NZ250986A - Electric fan heater with air flow and heating element control - Google Patents

Description

250986 _N-Z- patent ornrc 22 MAJ? 1995 ____ RECEIVED NEW ZEALAND PATENTS ACT, 1953 No.: 250986 Date: 28 February 1994 COMPLETE SPECIFICATION IMPROVEMENTS IN/OR RELATING TO FAN HEATERS We, PDL HOLDINGS LIMITED, a New Zealand company, of 14 Hazeldean Road, Christchurch, New Zealand hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- 250 9 g g This invention relates to fan heaters, in particular but not solely to heaters having a number of heat output settings.

Fan heaters typically have two heating elements and a single phase ac motor controlled by suitable switching means. The switch means determines how much voltage is applied across each element and across the motor to provide a range of fixed heat settings for a user, for example, high, low and fan only. Such heaters also normally have temperature sensors and cut-out switches or fuses in their circuits to provide overheat protection.

It is an object of the present invention to provide a fan heater or an alternative power circuit for such a fan heater which will regulate the flow of air to the power applied to the heating elements or which will at least provide the public with a useful choice.

Accordingly in one aspect the present invention consists in an electric fan heater comprising a housing incorporating air through flow openings, a fan and fan motor operable within said housing to produce the air through flow, heating elements within the housing to heat the air prior to discharge from the housing, an electrical control circuit including manually operable switching mechanism to selectively operate the heating elements at different power ratings and air flow control means arranged to reduce the delivery of air flow to be heated by the heating elements at a lower heat setting to maintain essentially the same comfort zone as at the air flow with the heating elements operating at a higher heat setting.

In a further aspect the invention consists in an electric fan heater comprising a housing incorporating air flow ingress and egress openings, electrically energisable heating elements operatively mounted in the housing to heat air before discharge from the egress opening, a fan and fan motor operable to produce an air flow from the ingress passing through the head housing and over the heating elements discharged through the egress opening, manually operable switch means in an electric control circuit the switch means being selectively operable to control the power rating to the electrical heating elements and with the same switching action to control the speed of the'fan* motor so that upon itching the heater to a lower heat setting the air flow is reduced by slowing the speed of the fan motor to deliver air heated to essentially the same comfort zone temperature as gtie greater air flow at the higher heat setting.

UJ I 1 The invention consists in the foregoing and also envisages constructions of which the Following gives examples.

-J ?5o 9 66 One preferred embodiment of the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows the general appearance of a domestic portable fan heater according to the present invention, Figure 2 shows an example of the circuit according to the present invention, and Figure 3 shows a rotary switch mechanism and power settings for the circuit and heater.

Referring to these drawings, Figure 1 generally shows by way of example a domestic fan heater having a housing 10, air through flow openings 11 and 12 with control switches 15, 16, 17 which are heat setting, thermostat and timer controls respectively. The timer switch 17 is an optional feature. Adjustable feet 18 and power cord 19 are standard, while a range of housing shapes and other external features are often provided. The main internal features of the front heater such as a fan, fan motor and heater circuit components are indicated schematically in Figures 2 and 3.

Figure 2 shows one preferred heater circuit in some detail including the rotary switch 15, with a number of settings for heating elements El and E2, fan and ac motor FM, fan voltage dropper FD, thermostat 16, timer 17 and overheat protector 20. The thermostat 16 and timer 17 perform self explanatory functions while the voltage dropper FD is typically a resistor which may be placed in series with the fan motor FM. Other components of the circuit are cord 19 for connection to mains power, 4-way active and neutral connectors 21 and 22, power and thermostat indicators 23 and 24, and an audible alarm circuit 25.

The control circuit is switched so that two heating elements are connected at one switch position with the heating elements in parallel, at a second position with one heating element only operating and at a third position with the two heating elements in series.

Figure 3 shows the rotary switch 15, heating elements El and E2 and fan motor connections in more detail. The rotary switch 15 has at least seven contact banks 1-7, seven input power terminals la-7a and five positions A-E to power the heating elements El and E2 and motor FM. In the present embodiment of the invention, power terminals la-4a are strapped together and connected to the mains active line while terminals 5a-7a are connected to mains neutral. The motor is connected between banks 1, 2 and 7 while the elements are connected between banks 3, 4, 5 and 6. The switch positions thereby 986 separate the heater with settings as follows: A: No power supplied (heater off).

B: Full power to motor and element El (medium heat).

C: Full power to motor with elements El and E2 in parallel (high heat).

D: Full power to motor only (cool fanning).

E: Reduced power to motor through voltage dropper FD with the elements in series (low heat).

The rotary switch is operable so that the fan motor is energised at all positions with the elements energised but at the position with the heating elements in series the motor speed is reduced by introducing a motor speed control means into the circuit.

The heat output in setting E is approximately one half of that in setting B and one quarter of that in setting C. However, with reduced fan power in setting E, the reduced flow of air is heated to essentially the same comfort zone temperature as at the higher air flow preserving an acceptable heat output for a user close to the heater. This provides an economy setting where the comfort zone for a user close to the heater is preserved.

Returning to Figure 2, the overheat protector 20 includes a bimetallic strip switch in parallel with a positive temperature coefficient (PTC) resistance both placed in the path of air leaving the heater. A thermal fuse may also be included. Most current to the elements El, E2 under normal operating circumstances passes through the strip and by passes the PTC resistance. In the event of a fault die strip bends open and current through the PTC resistance generates sufficient heat to maintain this condition without appreciably heating the elements.

In the present embodiment of the invention an audible alarm 25 is also effectively in parallel with the strip. Again, most current to the elements under normal operating circumstances passes through the strip and bypasses the alarm which has relatively high resistance. In the event of a fault however, current through the alarfn is sufficient to create an audible output without appreciably heating the elements. The alarm continues to operate until all power to the heater circuit is manually turned off.

Another advantage of the present invention is that with the low heat economy setting the slower operation of the fan reduces the decibel rating of the heater. At normal fan speed the heater has a decibel rating of 50-54. In low heat setting with the reduced fan speed the decibel rating drops by 10-12 decibels.

Thus, in accordance with the present invention, an electric fan heater is provided which will regulate the flow of air to the power applied to the heating elements. 350 986

Claims (8)

WHAT WE CLAIM IS:

1. An electric fan heater comprising a housing incorporating air through flow openings, a fan and fan motor operable within said housing to produce the air through flow, heating elements within the housing to heat the air prior to discharge from the housing, an electrical control circuit including manually operable switching mechanism to selectively operate the heating elements at different power ratings and air flow control means arranged to reduce the delivery of air flow to be heated by the heating elements at a lower heat setting to maintain essentially the same comfort zone as at the air flow with the heating elements operating at a higher heat setting.

2. An electric fan heater as claimed in Claim 1 wherein said electrical control circuit incorporates said air flow control means operable by the switching mechanism in tb*? control circuit.

3. An electric fun heater as claimed in Claim 1 or Claim 2 wherein the electrical control circuit is switched so that two heating elements are connected at one switch position with the heating elements in parallel, at a second position with one heating element only operating and at a third position with the two heating elements in series.

4. An electric fan heater as claimed in Claim 3 wherein the switching mechanism in the electrical control circuit is a rotary switch operable so that the fan motor is energised at all positions with the elements energised, but at the position with the b ating elements in series the motor speed is reduced by introducing a motor speed1 cofitrol means into the circuit.

5. An electric fan heater as claimed in any one of the preceding claims wherein the electrical control circuit provides override protection including an audible alarm which once activated is only turned off by cutting power to the switch mechanism. 25 0 9gg

6. An electric fan heater comprising a housing incorporating air flow ingress and egress openings, electrically energisable heating elements operatively mounted in the housing to heat air before discharge from the egress opening, a fan and fan motor operable to produce an air flow from the air ingress passing through the head housing and over the heating elements discharged through the egress opening, manually operable switch means in an electrical control circuit the switch means being selectively operable to control the power rating to the electrical heating elements and with the same switching action to control the speed of the fan motor so that upon switching the heater to a lower heat setting the air flow is reduced by slowing the speed of the fan motor to deliver air heated to essentially the same comfort zone temperature as the greater air flow at the higher heat setting.

7. An electrical fan heater as claimed in the preceding claims wherein the fan at the lower speed rating operates at a reduced noise level with the range of decibel ratings for the fan speed at the normal rating 50 to 54 and with the decibel rating at the lower speed rating between 10 and 12 decibels.

8. An electric fan heater when constructed arranged and operable substantially as herein described with reference to the accompanying drawings. END OF ClA ir i