration, the invention has been shown in the drawings
as embodied in apparatus 10 for mixing various materials, one of which is
liquid and the other of which is at least partially liquid. Herein, the
apparatus is specifically used to mix water with a liquid concentrate
having a relatively high solids content in order to dilute the concentrate
and produce a liquid slurry having a significantly lower solids content.
An appropriate additive may be introduced into the mixture if desired.
More specifically, the mixture produced by the apparatus 10 is used to coat
the rubber (e.g., rubber slabs or pellets) used in the manufacture of
tires in order to prevent the slabs and pellets from sticking together
during storage. In one particular example, the initial concentrate is
formed by dumping sacks of powder such as calcium carbonate into water in
a large storage tank (not shown) to create a liquid concentrate having a
solids content of about 55 percent by weight. Subsequently, the
concentrate is mixed with additional water and optionally with an
appropriate additive such as a thickener to form a diluted slurry for use
in coating the rubber. When the diluted slurry is used in conjunction with
pellets, it usually has a solids content ranging between 13 and 15 percent
by weight and is sprayed on the pellets. Slurry used with slabs is applied
by dipping the slabs into the slurry and has a lower solids content such
as 3-5 percent by weight.
The present invention contemplates the provision of relatively simple
apparatus 10 for mixing the concentrate and water in very accurate
proportions, the apparatus operating automatically and with need of very
little human supervision. As a result, the danger of producing an
improperly formulated slurry is virtually eliminated and, in addition,
labor costs are significantly reduced.
More specifically, the apparatus 10 includes a mixing tank 11 supported
within a main box-like frame 12. Concentrate from the large storage tank
is supplied to the tank 11 by way of a pipe 13 with the flow being
controlled by an air-actuated on/off relay valve 14 in the pipe. The valve
14 is controlled by one of five pilot valves (not visible) in a control
panel 15 on the front of the frame 12, each pilot valve being controlled
by an electrically actuated solenoid 16 and being supplied with
pressurized air via a line 17.
Water is selectively introduced into the tank 11 by means of a pipe 19 with
a relay valve 20 which is opened and closed in response to energization
and de-energization, respectively, of another one of the solenoids 16. A
third pipe 21 with a third relay valve 22 selectively admits additive into
the tank when a third solenoid is energized.
A discharge pipe 23 leads from the bottom of the tank 11 to the inlet of a
motor-operated pump 24 whose outlet communicates by way of a pipe 25 with
a large reservoir 40 (FIG. 4) located in a pit below the apparatus 10. Two
relay valves 26 and 26A (FIG. 2) are associated with the discharge line 23
and are controlled by the remaining two solenoids 16. A manually operable
drain valve 27 (FIG. 3) is connected into the line 23 upstream of the
valves 26 and may be opened for purposes of cleaning the tank.
From a mechanical standpoint, the apparatus 10 is completed by a
motor-operated mixer 30, by a digital weighing unit 31 and by an overflow
sensor 32. The mixer 30 is located at the center of the tank 11 and serves
to blend the concentrate, the additive and the water. The weighing unit or
scale 31 underlies the tank and produces an electrical signal (preferably
in digital form) which is representative of the instantaneous weight of
the materials in the tank. The overflow sensor 32 includes a
float-operated switch which, when triggered, causes the valves 26 and 26A
to open and the pump 24 to kick in so as to deliver excess slurry to the
lower reservoir 40.
In carrying out the invention, a programmable controller 35 is located
within the control panel 15 and may be programmed with the desired weights
of concentrate, water and additive to be introduced into the tank 11. The
controller 35 responds to the instantaneous weight signal from the scale
31 and effects opening and closing of the valves 14, 20 and 22 at
appropriate times so as to cause the desired weights of materials to be
introduced into the tank.
To explain the operation of the apparatus 10, let it be assumed that the
tank 11 is empty and that a particular formulation calls for 2,000 lbs. of
water, 10 lbs. of additive and 340 lbs. of concentrate. The operator
programs the respective weights into the controller 35 (see FIG. 5) and
then actuates a start switch to initiate a cycle. Thereupon, the
controller energizes the solenoid 16 associated with the relay valve 20
and thereby opens that valve to start adding water to the tank via the
line 19. After a small but predetermined weight of water has been supplied
to the tank, the controller responds to the signal from the scale 31 to
effect energization of the motor of the mixer 30. After 2,000 lbs. of
water have been added to the tank, the controller again responds to the
signal from the scale and de-energizes the first solenoid 16 and energizes
a second solenoid so as to close and open the valves 20 and 22,
respectively. Thus, the flow of water to the tank is cut off while the
flow of additive is initiated by way of the pipe 21.
When the signal from the scale 31 indicates that the total weight of the
material in the tank 11 is 2,010 lbs., the controller 35 de-energizes the
second solenoid 16 and energizes a third solenoid so as to effect closing
of the valve 22 and opening of the valve 14. The latter valve remains open
and concentrate is added to the tank 11 via the pipe 13 until the scale
signals that the total material weight in the tank is 2,400 lbs. The
controller 35 then effects de-energization of the third solenoid so as to
cause closing of the valve 14. After that valve is closed, the mixer 30
continues to operate for a predetermined period of time (e.g., 2 minutes)
and then is shut down by the controller. Thereafter, the controller
effects opening of the discharge valve 26.
Referring particularly to FIGS. 4 and 5, if the slurry supply in the
reservoir 40 is low, a float 37 in the reservoir transmits a signal to the
solenoid 16 for the discharge valve 26A and also to the controller 35 to
effect opening of the valve 26A and start-up of the pump 24 and thereby
cause slurry to be delivered from the tank 11 to the reservoir 26 via the
lines 23 and 25. Usually, the pump delivers between 125-200 lbs. of slurry
to the reservoir before the float transmits a signal to stop the pump and
close the valve 26A. The remaining slurry then is held in the tank 11
while slurry is discharged through an outlet pipe 38 in the reservoir to
the rubber coating operation. When the slurry level in the reservoir
drops, the float 37 again transmits a signal to effect re-opening of the
valve 26A and re-starting of the pump 24.
The discharge cycle described above is repeated until only a small quantity
(e.g., 40 lbs.) of slurry remains in the tank 11. At this time, the scale
31 signals the controller 35 to close the discharge valve 26 and start
another mixing cycle, at which time the steps described previously are
repeated. If the float 37 calls for slurry while the next batch is being
mixed, the closed valve 26 prevents a partially mixed blend from being
discharged to the reservoir 40.
From the foregoing, it will be apparent that the present invention brings
to the art new and improved apparatus 10 which automatically blends
accurate weights of materials to obtain an accurately proportioned blend.
Once the apparatus is started, it requires virtually no human supervision
other than occasional routine monitoring or unless the proportions of the
blend are changed during the course of a work shift. Such change can be
effected simply by reprogramming the controller 35 so as to switch between
a very highly diluted mixture for rubber slabs and a less diluted mixture
for pellets.
Those familiar with the art will appreciate that, in some cases, the pump
24 may be eliminated and the slurry discharged from the tank 11 by
gravity. In such a case, the float 37 need be connected only to the
solenoid for the discharge valve 26A and need not be connected to the
controller 35.
* * * * *
|
|
 |
|
 |
Description |
|
