Note: Descriptions are shown in the official language in which they were submitted.
42~
Inspection of foodstuffs for the presence of extraneous material
has frequently relied upon visual or tactile procedures which limit processing
rates and which are subject to operator error and inattention~
Previously, as in United States Patent 4,208,915, it has been
proposed to compress discrete, solid, form-retaining food products, e.g.,
frozen hamburgers, against a flexible membrane which can assume the shape of
the surface of the solid and transmit thereto, from a transducer, ultrasonic
sound which is used for inspection of the solid item in a manner similar to
that in which ultrasonic sound has previously been used for inspection of metal
parts and castings, welds in metal and the like.
The use of ultrasonic sound energy for examination of the human
body for diagnostic procedures in medicine is also known, e.g., "Diagnostic
Ultrasonics: Principles and Use of Instruments" by W.~. McDicken, published
1976 by John Wiley ~ Sons.
Ilowever, none of these previously proposed tec.hni~ues is suitable
for the continuous detection of extraneous materials in processed foodstuffs.
In accordance with the present invention, apparatus for detecting
the presence in a flowing, slurried foodstuff of extraneous material capable of
reflecting or absorbing ultrasonic sound energy comprises a conduit adapted to
form a passage for slurried foodstuff flowing in a longitudinal direction there-
through, ultrasonic transducer means associated with said conduit for radiating
ultrasonic sound energy throughout an entire cross-section of said slurried
foodstuff in said passage, said cross-section being substantially transverse to
said longitudinal direction, and ultrasonic sound-receiving means for receiving
said ultrasonic sound radiated throughout said entire cross-section of said
slurried foodstuff, whereby ultrasonic sound reflected or absorbed by said
extraneous material in said foodstuff may be detected to indicate the presence
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of said extraneous material.
Also in accordance with the present invention is a process for
detecting the presence in a foodstuff of extraneous material capable of reflect-
ing or absorbing ultrasonic sound energy which comprises -forming said foodstuff
into a pumpable slurry, forming said slurry into a flowing stream thereof
having a given cross-sectional area transverse to the direction of flow of
said slurry, radiating ultrasonic sound substantially transversely to said
direction of flow and entirely throughout the cross-sectional area thereof,
receiving ultrasonic sound emitted from said entire cross-sectional area of
said flowing stream of slurried foodstuff, and detecting ultrasonic sound sig-
nals reflected or absorbed by extraneous material in said slurried foodstuff
to indicate the presence thereof~
The apparatus and process of the present invention are highly
advantageous in that they may be used with processed fruits and vegetables,
soups, processed meats and the like while such are in a fluid condition, e.g.,
while they are flowing in a closed (or open) pipeline. Thus, flowable pasty
or comminuted fruits and vegetables, ketchup, ground meats and the like may
be monitored on a continuous basis during processing, and aqueous slurries of
fruits and vegetables may be checked for unremoved pits, seeds, stems, or
even for rotten cores.
The invention is described in conjunction with the following draw-
ings:
Figure 1 is a longitudinal view in elevation (partially schematic)
of an ultrasonic detection station installed in a conduit for a foodstuff slurry;
Figure 2 is a sectional view of Figure 1 taken in the plane 2-2
thereof;
Figure 3 is a sectional view in elevation of Figure 1 taken in the
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plane 3-3 thereof; and
Figure 4 is an enlarged interior view of a portion of the bottom
wall illustrated in Figure 3 illustrating the disposition of ultrasonic trans-
ducers thereon.
Cooked apple sauce 20 in pumpable, pasty form having water as its
continuous liquid phase and containing inclusions of air pockets is charged to
a conical hopper 24 at a rate sufficient to keep the throat 26 of hopper 24
covered by the air-containing apple sauce under normal, steady state operating
conditions.
The apple sauce 20 is delivered from the hopper 24 to a cylindrical
deaeration chamber 28 by a rotary vacuum gate 29. During normal, steady state
operation, the deaeration chamber 28 is maintained only partially filled with
apple sauce 30, and the chamber is evacuatecl through a conduit 32 disposed at
the top of the chamber 28. The evacuation conduit 32 enters the chamber 28 at
an opening 34 near the top thereof, and a depending annular sleeve 36 serves as
a shield to prevent splashing or other incidental entry into the conduit of
slurry discharged from the rotary gate 29. (The opening 34 and the bottom end
of the sleeve 36 are both well above the normal level of slurry in the chamber.)
A trap 38 is also provided in the conduit 32 leading to a vacuum source 40.
The deaeration chamber 28 provides a constant source of deaerated
apple sauce 30 to a positive displacement screw type pump 50 which pumps the
slurry through a closed cylindrical pipeline 55 to filling machinery 58 (in-
dicated schematically).
Disposed in the closed pipeline 55 upstream (toward the pump 50) of
the filling machinery 58 is an inspection station 60 at which the pumped
deaerated slurry is examined for the presence of foreign or extraneous material,
e.g., pits or pit fragments, by ultrasonic signals. An air-actuated diversion
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valve 62 is provided in the pipeline bet~een the inspection statlon 60 and the
fill;ng machinery SS.
The inspection station 6Q comprises a closed section of light
transparent polymeric conduit of polymethylmethacrylate or, preferably~ Lexan
~4~4-isopropylidenediphenol polymerized to a molecular weight of about
30,000-35,000). The station 60 consists of a central segment 70 or length of
line which is rectangular in cross-section, and two transition segments, 72,
74, one at each end of the rectangular central segment 70, to mate each end of
the rectangular central segment to the closed cylindrical pipelille 55 by means
of mating flanges 75, 76 and 77, 78.
Inspected, satisfactory apple sauce slurry passes through the di-
version valve 62 and is discharged through an exit port 79 for normal discharge
into a short length of line 55 leading through a flow control valve 80 to the
filling machinery 58, the flow control valve being adjusted to maintain the
closed pipeline 55 and inspection station filled with apple sauce slurry under
positive pressure at all times during normal processing.
As best illustrated in Figures 3 and ~ the central segment 70 of the
inspection station 60 consists of a short length of conduit of rectangular
(square) shape in which two adjacent walls of one transverse cross_section are
lined laterally across their outer surfaces with identical transducer arrays
84 and 86. Each array consists of two parallel rows of circular ultrasonic
transducers~ offset and staggered with respect to the other row. Thus each
array provides a series of transducers extending entirely a.cross the complete
width of one wall of the central segment to permit each array to sweep the
contents of an entire transverse cross section o-f the central segment 70 with
ultrasonic radiation.
Disposition of the arrays 84 and 86 on adjacent walls disposed at
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right angles to each other insures detection of minute splinters or slivers
possibly generating a minimal reflection in one direction, avoids shadowing of
particles by gas bubbles, and diminishes any "dead zone" at the transmission
sites caused by delays in effecting transition of the crystals and associated
electronic circuitry from the -transmit mode to the receive mode.
The individual transducers 88 are a ceramic solid solution of lead
zirconate and lead titanate and are dimensioned such that they oscillate and
may be driven at a frequency of approximately 2.25 M~lz. Each transducer 88 is
disposed with its radiating face in contact with the outer surface of the con-
duit wall 89, and transfer of ultrasonic energy thereto is aided by use of a
coupling gel therebetween.
As indicated above, the arrangement of the transducers in two
staggered, parallel pulse-echo arrays across the mounting wall 89 from one edge
thereof to the other, transverse to the direction of flow of the apple sauce,
permits transmission by the crystals, operated simultaneously in parallel, of a
continuous, full and uninterrupted curtain of ultrasonic energy through which
all of the apple sauce in the conduit must pass. ~se of the pulse-echo arrays
facilitates operation primarily based on signal reflections, rather than signal
absorbtion, and reduces vulnerability to interference by gas pockets when
detection of solid contaminants is desired.
The spacing in the rectangular central segment 70 between the inner
face of each of the mounting walls 89 and the inner face of the opposite,
parallel wall, determines the m~ir-lm length of the normal path the ultrasonic
energy must traverse, i.e., must cross and return by reflection. In the pre-
ferred embodiment this spacing is three inches, providing a normal signal path
for unimpeded signals of six inches.
The transducers 88 are fired simultaneously and in parallel by
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ultrasonic energy from an ultrasonic transmitter/receiver/detector 90 delivered
through a cable 92. A pulse repetition f_equency of300pulses/second is employ-
ed, and reflected ultrasonic signals are received by the transducers and
transmitted back to the transmitter/receiver/detector (by the same cable 92).
Circuitry in the receiver/detector determines an appropriate delay time for
particle transit and then transmits a pneumatic actuating command signal from
a source of pneumatic pressure 93 through a line 94 to the pneumatically
actuated diversion valve 62 whenever an abnormal signal is delivered to the
detector by the receiver, e.g., an extraneous reflection or absorption. (A
visual and/or audible indication of the reception of an abnormal signal may also
be presented on a cathode ray tube or buzzer respectively).
The apple sauce slurry flows through the inspection station under
pressure and under conditions of streamline flow. As indicated above, the
diversion valve 62 is opened by a command from the detector before it is reached
by a flow front which has been the source of an abnormal reflected signal to
the inspection station, and is held open by the command so as to discharge thro-
ugh a discharge port 95 therein to a receiver 96, a slug of material containing
all of the slurry in that front, e.g., for a period 50% longer in duration than
the duration of the abnormal signal.
Apple sauce slurry passing through the inspec~ion station and ~the
unopened~ diversion valve in a normal manner without generating an abnormal
signal is delivered to the filling machinery from the flow control valve 80 in
the conduit.
A variety of cooked and uncooked foods may be inspected in accordance
with the present i.nvention, especially those in which water is present as a con-
tinuous phase constituting at least about 30% or more by weight thereof.
Examples of foods suitable for inspection in accordance with the invention in-
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clude, interalia, minced or strained baby foods, (e.g. meats, fruits, vegetables,
and mixtures thereof), baloney, sausage fillings, liverwurst, frankfurter meat
and the like, tomato ketchup, gruel, puddings, and soups. In addition, pit-ted
or sectioned foods such as olives, peaches, prunes, and cherries, in whole or
sliced form, suspended in a continuous liquid medium such as water, sugar,
syrup, or olive o~l, may be inspected for the presence of pits, seeds and stems.
Similarly, whole fruits and vegetables such as onions and pota~oes may be
immersed in a continuous liquid transport medium (such as water) and non-
intrusively inspected for homogeniety, e.g., for the presence of rot-ten cores,
embedded solids, or other internal abnormalities.
As indicated, it is preferred to couple the signal from the trans-
ducer arrays through the wall defining the inspection chamber, and desirably
the wall of the inspection chamber is a material presenting a characteristic
impedance to the ultrasonic signal such that the wall couples the signal
efficiently from the transducer to the foodstuff. Such construction facilitates
sanitary maintenance and equipment repair. Alternately, however, the trans-
ducers may, if necessary, be mounted in the wall of the inspection chamber in
a pressure-tight manner with their signal-radiating faces in direct contact
with the flowing foodstuff. Thus, the inspection chamber may, if desired, be
2~ fabricated from a wide variety of suitable materials, including the preferred
polymers, stainless steel, and the like.
As further indicated, it is preferred to employ a reflective ultra-
sonic inspection procedure in which the signal-transmitting transducers are also
employed to receive the signal reflected from the foodstuffs being examined
(and from the opposed parallel signal-reflecting wall of the conduit). Such
pulse-echo technique is highly advantageous in avoiding or reducing generation
of extraneous signals by gas bubbles. It is possible, however, to use a through
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transmitted signal technique by stationing receiving transducers on the con-
duit wall opposite to, and facing towards, the signal-transmitting transducers.
In carrying out the present invention ultrasonic signals having a
frequency in the range of 0.5 to 20 h~lz may be employed, signals in the range
of about 1-5 h~lz being preferred. Generally the lower frequencies, e.g., 0.75
MHz are suited to detection of large objects such as pits unremoved from halved
peaches carried in water or sugar syrup, and frequencies in the range o 1 to
3 h~lz are useful in detecting splinters, chips, foil, solid fragments, wires,
monofilament nylon fishline as small as 0.003" in diameter, and the like.
Further the signal pulse repetition rate may suitably be on the order of 50 to
3000 pulses/second, although a repetition rate of from 100 to 2000 pulses/
second is preferred.
The area of the cross-section of slurried foodstuff may vary with
the continuous flow capacity desired, and is typically on the order of from 1
to 50 square inches. Normally the width of the conduit across which the ultra-
sonic signal is transmitted is from 0.5 to 10 inches.
Inspection of highly heterogenous foodstuffs may be implemented
electronically. Thus, for example, inspection for unremoved pits in cherries
suspended in water, can be facilitated by establishing an appropriate signal
response profile for a suspension of properly de-pitted cherries and then elec-
tronically comparing such profile with the signal profiles received during
operation to determine the acceptability of the foodstuff in process. Plums,
olives, pears and other whole and halved fruits may similarly be inspected, and
this technique of electronic comparison of signals for rejection of abnormal
material may also be used in the detection of rotten fruits and vegetables.
It is to be understood that the invention herein illustrated and
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described is to be limited only by the scope of the claims appended hereto and
that various changes, modifications and equivalents may be substituted without
departing from the true spirit of the invention.
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