GB2106681A - Safety apparatus for portable heating device - Google Patents

Abstract

A safety apparatus for a portable kerosene type heater (10) having a wick (12) includes a heat sensitive member (20) located near the combustion area of the heating device which senses the temperature and produces an indication signal when the sensed temperature exceeding a predetermined temperature generally equivalent to the maximum safe operating level of the heater. A temperature warning signal in the form of a continous audible tone is produced by a horn in response to the production of an indication signal by the heat sensitive member. The horn is powered by a DC power source, such as a battery, and a low power detector causes the horn to produce an intermittent audible signal when the available power in the battery drops below a predetermined level. <IMAGE>

Description

SPECIFICATION Safety apparatus for portable heating device The present invention relates to a safety apparatus for portable heaters and more particularly to a heat monitoring and warning device for use for example in kerosene burning portable space heaters.

Kerosene burning space heaters are safe under normal operating conditions and use, however, there is always a risk factor associated with combustible fuels. The risk factor increases with misuse, abuse and misapplication of the fuel by a careless consumer and this applies to otherwise safe portable kerosene heaters. The neglicence of the use might take the form of inadvertent use of improper or contaminated fuels, by misuse of the heater in a combustible area, by improper servicing of the heater, for example, by improperly positioning the wick too high, or by the presence of floor or rug contaminants becoming blocked in the primary air tube, thereby igniting the floor or rub.These negligent misapplications of portable kerosene heaters can result in overheating, which in turn can result in an operating temperature which will exceed the maximum safe operating temperature of the particular heater.

Attempts to deal with overheating of heaters have included flame extinguishing mechanisms and fuel shut off mechanisms. Such mechanisms are normally controlled by thermostatic devices such as bimetallic strips or Bourdan tubes which are placed near the combustion area and which release a spring loaded extinguisher element or the like in response to the burner reaching a predetermined temperature.

However, it has been found that these prior art devices are not totally effective when applied to portable kerosene type heating appliances. In particular, it has been found that a runaway fire may have already spread to the fuel supply or reservoir itself before the extinguisher has become actuated. In such an occurence, the runaway fire can continue even after the extinguisher mechanism is actuated and thus it serves little, if any, purpose. Accordingly, there is a significant need for a safety device for kerosene portable heaters which will adequately protect the consumer against inadvertent misuse of the consumer's own negligence.

According to the present invention, there is provided heat sensing apparatus for detecting an exces sivetemperature level in afuel burning heater which comprises a heat sensitive member located generally near the combustion area of the heating device, the said member having means for sensing the temperature near the combustion area and means for providing an indication signal when the sensed temperature exceeds a predetermined temperature which is above the maximum safe operating temperature and below the overheating temperature of the heating device; and warning means for generating a temperature warning signal in response to the heat sensitive member providing an indication that the said predetermined temperature has been exceeded.

The predetermined temperature is chosen to exceed the temperature corresponding to the maximum Btu-output temperature relationship of the heating device, but will be below the temperature corresponding to an overheating condition. This predetermined temperature value will of course be dependent upon the specific location of the heat sensitive member for a particular fuel combustible heating device. The precise location of the heat sensitive member will be determined with primary consideration being given to the particular relationship between heat (BTU) and temperature at that particular location.

Examples of such types of devices in which the invention can be employed are radiant and convection wick type heaters, specifically in the flame producing areas. Of couse, the invention can be employed in other types of devices as well. More than one heat sensor may be used for sensing at more than one location.

The warning signal can be either an audible signal a visual signal or any other type of signal which will provide a definite indication to a user of the heating device, so that the user can undertake definite safety measures in order to eliminate or reduce the dangerous conditions causing the overheating. Of couse, the invention can be used in conjunction with other conventional safety devices such as extinguishers and/or fuel shut off mechanisms. As mentioned above, the warning device according to the invention is intended to provide warning to a user that the heating device is or is about to become out of control, which may be the case even though flame extinguishers or other safety shut of mechanisms are being employed in addition to the warning means provided by the invention.

The apparatus may also include a DC power source to supply electrical energy to the warning device, and means for detecting the available power level of the power source and for producing a low power indication signal when the lower level falls below a predetermined power level, the warning means being arranged to generate a low power warning signal in response to the low power indication signal.

Accordingly, these constructions in accordance with the invention can provide a positive indication to a user of a portable heater that a safe operating temperature of the heater has been exceeded so that the user can commence undertaking measures to reduce the risk of harm to himself, other individuals and property. Of course, as mentioned, the invention can be used in combination with other safety devices such as flame extinguishing devices which cut off either the primary air supply or the fuel supply.

However, as mentioned above, since the heating device might already be in an overheating or runaway flame condition by the time one of these other safety devices will actuate, the present invention provides a means to positively warn a user so that any additional meansures can be undertaken.

The invention may be carried into practice in various ways and some embodiments will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a side elevation view, in partial cross section, of a convective mantle type kerosene wick heater illustrating a heat sensor and warning device embodying the principles of the invention; Figure 2 is a side elevational view, in partial cross section, of a heat chamber of a combination convective and radiant type kerosene wick heater illustrating positional locations for placing one or more temperature sensors according to the invention; Figure 3 is a side elevational view of a heat chamber of a convective kerosene wick heater, illustrating positional locations for placing one or more temperature sensors according to the invention;; Figure 4 is an electrical schematic diagram showing the components of the heat sensor device and the warning means according to the invention; and Figure 5 is an alternative embodiment of the invention, wherein the heat sensor is a thermomechanical device.

Referring to Figure 1, a conventional convective mantle type kerosene heater 10 is shown in partial cross section. The heater 10 comprises a wick element 12 surrounding a primary air tube 13. The primary air tube has an upper portion 14 and a middle portion 16. The wick extends into a fuel tank 18. When operating, the wick 12 will feed fuel to the upper edge of the wick where primary combustion will occur.

Disposed in the heat chamber region of the primary air tube is a heat sensitive member 20 in the form of a thermostatic switch. The thermostatic switch has contacts which are normally open but which close in response to the temerature of the environment in which it is placed exceeding a selected temperature. The predetermined temperature is selected to be above the maximum safe operating temperature but below the over-heating temperature of the heating device 10. The maximum safe operating level of the device will normally vary depending upon the design of the particular heater, but once that predetermined temperature is determined, a suitable heat sensitive member, in the form of a thermostatic switch for example, can be suitably chosen.

It is preferred that the heat sensitive member 20 be in a position so that it is a thermally reliable indicator of the operating condition of the particular heating with which it is used. As an alternative to or in addition to the position in the upper region of the primary air tube 14 shown in Figure 1,otherpossible positions include the middle region 16 of the primary air tube, the lower wick area in the fuel tank 18, the position designated 22 located generally level with the flame of the wick between the inner chimney and outer chimney.It should understood thatthe position of the heat sensor should be determined after obtaining the temperature-heat curve for several particular locations as described above, and then selecting one of those locations with primary consideration to the location yielding the most reliable temperature-heat curve. After that particular location is selected, a heat sensor should be chosen which switches at a temperature between the maximum safe operating temperature and the overheating temperature as described above. Multi ple heat sensor elements can be used, to detect overheating.

Referring back to Figure 1, the two leads 32,33 of the heat sensitive member 20 are connected to an electrical component box 34 having circuitry as illustrated in Figure 4.

Referring to Figure 4, the two electrical leads 32, 33 from the heat sensitive member 20 are connected in series with a DC power source 36, which is preferably a battery, and a transducer or horn 38. Thus, when a predetermined temperature is sensed, the thermostatic device 20 closes its contacts completing a series circuit through the horn causing the horn to produce a continuous audible signal. Connected in electrical parallel with the DC power source 36 is means 37 for detecting the available power level of the power source. When the DC power source falls below a predetermined power level, a low power indication signal is provided via lead 40 to energise the horn so that horn produces an intermittent audible signal. A user is thus warned that the battery should be replaced.

Referring now to Figure 2, a wick-type, radiant, heat chamber 111 is shown having a wick 112.

Positions 150, 151, 152, 153 designate proposed locations for a particular heat sensor member 20 according to the invention. The heat chamber 111 in Figure 2 is a combination convective heat and radiant type heater wherein the flame is disposed between an inner chimney 119 and outer chimney 121 creating a radiant heating effect outwardly of the outer chimney and a convective heating vertically via a combustion process at the wick 112. As with the first described embodiment, these proposed locations 150, 151, 152 and 153, as well as other possible locations, couid be tested to determine the preferred heat sensor location with primary consideration to the most dependable temperature-heat response curve for this particular heat convective-radiant type heater. Where more than one heat sensor is used, the leads from each heat sensor should be connected in electrical parallel with the leads from, the other heat sensors.

Figure 3 shows a wick-type, convective heat chamber 211 having a wick 212. Positions 250,251, 252 and 253 designate proposed locations for a particular heat sensor member 20 according to the invention.

Figures 1 and 5 illustrate a thermomechanical sensor 70 which can be used in addition to the thermostatic switch of Figure 1. The thermomechanical device comprises a bimetallic element 72 intended to be located generally near the combustion area of the heating device. The bimetallic element has a lever 73 which moves in response to a temperature change, and is positioned relative to a mechanical extinguisher 74 so that the extinguisher is activated when the predetermined temperature is reached.

Claims (8)

1. Heat sensing apparatus for detecting an exces sivetemperature level in a fuel burning heaterwhich comprises a heat sensitive member located general ly near the combustion area of the heating device, the said member having means for sensing the temperature near the combustion area and means for providing an indication signal when the sensed temperature exceeds a predetermined temperature which is above the maximum safe operating temperature and below the overheating temperature of the heating device; and warning means for generating a temperature warning signal in response to the heat sensitive member providing an indication that the said predetermined temperature has been exceeded.

2. Apparatus as claimed in Claim 1 further including a DC power source to supply electrical energy to the warning device, and means for detecting the available power level of the power source and for producing a low power indication signal when the power level falls below a predetermined power level, and in which the warning means generates a low power warning signal in response to the low power indication signal.

3. Apparatus as claimed in Claim 1 or Claim 2 in which the temperature warning signal is an audible signal.

4. Apparatus as claimed in claim 3 in which the temperature warning signal is a continuous audible signal and the low power warning signal is an intermittent audible signal.

5. Apparatus as claimed in any preceding claim in which the heat sensitive member is a thermostatic switch which changes its switching state in response to the sensed temperature exceeding the predetermined temperature.

6. Apparatus as claimed in any preceding claim further including a thermomechanical extinguisher device comprising a bi-metallic element located generally near the combustion area of the heating device having a lever which moves in response to temperature changes and an extinguisher activated by the lever when the predetermined temperature is exceeded.

7. Apparatus as claimed in any preceding claim including a plurality of heat sensitive members and in which the warning means is responsive to all of the heat sensitive members.

8. Heat sensing apparatus constructed and arranged substantially as herein specifically desribed with reference to and as shown in any one of Figures 1,2 and 3 in combination with Figure 4 of the accompanying drawings.