GB2168472A - Heating appliance control system - Google Patents

Abstract

A control system, for a heating appliance which comprises a combustion chamber in thermal communication with eg. a water jacket to be heated, a fuel fed burner operative in the combustion chamber, an inlet means for inflow of combustion air to the burner, an outlet flue for outflow of the products of combustion, comprises an inlet air flow control damper movable to impose variable constriction on the inflow of combustion air. Respective sensing chambers are provided for sensing temperature of the working medium and flue temperature, each providing by way of an actuating chamber a mechanical output to the damper in a direction to increase the constriction of inflow of combustion air in response to sensed temperature rise, and each being operatively associated with an adjustment means for adjusting the damper position for a given working medium temperature and flue temperature as the case may be. <IMAGE>

Description

SPECIFICATION Control system for fuel fed heating appliance This invention relates to control systems for heating appliances (such heating appliances being hereinafter referred to as being of the kind specified), comprising a combustion chamber, in thermal communication with a jacket or container for a medium to be heated (such as water or other fluid), a fuel fed burner operative in the combustion chamber, an inlet means for inflow of combustion air to the burner, an outlet flue for outflow of the products of combustion, and inlet air flow control means including a member (herein called the damper) movable relatively to an inlet duct or opening to impose variable constriction on the inflow of combustion air.

The invention is concerned specifically with a control system for heating appliances of the kind specified, which control system (hereinafter referred to as being a control system of the kind specified) includes a temperature sensing chamber, such as a phial, for sensing a control temperature, an actuating chamber, such as a bellows, for providing a mechanical output to effect relative movement between the damper and its associated inlet duct or opening, a conduit means connecting the sensing chamber and the actuating chamber, which chambers together with the conduit means contain a fluid (herein called the pressure responsive fluid) which undergoes a change of pressure in response to change of temperature sensed by the sensing chamber and produces the required mechanical output at the actuating chamber.

In conventional control systems of the kind specified, as applied to heating appliances of the kind specified, it is normal practice for the sensing chamber to be mounted in the jacket or container for the medium to be heated, e.g.

water, but despite movement of the damper to a position imposing greater constriction upon inflow of combustion air as the temperature of the medium rises, danger and/or damage can arise through occurrence of too high a temperature in the flue. The flue gases themselves may reach too high a temperature to be safely exhausted or the structure of the flue itself may be damaged after a period of service as a result of this temperature.

The limiting temperature which is safe, or is satisfactory from the point of view of avoiding long term damage, varies according to the particular form and application of the heating appliance.

The object of the present invention is to provide an improved control system by which safety and satisfactory service life can be achieved for a range of working temperatures of the medium to be heated, and for different installations of appliance of the kind specified.

According to the invention, there is provided for or in association with a heating appliance of the kind specified a control system of the kind specified wherein respective sensing chambers are provided for sensing temperature of the working medium and flue temperature, each providing by way of an actuating chamber a mechanical output to the damper in a direction to increase the constriction to inflow of combustion air in response to sensed temperature rise, and each being operatively associated with an adjustment means for adjusting damper position for a given working medium temperature and flue temperature as the case may be.

In a preferred arrangement in accordance with the invention, each of the adjustment means comprises an adjusting chamber connected by the conduit means to its associated temperature sensing chamber and including manually operable means for adjusting the effective volume of the adjusting chamber.

Whilst it would be within the scope of the invention for the sensing chambers to be connected to, and to produce, a mechanical output at an actuating chamber common to the sensing chambers, it is preferred that a separate actuating chamber shall be connected to each of the sensing chambers, and the outputs of the actuating chambers applied to the damper through mechanism which combines such outputs.

By provision of adjusting chambers connected to each of the temperature sensing chambers, it becomes possible to mount the adjusting chambers in proximity to each other, for example on a control panel, thereby enabling adjacent presentation of their manually operable means to be achieved.

The invention will now be described by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a diagrammatic view of one embodiment of a control system of the kind specified in accordance with the invention applied to a heating appliance of the kind specified; and Figure 2 is a similar view of an alternative embodiment.

The heating appliance of the kind specified (not shown in detail in the drawings) may be a cooking stove or boiler, in each case provided with a combustion chamber containing a fuel-fed burner to which combustion air is admitted through an inlet opening 10 and from which gaseous products of combustion are exhausted through a flue (not shown but assumed to traverse the location marked 11).

Surrounding the combustion chamber or otherwise placed in communication therewith, is a jacket or container which contains the medium to be heated, for example water, and this will extend near a location marked 12.

At the location 12 is a heat sensing chamber 13, such as a probe or phial, and a fur ther heat sensing chamber 14 is provided at the location 11 so that these two chambers respectively sense the temperature of the medium to be heated and flue temperature (which may be the temperature of the gaseous products of combustion or the brickwork or refactory structure which constitutes the flue duct itself).

Control over the admission of combustion air through the inlet 10 is effected by a damper 15 movable as indicated by the arrow 16 to impose a variable degree of constriction with the respect to the inlet 10. The damper 15 is carried by an arm 17 which is pivotally mounted for angular movement about a horizontal axis 18 near its upper end.

The temperature sensing chamber 13 is connected to an actuating chamber 19 by a conduit 20, these chambers and the conduit containing a pressure fluid 21 which produces, in response to increase in temperature, an increasing pressure. The chamber 19 may be in the form of a bellows which thus applies operating force against the arm 17 tending to move this in a clockwise direction about its pivot 18 in response to temperature rise of the medium to be heated. This action takes place against a return spring 22, the bellows 19 and spring 22 being seated against opposite walls of a housing 23.

The temperature sensing chamber 14 is connected to a further actuating chamber in the form of a bellows 24 by a conduit 25, the chambers 14, 24 and conduit 25 likewise containing a pressure fluid providing an increase in pressure in response to sensed temperature. Thus, shouid the flue temperature rise to above a predetermined safe or acceptable value, the upper end of the arm 17 will be moved to the right by the bellows 24 act ing between the housing and the upper end of this arm, and the damper moved towards or into a closed position.

To enable the initial setting of the damper to be adjusted to provide the desired control characteristic with respect to both medium temperature and flue temperature, two adjust ment means are provided in operative association respectively with the sensing chambers 13 and 14.

For the former, the adjustment means takes the form of a mounting rod 26 which may be screw threaded and rotatable by a knob (not shown) to move it endwise as indicated by arrow 27. This shifts the pivotal axis 18 hori zontally and, for given degrees of expansion of the bellows 19 and 24, adjusts the position of the damper 15.

The adjustment means associated with chamber 14 comprises a further chamber in the form of a bellows 28 connected in effect in series in the conduit 25 and having one wall 29 maintained in a fixed (horizontal) posi tion, possibly adjustable by means of an abut ment member 30 contained in a subordinate housing 31.

Its opposite end wall, loaded by a spring 32 is adjustable horizontally by means of a manually operable member 33, such as a screw threaded rod operating through a nut formation in the housing 31, having an external manually operable knob.

The volume change of the bellows 28 brought about by adjusting the position of the member 33 changes, in the opposite sense, the volume of the bellows 24; and hence the position of the upper end of the arm 17 causing the damper to move towards or away from the inlet opening 10, as shown by arrow 16.

In the embodiment shown in Fig. 2, parts corresponding to those already described are designated by like reference numerals and the preceding description is to be deemed to apply.

In this embodiment, instead of providing wholly mechanical adjustment means, such as the rod 26, the position of the pivotal axis 18 is fixed by reason of its pivotal mounting being provided by the inner end of a bracket arm 35 of fixed length in the housing 23.

The conduit 20 is however provided with an adjustment means similar to that provided in the conduit 25 and comprising a bellows 36, an abutment member 37, a loading spring 38 contained in a subordinate housing 39, provided with an adjusting member 40 similar to the member 33. Adjusting the volume of the bellows 36 produces an adjustment in the opposite sense of the bellows 19, and a consequential change in the position of the damper 15.

The two adjustment means can conveniently be mounted in proximity to each other, for example on a control panel and the operating knobs of the members 33 and 40 presented in side-by-side relationship if required.

Claims (7)

1. For or in association with a heating appliance of the kind specified a control system of the kind specified wherein respective sensing chambers are provided for sensing temperature of the working medium and flue temperature, each providing by way of an actuating chamber a mechanical output to the damper in a direction to increase the constriction to inflow of combustion air in response to sensed temperature rise, and each being operatively associated with an adjustment means for adjusting damper position for a given working medium temperature and flue temperature as the case may be.

2. A control system as claimed in Claim 1 wherein each of the adjustment means com prises an adjusting chamber connected by the conduit means to its associated temperature sensing chamber and including manually oper able means for adjusting the effective volume of the adjusting chamber.

3. A control system as claimed in Claim 2 wherein a separate actuating chamber is connected to each of the sensing chambers, and the outputs of the actuating chambers are applied to the damper through mechanism which combines such outputs.

4. A control asystem as claimed in either Claim 2 or Claim 3 wherein the adjusting chambers are mounted in proximity to each other for adjacent presentation of their manually operable means.

5. For or in association with a heating appliance of the kind specified a control system substantially as hereinbefore described with reference to and as shown in Fig. 1 of the accompanying drawings.

6. For or in association with a heating appliance of the kind specified a control system substantially as hereinbefore described with reference to and as shown in Fig. 2 of the accompanying drawings.

7. Any novel feature or novel combination of features disclosed herein and/or shown in the accompanying drawings.