US3424378A

US3424378A - Automatic heat control apparatus

Info

Publication number: US3424378A
Application number: US525658A
Authority: US
Inventors: John Martin
Original assignee: Fabricacion de Maquinas SA de CV
Current assignee: Fabricacion de Maquinas SA de CV
Priority date: 1966-02-07
Filing date: 1966-02-07
Publication date: 1969-01-28
Anticipated expiration: 1986-01-28

Description

Jan. 28, 1969 J. MARTIN AUTOMATIC HEAT CONTROL APPARATUS Filed Feb. 7, 1966 43 MODULATING VALVE INVENTOR ATTORNEYS United States Patent Ofice 3,424,378 AUTOMATIC HEAT CONTROL APPARATUS John Martin, Monterrey, Nuevo Leon, Mexico, assignor to Fabricacion de Maquinas, Monterrey, Nuevo Leon, Mexico, a corporation of Mexico Filed Feb. 7, 1966, Ser. No. 525,658 US. Cl. 236-15 5 Claims Int. Cl. F23n 1/02; F23c 1/08; G05d 23/00 The present invention relates to automatic control apparatus for heating, and more particularly to a means for supplying varying amounts of heat at constant temperature to an enclosed structure. While the invention will be described herein with reference to a glass annealing lehr, it will be appreciated that its utility is not in in fact so limited. 2

In glass annealing lehrs it has always been a problem to maintain a plurality of zones at different predetermined temperatures as glass articles of various sizes and shapes pass therethrough. In each zone and depending upon the temperature of the articles passing therethrough, such articles either give up heat to that zone or they absorb heat from it. It is essential however, that regardless of which way the heat transfer is taking place, that the temperature in the zone remains constant. Heat losses or gains by the ware in the various temperature zones are governed to a large extent by the mass of the glass articles being transported therethrough.

Accordingly, it is the principal object of the present invention to provide an automatic control apparatus primarily for use in connection with glass annealing lehrs which is effective to maintain constant predetermined temperatures at a plurality of zones within the lehr by supplying varying amounts of heat at constant temperatures.

A further object of the present invention is to provide an apparatus for supplying the combustion products of a burner together with secondary air under positive pressure mixed with such products to the interior of the structure to be heated.

A further object of the present invention is to interconnect the primary and secondary air supply valves of the system so that throughout the complete range of adjustment thereof, there is a fixed ratio between primary combustion air and secondary air.

Other objects will become apparent to those skilled in this art from a consideration of the following detailed description when read in conjunction with the attached sheet of drawings the single figure of which shows in schematic form a preferred embodiment of a control apparatus in accordance with the present invention.

In general, the objectives of the present invention are achieved by utilizing inconjunction with a return fuel flow type of burner in which the fuel and combustion air supply controls are interconnected for automatic operation, a secondary air supply which enters the space to be heated along with the products of combustion from the burner, and in which the control for said secondary air is interconnected with the control for. the primary air in such a way that there is a fixed ratio between the two. A simple thermocouple temperature sensing means positioned within the lehr is utilized to operate a control signal generator to control a servomotor for simultaneously varying the adjustment of the valves controlling the supply of primary and secondary air. As soon, therefore, as the thermocouple calls for more heat, the primary combustion air is automatically increased and this being slaved to the fuel supply to the burner, the burning rate is correspondingly increased. At the same time the amount of secondary air is also increased in direction proportion to the increase of primary air so 3,424,378 Patented Jan. 28, 1969 that additional heat but at the same temperature is supplied to the lehr.

Referring now to the attached sheet of drawings for a detailed description of the present invention, the burner is shown at .10 positioned to direct its combustion products into the interior of the lehr through a baffie structure indicated at 12. The glassware to be annealed is transported through the lehr on a wire belt 14 which is positioned immediately above the baffle 12. The hot gases from the burner 10 therefore, pass upwardly through the wire belt 14 to contact the Ware on the belt and depending upon the temperature of the ware, it either increases in temperature to assume the same temperature as the temperature of the hot gases or it gives up heat to those gases in order to fall to the temperature thereof.

Primary combustion air for the burner 10 is supplied from a motor-pump combination 16 through the line 18, while secondary air is supplied from a motor pump combination 20 through the line 22. A pair of modulating

valves

24 and 26 are connected in

lines

18 and 22 respectively, and these valves are preferably of identical structure, but they may be of different size. These valves, 24 and 26, are basically rotary valves, but they also have an axial adjustment of the rotary member. By changing the axial adjustment of the rotory member, in one or both valves, it is possible to achieve any desired ratio between the openings of the two valves when their rotary movement is mechanically coupled to each other. As indicated in the single figure of the drawings, the

valves

24 and 26 have their actuators interconnected by a mechanical linkage 28, in order to be driven in unison by a common drive servomotor 30.

A thermocouple 32 positioned beneath and adjacent to the traveling wire belt 14 senses the temperature of the gases at that point, and this thermocouple is connected to a control unit 34 which generates a signal proportional to the temperature sensed by the thermocouple 32, and drives the servomotor 30 to position the

valves

24 and 26.

As is more fully disclosed in my copending application Ser. No. 511,167, now US. patent 3,269,448, the rate of feed of fuel to the burner 10 is automatically slaved to the primary combustion air. The burner 10 is of the so-called return fuel fiow type so that oil under positive pressure from the motor combination 36 is fed to the burner 10 through the line 38, and a portion of this flow is returned through the line 40 to a modulating valve 42. This is a diaphragm type valve of the type described in the aforementioned copending application, and the positioning of the diaphragm member is under the automatic control of the primary air supply by means of a control air line 43 tapped off of line 18 which leads into the valve 42. By controlling the back pressure of the fuel in the return line 40 therefore, as soon as there is an increase in the demand for primary combustion air, there is a corresponding increase in the delivery of fuel to the burner.

The burner is of the type which will operate on either gas or liquid fuel, and a similar arrangement is shown at the top of the figure for slaving the flow of gas to the burner 10 through a modulating valve 44 in the gas line 46, and the modulating valve 44 is under the control of the primary combustion air by a control air line 48 with primary combustion air line 18 and leading into the modulating valve 44.

In the secondary air line 22, and ahead of the pump 20, there is positioned a valve member 50' controlled by a servomotor 52. The servomotor 52 in turn is controlled by a thermocouple 54, which senses ambient temperature. In this manner the rate of delivery of secondary air is controlled by the ambient temperature.

The actual temperature of the gases issuing from the burner may be sensed by a further thermocouple 56 to actuate an indicator 58.

From the foregoing, it is believed that those skilled in the art will readily appreciate that there is herein shown and described a new and useful control apparatus for use with direct fired burners wherever heat is to be delivered to an enclosed structure in varying amounts but at a constant temperature. While a preferred embodiment has been herein shown and described, applicant claims the benefit of a full range of equivalents within the scope of the appended claims.

I claim:

1. Apparatus for supplying varying amounts of heat at constant temperature to an enclosed structure comprising:

a burner for supplying heat directly to the interior of the structure;

means including a valve for supplying air under positive pressure to mix with the combustion products as they enter the interior of the structure;

means responsive to the temperature within the structure for generating a control signal proportional thereto;

means including a valve for supplying primary combustion air under positive pressure to said burner;

means interconnecting said valves to maintain a fixed ratio in their setting throughout a full range of adjustment thereof;

and means for adjusting said valves automatically in response to said control signal; whereby the temperature within the structure is maintained constant while varying the amount of heat supplied thereto.

2. Apparatus for maintaining a constant temperature Within an enclosed structure comprising:

a direct fired burner positioned to direct its combustion products into the structure to be heated;

a means including an adjustable valve for supplying ambient air under positive pressure to mix with the combustion products as they enter the interior of the structure to be heated;

means including an adjustable valve for supplying combustion air under positive pressure to said burner;

means for automatically controlling the supply of fuel to said burner in proportion to the supply of primary Combustion air thereto;

connection means interconnecting said adjustable valves for simultaneous adjustment of the opening thereof;

temperature sensing means within said structure;

and means connected to said sensing means and said connection means for automatically controlling the degree of opening of said adjustable valves in accordance with the temperature in structure to be heated; whereby the temperature within the structure is maintained constant while varying the amount of heat supplied thereto.

3. The combination defined by claim 1 and including means for controlling the amount of secondary air in accordance with ambient temperature of said secondary air.

4. The combination defined by claim 2 and including means for controlling the amount of secondary air in accordance with the ambient temperature of said secondary air.

5. A method of maintaining constant temperatures within a space to be heated over a wide range of heat supplied to the space with comprises:

(a) supplying fluid fuel and primary air to a burner, said primary air supporting the combustion of the fuel;

(b) supplying heat to the space by directing into such space the combustion products of said burner;

(c) sensing the temperature in the space to be heated and developing a control signal proportionol thereto;

(d) diluting the combustion products with secondary air in accordance with said control signal;

(e) and maintaining a constant ratio between primary and secondary air for all firing rates of the burner in order to maintain a constant temperature of the space to be heated over a wide range of heat inputs.

4/ 1935 Dreifein. 9/ 1951 Osterman. 6/ 1942 Krogh.

EDWARD 1. MICHAEL, Primary Examiner.

US. Cl. X.R. 126-39

Claims

1. APPARATUS FOR SUPPLYING VARYING AMOUNTS OF HEAT AT CONSTANT TEMPERATURE TO AN ENCLOSED STRUCTURE COMPRISING: A BURNER FOR SUPPLYING HEAT DIRECTLY TO THE INTERIOR OF THE STRUCTURE; MEANS INCLUDING A VALVE FOR SUPPLYING AIR UNDER POSITIVE PRESSURE TO MIX WITH THE COMBUSTION PRODUCTS , AS THEY ENTER THE INTERIOR OF THE STRUCTURE; MEANS RESPONSIVE TO THE TEMPERATURE WITHIN THE STRUCTURE FOR GENERATING A CONTROL SIGNAL PROPORATIONAL THERETO; MEANS INCLUDING A VALVE FOR SUPPLYING PRIMARY COMBUSTION AIR UNDER POSITIVE PRESSURE TO SAID BURNER;