CONDITION SENSING AND ALARM UNIT AND CIRCUIT THEREFOR

• US 3,594,752 A
• Filed: 07/07/1969
• Issued: 07/20/1971
• Est. Priority Date: 07/07/1969
• Status: Expired due to Term

• Current Assignee: Ahdor H. Alton
• Original Assignee: Ahdor H. Alton
• Inventors: Alton, Ahdor H.
• Application Number:
  US04/839,520
• Time in Patent Office: 743 Days
• US Class Current: 340/585
• CPC Class Codes: F25D 29/008 Alarm devices
• CPC Class Codes: G01K 3/005 Circuits arrangements for indicating a predetermined temperature fire detection G08B17/00

Abstract

A readily mountable self-contained temperature sensing and alarm unit having a housing adapted to be mounted on the outside of a refrigerator truck, trailer, railroad car, or other refrigerated container, the housing encasing an alarm lamp, and a temperature sensor preferably attached to the end of an elongated tubular member extending from the rear of the housing to pass through a small opening in the wall of the refrigerated container. The housing may resemble and be of a size of an automobile head light or smaller and include a light dispersing cover plate on the outer front wall of the housing occupying most of the area of the housing so the energization of the alarm lamp is readily visible from many viewing angles. Control circuitry for the alarm lamp preferably is arranged on a printed circuit board having a portion thereof cut out to enable the printed circuit board to fit substantially completely around the alarm lamp within the housing. The control circuitry responds to the temperature sensor by energizing the alarm lamp which preferably flashes on and off when the temperature sensor, which may be a thermistor, senses a temperature above a safe temperature for the product carried within the refrigerated container.

Claims

1. A temperature sensing and alarm unit for sensing temperature within a refrigeration car, truck or other refrigerated container and giving an alarm indication at the exterior of the refrigerated container, comprising:

a dusttight housing having means for mounting the same to an exterior surface of said refrigerated container, said housing having an opening in the front thereof;

a visible alarm indicating means mounted on said housing and visible from outside of the same for giving a warning that the temperature within said container is beyond a predetermined desired temperature range;

an elongated member extending from the rear of said housing and adapted to extend through a relatively small opening in said refrigerated container;

a temperature responsive electrical element on the end of said elongated member to be positioned in temperature sensing relation with the environment within the refrigerated container and having an electrical characteristic which varies with temperature;

electronic circuit means mounted within said housing with said alarm indicating means, said electronic circuit means having input terminals connected through said elongated member to said temperature responsive element on the end thereof and having output terminals connected to said alarm indicating means for selective energization thereof;

said electronic circuit means having two circuit portions each having inputs connected in common to said input terminals and each circuit portion being responsive to a different value of said temperature responsive element, each of said circuit portions having an output connected to said alarm indicating means and both of said circuit portions being in said alarm blocking state when the value of the electrical characteristic of said temperature responsive element indicates that the temperature in the refrigerated container is within a predetermined desired temperature range, one of said circuit portions changing to an alarm energizing state when the electrical characteristic of said temperature responsive element has a value indicating that the temperature is above one of the limits of said range to give warning of such temperature, and the other of said circuit portions changing to an alarm energizing state when the electrical characteristic of said temperature responsive element is a value indicating that the temperature in the refrigerated container is below the other limit of said range, said circuit portions thus monitoring the upper and lower temperature limits of said predetermined desired temperature range.

2. The temperature sensing and alarm unit of claim 1, wherein said alarm indicating means is a lamp substantially centrally located within said housing and wherein said electronic circuit means includes components mounted on a circuit board surrounding said alarm indicating lamp, said circuit board having an opening which enables the positioning of said circuit board within said housing to substantially circumscribe said alarm indicating lamp.

3. The temperature sensing and alarm unit of claim 1, further including a manually operable selector means including a switch connected in circuit with said two circuit portions, one condition of said switch enabling said two circuit portions to be responsive to said temperature responsive elements to give warning above and below said upper and lower temperature limits, and another condition of said switch disabling said one of said circuit portions to provide only one temperature limit which is monitored.

4. The temperature sensing and alarm unit of claim 3 wherein said another condition of said switch also varies the value of the temperature responsive element which causes said other circuit portion to operate in said alarm energizing stAte.

5. A temperature sensing and alarm unit for sensing temperature within a refrigeration car, truck or other refrigerated container and giving an alarm indication at the exterior of the container, comprising:

a housing having means for mounting the same to the exterior surface of the refrigerated container;

an alarm indicating means mounted in said housing for giving a warning that the temperature within said container is above a predetermined desired temperature limit;

an elongated member extending from the rear of said housing and adapted to extend through a relatively small opening in the refrigerated container;

a temperature responsive element on the end of said elongated member to be positioned in temperature sensing relation with the environment within the refrigerated container;

heat isolation means which is a poor transmitter of heat positioned between said elongated member and said temperature responsive means which heat isolation means isolates said temperature responsive element from said housing to reduce transmission of heat from said housing to said temperature responsive element; and

circuit means connected between said temperature responsive elements and said alarm indicating means for energizing said alarm indicating means when said temperature responsive element senses a temperature above said desired predetermined temperature limit.

6. The temperature sensing and alarm unit of claim 5 wherein said alarm indicating means is a lamp, and said circuit means includes a flashing circuit for flashing said alarm indicating lamp on and off when said circuit means is energized in response to said temperature responsive element sensing a temperature above said predetermined temperature limit.

7. The condition sensing and alarm circuit of claim 5 wherein said housing is a dusttight housing having a large opening in the front thereof, said alarm indicating means is a lamp mounted behind said opening, and there is provided a light transmitting member secured to said housing covering said opening, the housing and light sensing member thereby resembling an automobile headlight.

8. The temperature sensing and alarm unit of claim 7 wherein said alarm indicating means is a lamp substantially centrally located within said housing and wherein said circuit means includes components mounted on a circuit board surrounding said alarm indicating means, said circuit board having an opening which enables the positioning of said circuit board within said housing to substantially circumscribe said alarm indicating lamp.

9. A condition sensing and alarm circuit comprising:

a condition responsive element to be positioned in condition sensing relation with a variable condition environment which is to have the condition thereof monitored, said condition responsive element having an electrical characteristic which progressively varies with changes of condition, the value of said condition responsive element corresponding to the value of the condition being monitored;

alarm indicating means for giving warning that the condition of said variable condition environment is beyond a given upper value or below a given lower value defining a range of condition values; and

electronic circuit means having input terminals connected to said condition responsive element and having output terminals connected to said alarm indicating means for selective energization thereof, said electronic circuit means having two circuit portions each having their input in common with said input terminals and each circuit portion being responsive to a different value of the electrical characteristic of said condition responsive element, each of said circuit portions having an output connected to said alarm indicating means and both of said circuit portions being in alarm blocking conditions when the electrical characteristics of said condition responsive element has a value indicating that the value of said condition is within said predetermined range of condition values, one of said circUit portions changing to an alarm energizing state when the electrical characteristic of said condition responsive element indicates that the value of the condition is above said given upper value to give warning of such condition and, the other of said circuit portions changing to an alarm energizing state when the electrical characteristic of said condition responsive element is of a value which indicates that the value of the condition is below said given lower value, said circuit portions thus operating to monitor the limits of said predetermined desired range of condition values.

10. The condition sensing and alarm circuit of claim 9 further including selector means including a switch connected in circuit with said two circuit portions, one condition of said switch enabling said two circuit portions to be responsive to said condition responsive element to give warning above and below said upper and lower condition values, and another condition of said switch disabling said one of said circuit portions to provide only one condition value which is monitored.

11. The condition sensing and alarm unit of claim 10 wherein said another condition of said switch also varies the value at which the condition responsive element causing said other circuit portion to operate in said alarm energizing state.

12. The condition sensing and alarm circuit of claim 9 wherein said alarm indicating means is a lamp.

13. The condition sensing and alarm circuit of claim 12 further including a flashing circuit electrically interconnected between the outputs of said two circuit portions and said alarm indicating lamp to flashingly control said alarm indicating lamp when either one of said two circuit portions is energized in response to said condition responsive element sensing a condition value above or below said range of condition values.

14. The condition sensing and alarm circuit of claim 9 wherein said condition responsive element is a thermistor.

15. The condition sensing and alarm circuit of claim 9 wherein each of said circuit portions includes first and second current controlling devices interconnected to have opposite relatively highly conductive and nonconductive conditions at a given time;

said condition responsive element being connected to a pair of corresponding current controlling devices of said circuit portions wherein one of said noncorresponding current controlling devices is normally in a relatively highly conductive condition and the other is normally in a relatively nonconductive condition, said condition responsive element being responsive to the condition value sensed at one end of a desired range of condition values for producing a control signal for reversing the conductive conditions of the current controlling devices of one of said circuit portions, and being responsive to the condition value at the other end of said desired range of condition values for producing a control signal therefrom for reversing the conductive conditions of the current controlling devices of the other circuit portion, said alarm indicating means being responsive to the reversal of the conductive conditions of said current controlling devices of said circuit portions by said condition responsive element for producing an alarm indication.

16. The condition sensing and alarm circuit of claim 15 wherein each of said current controlling devices of each circuit portion has a control terminal and a pair of load terminals, said noncorresponding current controlling devices of said circuit portions having their control terminals connected to said condition responsive element and their load terminals connected to a voltage source, the other current controlling devices of said circuit portions having their control terminals coupled to bias voltage sources and their load terminals connected to a voltage source, the terminals of the current controlling devices of each circuit portion being interconnected rapidly to reverse their conductive conditions when one of same is triggered into An opposite conductive condition by said condition responsive element.

17. The condition sensing and alarm circuit of claim 16 further including first means connectable to the bias voltage source of one of said circuit portions for changing the bias at the control terminal of the associated current controlling device to change the value of said one end of the range of condition values at which the conductive conditions of the associated current controlling devices reverse, and second means connectable to the other of the current controlling devices of said other circuit portion to disable said other circuit portion and render it nonresponsive to changes of said condition responsive element.

18. The condition sensing and alarm circuit of claim 17 wherein said first means is a resistor having one end thereof connected to the control terminal of one of the current controlling devices of said one circuit portion and the other end thereof connected to one terminal of a switch;

and said second means is a rectifier having one of its terminals connected to the control terminal of one of said current controlling devices of the other circuit portion, and its other terminal connected to said contact of said switch, and the other terminal of said switch being connected to a point in common with the terminals of said current control devices.

19. A lamp energizing circuit comprising:

an incandescent lamp to be energized by a voltage source to emit visible light therefrom, said incandescent lamp having a relatively low electrical resistance when in a cold deenergized condition and a relatively high electrical resistance when in a hot energized light emitting condition;

a current controlling device having a control terminal for receiving a lamp energizing control signal to render said current controlling device conductive fully to energize said incandescent lamp to a visible light emitting condition, said current controlling device having a pair of load terminals connected in series between the voltage source and said incandescent lamp to pass light emitting energizing current therethrough; and

a resistor connected to the load terminals of said current controlling device for shunting said current controlling device with a small amount of current which flows through said incandescent lamp when said current controlling device is nonconductive to maintain said incandescent lamp in a heated condition with no readily visible light emitted therefrom, so that the resistance value of said incandescent lamp is substantially increased from its normal cold resistance condition.

20. The condition sensing and alarm circuit of claim 19 further including a rectifier connected in series with the load terminals of said current controlling device and the voltage source connected thereto to prevent damage to said current controlling device by inadvertent connection to a voltage source of the wrong polarity.