U.S. patent number 3,792,493 [Application Number 05/303,904] was granted by the patent office on 1974-02-12 for door actuated time recorder.
This patent grant is currently assigned to Intelligence Services Products Division, Inc.. Invention is credited to David C. Hughes.
United States Patent |
3,792,493 |
Hughes |
February 12, 1974 |
DOOR ACTUATED TIME RECORDER
Abstract
A security system for detecting the opening or closing of the
door of an enclosed area incudes an enclosure having a digital
clock which drives a binary register, the binary register providing
a binary decimal code a measure of time. The door includes a fin
having a pair of magnets which enter a slot in the enclosure when
the door is closed and are removed therefrom when the door is open.
A detector and associated circuitry in the enclosure sense the
presence of the magnets and provides a signal to a storage register
each time the door is opened or closed, thereby causing the storage
register to sample and hold the binary decimal code provided by the
binary register at the time of an opening or closing. The storage
register is coupled to an illuminated display by decoder/drivers,
thereby causing the stored time to be displayed in arabic numerals.
In addition, the outputs of the storage register are coupled to the
writing styluses of an electromechanical recorder in the enclosure.
A motor in the recorder, in response to the detection, moves a
voltage sensitive paper under the styluses, thereby causing the
stored time to be recorded in binary decimal code on the paper.
Thus, each opening or closing of the door is recorded. The
enclosure includes a transparent window through which several such
writings on the paper are visible, and another transparent window
through which the illuminated display is visible at a distance.
Inventors: |
Hughes; David C. (Cos Cob,
CT) |
Assignee: |
Intelligence Services Products
Division, Inc. (Syosset, NY)
|
Family
ID: |
23174207 |
Appl.
No.: |
05/303,904 |
Filed: |
November 6, 1972 |
Current U.S.
Class: |
346/20; 346/93;
346/42; 368/6; 346/150.1 |
Current CPC
Class: |
G07C
1/32 (20130101); G07C 3/12 (20130101) |
Current International
Class: |
G07C
1/32 (20060101); G07C 1/00 (20060101); G07C
3/00 (20060101); G07C 3/12 (20060101); G07c
001/10 () |
Field of
Search: |
;346/20,42,79,80,93,74CH,74E,74S,74SB,74SC ;340/274,275
;58/152R,145R,39.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hartary; Joseph W.
Attorney, Agent or Firm: Levine; Alan A. Breitenfeld &
Levine
Claims
What is claimed is:
1. A security system for an enclosed area having a door,
comprising:
a. means for providing a periodic pulse signal;
b. means responsive to the pulse signal for providing a continuous
indication of time;
c. a detector for sensing each opening or closing of the door;
d. means responsive to the detector for sampling and storing the
indication of time corresponding to the time when the last sensed
opening or closing of the door occurred; and
e. means coupled to the sampling and storing means (d) and to the
detector, for providing a written record of the time when each of
the sensed openings or closings of the door occurred,
said means for providing a written record including signal
sensitive paper, means for linearly moving in succession a
different section of the signal sensitive paper past a
predetermined location each time an opening or closing of the door
is sensed, and means for applying a signal to the section of paper
moving past the predetermined location; thereby writing the time of
said opening or closing of the door.
2. A security system as defined in claim 1 wherein the means for
providing a continuous indication of time include means for
correlating the time indication provided with a real time
reference.
3. A security system as defined in claim 1 wherein the detector
includes magnetic means which are actuated by the opening or
closing of the door, and means for sensing the presence therein of
the actuated magnetic means.
4. A security system as defined in claim 1 further including:
a digital display device; and means coupled to the sampling and
storage means (d) for driving the display device, whereby the
display device provides a visible indication of when the door was
last opened or closed.
5. A security system as defined in claim 4 wherein the means for
providing a continuous indication of time includes means for
correlating the visible indication provided by the display device
with a real time reference.
6. A security system for an enclosed area having a door,
comprising:
a. means for providing a periodic pulse signal;
b. means responsive to the pulse signal for providing a continuous
indication of time;
c. a detector for sensing each opening or closing of the door;
d. means responsive to the detector for sampling and storing the
indication of time corresponding to the time when the last sensed
opening or closing of the door occurred; and
e. means coupled to the sampling and storing means (d) and to the
detector, for providing a written record of the time when each of
the sensed openings or closings of the door occurred, said means
for providing a written record including
voltage-sensitive paper,
means for moving sections of the voltage-sensitive paper past a
predetermined location each time an opening or closing of the door
is sensed, and
means for providing a voltage across the thickness of the section
of paper moving past the predetermined location, thereby writing
the time of said opening or closing of the door.
7. A security system as defined in claim 6 further including means
for applying a voltage to the paper indicating whether the movement
of the door is an opening or a closing.
8. A security system as defined in claim 6 wherein the means for
moving the voltage-sensitive paper includes:
a voltage source,
a motor, and
means for driving the motor a predetermined amount when the voltage
provided by the voltage source exceeds a predetermined value and an
opening or closing of the door is sensed, and
wherein said means for applying a voltage across the thickness of
the section of paper moving past the predetermined location is
responsive to movement of said motor.
9. A security system as defined in claim 8, wherein the continuous
indication of time is in binary decimal code; and wherein said
means responsive to the movement of the motor include:
a switch connected to the voltage source;
a cam driven by the motor for closing the switch momentarily each
time the door is opened or closed;
a roller electrically connected to the switch;
a plurality of writing styluses arranged in parallel adjacent the
roller, the space between the writing styluses and rollers defining
the predetermined location; and
means coupled to the sampling and holding means (d) for selectively
grounding said writing styluses according to the binary decimal
code corresponding to the time the door is opened or closed,
thereby providing a writing on the paper which indicates in binary
decimal code the times when the door is opened or closed.
10. A security system as defined in claim 9 wherein said means for
selectively grounding said writing styluses include a plurality of
solid state switches, each of said solid state switches being
connected to only one of the writing styluses.
11. A security system as defined in claim 8 wherein the voltage
source includes a power supply, a current source connected to the
power supply, a capacitor connected to the output of the current
source, whereby the capacitor may be charged to a voltage which
exceeds the output voltage of the power supply and is sufficient
for writing on the voltage sensitive paper.
12. A security system as defined in claim 11 wherein the security
system includes means for delaying the writing of a time
corresponding to the opening or closing of the door until the
capacitor has been charged to a writing level.
Description
The subject invention relates to security systems, and in
particular to a security system for permanently recording the time
of each opening or closing of the door of an enclosure, and for
providing an illuminated display of the time of the last recorded
event. The invention finds particular utility in connection with
the cargo doors of a vehicle.
Each year people in the business of transporting goods lose money
because goods are stolen from warehouses and vehicles used to
transport the goods. In an attempt to minimize loses, and to
determine the place or places where the thefts are occuring, seals
have been placed on vehicle doors after the vehicles have been
loaded. Thus, if a vehicle is dispatched with a seal and arrives at
its destination with the seal broken and goods missing, it is known
that the theft occurred while the goods were in transit and in the
custody of known personnel. However, vehicle drivers usually carry
a supply of seals with them, and hence are free to open and reseal
the vehicle doors at will. In addition, due to human falibility,
the sealing process is seldom carried out properly. Moreover, even
when the seal is properly applied the use of seals has not been
very effective because the time during which a seal is broken and a
theft occurs is not known with any degree of accuracy. For example,
if a sealed truck is driven by more than one driver and the drivers
forget to check the seal when the switching of drivers takes place,
or if a driver stops overnight and neglects to check the seal when
he resumes his trip, the time or place of the theft and the
custodian of the truck at the time of the theft will not be
known.
Accordingly, it is an object of the present invention to provide a
security system which automatically records on a permanent record,
the time of each opening and closing of the door of an enclosure,
such as a truck, thereby providing information with regard to when
a theft has occurred, and, in the case of a vehicle, identifying
the custodian of the vehicle at the time of the theft.
It is another object of the present invention to provide a security
system which automatically displays a sealing number with each
closure of the door, the sealing number being related to the time
of the closure.
It is still another object of the present invention to provide an
electromechanical security system which detects and records the
opening and closing the doors of an enclosed area for a
predetermined amount of time after its primary source of electrical
power has been removed.
Additional objects and features of this invention will become
apparent by reference to the following description in conjunction
with the accompanying drawings, in which:
FIG. 1 is a perspective view of a mobile security system according
to the invention;
FIG. 2 is a schematic block diagram of the security system;
FIG. 3 is a schematic block diagram of a part of the security
system which provides the visual indication and some or its
connections to that part of the security system which provides a
written record;
FIG. 4 is a schematic block diagram of a part of the security
system which provides the written record of the times when the door
being monitored is opened and closed;
FIG. 5 is a set of waveforms which are useful for describing the
sequence of events occurring within the security system each time
the door being monitored is opened or closed; and
FIG. 6 is a fragmentary cross-sectional view of the security
system, showing part of an electromechanical recorder and a window
for displaying the written record of the openings and closings of
the door.
A security system, according to the invention, which provides a
written record of the time during which the door of an enclosure
were opened or closed, and an illuminated indication of the time
when the door was last opened or closed, is shown in FIG. 1. In the
following description, the invention will sometimes be referred to
as associated with a truck having doors being monitored. However,
it is to be understood that the invention can be used with any
enclosure having an access door which it is desired to monitor.
The system chosen to illustrate this invention is housed within an
enclosure 13 (FIG. 1) having a slot 14. The door 12 to be monitored
is furnished with a fin 11, in which two magnets 10 are embedded,
the fin moving into slot 14 when the door is closed and moving out
of slot 14 when the door is opened. Within the enclosure 13 there
is located an electromechanical system which responds to the
presence or absence of magnets 10 in the slot 14 and provides, in
binary decimal code, a written record of the times when the door 12
was opened or closed and, in arabic numerals, an illuminated
display of the time when the door was last opened or closed. The
written record sets forth the time in weeks, days, hours, and
minutes, and is visible through the transparent window 15. The
illuminated display sets forth the time of the last opening or
closing in days, hours, and minutes, and is visible through the
transparent window 16.
In general, the electromechanical system, a block diagram of which
is shown in FIG. 2, includes a crystal oscillator 17, which because
of its stability functions as a digital clock. In the system, the
crystal oscillator 17 is connected to a divider 18 which provides
several outputs. One of the outputs is a one pulse per minute
signal and the other outputs are signals having higher repetition
rates. The signals from the divider 18 are separately connected to
the terminals of a switch 19 whose wiper arm may be used to select
one of the signals for driving a binary counter 20. In response to
the one pulse per minute signal, the binary counter 20 provides, in
binary decimal code, a measure of time in minutes, hours, days, and
weeks. As more fully described below, the higher frequency outputs
of the divider 18 and the switch 19 may be used to accelerate the
count in binary counter 20 when it is desired to correlate the time
reading in the counter with a particular time reference such as
eastern daylight saving time.
The binary outputs of counter 20 are connected to the inputs of a
storage register 21. When the magnets 10 are moved into or out of
the enclosure 13, a detector 22 applies a signal to a record logic
circuit 23. The record logic circuit 23, in turn, activates a
digital recorder 24 and sends a signal to the storage register 21,
thereby causing the storage register to sample and hold the binary
decimal code provided by binary counter 20. The coded time
information in the storage register 21 is then coupled to the
digital recorder 24 where it is reduced to a writing. That part of
the binary decimal code which corresponds to time information in
terms of minutes, hours, and days is also coupled to a
decoder/driver unit 25 which drives the incandescent tubes of a
visual display unit 26.
Referring to FIG. 3, the binary counter 20 includes nine counter
units 28 (not all shown), a typical unit being the Motorola 7490
circuit, which are interconnected according to ways which are well
known in the art so as to provide from a periodic pulse signal
seven sets of outputs, each set of outputs 29 providing in parallel
form bits which define a number in binary code. When the one pulse
per minute signal from the switch 19 is connected to the binary
counter 20, the seven output sets provide minutes, tens of minutes,
hours, tens of hours, days, weeks, and tens of weeks numbers in
binary decimal code.
Storage register 21 includes seven storage units 30 (not all
shown), the Motorola 7475 circuit being typical, each of which is
connected to one of the sets of outputs 29 and to the record logic
circuit 23 via line 31. When, as more fully described below, the
logic circuit 23 applies a digital command signal to the register
21, the storage units 30 sample and hold the time information
provided by the seven sets of outputs.
Each of the storage units 30 corresponding to the minutes, tens of
minutes, hours, tens of hours, and day numbers is coupled by a
decoder/driver 32 (not all shown), such as the Motorola 7447
circuit, in the decoder/driver unit 25 to an incandescent display
device 33 such as the RCA DR 2010 Numitron. Thus, five Numitron
devices 33 in the visual display unit 26 provide, in arabic
numerals, the time when the digital command signal is applied to
the storage register 21, this time being related, as more fully
described below, to the opening or closing of the door 12. It
should be noted that because the storage register 21 holds the
sampled binary decimal code, the Numitron devices provide a display
of the sampled time until a subsequent opening or closing of the
door 12 occurs. Thus, the visual display unit 26 always indicates
the last opening or closing of the door.
As shown schematically, by lines 35-39 connected to brackets, the
binary outputs of the storage units are connected to the digital
recorder 24, and are used therein, as more fully described below,
to control writing styluses.
In FIG. 4, there is shown a pair of magnetic reed switches 41, the
switches being grounded at one end and connected at the other end
to a line 43. Adjacent to the switches 41 there is located a pair
of magnets 42. The magnets 42 and switches 41 make up the contents
of the detector 22 (shown in FIG. 2) and, physically, are located
in the walls of the slot 14 in enclosure 13 (see FIG. 1). The
magnets 42 are disposed in the walls in a parallel opposing
arrangement (FIG. 4) but at sufficient distance apart so their
fields do not neutralize each other. Each magnet 42 is spaced with
its associated switch 41 so as to produce a closing. Neutralization
of the fields of magnets 42 will occur only when two magnets of
sufficient strength and appropriate polarity are introduced into
the slot as is the case when fin 11 enters. Thus the door is
registered OPEN when either switch 41 is closed but will only
register CLOSED when both switches 41 are open.
Line 43 is connected within the record logic unit 23, via resistor
44 to a grounded capacitor 45, to one end of a resistor 46 whose
other end is connected via line 47 to a power supply 48, and to the
input of an inverter 49. When the switches 41 are closed, the input
to the inverter 49 is determined by the power supply 48 and the
voltage divider, i.e., the resistors 44 and 46, and when the
switches 41 are open, the input to the inverter 49 is determined by
the power supply, the resistor 46 and the capacitor 45. Thus, when
the door 12 is open, the switches 41 are closed and the voltage at
the input to the inverter is low relative to the voltage present at
that input when the door 12 is closed, the switches 41 are opened
and the capacitor 45 is charged.
The output of the inverter 49 and the output of a flip-flop 52 are
separately connected, via lines 50 and 53, respectively, to the
input terminals of an EXCLUSIVE OR gate 51. The output of the
EXCLUSIVE OR gate 51 is connected via line 54 to the trigger
terminal of a flip-flop 55 and the output terminal of the flip-flop
55 is connected via line 56 to an input terminal of an AND gate 57.
The power supply 48 is connected to a current source 59 and the
current source 59 is connected via line 60 to a grounded storage
capacitor 61. In addition, line 60 is connected to one end of a
resistor 62. The other end of resistor 62 is connected to one end
of a grounded resistor 63 and, via line 64, to the other input of
the AND gate 57. In effect, resistors 62 and 63 comprise a voltage
divider which is in parallel with the storage capacitor 61, the
output of the voltage divider being connected to the AND gate 57.
The output of the AND gate 57 is connected to the gate terminal of
a silicon controlled rectifier (SCR) 68 via a resistor 65, the gate
terminal also being connected to ground by a resistor 66. In
effect, the output of the AND gate 57 is connected to the gate
terminal of an SCR 68 by a voltage divider. The cathode of the SCR
68 is grounded and its anode is connected to one of the terminals
of a motor 67. The other terminal of the motor 67 is connected to
the power supply 48. The circuitry described in this paragraph
functions as follows.
Referring to FIGS. 4 and 5, if it is assumed that at a time prior
to t.sub.1, the door 12 is open and the voltage on the output line
53 of the flip-flop 52 is high (see voltage waveform A in FIG. 5),
the high output voltage on line 50 from inverter 49 (see voltage
waveform B) plus the high on line 53 causes the voltage on the
output line 54 of the EXCLUSIVE OR gate 51 to be low (see voltage
waveform C). The output line 56 of the flip-flop 55 (see voltage
waveform D) has been set low. If the capacitor 61 is fully charged,
the voltage on line 64 will be high (see voltage waveform E).
However, since the voltage on line 56 is low, the voltage at the
output of the AND gate is low and will keep the SCR 68 in a
non-conductive state. When, at a time t.sub.1, the door 12 is
closed the output voltage of the inverter 49 drops to a low state
(see voltage waveform B). The low input on line 50 and the high
input on line 53 cause the output of the EXCLUSIVE OR gate 51 to
rise to a high voltage state (see voltage waveform C). In turn, the
high input to the flip-flop 55 causes the output of the flip-flop
to go to a high voltage state (see voltage waveform D), thereby
causing, via the AND gate 57, the SCR 68 to conduct. Conduction by
the SCR 68 turns the motor 67 on.
The motor 67 is mechanically coupled, via a gear train 71 (see
FIGS. 4 and 6) to a sprocket drive 76, and to a shaft 72 on which
there are mounted three cams 73, 74, 75. Cam 73 is used to control
the state of a single pole double throw switch 77 whose movable
contact is grounded. One terminal of the switch 77 is connected to
the anode of the SCR 68 and the other terminal is connected to one
end of a resistor 80. The other end of resistor 80 is connected to
a grounded capacitor 81, to one end of a resistor 82 whose other
end is connected via line 47 to the power supply 48, and to the
input of an inverter 83. In turn, the output of the inverter 83 is
connected to the flip-flop 52 and as previously mentioned, via wire
31, to the storage register 21. When the motor 67 is at a
standstill, the movable contact of the switch 77 is connected to
the resistor 80. This switch condition is indicated by the lower
level line in waveform F in FIG. 5. However, when the motor begins
to rotate at for example time t.sub.2, the cam 73 throws the
movable contact of the switch 77 into contact with the anode of the
SCR 68. The thrown switch condition is indicated by the higher
level line in waveform F. When the grounded movable contact of the
switch 77 is disconnected from the resistor 80, the voltage input
to the inverter 83 rises and as a result, a voltage drop is
provided over line 31 which causes the storage units 30 in the
storage register 21 to sample and hold, as previously described,
and causes the flip-flop 52 to go from its initially assumed high
voltage state to a low voltage state (see waveform A). Thus, the
inputs to the EXCLUSIVE OR gate 51 again have the same state (low)
and the voltage state on its output line 54 drops without affecting
the flip-flop 55. As will become apparent, this action prepares the
circuit for another cycle of operation. It should be noted that
when the cam 73 throws the switch 77 the motor is connected at one
end to ground thereby causing the total voltage from the power
supply 48 to be applied to the motor and reducing the voltage
across the SCR to zero.
At a point during the time that the cam 73 keeps the movable
contact of the switch 77 in contact with the motor, for example at
time t.sub.3, cam 75 throws the movable contact of a switch 86 into
contact with line 60. The thrown state of the switch is indicated
by the higher level line of waveform G in FIG. 5. The armature of
the switch 86 is connected to a metallic roller 87 (FIGS. 4 and 6)
which is insulated from the enclosure and over which a voltage
sensitive paper 104 passes. As more fully described below, it is
the discharge from the capacitor 61 through the roller 87 and the
voltage sensitive paper which causes a writing to take place.
At a point during the time that the motor 67 is grounded and the
capacitor 61 is connected to the roller 87, for example at time
t.sub.4, the cam 74 closes a switch 88 (FIG. 4). The closed state
of switch 88 is indicated in FIG. 5 by the higher level line in
waveform H. The movable contact of the switch 88 is connected via a
resistor 89 to the power supply 48, and a terminal of the switch 88
is connected via line 90 to the flip-flop 55. When the cam 74
closes the switch 88, a high voltage is applied to the flip-flop 55
and the flip-flop 55 is reset in preparation for another cycle.
During the time that the high voltage is being applied to the
flip-flop 55, at for example time t.sub.5, the cam 75 disconnects
the storage capacitor 61 from the high voltage roller 87.
Thereafter, the cam 74 opens the switch 88, at time t.sub.6, and
cam 73 throws the switch 77 at time t.sub.7. It should be noted
that at this point in the sequence all of the switches 77, 86, and
88 are in their initial positions.
Moreover, it should be noted that when switch 77 returned to its
initial position, the ground was removed from the anode of the SCR
68 and the motor 67. Since the reset signal applied to the
flip-flop 55 causes the output voltage on line 56 to go low, the
output from the AND gate on line 69 (see waveform E) is low and
keeps the SCR 68 in a non-conductive state.
As previously mentioned, the outputs of the storage register 21 are
connected to the digital recorder 24. In FIG. 4 all of the outputs
represented by lines 35-39 in FIG. 3 are represented by the single
line and bracket 95. Although only one circuit is shown in FIG. 4,
each of the actual outputs is connected, for example, by a resistor
96 to the base of a switching transistor 97 having a grounded
emitter. In turn, the collector of trans-istor 97 is connected by a
resistor 99 to one of the styluses 100. In addition to the outputs
from the storage registers, the output of inverter 49 is connected
via line 50 and a resistor 101 to the base of a transistor 102
having a grounded emitter, its collector being coupled to one of
the styluses 100 by a resistor 103. The styluses 100 are arranged
in parallel and abut against the part of the voltage sensitive
paper 104 (FIG. 6) which is in contact with the roller 87. Thus,
when the storage capacitor 61 is connected to the roller 87 by
switch 86, its discharge (see wave-form E at time t.sub.3) takes
place only through those styluses 100 which are rendered conductive
by the inputs to the transistors coupled to the styluses, i.e., the
output of the storage register 21. The discharge process causes
marks to be made on the voltage sensitive paper 104 which are
related to the binary digital code held in the storage register 21,
and a mark, due to the output of inverter 49, which indicates
whether the recording corresponds to the time of an opening or
closing of the door.
In the sequence of events described, it was assumed that the door
12 was moved from an open to a closed position. If at time t.sub.8
the door 12 is opened, the output of the inverter 49 is caused to
rise (see voltage waveform B) to a high voltage state. Since the
output of the flip-flop 52 is, at that time, at a low voltage
state, the outputs of the EXCLUSIVE OR gate 54 rises causing the
reset flip-flop 55 output to rise. If the voltage across capacitor
61 has had a chance to build up to a level which is sufficient for
writing purposes, the SCR 68 is again fired and another writing
takes place. If the voltage across the capacitor 61 is too low for
writing, the firing of the SCR 68 is delayed until the current
source 59 has charged the capacitor 61. Typically the voltage
required across the capacitor 61 to cause the SCR 68 to be fired is
approximately 300 volts, and is a level which is dictated by the
requirements of the voltage sensitive paper 104 used.
Although the capacitor 61 and the current source 59 could be
replaced with a b 300 volt power supply, the arrangement described
is preferred when the security system is to be used with a truck or
the like which is already equipped with a 6 or 12 volt power
supply.
Preferably, the power supply 48 is located within the enclosure 13
and is a battery which is continuously charged by the power supply
in the truck. Thus, if for any reason the external power is lost,
the system will continue to operate. Although it is not shown, the
illuminated display may be used to indicate the loss of power. The
latter may be achieved by connecting the power supply of the truck
to the circuits associated with the display, and to the power
supply 48, the power supply 48 only being connected to the circuits
associated with the recorder. Thus, if the power supply on the
truck is disconnected or ceases to operate, the illuminated display
will be extinguished but the recorder will continue to operate for
a period of time determined by the capacity of the battery within
the enclosure 13.
Referring to FIGS. 2 and 4, it may be noted that line 31 is
connected to a switch 106 which is grounded. When switch 106 is in
the closed position, the storage register 21 continuously samples
the binary counter 20 and the display unit 26 operates
continuously. In this mode of operation, the switch 19 may be used
to apply the higher frequency signals from the divider 18 to the
binary counter 20 until the time shown by the display unit 26
corresponds to a desired reference such as eastern daylight time or
the like. Once the display has been caused to correspond to a
particular reference, the switch 106 may be moved to its open
position and the system will operate as previously described.
Since the operation of the system requires that the switches 77,
86, and 88 operate sequentially, and that the most recently
recorded times be visible without having to open the enclosure 13,
a mechanical arrangement of parts for the recorder such as is shown
in FIG. 6 is preferred. Referring to FIG. 6, it may be seen that
the motor 67 is mounted on the base 110 of the enclosure 13 between
a back wall 111 and a partition 112 (partly shown) which is
parallel to the back wall. Partition 112 and back wall 111
rotatably support the rod 72 on which the cams 73-75 (not all
shown) are mounted. Partition 112 and back wall 111 also support
between them the sprocket drive 76, the high voltage roller 87, via
insulated bearings (not shown), a rod 105 for supporting the supply
roll of voltage sensitive paper 104, and a rod 114 which supports
an insulated block 115 carrying the styluses 100. In addition, the
partition 112 and back wall 111 support a pair of rods on which the
switches 77, 72, and 86 (not all shown) are mounted, the switches
having followers which, respectively, ride the cams 73-75. It
should be noted that the voltage sensitive paper 104 extends from
the rod 105, passes between the styluses 100 and the high voltage
roller 87, under the transparent window 15, on to the sprocket
drive 76, and then to a take-up roller (not shown). Thus, when the
motor 67 is turned on, the gear train 71 rotates the cams 77-75 and
the sprocket drive 76, thereby sequentially operating the switches
72, 77, 86 and advancing the resulting writings on the voltage
sensitive paper 104 under the transparent window 15. The size of
the window is preferably large enough so that several most recently
recorded openings and closings on the paper are visible at any one
time.
To insure that the security system itself is not tampered with, it
is preferred that the enclosure 13 and the transparent windows 15
and 16 (see FIG. 1) be made from metal and unbreakable or
bullet-proof glass, respectively. Further, since the top 27 of the
enclosure must be opened periodically to reload the system with
voltage sensitive paper, it is preferred that a hidden combination
lock (not shown) be provided to keep the top secure and that the
combination of the lock be known only by trusted personnel.
In summary, a secure enclosure 13 houses an illuminated display and
an electromechanical recorder which respond to the opening or
closing of a door 12. Each response causes the time of the event to
be incandescently displayed in arabic numerals and permanently
recorded in binary decimal code on voltage sensitive paper. The
system operates from a low voltage source such as is found on
vehicles and as a result, the system may be used to monitor the
cargo doors of vehicles, the information obtained from the system
being useful to determine when thefts occur.
Although the embodiment of the invention described herein provides
a coded record on voltage sensitive paper, other embodi-ments of
the invention could, in place thereof, utilize equivalent
imprinters which are heat, pressure or light sensitive to provide
coded or uncoded e.g., arabic, written records. Moreover,
equivalent displays which are luminescent, florescent, etc. may be
substituted by those skilled in the art for the incandescent
display described, and movers other than the D.C. motor, e.g.,
stepping motors, solenoids, may be used to drive the recorder.
Accordingly, it is to be understood that the description herein of
a preferred embodiment, according to the invention, is set forth as
an example thereof and is not to be construed or interpreted as a
limitation on the claims which follow and define the invention.
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