US3760397A

US3760397A - Alarm system

Info

Publication number: US3760397A
Application number: US00090338A
Authority: US
Inventors: J Taggart
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-11-17
Filing date: 1970-11-17
Publication date: 1973-09-18
Anticipated expiration: 1990-09-18

Abstract

A photocell-activated intruder alarm system, including a control circuit adapted to automatically adjust system operation to ambient light conditions and adapted to facilitate bore sighting of the apparatus on an external light source. A time delay inherently present in said circuit provides delay in arming of the alarm after activation of the system, whereby a user may remove himself from the protected area without discharging the alarm.

Description

1 States Patent Sept. 18, 1973' 1 ALARM SYSTEM 7 [76] Inventor: Josh B. Taggart, Box 366, Rt.'5,

Bristol, Tenn. 37620 [22] Filed: Nov. 17, 1970 [21] v Appl. No.: 90,338

[56] References Cited UNITED STATES PATENTS 3,636,532 l/l972 Apple 340/258 B 3,329,946 Robbins 340/258 B 3,189,883 6/1965 Lucas et al... 340/258 B 3,585,621

6/1971 DiCello 340/237 S Primary ExaminerDavid L. Trafton Attorney-Frank P. Cyr

[57] ABSTRACT A photocell-activated intruder alarm system, including a control circuit adapted to automatically adjust system operation to ambient light conditions and adapted to facilitate bore sighting of the apparatus on an external light source. A time delay inherently present in said circuit provides delay in arming of the alarm after activation of the system, whereby a user may remove himself from the protected area without discharging the alarm.

8 Claims, 4 Drawing Figures I 2 a Z 1a v '51 LIGHT SENSOR EXTElggslcllGHT 5 BORE SIGHT INDICATOR 2/ STANDBY POWER 27 l SMOKE/HEAT CONTROL UNIT I JUNCTION DETECTOR AND BOX 2 MODE SELECTOR EXTERNAL 25 l 9 V ALARM LINE POWER 4 23 POWER TRANSFORMER I INTERNAL ALARM I L I0 J AUXILIARY LIGHT SENSOR Patented Sept. 18, 1973 2 Sheets-Sheet l 1055mm woo:

e rmQEuEE I N VEN '1 OR. B TAGGART A TTORNE V 2 Sheets-Sheet z Patented Sept. 18, 1973 E OUT THRESHOLD QUESCENT VALUE 0.5

POTNT OF LIGHT TIME INTERCEPTION FIG. 4 E OUT 05 0V APPLICATION OF LIGHT 52 IN 'E.\"i 0R JOSH B. TAGGART ATTORNEY DEVICE FOR SUPPORTING SHEET MATERIALS The present invention relates to a device for supporting a load of sheets thereon, more particularly, to such a device wherein the sheets are positioned edgewise on a supporting surface and lean against an upright wall and the device is positionable in a vertical or rearwardly inclined position.

In the production of flat glass, various forms of load supporting devices have been used to hold the unit loads of glass sheets as they come from the production line. Similar or other forms of load supporting devices have been used for holding such loads of glass sheets in warehouses during storage or in vehicles during transportation. Such devices have also been provided with wheels to facilitate the movement of loads of sheets over relatively short distances, such as from the production plant to a shipping dock or a warehouse. Since such devices are generally provided with raised load supporting surfaces they can be lifted or carried with their loads in place by fork lift trucks or other handling apparatus so that it is not essential that the devices be always equipped with wheels.

These supporting devices are generally loaded by individually carrying each sheet over the front edge of the supporting surface and releasing the sheet so that its face leans against a wall extending upwardly from the rear portion of the load supporting surface. Each subsequently loaded sheet thus rests against the face of the previously loaded sheet. Unloading of this device is accomplished by the reverse sequence of the above operation. The loading and unloading operations thus require that the front of the supporting device be unobstructed by any load retaining wall or other structure. Basically, the supporting devices comprise a raised load supporting deck or surface and a rear wall upstanding from the rear portion of the supporting deck :so that when the device is viewed from the end thereof the supporting surface and wall define a substantially L-shaped structure.

During the loading and unloading operation the sheets which may be on the device at any given time must be stably supported. Since it is undesirable to provide any form of retaining structure on the front portion of the supporting device it is generally provided that the upstanding wall is inclined rearwardly and the sheets are leaned against this inclined wall. Such a structure is relatively inefiicient because the volume of storage space required for accommodating a storage device is disproportionate with respect to its load bearing capacity. When it is necessary to accommodate a large number of supporting devices loaded with sheets, the inefficiently used storage space increases directly in proportion to the number of devices being stored.

It is therefore the principal object of the present invention to provide a novel and improved device for supporting a load of sheets and requiring a minimum of storage area.

It is another object of the present invention to provide a supporting device for sheet material which enables sheets of glass and other material to be economically and efficiently stored, handled and transported.

It is a further object of the present invention to provide a device for supporting a load of sheets thereon in vertical position and upon which the sheets may be efi'b ciently loaded or unloaded.

According to one aspect of the present invention, the device for supporting a load of sheets may comprise supporting surface means having front and rear leg means. Wall means are upstanding from the rear portion of the load supporting surface means so as to support a load of sheets placed edgewise on the supporting surface and leaning against the wall means. The rear leg means comprises movable rear leg means pivotally mounted on the supporting device to pivot between a position in which the wall means is substantially vertical and another position in which the wall means is inclined rearwardly from the bottom to the top thereof.

The supporting surface means and the wall means essentially define an L-shaped structure and a movable leg or legs may be pivotally mounted from a point on the wall means above the supporting surfaces. A catch member is pivotally mounted on the device and locks the movable rear leg in a position wherein the supporting device is inclined. The catch member can be pivoted to a vertical position in which it is inoperative to enable the movable rear leg to be pivoted to a position in which the supporting device is substantially vertical. A retaining member may be provided to pass over and in front of the load of sheets and be detachably connected to the upper portion of the wall means and/or to the front portion of the supporting surface means.

The movable rear leg may also be pivoted to the lower portion of the supporting device so that when the device is in the inclined position the rear portion of the device will be supported at the junction of the supporting surface and upstanding wall means.

The supporting device of the present invention is particularly advantageous since during loading the device can be positioned with its rear wall inclined and the loaded device can then be stored in a vertical position in which it occupies a considerably smaller space. The floor space occupied by a loaded device in a vertical position is up to 45% less than for other known storage devices. Accordingly, the given area of a storage room, a transport container or vehicle can hold a considerably greater number of loaded devices of the present invention than previously known sheet supporting devices. It is apparent that while the rear wall of the storage device should be inclined during loading and unloading operations it is not necessary that the wall be inclined when the device has been loaded and is being stored or transported. At these times when the supporting device is in a vertical position the load is retained in position by suitable retaining straps or bars.

Other objects and advantages of the present invention will be apparent upon reference to the accompanying description when taken in conjunction with the following drawings, which are'exemplary, wherein;

FIG. 1 is an overall perspective device according to the present invention and looking at the rear thereof;

FIG. 2 is a perspective view but in enlarged scale showing details of the construction of the catch member on the supporting device of FIG. 1;

FIG. 3 is a side elevational view of a modified supporting device; and

FIG. 4 is a side elevational view of a portion of still another modification of the load supporting device according to the present invention.

Proceeding next to the drawings wherein like reference symbols indicate the same parts throughout the various views, a specific embodiment and modifica- As seen therein a control module 2 forms the heart of the system and includes generally a control unit and mode selector means 4, bore sight indicator 6, light sensor means 8, and internal alarm 10. Control module 2 will typically comprise a single compact unit, and as such unit will commonly be positioned in an area such as a room of a dwelling place desired to be protected. The module 2 is preferably housed in an attractive case or the like which blends in well with the surrounding environment.

Control unit and mode selector means 4, which will hereinafter be described in greater detail, performs the various control functions for the system and also includes switching means for powering the system and arming the alarm. Electrical power for module 2 is shown as being fed to means 4 by a line 25. Such power originates as line power at 12 and is stepped down in voltage at transformer 14 so that all potentials within the system are relatively low and therefore safe for the user. Transformer 14 is shown in the Figure as a separate unit external to module 2 but it will of course be clear that such element could as well be contained within module 2 itself. Similar considerations apply to the standby power unit 14. This unit, which is seen to be in communication with means 2 via the

lines

27 and 29, may simply comprise a battery pack or the like and furnishes power to means 4 by line 29 in the event of line power failure. The unit 16 is thus shown as residing external to module 2 but again could clearly be merged into the basic module 2 if so desired.

Control unit and mode selector means 4 is seen to be provided with an input via line 31 from light sensor 8. The latter, which may be a conventional photocell or the like, is, in accordance with the invention sighted upon a remote external light source 18. Source 18, further in accordance with the invention, may be any convenient illuminating source, including for example, a common room lamp, a reflecting surface, or a window accessible to external daylight. Source 18 will typically be considerably. removed from sensor 8 e.g., by being placed at the opposite side of a protected room. Sighting of sensor 8 upon source l8'is accomplished by physically manipulating module 2 to yeild appropriate indication in bore sight indicator 6 (connected to means 4) that optimal sighting has been achieved. The precise manner in which this action occurs will be set forth subsequently. Let it suffice for present to point out that after means 4 has appropriately been set for bore sighting, indicator 6 which may be a meter or light--- is observed as the orientation of module 2 is varied, the circuit of means 4 being such as to effect responses at indicator 6 which can be analyzed to determine the accuracy of sighting.

Once the sensor 8 of module 2 is thus accurately sighted on source 18, control unit and mode selector means 4 is adjusted to the "arm" mode, and thereafter fluctuations in light intensity falling upon sensor 8 which are of the type caused by an intruder passing between sensor 8 and source 18 will be detected at means 4 which will in turn activate internal alarm 10.

While the elements thus far described are capable of operating as a system without additional detection devices, the system will typically include additional sensors such as auxiliary light sensor 19, and smoke/heat detector 21. Sensor 19 may thus be used in the precise manner described in connection with sensor 8 to protect additional areas possibly remote from the area where module 2 is located, the auxiliary sensor being connected to module 2 at means 4 by the line 33. Obviously a plurality of such sensors may, if desired, be so employed. Similarly a smoke/heat detector 21 which may be of any conventional design may be connected back to module 2, and provide signals thereto indicative of dangerous heat or smoke conditions, such signals serving ultimately to activate alarm 10. In order to add flexibility to the system, smoke/heat detector 21 which may be one of a plurality of such units will typically be joined to module 2 by a junction box 19 which has connection means for a plurality of such detectors. Such box 20 may also serve as a connecting link between means 4 and an external alarm 23. The external alarm 23 will typically be conspicuously mounted outside a building or the like and may be activated commonly with or independent of internal alarm 10.

FIG. 2 is a simplified schematic electrical diagram for the control module portion of the system. Switching means for activating this circuit and switching its output and input to the various detectors and alarms etc. of FIG. 1, are for purposes of simplicity not shown, but are conventional, such switching being activated in accordance with the desired mode of operation of the system.

As seen in FIG. 2 a closed loop circuit is provided consisting of a DC. differential amplifier (transistors 20 and 22), a DC. amplifier (transistor 28),.and an emitter follower (transistor 24). Transistor 26 serves as a DC. amplifier to provide a large signal to resistor 30. The latter, while shown for purposes of the present diagram as a resistor, actually corresponds to bore sight indicator 6 of FIG. 1 and may in practice comprise a light bulb or a current measuring meter.

The photocell 36 of FIG. 2 corresponds to light sensor 8 of FIG. 1. Resistor 38 and capacitor 40 form a long time constant with respect to the transient signal to be sensed 'via photocell 36, thus keeping the closed loop from cancelling the desired signal.

Due to the fixed voltage applied to the base of transistor 22, the voltage across resistor '50 will remain approximately constant whenever transistor 22 is conducting. (It will be noted that transistor 22 will always be conducting when the loop stabilizes, since it is the only source of current for the base of transistor 28.) Thus we can write:

where E, is the supply voltage for the circuit.

At turn-on, capacitor 40 is discharged; thus the voltage at the junction of

resistors

42 and 44 will be at or near ground. The value of resistor 42 is made sufficiently small to force all the current through transistor 20 under these conditions, so that With transistor 22 off, transistor 28 is also off and capacitor 40 starts to charge toward E through

resistors

38 and 46. Emitter follower 24 prevents loading of the time constant and transfers the voltage on capacitor 40 so that V, E V 0.5. (where V voltage at junction of resistors 42 & 44.);

where V is the voltage on capacitor 40.

As V increases in value, the voltage drop across resistor 42 in parallel with the photocell is slowly reduced, decreasing i (the base current of transistor 20) until i multiplied by the D.C. current gain of transistor 20 (h,, is less than K At this point transister 22 starts to conduct, increasing until transistor 28 conducts, reducing the voltage at the collector of transistor 28 until capacitor 40 ceases to charge. The loop stabilizes at this point.

As light impinges on photocell 36, the resistance of this device decreases, becoming muchsmaller in value than resister 42. This momentarily increases i decreasing l cutting off transistor 28, allowing capacitor 40 to charge further and stabilize at a higher value. After restabilization and I both return to essentially their initial values.

Resistor 48 is of such value that the drop across it is small compared to the base-to-emitter drop of transistor 28. Thus the output under quiescent conditions will be approximately 0.5 volts under a very wide range of resistance values for photocell 36, in consequence of which the circuit is self-adjusting for a corresponding wide range of ambient lighting conditions. When the light to photocell 36 is interrupted the value of is reduced and l is increased by this b xhfa of transistor 20. This produces a positive signal at the 'circuit output 32 of. a magnitude in voltage dependent on the value of load resistor 34 (corresponding e.g., to

alarm resistor 48 and K If thelight is permanently interrupted the output E will slowly decay to its original value as shown in FIG. 3.

By setting a threshold level for activation, any number of devices, (such as an alarm, a relay,.a counter, a computer input, etc.) can be activated by the said output. It is also noted that by applying a f xed voltage other than zero to the emitter of transistor 28and to the bottom of resistor 34, the quiescent value can be varied over a range of values, including a negative value. Thus the present device can be set so that it is compatible with external devices with various trigger or threshold levels.

It is noted that the circuit ofFlG. 2 will sense sudden increases in light intensity as well as decreases. The output for a step increase is thus just the opposite in polarity, as shown in FIG. 4. This feature is utilized in bore sighting. In particular as a highly directional light cell is pointed toward a light source, the sudden negative swing at the output --as shown in FIG. 4- cuts off transistor 28. The only current then flowing through the base of transistor 26 is the capacitor 40 charge current via resistors 38and 46. Since resistor 38 is much larger than resistor 46, this current is too small to light delay in arming of the alarm following activation of this mode of system operation, may also be appreciated from the graph of FIG. 4. In particular, it will be observed therein that a considerable time period is present between a point such as 52 where E has dropped 'to zero and the point where quiescent voltage is attained. This same period is, of course, present following initial arming, and serves admirably to enable the system user to remove himself from presence of the photocell without effecting discharge of the alarm.

While the present invention has been particularly set forth in terms of specific embodiments thereof, it will be appreciated in view of the instant disclosure, that numerous variations upon the teaching are now enabled, which variations are yet within the true scope of this teaching. Accordingly, the invention is to be broadly construed and limited only by the scope and spirit of the claims now appended hereto.

' Iclaim:

.]l. A light sensor-activated intruder alarm system, comprising: 3

' a. light sensor means sightable on a spaced light source;

b. a control unit connected to receive the output from said light sensor means, said unit including means for providing a signal output at a relatively fixed quiescent level in the presence'of slow light changes at said sensor and at levels detectably removed from said quiescent level in the presence of transient light changes at said sensor, said means comprising a self-stabilizing DC closed loop circuit in series with said sensor, said loop including amplifier means and having a relatively long time constant with respect to said transient signals, but not with respect to said slow light changes sought to be compensated; r bore. sight detector means connected tosaid signal output .of said loop, said means being adapted to provide indication of sudden increases in light at said sensor, whereby sighting of said sensor on said light source may be detected; and I d. alarm means connected to said signal output, said means being adapted to provide indicationof sudden decreases in light at said sensor, whereby intrusion between said sensor and said light source may 'be detected.

2. Apparatus in accordance with claim 1, wherein said bore' sight detection means comprises an indicator lamp and D.C. amplifier means for receiving said signal output and providing power to said lamp in accordance with said signal output.

3. Apparatus in accordance with claim 1 wherein said sensor comprises a photocell, the resistance of which varies in response to the incident light level and wherein said loop includes differential amplifier means, the output from one side of said photocell being .one input to said differential amplifier means, and the output from said differential amplifier means being provided in series to the other side of said photocell for feeding back in said loop.

4. Apparatus in accordance with claim 3, wherein said control unit includes power switching means and means for switching said system to an arm mode, said RC circuit means having a sufficient time constant to provide upon switching to said arm mode a sufficient delay in said signal output attaining said quiescent level to permit the system operator to remove himself from the intruder detection zone of said system.

5. Apparatus in accordance with claim 1 including a plurality of light sensors.

6. Apparatus in accordance with claim 5 including a plurality of said alarm means, at least one of said means ferential amplifier means back to said sensor.

Claims

1. A light sensor-activated intruder alarm system, comprising: a. light sensor means sightable on a spaced light source; b. a control unit connected to receive the output from said light sensor means, said unit including means for providing a signal output at a relatively fixed quiescent level in the presence of slow light changes at said sensor and at levels detectably removed from said quiescent level in the presence of transient light changes at said sensor, said means comprising a self-stabilizing DC closed loop circuit in series with said sensor, said loop including amplifier means and having a relatively long time constant with respect to said transient signals, but not with respect to said slow light changes sought to be compensated; c. bore sight detector means connected to said signal output of said loop, said means being adapted to provide indication of sudden incReases in light at said sensor, whereby sighting of said sensor on said light source may be detected; and d. alarm means connected to said signal output, said means being adapted to provide indication of sudden decreases in light at said sensor, whereby intrusion between said sensor and said light source may be detected.

2. Apparatus in accordance with claim 1, wherein said bore sight detection means comprises an indicator lamp and D.C. amplifier means for receiving said signal output and providing power to said lamp in accordance with said signal output.

3. Apparatus in accordance with claim 1 wherein said sensor comprises a photocell, the resistance of which varies in response to the incident light level and wherein said loop includes differential amplifier means, the output from one side of said photocell being one input to said differential amplifier means, and the output from said differential amplifier means being provided in series to the other side of said photocell for feeding back in said loop.

5. Apparatus in accordance with claim 1 including a plurality of light sensors.

6. Apparatus in accordance with claim 5 including a plurality of said alarm means, at least one of said means together with said control unit, bore sight indicator, and at least one of said light sensors being contained within a compact module.

7. Apparatus in accordance with claim 6, further including smoke/heat detector means connected to said control unit, said control unit further including means adapted to discharge at least one of said alarm means upon receipt of a signal from said detector means indicative of smoke or heat.

8. Apparatus in accordance with claim 3, wherein an emitter follower and RC circuit means couples said differential amplifier means back to said sensor.