Sensor for monitoring an article

A sensor has a substrate with a first surface having a substantial area, a conductive trace defining a conductive path on the substrate between first and second locations, and an adhesive on the first surface for adhering the sensor to an object to be monitored in an operative state. A weakening is provided in the substrate to cause separation/tearing of the substrate in a predetermined fashion as an incident of a force being applied to the substrate with the sensor in the operative state tending to peel the sensor off of the object to be monitored. The conductive trace is arranged on the substrate so that as the substrate separates/tears in the predetermined fashion, the conductive path defined by the conductor trace is interrupted.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to sensors of the type that can be adhered to an 
article to be monitored and which change state as an incident of being 
removed from the article. 
2. Background Art 
For decades, purveyors of articles who display the articles for consumer 
inspection have sought effective systems for preventing unauthorized 
removal of these articles from the display area. Designers of these types 
of systems have contended with many objectives which are often competing 
with each other. Most significantly, it is important that the system 
effectively deter theft. Cost is always a significant consideration in the 
design of such systems. It is also important that the systems be user 
friendly, i.e., that they can be easily and consistently activated. The 
more complicated the systems become to operate, the more likely it is that 
employees will improperly set the systems up or altogether avoid 
activation thereof. At the same time, it is desirable that these systems 
be relatively unobtrusive. Large, electronic sensors on a relatively small 
article may detract from the visual appeal to the potential consumer. On a 
small article, a relatively large profile sensor may also inhibit 
effective inspection of the article. 
One sensor design that meets a number of the above objectives is that which 
uses a flexible substrate as the main body of the sensor. A conductive 
trace is provided on the substrate, with an adhesive applied to the 
substrate to facilitate adherence of the sensor to an article to be 
monitored. The tenacity and the location of the adhesive may be selected 
to cause part of the conductive trace to remain on the substrate and part 
on the article as the substrate is peeled away from an article to which it 
is adhered. The sensor is electrically connected to a monitoring system 
which produces a detectable signal as an incident of detecting that the 
conductive path defined by the trace has been interrupted. 
One version of this sensor applies adhesive at only selected locations on 
the substrate and over the trace. When the substrate is peeled off, the 
adhesive is designed to maintain a part of the trace bonded to the 
article. The unbonded portion of the trace separates with the substrate to 
cause interruption of the conductive path defined by the trace. 
It is also known to cause part of the trace to be bonded more securely to 
the substrate than with the adhesive layer over part thereof, and another 
part to be more securely held to the adhesive layer than to the substrate. 
This produces the same effect upon the substrate being peeled from the 
article to which the sensor is attached. 
In both of the above versions, the substrate is designed to remain 
substantially intact as the substrate is peeled from the article that is 
monitored. 
SUMMARY OF THE INVENTION 
In one form of the invention, a sensor is provided for attachment to an 
article to be monitored. The sensor has a substrate with a first surface 
having a substantial area, a conductive trace defining a conductive path 
on the substrate between first and second locations, and an adhesive on 
the first surface for adhering the sensor to an object to be monitored in 
an operative state. A weakening is provided in the substrate to cause 
separating/tearing of the substrate in a predetermined fashion as an 
incident of a force being applied to the substrate with the sensor in the 
operative state tending to peel the sensor off of the object to be 
monitored. The conductive trace is arranged on the substrate so that as 
the substrate separates/tears in the predetermined fashion, the conductive 
path defined by the conductor trace is interrupted. 
The adhesive may be applied over the conductive trace. 
In one form, the weakening includes one of a U-shaped cut and a V-shaped 
cut at least partially through the substrate. 
The substrate may have a connecting portion to be operatively engaged with 
a monitoring system for the sensor, with the first and second locations 
being on the connecting portion. 
The weakening may include first and second spaced weakening cuts at least 
partially through the substrate. 
In one form, the substrate has a frangible portion between the first and 
second weakening cuts so that the substrate separates/tears along the 
first and second cuts as an incident of the force being applied to the 
substrate tending to peel the substrate off an object to be monitored and 
tears the frangible portion between the first and second cuts. 
The first and second cuts may be configured and spaced so that with the 
substrate separated/torn along the first and second cuts and the frangible 
portion of the substrate torn, a discrete portion of the substrate 
separates from the remainder of the substrate. The adhesive may be 
provided on the discrete portion of the substrate so that the discrete 
portion of the substrate remains adhered to the object to be monitored, 
with the remainder of the substrate separated from the object. 
The conductive trace and the conductive path may extend across the discrete 
portion of the substrate so that the conductive path is interrupted as an 
incident of the discrete portion of the substrate separating from the 
remainder of the substrate. 
The conductive trace may extend across the frangible portion of the 
substrate without crossing either of the first and second weakening cuts. 
The substrate may be made from a polyester sheet. 
A dielectric coating may be provided on the substrate at the connecting 
portion. 
The one of a U-shaped cut and a V-shaped cut may open in one direction. A 
second, cut, having one of a V shape and a U shape, may be provided at 
least partially through the substrate opening oppositely to the one 
direction. 
The sensor may be provided in combination with an object to be monitored to 
which the sensor is adhered in the operative state. 
The sensor may further be provided in combination with a monitoring system 
electrically connected to the conductive trace at the first and second 
locations. The monitoring system may have structure for detecting when the 
conductive path is interrupted and for producing a signal as an incident 
of the detecting structure detecting that the conductive path is 
interrupted. 
The invention may also include in combination with the above a structure 
for receiving the signal and, as an incident thereof, causing production 
of a separate signal that can be audibly or visually detected. 
The substrate may be made partially or wholly from a flexible sheet. 
In another form, the invention contemplates a sensor for attachment to an 
article to be monitored, with the sensor including a substrate having a 
first surface with a substantial area, a conductive element on the first 
surface, and an adhesive on the first surface for adhering the sensor to 
an object to be monitored in an operative state. A weakening is provided 
in the substrate to cause tearing of the substrate in a predetermined 
fashion such that a discrete portion of the substrate separates from the 
remainder of the substrate as an incident of a force being applied to the 
substrate with the sensor in the operative state tending to peel the 
sensor off an object to be monitored. The conductive element has a first 
state with the sensor in the operative state and a second state with the 
discrete portion of the substrate separated from the remainder of the 
substrate. With this arrangement, a monitoring system can be used to 
detect the first and second states of the conductive element and to 
produce a signal indicative of the fact that the conductive element has 
changed from the first state into the second state.

DETAILED DESCRIPTION OF THE DRAWINGS 
A sensor, according to the present invention, is shown at 10 in FIGS. 1 
through 10. The sensor 10 consists of a substrate layer 12 made of 
flexible material. A suitable material for this substrate layer is 
polyester, which may be on the order of 0.005 inch thick. A suitable 
polyester material is available commercially and sold under the trademark 
MYLAR.TM.. The substrate layer 12 is defined by a generally rectangular 
body 14 and a connecting portion 16, with the body 14 and connecting 
portion 16 being joined by a neck 18. 
A conductive trace 20 is conventionally applied to the underside 21 of the 
substrate layer 12. The conductive trace 20 is formed in a circuitous path 
to define a continuous conductive path between first and second locations 
22, 24 on the connecting portion 16 of the substrate layer 12. A grounding 
trace portion 26 extends from the connecting portion 16, between the first 
and second locations 22, 24, across the neck 18 to an intermediate 
location on the body 14. 
According to the invention, the substrate layer 12 has a weakening, in this 
case at two spaced locations 28, 30. The weakening at the location 28 
consists of a continuous V-shaped cut 32 extending into the substrate 
layer 12. In a preferred form, the cut extends fully through the substrate 
layer 12. However, the invention contemplates that the cut 32 may extend 
only partially through the substrate layer 12. The cut 32, as all other 
weakening cuts described hereinbelow, may be defined alternatively by 
serrations which extend either partially or fully through the substrate 
layer 12. The V shape of the cut 32 opens towards a circular cut 34, which 
extends through approximately 290.degree., producing a U shape with an 
opening at 35 between spaced ends 36, 38 which are spaced equidistantly 
from two legs 40, 42 defining the cut 32. The cut 34 extends fully through 
the substrate 12, but may also be formed only partially through the 
substrate 12. A frangible portion 44 resides between the end 36 of the cut 
34 and the leg 40 of the cut 32. A similar frangible portion 46 resides 
between the end 38 of the cut 34 and the leg 42 of the cut 32. 
The weakening at the location 30 has a similar, but reversed, arrangement 
of cuts. In this case, a V-shaped cut 48, corresponding to the cut 32, 
opens oppositely to the cut 32 and towards a circular, U-shaped cut 50, 
with the cuts 48, 50 having the same relative position as the cuts 32, 34. 
An adhesive layer 52 is applied over the underside 21 of the substrate 
layer 12 over substantially the entire surface of the body 14. Through the 
adhesive layer 52, the sensor 10 is maintained in an operative state on an 
object 54 to be monitored. Two-sided adhesive tapes are commercially 
available that are suitable for this purpose. One suitable tape is 
Scotch-brand "transfer tape" #9690 with a thickness of 0.005 inch. The 
adhesive layer 52 is tenacious enough that with the sensor 10 in the 
operative state, any attempt to peel the sensor 10 from the monitored 
object 54 will cause the substrate layer 12 to separate/tear in a 
predetermined fashion at the weakening. The weakening at the exemplary 
location 28 is designed so that a peeling of the substrate layer 12 
adhered to the object 54 causes the substrate layer 12 to separate at the 
cuts 32, 34 and to rupture the frangible portions 44, 46 therebetween, 
thereby causing a discrete portion 55 of the substrate layer 12 to become 
separated from the remainder of the substrate layer 12. The depth of the 
cuts 32, 34 and the tenacity of the adhesive are selected so that the 
substrate layer 12 will not inadvertently separate along the cuts 32, 34 
in normal use, yet will separate/tear in a predetermined fashion when 
someone tampers with the sensor 10. 
The most anticipated strategy for tampering involves peeling the sensor 10 
off of the object 54 by grasping the neck 18 and connecting portions 16 of 
the substrate layer 12 and exerting an upward and right-to-left force 
thereon in FIGS. 1-5. However, the invention is directed to preventing 
breach of security by a left-to-right peeling. Under this left-to-right 
peeling action, separation of the substrate layer 12 is initiated at the 
edge 56 of the U-shaped cut 34. The separation continues over the full 
extent of the cut 34 up to and through the frangible portions 44, 46 to 
the cut 32, progressing therethrough to the apex 58 of the cut 32 
whereupon the discrete portion 55 becomes fully separated from the 
remainder of the substrate layer 12. The cuts 32, 34 and 48, 50 are 
reversed so that the edge 59 of the U-shaped cut 50 will initiate 
separation of the substrate layer 12 as a result of a right-to-left 
peeling of the sensor 10 in FIGS. 1-6. 
All four corners 60, 62, 64, 66 of the body 14 are rounded to deter 
tampering as is facilitated by a sharp corner. This configuration 
addresses tampering undertaken by peeling from left to right which might 
be attempted by a thief to avoid the more obvious right-to-left peeling 
facilitated by the accessible and graspable neck 18 and connecting portion 
16 of the substrate layer 12. 
According to the invention, the sensor 10 is designed so that as it is 
peeled from the monitored object 54, separation/tearing, in the 
predetermined fashion described above, causes the conductive trace 20 to 
be broken to thereby interrupt the conductive path between the first and 
second locations 22, 24. In this embodiment, one leg 68 of the conductive 
trace 20 is located between the cuts 32, 34 and extends across the 
frangible portions 44, 46. Another leg 70 of the conductive trace 20 
extends between the cuts 48, 50 across like, frangible portions 72, 74 
therebetween. When the frangible portions 44, 46 rupture, the conductive 
trace leg 68 severs. Similarly, when the frangible portions 72, 74 
rupture, the trace leg 70 likewise breaks. This situation can be seen most 
clearly in FIG. 6. 
Right-to-left peeling causes separation of the substrate layer 12 initially 
at the edge 59. The separation continues along the cut 50 towards the legs 
76, 78 of the cut 48. The separation/tearing eventually reaches the ends 
80, 82 of the cut 50 and continues across the frangible portions 72, 74 to 
the ends 84, 86 of the cut legs 76, 78. The separation continues along the 
cut 48 to the apex 89, whereupon a discrete portion 90 of the substrate 
layer 12 becomes separated from the remainder of the substrate layer 12. 
The fracturing of the conductive trace 20 is detected through a monitoring 
system 92. The monitoring system 92 includes a connector 94 (FIGS. 8 and 
9) which both electrically and mechanically connects the sensor 10 to the 
monitoring system 92. More particularly, the connector 94 has a housing 96 
with parts 98, 100 which are joined at a hinge 102. The hinge 102 allows 
the housing parts 98, 100 to be pivoted, as indicated by the double-headed 
arrow 103, relative to each other between an open position in FIG. 8, and 
a closed position, wherein conductors 104, 106 on the connector 94 are 
electrically connected to the trace 20, on each at the locations 22, 24. A 
projecting stud 108 on the connector part 98 projects through a cut-out 
110 in the substrate layer 12 and into a seat 112 defined on the other 
connector part 100. Cooperating latch elements 114, 116 cooperate to 
maintain the connector 94 in the closed position, wherein the connecting 
portion 16 of the substrate layer 12 is mechanically locked in a position 
wherein the conductive trace 20 is in electrical contact with the 
conductors 104, 106. The conductors 104, 106 are operatively connected to 
the monitoring system 92 through cables 117, 118. 
A specific, suitable design of the monitoring system 92 can be arrived at 
by one skilled in the art. Many commercially available systems exist which 
would perform adequately. Generally, the monitoring system 92 has 
detecting means 119 for detecting two different states for the sensor 10, 
one with the conductive trace 20 defining a continuous conductive path 
between the first and second locations 22, 24, and a second state wherein 
the conductive trace 20 is interrupted between the first and second 
locations 22, 24. In response to detecting the second state, the detecting 
means 119 produces a signal to a signal producing means 120, which 
generates a signal that can be sensed, i.e., audibly or visually. 
To facilitate mounting of the sensor 10, a release layer 122 is provided 
over the adhesive layer 52. By producing a cut 124 at the mid-portion 
thereof, peeling of the release layer 122 is facilitated to expose the 
adhesive layer 52 for application thereof to the object 54. 
A dielectric layer 126 can be applied over the substrate layer 20 at the 
connecting portion 16 and neck 18 thereof to prevent accidental shorting 
between the first and second locations (or intentional shorting thereof by 
a potential thief). 
To assemble the sensor 10, the connector 94 can be pre-attached. In this 
state, the user need only peel off the release layer 122 and press the 
sensor 10 into the operative position. Alternatively, the sensor 10 can be 
pre-applied, after which the connector 94 is attached thereto. 
The foregoing disclosure of specific embodiments is intended to be 
illustrative of the broad concepts comprehended by the invention.