An electronic flow meter utilizes a light source for directing
a beam of light onto a light responsive sensing device, such as
a photocell. As solids flow through a hose, they interrupt the light
beam, changing the light intensity impinging on the photocell. This
change in light intensity alters the output voltage of the photocell
in direct proportion to the flow of solids through the hose. The
changes in voltage are digitized and transmitted to a computer which
utilizes this information in calculations indicating the weight
of the solid that has passed through the hose.
What is claimed is:
1. Apparatus for measuring the flow of bulk solids pneumatically
conveyed through a hose comprising:
a detector including a light source and a light responsive sensing
device arranged to receive a beam of light from said source, the
detector being joined to the hose in such a manner that the solids
pass through said light beam to vary the intensity of light impinging
on said sensing device thereby changing the output voltage of said
means for sampling and digitizing said output voltage;
a memory for accumulating digitized data produced by said sampling
and digitizing means, said memory also storing a constant representative
of the type of solids conveyed through the hose; and
means for computing the weight of solids passing said detector
by dividing the accumulated digital data by said constant.
2. Apparatus as set forth in claim 1 wherein said sensing device
is a photocell.
3. Apparatus as set forth in claim 1 wherein said sensing device
employs fiber optics.
4. Apparatus as set forth in claim 1 wherein said detector comprises
a tube having a central portion of substantially rectangular cross-section,
said light source and the light responsive sensing device being
located at said central portion on opposite sides thereof, respectively.
5. Apparatus as set forth in claim 4 wherein said sensing device
is a photocell.
6. Apparatus as set forth in claim 4 wherein said sensing device
employs fiber optics.
BACKGROUND OF THE INVENTION
The present invention relates to measurement of the flow of solids
pneumatically conveyed through a hose and particularly, to electronic
flow meters for measuring the flow of insulation passing through
the hose of an insulation blowing machine.
For installing blown insulation, the industry has established recommended
guidelines for insulation density per square foot of area covered.
The present method of measuring the amount of insulation blown is
to count the number of standard-sized bags consumed in the blowing
operation, and the consumer relies on the contractor to use the
proper number of bags. With this method of measurement, however,
the industry has suffered a fraud problem. This problem is documented
in the INSULATION PROFESSIONAL, Spring, 1983 a publication by Owens-Corning
Fiberglas Corporation, and in the ICAA NEWS, June 1983 a publication
by the Insulation Contractors Association of America. The problem
is characterized by some contractors puffing the insulation with
air and thinly spreading it so that fewer bags of insulation per
square foot are installed than the industry guidelines require.
After the insulation has been installed, it is impossible to measure
the amount that was actually blown without removing and weighing
Various flow measuring devices are known for sensing characteristics
of materials passing through a conduit. For example, U.S. Pat. No.
4231262 issued to Richard H. Boll et al on Nov. 4 1980 teaches
the use of a flow meter for measuring the flow of particulate solids
by taking differential pressure measurements along points of a venturi
through which the solids are funneled; and U.S. Pat. No. 3800147
issued to James J. Shea et al on Mar. 26 1974 discloses the use
of a turbidimeter with automatic color compensation for sensing
low turbidity concentrations in fluids of various colors. However,
neither of these devices is capable of measuring the flow of bulk
solids, such as loose fill insulation.
SUMMARY OF THE INVENTION
The present invention measures the weight of insulation actually
passing through the hose of an insulation blowing machine. More
particularly, a flow detector is placed in the hose, the detector
comprising a light source and a light responsive sensing device.
As solids flow past the detector, they interrupt a light beam emanating
from the light source, thus changing the output voltage of the sensing
device in direct proportion to the flow of solids through the hose.
The changes in voltage are sampled and digitized for transmittal
to a computer which determines the weight of the bulk solid flowing
through the hose during a particular period of time.
DETAILED DESCRIPTION OF THE INVENTION
The present invention now will be described in further detail with
reference to the accompanying drawings wherein:
FIG. 1 is a side elevational view of an electronic flow detector
portion of the invention;
FIG. 2 is a top plan view thereof;
FIG. 3 is an end view thereof;
FIG. 4 is an exploded sectional diagrammatical view thereof taken
along line 4--4 of FIG. 2; and
FIG. 5 is a block diagram of an electronic flow meter according
to the invention.
Referring to FIGS. 1-4 a preferred embodiment of a bulk solid
flow detector 10 is illustrated. The detector 10 includes a tube
(preferably metal) through which the bulk solids pass when the tube
is joined to the hose of an insulation blowing machine (not shown).
The tube is circular at its ends (FIG. 3) and has a substantially
rectangular cross-section (FIG. 4) at its central portion 12. A
light source 14 and a light responsive sensing device 16 are positioned
on opposite sides of portion 12 in such a manner that a beam of
light from source 14 is directed towards the sensing device 16.
In the embodiment illustrated, the sensing device 16 is a photocell.
However, it will be appreciated that other types of known sensors
may be employed, such as those utilizing fiber optics.
As solids flow past the detector, the amount of light from source
14 impinging on sensor 16 varies, thus changing the sensor's output
voltage. The voltage changes are sampled and digitized and then
are transmitted to a computer where the information is used as data
indicative of the weight of bulk solid material flowing past the
detector 10. The manner in which the computer functions will be
described in detail hereinafter.
The tube portion 12 of the detector is formed with a rectangular
cross-section for the reasons:
(1) that it provides flat surfaces for the light source 14 and
the sensor 16;
(2) that it concentrates the flowing solids within the beam of
light between the source and the sensor; and
(3) that it deflects the bulk solid material away from the lenses
of the sensor and the light source thereby avoiding the scratching
of said lenses which otherwise would decrease the accuracy of the
The formed area of the tube is a function of the tube diameter.
It is dimensioned to minimize the difference in cross-sectional
area from that of the tube's ends while concentrating the flowing
material within the light beam to the sensor 16.
The tube's diameter at its ends is determined by the volume capability
of the conveying system being used, and it preferably is the same
as the diameter of the hose to which it is attached. The standard
size hose diameter used in blowing insulation is three inches.
The assembly of the bulk solid flow measuring detector 10 (FIG.
4) begins with the introduction of flat glass lenses 18 and 20 into
apertures 22 and 24 respectively, on opposite sides of portion
12 of the detector. The lenses are mounted flush to the internal
surface of portion 12. A sensor holder 26 is mounted over lens 20
and sensor 16 is attached to holder 26. A light source holder 28
is mounted over the lens 18 and light source 14 is attached to
A direct relationship exists between the flow of bulk material
through the hose and the detector and changes in the intensity of
light impinging on the sensor. These changes produce a varying voltage
at the output of the sensor. The sensor's output voltage is directed
to an analog-to-digital converter 30 which samples and digitizes
the cell's analog output voltage. A sampling rate of one thousand
(1000) times per second is suitable. The digitized data produced
by the samplings is accumulated in a computer memory 32 and is representative
of the amplitude of the voltage levels at the sensor's output.
Through experimentation utilizing the apparatus just described,
it has been discovered that each type of insulation appropriate
for installation by blowing has a distinctive constant which is
directly related to its physical characteristics. This constant
is determined by blowing a sample of known weight past detector
10 and accumulating in memory 32 digitized data derived from the
detector's output. The constant is arrived at by dividing the accumulated
data by the weight.
By repeating the experimentation just described for different insulating
materials, a catalog of constants is developed, and these constants
(referred to hereinafter as "constants of proportionality")
are stored at appropriate identifiable locations in memory 32.
The manner in which the invention is utilized during normal operation
to measure the weight of a known material which is being blown now
will be described.
First, the operator informs the computer of the material's identity,
utilizing the keys of a keyboard and display unit 34. This results
in the memory 32 being accessed to retrieve therefrom the constant
of proportionality for that material. From the time the blowing
machine is turned on, the flow meter accumulates digitized data
in the manner previously described, provided there is movement of
the material through the detector. A software program, also retained
in memory 32 instructs the computer's central processing unit 36
to solve the following equation to determine the weight of material
The results of the calculation are continuoulsy displayed on the
display portion of unit 34. A final printout stating the date, as
well as the type and weight of the material blown, is provided by
a printer 38 actuated in response to a command instituted by appropriate
operation of the keyboard of unit 34.