U.S. patent number 3,711,848 [Application Number 05/114,306] was granted by the patent office on 1973-01-16 for method of and apparatus for the detection of stolen articles.
This patent grant is currently assigned to I. D. Engineering, Inc.. Invention is credited to Henry J. Martens.
United States Patent |
3,711,848 |
Martens |
January 16, 1973 |
METHOD OF AND APPARATUS FOR THE DETECTION OF STOLEN ARTICLES
Abstract
A system for detecting the unauthorized removal of protected
articles from a designated area comprising a harmonic generator
circuit made up of a semiconductor diode chip and a pair of
antennas adapted to receive a radio frequency signal at a first
frequency and transmit a second radio frequency signal at a second,
relatively higher frequency. Transmitting and receiving means are
positioned adjacent an exit area for actuating the circuit and an
alarm when protected articles approach the area, and means are
provided for deactivating the circuit when the protected article is
legitimately purchased. The generator circuit can be manufactured
at very low cost thereby permitting, when a legitimate sale is
made, permanent deactivation of the circuit without removing or
otherwise handling the tag or label carrying the circuit.
Inventors: |
Martens; Henry J. (Lynnfield,
MA) |
Assignee: |
I. D. Engineering, Inc. (Lynn,
MA)
|
Family
ID: |
22354428 |
Appl.
No.: |
05/114,306 |
Filed: |
February 10, 1971 |
Current U.S.
Class: |
340/572.2;
343/701; 343/720; 340/572.3; 340/572.7 |
Current CPC
Class: |
G08B
13/2431 (20130101); G08B 13/2474 (20130101); G08B
13/2422 (20130101) |
Current International
Class: |
G08B
13/24 (20060101); G08b 021/00 () |
Field of
Search: |
;340/280,258 ;325/8 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Caldwell; John W.
Assistant Examiner: Slobasky; Michael
Claims
I claim:
1. A system for detecting the unauthorized removal of protected
articles from a predetermined area comprising
a. a semiconductor diode chip having a cathode and an anode,
b. first and second antenna means respectively electrically
connected to said cathode and said anode of said diode chip, said
antennas being shaped and dimensioned to receive radio frequency
signals at first predetermined frequency level and to retransmit
said signals at a second predetermined, relatively higher radio
frequency level,
c. carrier means for carrying and embedding said diode chip and
said antennas for convenient concealment in or association with the
article to be protected,
d. at least one receiving and transmitting unit positioned near the
exit from said area, said unit transmitting radio frequency signals
at said first frequency level and receiving radio frequency signals
at said second radio frequency level,
e. alarm means electrically connected to and actuated by said
receiving and transmitting unit when a protected article is in the
detectable area around said unit, and
f. deactivating means for permanently deactivating the harmonic
generator circuit when said protected article has been legitimately
purchased and without requiring disassociation of such circuit from
said article, said deactivating means comprising a power signal
source for transmitting radio frequency signals at a predetermined
power level, and antenna means, the power level of said power
signal means being substantially higher than the power level of
said signal emitted by said receiving and transmitting unit thereby
permanently deactivating said harmonic generator circuit.
2. The system of claim 1 wherein said second radio frequency level
is approximately twice the frequency of said first frequency level,
and the output power of said power signal source is approximately
ten times the output power of the transmitted radio frequency
signal of said receiving and transmitting unit.
3. The system of claim 2 wherein said receiving and transmitting
unit comprises a transmitter including a source of high frequency
energy, a filter, and a transmitter antenna, and a receiver
comprising a receiving antenna, a band pass filter, a receiver
adapted to receive signals of predetermined frequency approximately
double the frequency of the signals emitted by said transmitter,
and alarm means actuated by said receiver in response to the
penetration of a protected article which has not been deactivated
into the area of said transmitter.
4. The system of claim 1 wherein said first and second antennas
each include a relatively pointed leading end portion adapted to
contact and be electrically connected to the cathode and anode,
respectively, of said diode chip.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to theft detection
apparatus and more particularly to a method of and apparatus for
detecting the passage of articles past predetermined check points
and signaling such passage so that the person or persons
surreptitiously removing such articles from the premises can be
apprehended.
Shoplifting has long posed a considerable problem to retail
business establishments, with the magnitude of such problem growing
yearly. Numerous methods have been tried in order to reduce the
loss caused by shoplifting, including various systems of personnel
surveillance and, more recently, by means of electrical and
mechanical theft detection devices or systems. The use of personnel
to detect and apprehend shoplifters has obvious shortcomings. The
use of floor walkers, security guards and the like constitutes a
considerable business expense, oftentimes exceeding the amount
saved as a result of reduced pilferage. In addition, the presence
of security personnel is often at the sacrifice of the good will of
the business for whom such personnel are hired, with the loss of
good will being considerably magnified where customers thought to
be shoplifters are mistakenly apprehended.
The provision of an electrical or mechanical theft detection system
does of course obviate the above noted problem with respect to
security personnel, but these systems have in the past not proven
entirely satisfactory for a number of reasons. Systems
representative of the prior art include U.S. Pat. Nos. 2,774,060;
3,493,955; and 3,500,373. The detection device disclosed in U.S.
Pat. No. 2,774,060 for example, requires that the tag or label
mounting the detection circuit be removed by the cashier, which
adds to the checkout time, a source of possible customer
dissatisfaction, as well as permitting removal of the tag or label
by an individual who wishes to pass such article undetected through
the checkout point.
Although permanent attachment of the detection device to the
protected articles is suggested in the prior art, reference being
made to U.S. Pat. No. 3,493,955, the method disclosed therein of
deactivation and subsequent activation is not entirely
satisfactory. Furthermore, in previous systems employing devices
which may be permanently attached to the goods, the size and/or
cost of the device are inhibiting factors against the use of such
devices on a widespread basis.
SUMMARY OF THE INVENTION
With the above in mind, a primary object of the present invention
is to provide a harmonic generator circuit which is simple and
reliable and which will function to actuate an alarm circuit or the
like when articles have surreptitiously passed a predetermined
checkpoint such as the cashier's checkout area.
A further object of the present invention is to provide such a
harmonic generator circuit which is both relatively small in size
and inexpensive to manufacture. In accordance with the invention,
the circuit is embodied in a relatively small tag or label which
can be conveniently embedded or concealed within articles desired
to be protected. In view of the substantially reduced cost of
manufacture of each tag or label, the same can be left concealed or
hidden in such articles when the same are purchased, and simply
deactivated at the checkout point to prevent actuation of the alarm
which would otherwise occur when the purchaser leaves the
store.
A further object of the present invention is to provide a harmonic
generator circuit which operates at relatively high frequency
thereby precluding inadvertent actuation of the circuit by
unprotected metallic articles passing through the checkout
area.
A still further object of the present invention is to provide a new
method of manufacture of the harmonic generator circuit, in which a
continuous strip of longitudinally spaced circuits can be formed,
assembled and thereafter cut into predetermined lengths.
A further object of the present invention is to provide a generator
circuit which is readily adaptable to other areas of surveillance
in addition to the environment disclosed. In view of the size,
reliability and low manufacturing cost, the invention can be used
as well in the surveillance of personnel to detect the passage of
unauthorized persons through predesignated areas.
These and other objects will become apparent to those skilled in
the art as the following description proceeds, in particular
reference to the application drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view illustrating a doorway having mounted
on either side thereof a transmitting and receiving unit for
detecting the presence of protected articles which have
surreptitiously passed the cashier checkout counter;
FIG. 2 is a perspective view showing a typical checkout counter,
having associated therewith means for deactivating protected
articles which have been legitimately purchased;
FIG. 3 is a sectional view through a tag or label constructed in
accordance with the present invention, taken on line 3--3 of FIG.
4;
FIG. 4 is a plan view of the tag or label of FIG. 3;
FIG. 5 is a diagrammatic view of the transmitter unit used in the
present invention;
FIG. 6 is a diagrammatic view of the receiver and alarm circuit
used in accordance with the present invention;
FIG. 7 is a diagrammatic view of the deactivation circuit
constructed in accordance with the present invention;
FIG. 8a is a plan view of a diode chip constructed in accordance
with the present invention;
FIG. 8b is a side elevational view of the diode chip;
FIGS. 9-13 comprise top plan views of various forms of antennas
which can be used in combination with the diode chip 28 to form the
harmonic generator circuit;
FIG. 14 comprises a longitudinal sectional view taken on line
14--14 of FIG. 15 showing the top half of a tape member or the like
carrying a metalized antenna pattern on the bottom side
thereof;
FIG. 15 is a bottom plan view of the tape shown in FIG. 14;
FIG. 16 is a longitudinal sectional view taken on line 16--16 of
FIG. 17, showing a mating tape member carrying a metalized antenna
pattern on the bottom thereof for subsequent association with the
member shown in FIG. 14;
FIG. 17 is a bottom plan view of the tape member of FIG. 16;
FIG. 18 is an isolated, reduced view of the diode chip constructed
in accordance with the present invention;
FIG. 19 is a longitudinal sectional view taken through the
assembled harmonic generator circuit of the invention, and
FIG. 20 is a top plan view of the assembly of FIG. 19.
DETAILED DESCRIPTION OF THE INVENTION
Referring now in more detail to the drawings, wherein like parts
are indicated by like reference numerals, and initially to FIGS. 1
and 2, there is illustrated therein a typical environment in which
the present invention may be used to advantage. These figures are
intended to depict a typical checkout and exit arrangement in a
department store or the like, with the exit being indicated by door
25 on either side of which is mounted a transmitter and receiver
unit 26, the construction of which is shown diagrammatically in
FIGS. 5 and 6 and which will be discussed in detail when specific
reference is made to these figures.
FIG. 2 illustrates a typical checkout area, comprising checkout
counter C and cash register 37. Disposed laterally of the counter
at the exit end thereof are deactivating units 38 and 39 between
which the protected articles purchased in an authorized manner can
be passed for deactivation of the harmonic generator circuit.
Referring now to FIGS. 3 and 4, a tag or label 27 has embedded
therein the harmonic generator circuit of the present invention,
which comprises a diode chip 28 and metal antennas commonly
designated at 29. The diode chip may comprise a conventional
point-contact diode but preferably comprises a Schottky diode, the
characteristics of which are well known in the art. As will be
explained in more detail when specific reference is made to FIGS.
14-20, the anode and cathode of the semi-conductor diode chip 28
are connected respectively to the antennas 29. The circuit can be
embedded or encased in the tag or label 27 in a known manner which
forms no part of the present invention. It will further be
understood that the form of carrier for the circuit will normally
depend upon the ultimate desired use of the circuit, with the tag
27 representing a typical use where the circuit can be conveniently
concealed in articles to be protected.
The harmonic generator circuit just described is capable of
receiving a radio signal at one selected frequency, which will be
called F.sub.o, and transmitting a radio signal at twice this
frequency, 2F.sub.o. Although the particular frequency employed is
not critical, preferably high frequency ranges are employed in
order to preclude false actuation of the system by unprotected
metallic articles passing through the checkpoints. A typical
operating frequency, for example, would be F.sub.o at 912
megacycles, so that the generator circuit transmits a radio signal
at 2F.sub.o or 1824 megacycles. It will be understood that these
frequencies are exemplary, and that other frequency ranges could
also be satisfactorily employed.
Referring to FIG. 5 and 6, each of the transmitter and receiver
units 26 comprises a transmitter circuit shown in FIG. 5 and a
receiver circuit shown in FIG. 6. The transmitter circuit includes
a high frequency generating source 30, a filter 31, and a
transmitting antenna 32. Each of these components is commercially
available and per se forms no part of the present invention.
The high frequency source 30 delivers a continuous, non-modulated
radio frequency signal through the filter 31 to the transmitting
antenna 32 which provides radiation of the radio frequency signal
at the selected frequency F.sub.o in the direction of the doorway
25. The filter 31 functions in the usual manner to assure passage
of signals of such predetermined frequency and to suppress higher
harmonics of such frequency.
Referring to FIG. 6, the receiving circuit comprises a directional
receiving antenna 33, a band pass filter 34, a receiver 35, and
alarm means 36, which can comprise a flashing light, bell, or other
audible or visual alarm. In a manner well-known in the art, the
band pass filter 34 will only pass radio signals within
predetermined frequency limits, with the limits being selected in
the present instance to include the frequency 2F.sub.o, 1824
megacycles. Satisfactory limits for the band pass filter can be,
for example, between 1775 and 1875 megacycles, and it will be
understood that the receiver 35 is sharply tuned only to signals in
this range. The receiving of signals in this range by the receiver
35 actuates the alarm 36 thereby indicating passage through the
doorway 25 of articles that are protected and that have not been
processed through the checkout counter as authorized. All of the
components 33-36 are similarly conventional and commercially
available.
Referring to FIG. 7, there is illustrated therein the power circuit
for deactivating the harmonic generator circuit as protected
articles are processed through the checkout counter after
legitimate sale. The power circuit includes antennas 38 and 39 and
generating means 40 coupled therewith for providing a power signal.
The frequency of the power signal is selected to be approximately
F.sub.o, and the power output is approximately 10 watts,
substantially higher than the power output of the high frequency
source 30, which is preferably at or less than 1 watt.
When a protected article is processed subsequent to a legitimate
sale, the sales clerk passes the protected article or package
through the electromagnetic field between the antennas 38 and 39.
The relatively high output of the power source 40 functions to burn
out and thus permanently deactivate the tag or label 27 associated
with the article whereby the article may freely pass through the
doorway 25 without actuation of the units 26 as the merchandise
leaves the store. The electromagnetic energy radiated by the
antenna 38 will be absorbed by the antenna 39 thereby preventing
radiation outside the system.
Referring to FIGS. 8a and 8b, the semiconductor diode chip 28
includes an anode 42 formed on the top of the diode chip and a
cathode 43 which forms the bottom of the diode chip.
FIGS. 9-13 illustrate various shaped antennas 41 which extend to
either side of the diode chip 28 and are electrically connected
respectively to the cathode 43 and anode 42. In these figures, the
circuit is shown embedded in the tag 27. The diode chip 28 is
preferably of a preselected polarity, and the shape or design of
the particular antenna 41 employed is based on which antenna design
will perform the best in view of the polarity of the
electromagnetic field radiated by the transmitter antenna 32.
There is illustrated in FIGS. 14-20 the preferred method of
manufacturing the harmonic generator circuit in accordance with the
present invention. Referring to FIGS. 14 and 15, a tape member 44
has a thin metalized antenna pattern 45 formed thereon which
comprises one-half of the antenna assembly. It will be noted that
the antenna pattern 45 is pointed at one end as shown at 48. The
tape 44 can be constructed of any suitable material, with the
underside of the tape containing the metalized antenna section
being preferably coated with glue, and the exterior surface of the
tape being preferably coated with vinyl or similar plastic
material.
FIGS. 16 and 17 are generally similar to FIGS. 14 and 15, with the
underside of the tape member 46 being formed with a similar
metalized section 47 having a pointed end portion 49, the direction
of which is opposite to the direction of the pointed end 48 of the
metalized section 45 of the tape 44. The tape 46 is also preferably
provided with glue on the underside thereof carrying the metalized
antenna section and vinyl on the opposite, exposed side.
Referring to FIGS. 19 and 20, the tape members 44 and 46 are shown
superimposed, with the faces thereof carrying the antenna sections
being in contact. As will be seen from the centerline passing from
top to bottom through these several figures, the pointed end
regions 48 and 49 of the antenna sections overlap and are designed
to extend respectively over and under the diode chip 28 which is
positioned therebetween in the manufacturing process. The
electrical contact between the cathode and anode of the diode chip
28 and the antenna sections 48 and 49 is preferably by pressure,
effected during the assemblying of the circuit. During such
assembly, the glued material on the contacting sides of the tapes
44 and 46 can be activated so as to firmly bond the tape members
together as shown in cross section in FIG. 19. The assembly thus
constitutes a completely embedded diode chip and electrically
connected antenna sections, with the exposed surfaces of the tape
being vinyl coated and thus highly resistant to the typical
environments to which the circuit is subjected.
As above indicated, the size of the harmonic generator circuit
assembly can be varied and is to a large degree controlled by the
length of the antenna portions. In the assembly illustrated in
FIGS. 19 and 20, the length of the assembly is approximately two
inches, the width is approximately one-half inch, and the thickness
is approximately twenty-thousandth of one inch. It will thus be
seen that the assembly can be concealed without difficulty in
clothing, for example. Where higher frequencies are employed, the
length of the assembly can be made even shorter, thereby further
enhancing concealment of the assembly.
The manner in which the harmonic generator circuit of the present
invention functions should be apparent from the above description.
To briefly summarize, protected articles, that is articles on or in
which the assembly is carried, are normally processed through the
checkout counter C, and articles that are so protected are passed
between the antennas 38 and 39 after legitimate purchase. The power
signal produced by the power source 40 functions to permanently
deactivate the assembly thereby permitting passage of the protected
article through the doorway 25 when the customer leaves the
store.
When a customer attempts to leave the premises through door 25 with
a protected article that has not been paid for and deactivated, the
article enters the radiation pattern of the transmitter antenna in
the units 26. The harmonic generator circuit in the tag or label 27
will transmit a signal at approximately 1824 megacycles. The radio
signal at such higher frequency will be received by the receiver 35
which in turn will actuate the alarm 36, thereby alerting store
personnel of the theft.
It will thus be seen that the objects of the present invention have
been accomplished. There has been provided a harmonic generator
circuit which is extremely simple in construction and highly
reliable in use. The construction of the device itself, coupled
with the unique method of manufacturing the same, permits
manufacture at very low cost thereby allowing deactivation of the
device at the checkout counter, concealment of the device without
removal of the same at the checkout counter, a decided disadvantage
with prior art assemblies of this general type. In lieu of removal,
the device can simply be activated in the disclosed manner and the
assembly left in its concealed position. The operating frequencies
are such that inadvertent actuation by metallic articles is
virtually precluded.
* * * * *