US1739882A - Temperature-control apparatus - Google Patents

Description

Dec. 17, 1929. c, WILHJELM Q TEMPERATURE CONTROL APPARATUS Filed Oct. 8, 1925 8% W M fi M. u m d M? v JW R lldwl Patented De: 17, 1929 PATENT OFFICE cnnIsTrAN wILHJnLmor PHILADELPHIA, PENNSYLVANIA 'rnmrEnArnnn-coNmoL APPARATUS Application filed October 8,v 1925. Serial No. 61,374.

This invention relates to a new method and apparatus for controlling the operation of the fuel supply valves to an oven or furnace equipped with an electrically operated temperature controlling device, such for lnstance as a pyrometer or like device.

In the art it has been generally accepted as standard practice to employ two electric contacts in the controll ing device. The operation of one of said contacts causes the opening of the supply valves. The operation. of the other contact causes the closing of the supply valves.

For instance, when controlling the supply of fuel to an oven by means of a pyrometer,

it is general practice to arrange the operation of the control valve or valves between two extreme predetermined limits. temperature in the furnace decreases, the so called low contact in the controlling device is closed to cause the valve to open to its maximum extent, and when the temperature after a while increases beyond the desired point,

the so called high contact is closed to cause the valve to close to its minimum extent. The furnace will then quickly cool off, and again the low contact will be closed to cause the control valve to open, and so on.

This method of control is wasteful, inac- '30 curate and unreliable, because it makes it very difficult to maintain an even temperature within the furnace, due to the continuous heating and cooling off of the furnace.

The pbject of this invention is to provide a controlling device having three contacts low, normal and high, and to provide suitably improved'apparatus for operating the control valves in accordance with the opera-- tions of the controlling device.

My invention is embodied in an apparatus so arranged, that when the temperature is low, 'andthe low contact is closed, the supply valve will be fully opened. When the temperature is high, the high contact is closed and the valve will be closed, all as above described under the present practice. However, when the temperature is normal or within a few degrees, minus or plus, thereof, the normal contact is closedand the control valve:

caused to automatically take a position be- When the A tween open and'closed position, or half way,

where it will remain so long as the temperature is within desired or permissible limits.

The center or normal contact operates a switch to. cause the valve to operate alternately towards open or closed position depending upon the position of the valve at the moment the contact is-closed.

That is to say, when the valve is fully open and the normal contactis closed, the valve will be closed one halfand vice versa. u

In practice it is entirelypractical to so adjust a furnace supply valve that in its cen-' tral or half open position, therequired supply of fuel is admitted to maintain the temperature within the furnace at the desired point or within a few degrees minus or plus. nd only in extreme cases will it be necessary to open or close the valve to its greatest extent.

This new apparatus and method of control results in stable temperature conditions in the furnace, hence it is economical, accu-- rate and dependable.

.In the drawing accompanying this specification I have disclosed in diagrammatic form pin 13 with which a slot 14 in the lever 11 engages. ,The lever 11 extends beyond the pin 14 and is-pivoted at 15. The particular arrangement respecting the operation of the lever 11 is not shown. It maybe similar to that disclosed in an application filed by G. H. Johansonon August'25, 1925; Serial Number 52,449, renewed. Suflice it to state, that when the lever 12 is operated, the lever 11 swings on its pivot 15 to open or closethe valves 5 and 6.

The furnace 1 is provided with a temperature registering device of any approved form v such for instance as a thermocouple 16 which ing the depressor bar.

The numeral 30 denotes a reversible motor, the direction of rotation of which depends upon the direction of the current entering the field windings at either 31 or 32. The armature winding is connected by wire 33 to one side of the line 34. The other side of the line 35 is connected by wire 36 to the three lower fixed control contacts 20, 22 and 24.

The lever 12 is pivoted to a crank 37 fast on a shaft 38 which is rotated by suitable reducing gearing 39 from the motor shaft 40.

The numeral 41 denotes a motor stop switch adapted to close the contacts 42 and 43 under the influence of a spring 44. The switch 41 is opened by a lever 45 pivoted at 46. The lever is pivoted at 46 and connectedat 47 to a link 48 the other end of which is connected to the aforesaid pin 13 in the lever 12. The switch 41 is arranged to be closed when the normal pyrometer contacts 22 and 23 are closed. r

Two other motor'stop switches 50 and 51 are provided. The switch 50 normally closes contacts 52 and 53, and the switch 51 normally closes contacts 54 and 55. Springs as 56 tend to keep the switchesclosed as shown.

The switches are opened alternately by a' striker 57 which is pivoted at 58 and has a bifurcated end 59 which embraces a in the extreme end of the lever 12.

The pin 60 also enters a slot in a snap switch blade 62 pivoted at 63 and designed to operate a switch body 64 to alternately close the contacts 6566 and 6768. The stem 69 of the body 64 is conducting and connected to pin 60 the contacts 65 and 67 as shown. The body.

64 is kept u wards in engagement with the snap switch blade 62 by a spring 70.

The diagram illustrates the (parts in POSI- tion while the normal or desire temperature prevails within the furnace during which time the valves are'ifalf opened and the crank 37 is in central position. ile this'condition exists, the normal co ta'cts 2223 are being periodically closed bye depressor bar 27, but this closing does not affect the circuit. At this time the motor stands still, the cur rent passing from the line 35 to wire 36, contacts 22-23- and'wire 71 to contact 43-42 which are open.

The other side of the line is also ope current-passing front the line 34 to wir 33, through the motor, 31, wire 72 to switch 50, contacts 52-53, wires 7 3-7 4, contacts 66-65,

switch stem 69 and wire 75 to switch 41 which is open. Also the path of the current is traceable from the motor at 32 through wire 76 to switch 51, contacts 54--55 and wire 77 to contacts 6867 which are open.

Wire 74 leads to the high contacts 24 and 25 which are open, and wire 78 leads from wire 7 7 to the lowicontacts 20-21 which are also open. It follows, that so long as the normal contacts 22'23 are depressed, the valves remain half open as is indicated by a short heavy line in each valve.

If now the temperature falls below the.

required minimum, the pointer 19 will move in over the low contacts 20 and 21 which w1ll be periodically closed. Current will then pass from the line 35 to.wire 36, contacts '2021, wires 7 8-7 7 contacts 55-s54, switch an operation of the snap switch 62 by the pin 60 in said leyer, but without affecting the circuit. i

The pin 60, however, moves the striker 57 on its pivot 58 to the right towards the low limit switch 51. The striker hits said switch to open the contacts 54.55 and the motor stops, these two contacts being in the live motor circuit as aforesaid. The valves are now fully opened and the fuel supply to the furnace increased, consequently the temperature rises, and the pyrometer pointer is again moved in over normal contacts 2223 to depress the same.

The circuit is now as follows: From the line 35, wire 36, contacts 22--23, wire 71, contacts 43-42 (which were closed as aforesaid) switch 41, wire 75 to 69, contacts 65- 66, wires 7 47 3, contacts 5352, switch 50, wire 72 to 31, through motor and wire 33 to line 34. The motor'starts, but in the reverse direction and moves the crank 37 back to normal osition. Consequently the pin 13 is lifted to actuate link 48 to open the switch 41 to break the motor circuit at 4243 to stop the motor. r

Also the lever 11 is operated to close the valves to normal or half way position as shown, and the pin 60 moves the snap switch 62 back into the positiom shown and also when the crank 37 reached normal position, hence as a matter of convenience switch 41 is termed the normal stop switch.

If now the temperature rises beyond the desired point, the pyrometer pointer will move over to depress the high contacts 2425.

Then the circuit will be from line 35, Wire 36,

contacts 2425, wires 747 3, contacts 53-52, switch 50, wire 72 to 31 and through motor to 33 to line 34.

Hence the motor commences to operate in the same direction as last described and moves crank 37 to high position. Pin 13 is therefore moved to the right in the drawing and swings lever 11 to the right also to close the supply valves. The link 48 is lowered to raise arm 45 to permit the switch 41 to close contacts 4243.

Also the pin 60 is moved to the right and causes the striker 57 to hit the high limit switch 50 to break the motor circuit at 5253 and the motor stops. And the snap switch] point 80 engages the pin 81 in thebody 64 to break the contacts 6566 and close the contacts 67 -68.

As the temperature now drops, the pointer 19 is again moved to depress thenormal contacts and the circuit is as above described through'contacts 4342, switch 41, wire to 69, but now through 6768 to wire 77, switch 51 and wire 76 to motor to line. The motor starts and moves the crank 37 back to normal, thereby operating pin 13 to actuate lever 11 to close the valves half way, and also to actuate link 48 (raisingit) to break the motor circuit at 4243 and the motor stops. Pin 60 has at this time operated the snap switch blade 62 but without affecting the circuit. It has also operated the striker away from the switch 50 and-the latter closes contacts 5253, and all the parts are back into normal position.

To sum up: So long as the temperature within the furnace is normal, 1. e., within the limits required for successful operation, the normal contacts 2223 are periodically depressed, but the circuit is not affected because contacts 4342 are open.

When the temperature falls so thatthe low contacts 20-21 are operated, or rises, so that the high contacts 2425 are operated, a cirzuit through the motor will be establishe In the first case (low) the circuit will be by way of closed contacts 5554 to motor contact 32 to-start the motor running in one direction.

In the second case (high) the circuit will be by way of closed contacts 53-52 to motor contact 31 to start the motor running in the oppositedirection to close the valves.

In both cases, when the motor has been operated to such an extent that the valves are either fully open (on the low side) or fully closed (on the high side) the striker 57 is tacts 42-43 are closed.

When thenormal condition is restored, the

normal contacts 2223 will again be operated and establish a circuit through the motor by way of the now closed contacts 42- 43 to either of the motor contacts 31 or 32 to restore the circuit to normal.

The switch 41 is operated to stop the motor when normal conditions have been restored at which time the switch is opened.

The switch 64 alternately establishes connection with thenormal contacts 22-23 and the motor after eitherthe low or high contacts have been operated.

The switch 50 breaks the motor circuit through contact 31 when the high contacts 24-25 have been operated.

The switch 51 breaks the motor; circuit through the contact 32 when the low contacts 20- 21 have been operated.

From the foregoing it will be clear that the apparatus stabilizes the temperature conditions in that variations within given limits do not affect the valve operating mechanism. whereas heretofore, variations sufficient to move the pyrometer pointer from high to low or vice versa immediately caused the valve operating mechanism to act with consequent rather violent disturbances or changes in the fuel supply, which in turn affected the temperature in a violent jumping manner.

The apparatus is very simple in construe tion and wholly automatic in operation. In

practice the several switches and other parts in connection with a furnace using fuel con-v trolled by valves, nevertheless it will be obvious that the invention may be applied to the same advantages in connection with furnaces heated by other means.

The foregoing is thought to clearly set forth the invention and the-advantages re-' sulting therefrom and while I have disclosed it in its preferred form, nevertheless it will be understood that I do not desire to limit myself to the exact disclosure, but that changes and alterations may be made without depart ing from the principle of the invention or th scope of the appended claims.

I claim 1. A system for regulating the temperature in a furnace having a fuel supply controlled by a valve comprising a main electric o u o o circuit, a motor therein for operating the through the'motorto operate the valve in response to temperature changes within the furnace, means for breaking the motor circuits, when the valve operations have been completed and for closing other operating circuits through the motor to operate the valve back to said predetermined position and to open the said main circuit.

2. A system for regulating the temperature in a furnace having a fuel supply controlled by a valve comprising a main electric circuit, a reversible motor therein for operating the valye, means in said circuit for maintaining it-norm'ally open and for maintaining the valve in a predetermined position whilethe temperature within the furnace fluctuates between predeterminednormal limits, a pyrometer inthe circuitfor closing operating circuits through the motor to operate the valve in' response to temperature changes Within the furnace, switches operated by said reversible motor for breaking the motor circuits when the valve operations have been completed and forclosing other operating circuits through the motor to operate thevalve back to said predetermined positions and to open the said main circuit.

3." A system for regulating the temperature in a furnace having a fuel supply controlled by a valve comprising an electric normally open main circuit, a motor therein for operating the valve, means in the main circuit responsive to temperature changes wlthin the furnace for automatically closing opcrating circuits through the motor to operate the valve to compensate for said temperature changes and for closin said main clrcuit, means for automatically breaking said motor operating circuits when the valve has been operated and for closing other operating motor circuits to restore the valves to original positions and cause said main clrcultto be 4 A system for regulating the temperature circuit for breaking the motor circuits when the valve operation has been completed and for closing another circuit through the motor to operate the valve back to normal condition and open said main circuit.

5. A system for regulating the temperature in a furnace having a fuel supply controlled by a valve comprising a valve operating mechanism, a main electric circuit for actuating the latter, means in said circuit for malntammg the electrical condition thereof unchanged to insure non-operation of the valve 'while the temperature within the furnace fluctuates within a predetermined normal operating range, automatic means for actuating said valve operating mechanism to operate the valve in immediate response to variations in temperature within the furnace outside said predetermined range, means for automatically stopping the operation of the valve operating mechanism when the operation of the valve has been completed, other means for again actuating said valve operating mechanism to reverse the aforesaid operation of the valve and for restoring the unchanged condition of said circuit.

6. A system for regulating the temperature in a furnace having a fuel supply controlled by a valve comprising a reversible motor for operating the valve, a main electric circuit for actuating the motor, means in said circuit for maintaining the electrical condi- I tion thereof unchanged to insure non-operation of the valve while the vtemperature within the furnace fluctuates within a predetermined normal operating range, automatic means for actuating said motor to operate the valve in immediate response to variations in temperature Within the furnace outside said predetermined range, means for automatically stopping the operation of the motor when the operation of the valve has been completed, other means for again actuating said motor to reverse the aforesaid operation of the valve and for restoring the unchanged condition of said circuit. i

I CHRISTIAN WILHJELM.

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