US1767637A - Temperature-control apparatus - Google Patents

Description

June 24, 1930. Q WILHJELM 1,767,637

TEMPERATURE CONTROL APPARATUS Filed June 26, 1929 Patented June 24, 1930 UNITED STATES PATENTPOFFICE mrs'rrm wmnzrm, or rnmannrrfim, rmmsnvmra TEMPERATURE-CONTROL arrana'rus Application filed June 26,

My invention relates to improvements in temperature control apparatus adapted for use in connection with a furnace which is heated by oil or gas, the admittance or supply of which is controlled by one or more valves.

The object of my invention is to provide an apparatus having certain novel features 'of construction and operation whereby an overshooting of the temperature is prevented, particularly during the heating up period, and whereby an almost perfect control is assured while the furnace operates at its predetermined operating temperature.

My invention includes other more or less important features, all having as their object and function the provision of an automatic temperature control apparatus adapted for use under the many varyin COIldltiOIlS of modern furnace practice. prefer, however, to explain the apparatus in detail before elaborating or commenting upon the advantages and objects of my invention to a greater. extent than hereinabove, so much more so, asthe apparatus is of a somewhat complicated nature.

Referring therefore to the accompanying drawing which is a wiring diagram the reference numeral 1 denotes a furnace which is heated by fuel supplied through a pipe 2 controlled by a valve 3. A thermostat of commercial type is mounted in the furnace wall and responds to temperature changes within the furnace. The thermostat ma consist of an expansible metal rod 4 whic is mechanically connected at 5 to a metal tube 6 having a different co-efficient of expansion than the rod.

The tube is fixed in the thermostat frame 7 which is mounted immovably in any usual manner. The rod is provided with a rack 8 for operating a gear 9 on the indicator shaft 10 which carries a pointer 11 for indir eating temperature changes on a scale 12.

The indicator shaft 10 carries three nonconducting cams 13, 14 and 15 adaptedto close respectively three pairs of contacts 16, 17 and 18. Each pair comprises a fixed contact and a movable contact which latter is actuated by the djacent disk in an obvious 1929. Serial No. 373,741.

manner. The arms are conveniently mount-v ed on a base 19 from which depends a support 20. On the latter is pivoted at 21 a fibre cam 22 adapted-to operate two pivoted conducting contact arms-23 and 24 with respect to two fixed contacts 25 and 26.

At the top of the cam 22 there is pivoted at 27 a substantially T-shaped finger 28 having an armature 29 adapted to be attracted by an electromagnet 30. The finger 28 is extended upwards and carries a button 31 which is kept in frictional contact with the disk 13 by spring 32 between the finger 28 and the cam 22. The two latter elements are thus mounted to oscillate together on the pivot 21, and in addition the finger may oscillate on the pivot 27 towards and away from the cam 22 and the magnet 30.

The complete mechanical construction of because they may be varied as desired so long as the several parts are. arranged to function as hereinafter set forth.

The contacts 17 and 18 control the circuits through two relays which comprises a relay coil 33 having a non-conductin armature carrying a top and a bottom con ucting bar 34 and 35 respectively, and a second relay coil 36 having a non-conducting armature also carrying a top and bottom conducting bar 37 and 38 respectively.

The armatures are normally in lowered positions as shown, in which casethe bottom bars 35 and 38 serve to bridge contacts 3940 and 41-42 respectively. When the relay coils are energized, the armatures are lifted and the top bars 34 and 37 then bridge contacts 43- 21 and 45-46 respectively.

The numeral 48denotes a motor which drives a timing cam 49 adapted to open and close'certain circuits through two pairs of contacts 51 and 52 respectively, suitably mounted on fixed bases.

The reference numeral 55 denotes a reversible electric motor which rotates a crank disk 56. To the latter there is pivoted a link 57 which is pivotally connected at 58 to a valve operating lever 59 which in turn is pivoted-on an adjustable floating pivot 60 carried by a base arm 61. The free end of the lever 59 is connected to the valve 3 by a link 62. One end of the base arm 61 is pivoted at 63 underneath the lever 59. The other end of the base arm is pivoted on a nut 64 threaded on an endless screw shaft 65 suitabl driven by a second reversible motor 66 y way of a reducin gearing 67 and an. interposed timing clutc mechanism which comprises the'fol owing elements.

The screw shaft 65 carries a gear, 101 which 104 and the latter with the two clutch members 107 and 108-will travel on the screw threaded shaft 103. without rotating the latter. I 1

Eventually, however, either of the members 107 or 108 w1ll reach and engage either of the clutch members '109 or 110, respectively. When this occurs, either of the latter and the shaft 103 will be rotated and through the are 102.and 101will rotate the shaft 65.

, e members 109 and 110 are ad'ustably carried by the shaft 103 in any well' known manner as by locknuts for instance, not shown, consequently the period elapsing between .the time whenzthe pinion 104 starts to rotate and until the shaft 103 is rotated, may be adjusted'and regulated because the distances between the clutch members 107 and 109 on the one side, and between the clutch members 108 and 110 on the other side are adjustable bymoving the members 109 and 110 along the shaft 103.

The arm 61 has pivoted thereto a link 68 which operates a bell crank 69 in a limit switch comprising two pivoted conducting contact arms 70 and 71 and two fixed contacts 72 and 73. The link 57, operated from the first reversible motor 55,'also operates a bell rank 74 in another limit switch which comprises two pivoted conducting contact arms 75 and 76, and two fixed contacts 77 and 78. The bell crank 74 also carries a pin" 79 which operates an arm 80 pivoted at 81 and which arm carries a flapper contact 82.

The drawing shows t e parts intheir positions while the furnace is running at its opand closed position of its initial stroke.

18 to say, in order to maintain the o crating crating temperature. At this time the valve is in a position half way between the open That temperature inthe furnace the va ve must necessaril be open to an extent where the fuel supp y balances the fuel demand.

However, before reaching this operating position, the valve has had an initial movevery slowly.

ment from its closed position to an extent greater than required for operating purposes, or the furnace would never heat up, or only Therefore, when the temperature is near the operating or control point as it is called, the valve is moved back to a half way position or the temperature would overshoot.

Again, it would be understood that the half way position is not between fully open and fully closed, but half way between the limits either way within a zone suitable for regulating the particular furnace at whatever work is performed.

During the undisturbed operation of the furnace, it will be seen, that there is no current passing through the apparatus, except that the timing motor cam 49 is periodically closing a circuit from the line, through wire 100, contacts 51 to the magnet 30 and out. Consequently the magnet is energized periodicall to attract armature 29 on finger 28, but t is movement which is in the nature ofa click or snap does not accomplish anything at this time.

Let us assume, however, that for some reason the temperature decreases. The rod 4 will then contact and turn the shaft 10 and thedisksclockwise and contacts 17 will close and establish a circuit as follows.

From the line, to wire 90, to 17, to wire 91, to contacts 23-25, wire 92 to relay 36 the parts '5759 and 62, the arm 59 moving to the left on pivot 60. At the same time,

however, the link 57 will also operate bell crank 74 until it engages contact arm 75 and breaks the motor circuit at 77. When this happens the arm 80 will have been moved on pivot 81 by the pin 7 9 so that flapper contact 82 now touchescontact 78 and the motor 55 stops.

In nearly all cases, this movement of the valve will be sufficient to admit enough additional fuel to check the drop in temperature and in actual practice, the temperature line on the usual recording graph shows hardly any deviation from a straight line and the temperature will go back to normal.

Now it will be seen that when the disks turn clockwise, the button 31 is moved to the opened, the relay 36 circuit is broken and the armature falls down thereby breaking the motor circuit at 3746.

The droppin of the armature, however, closes a motor circuit from the line through lower relay contacts 42-4140-39 to wire 99 to flapper contact 82, to 78--76 to the initial motor and out. Consequently the motor operates in the opposite direction and moves (closes) the valve back to a new normal position, because the closing movement is of lesser extent than the opening movement in that flapper contact 82 makes a quick break but has a slow closing movement as is obvious.

However, let us consider that the drop in temperature is greater than that assumed above. In that event contacts 16 will also be closed and a second motor circuit will be closed from the line to 37-45, wire 96, 73-71, to balancing motor 66 and return through wire 97, contacts 16 and back to the line.

In this event, the two motors start running practically at once, but the balancing motor does not move the valve immediately, there bein a time lag interposed until theclutch mem er on the pinion 104 reaches the clutch member- 110 on the shaft 103 as explained above.

The balancing motor 66, will now start and operate the endless screw to move pivot 64 and lever 61 to the right on pivot 63, hence also move pivot 60 to the right and thus swing the arm 59 to the left around pivot 58 and thereby cause a still further opening of the valve. The balancing motor will also through the link 68 gradually move 'bell crank 69 towards the arm 71 and if the movement of the motor 66 is permitted to continue, the arm 71 will eventually be swungiaway from 73 and the balancing motor circuit will be broken. When this happens, the valve will be fully open.

In nearly all cases it is not necessary nor desirable to continue the operation of the balancing motor until the valve is fully opened because to do so will cause a violent rise in the temperature which may cause overshooting. Therefore, the apparatus is designed so that the balancing motor is stopped as soon as the temperature rises towar s the control point and the initial motor is operated to cause a closing movement of .the valve in order to prevent a too great rise I of the temperature caused by the operation of the balancing motor, which is always set to cause a quick correction.

. These two operations are accomplished as follows. The temperature will have commenced to rise because of the partial opening of the valve. The thermostat rod 4 will therefore commence to expand and move the disks 13, 14 and 15 slightly anticlockwise. This movement, however, includes a clockthrough relay 36 at 25 in the anticipator switch mechanism. The connection between .23 and 25 will therefore remain broken so long as the temperature keeps going up. As a result, the relay armature 38 will drop and the balancing motor circuit will be broken at 45 and further opening movement of the valve ceases.

At the same time, when the relay 36 is deenergized the circuit mentioned above is established through lower relay contacts to wire 99 to flapper contact 82-which had been moved into engagement with contact 7 8-to contacts 7 8 and 76 to the initial motor 55 and out through wire 94.

The closing of this last mentioned circuit moves initial motor 55 in the direction opposite to its initial movement and causes a closingmovement of the valve to anticipate and check a too great fuel supply as above explained. The circuit is broken when the bell crank 7 4 moves flapper contact arm to break the circuit at 78 and the motor 55 stops.

It should again be noted, however, that the valve is at this time not moved back or closed to its former position, because, before the first closing movement of the valve occurs, it has received first an initial opening movement and secondly a further balancing opening movement. Therefore, when the initial motor now operates to close the valve, this .closing movement is necessarily of a lesser extent because the flapper contact 82 snaps away from the contact 78 in less time than it takes to move 82 over into engagement with 78.

At this time, therefore, the normal position of the valve while the furnace operates at desired predetermined temperature is half way between fully open and fully closed position so that when a change in temperature occurs, the initial stroke of valve will cause it to be shifted to a new normal position in order that the correct quantity of fuel may be supplied in response to the changed demand.

We have now turned the corner and the temperature is on the increase back to normal, and continuing the description, it will be seen that if the temperature continues to rise there will be no further shifting of the valve by the balancing motor, but there will be one or more operations of the initial motor because, although the temperature keeps going up we do not know whether it will ever reach the normal operating control point and it is therefore necessary to do two things.

First the valve must be opened again to insure additional fuel supply so that the control point temperature may be reached within the time necessary or desirable for that particular furnace job. Secondly, the valve openings and closings must be taken care of in time to insure that the temperature does not go beyond the control point.

2325 as aforesaid.

. The cam 49 is arranged to make one revolution during each time lag period of the furmotors because both relays are nace, i. e. the time which elapses before the tem erature reacts in response. to a change in the' uel supply.

At the end of each time lag period, therefore, the cam 49 .will close contacts 51 to es tablish' a circuit throu h the magnet 30 and back. The magnet wil be energized, attract armature 29 and fin er 28 on the pivot 27 against the tension o spring 32, thereby releasing the frictional contact between the;

button 31 and disk 13.

This release lasts for about one or two 7 seconds only after which the magnet 30 is deenergized because the contacts 51 will open vas soon as the cam 49 asses by them. Therefore the spring 32 wi 1 again .pull the button 31 into contact with the disk 13. During the momentary release of the button 31 and finger 38, the spring 50 will however move arm 23 to engage contact 25 to again momentarily close the initial relay circuit through relay 36 tovmotor 55. The valve will therefore again receive an opening movement until the initial motor circuit is again broken at 77 as above described, and flapper contact 82 will again engage contact 78. This opening movement is however very slight and may be adjustably delayed by adjusting the contacts in arm 25 as shown.

If new the temperature continues to rise during the next succeeding time lag period and before the cam 49 closes contacts 52, the continuing anti-clockwise movement of the disk 13 will again move the finger 28, as before, to break the relay 36 circuit at 2325. The armature will drop and again establishing a circuit via 42-41403999-82' 7 87 6 to initial motor and cause a movement on the part of the initial motor 55 to close the valve. When now the interrupter 49 closes contacts 52, nothing will ha pen to the own.

If, however, the rise in temperature is too slow or stops or even tends to drop again, then the. cam 48 will through contacts 52 close a circuit to the balancing motor 66 via wire 120 andstart the motor to cause an ad- .ditional movement of the valve.

This movement, however, will be stopped y the cam 22 is swung to the left in the draw-v ing and the relay 36 circuit remains open at assoon as the drop in temperature has been arrested, because now the disks will again turn anticlockwise to swing the finger 28 and cam 22 to the left to break the relay 36 circuit at 2325 and the motors stop. The latter are now operated back into their normal position because of the initial motor. circuit through the lower relay contacts and because of the circuit to' the balancing motor 66 through contacts 52 and wire 120 which operates the balancing motor in the opposite direction.

From the foregoing it will be clear that when the temperature drops, the motors will be operated'to open the valve to admit more fuel; But when the drop has been checked and the temperature goes back to the control point, the operations of the motors are governed by the mechanisms which include the anticipator switch and the timing cam.

The anticipator switch seeks to break the motor-relay circuits ahead of the time when the valve should be closed while the temperature goes up. The timing cam closes the motor-relay circuits immediately after they are broken'if the break occurs too soon within a time lageriod, because in the latter event, the'valve s ould not be closed but should be opened.

This is the main distinguishing feature of my invention. It will be seen that contrary to usual practice, which closes the valve when the temperature goes back to normal, this 'invention provides mechanism which opens the valve in order to anticipate a lag in the rise, and which mechanism so operatesthe motors that even a large opening movement may be obtained.

On the other hand, due to the timing feature, the valve is prevented from opening more than necessary and the valve is so regulated that it is back in a new normal position, halfway between the limits of its new initial stroke correspondin to the new fuel demand required by the c anged condition in the furnace. This has in and of itself nothing to do with the temperature, the changes in which are merely the result of the new conditions, because it will readily be seen that with a heavy load a furnace requires more fuel for a given temperature than with a less heavy load. Therefore, an a paratus which merely varies the fuel supp y in proportion to the change in temperature and at a corresponding rate is not satisfactory.

We can now briefly consider the operation when the temperature increases from normal. At this time the disk will turn anti-clockwise and relay 33 will be energized via 90- 18-2426 and wire 115. The armature of the relay will be pulled up and current will as from the line to 34-43 and wire 116- 8-7 6 to initial motor 55 starting the latter to actuate the valve mechanism to close the valve, and the initial motor circuit will then at, 77 and stop after flapper contact 82 has at this time be broken at 76-78 and flapper contact 82 will engage contact 77. Also, the

balancing motor circuit will be closed from the line to 34-44 and wire 117-72-70 to cause the balancing motor to give the valve an additional closing movement. Finally we will have the same circuit as before from the line to flapper contact 82 to 77 and 75 to start the initial motor to open the valve, all in the reverse direction to that described above.

However, as the temperature now is going down due to the decreased fuel supply, the valve having been operated to close, the disks will again turn clockwise, cam 22 will break the relay 33 circuit at 2426, the relay drops out and no further movement of the valve will be made by the motors.

The cam 48 however, will again function to reset the finger 28 to momentarily close the relay 33 circuit at 24-26 to operate the initial motor first to close and then to open the valve until the control point is reached. When the rise has been checked, and the temperature starts to drop back to normal, the anticipator switch will operate as before, and if the movement back to normal is too fast so that there is danger of overshooting, the timing cam 48 will again operate to reset the finger 28 and operate the balancing motor to close the valve.

The foregoing is thought to clearl explain the invention and its operation if the temperature varies plus or minus. The apparatus however, has also superior advantages during the heating up period.

At room temperature the thermostat is contracted and the disks 13, 13 and 15 will be in a position in which the two pairs of contacts 16.and 17 are closed while contacts 18 are open. These room temperature positions are not shown. When then the main supply line is closed, the initial motor is started as before and also the balancing motor. The latter, however, is stopped to prevent atoo violent rise and the initial motor is operated back to its half way position, all as explained above, when the apparatus operated to check a drop in temperature.

If the temperature continues'to rise without additional fuel there will be no further shifting of the valve by the balancing motor.

What will happen if temperature contmues to climb is :That for every revolution of the time lag cam 48, magnet 30 will be energized and release friction button 31 from the contact disks for a second or so, and while being de-energizedcoil 30 will again allow 31 to drop back on disk 13.

While suspended in the a1r the spring 50 will force the contacts 2325 together and bring button 31 back to a center position. Closing of contact 23-25 Wlll energize relay coil 36 and send current from 46, 77-75 to opening field on initlal motor 55 and the valve will open from normal, break contact swung in contact with 78. v v

If now the temperature goes up in the following lag period before time lag cam 48 closes contacts 52 it is obvious that the movement of disc 13 in response to the temperature will thru finger 28 break the circuit at 2325 'for relay coil 36 and as explained before this will result in a movement back to normal by the initial motor and when time lag cam 49 closes contact 52 there will be no motion of the balancing motor 66 as both relays 33 and 36 are de-energized.

It is evident that so long as the temperature moves up towards the control point the action explained above will continue torepeat itself in each time lag period. If however the temperature remains unchanged or shows a tendency to drop, the action of disk 13 on arm 31 does not effect a break of contact 23-25 and the relay 36 remains closed causing the initial motor 55 to go back to open and the interruptor to cause motor 66 to operate to further open the valve. As soon as the temperature again increases, the anticipatorbreaks the circuit at 2325. Relay 36 falls out and the initial motor goes back to normal and thus checks the movement of the temperature at the same time as no further movement of the balancing motor takes place unless the temperature goes down or ceases to go up.

It is evident that this arrangement will cause the valve only to be opened exactly the amount required as the temperature goes up. The reverse action takes place when the temperature goes high. This 'feature is absolutely essential on temperature control jobs where the fluctuations are very great due to very great and sudden load changes. It is also essential where a furnace is started from cold and where the control is expected to allow the temperature to raise to a certain point and then hold the temperature at that temperature without materially overshooting this point.

This control system'as described w1ll function as follows when furnace heats up., It

will open the valve in order to bring the temperature up to the desired point. If the temperature begins to rise, the opening of the valve is stopped and counteracted to prevent a too rapid rise. If however the rise appears to be too slow, the valve will be further opened to insure the rapidity of rise desired. When the temperature is outside a small zone 5 or 10 on either side of the control point, the valve is moved quickly whlle the temperature has a tendency to move away from the control point.

When the temperature is inside of the small zone, only slight corrections are necessary to the valve to bring the temperature to the control point. The anticipator device in normal practice does not interfere with the valve movements while the temperature is maintained within narrow limits.

While the invention has been described as functioning to control the operations of a fuel supply controlled by a valve for ma1ntaining a predetermined temperature within the furnace, means for opening said valve to increase the fuel supply in the event the temperature decreases, mechanism for prematurely closing the valve when the temperature thereafter begins to increase and means for opening the valve during said increase if the said premature closing of the valve occurs within the time lag period of the furnace.

2. The combination of a furnace having a fuel supply controlled by a valve for maintaining a predetermined temperature within 7 the furnace, means for closing the valve to decrease the fuel supply in the event the temperature increases, mechanism for prematurely opening the valve when the temperature thereafter begins to decrease and means for closing the valve if the said premature opening of the valve occurs within a time lag period of the furnace.

3. The combination of a furnace having a fuel supply controlled by a valve for maintaining a predetermined temperature within increase the fuel supply in the event the temperature decreases, means for closin the valve when the temperature again begms to increase and means for prematurely opening the valve to anticipate a temperature la while the temperature rises toward the sai predetermined temperature.

4. The combination of a furnace having a fuel supply controlled by a valve for maintaining a predetermined temperature within the furnace, means for closing said valve to decrease the fuel supply in the event the temperature increases, means for openin the valve when the temperature again begins to decrease and means for prematurely closing the valve to anticipate a temperature lag while the temperature decreases towards the said predetermined tem rature.

5. The combination 0 a furnace having a fuel supply controlled by a valve for ma1n-. taining a predetermined temperature within the furnace, means foroperating said valve to vary the fuel supply in the event the temperature changes within the furnace, means or operating said valve in a direction opposite to the direction of its first said 0 eration when the change in the temperature as been checked and means. for rematu'rely operatlng the valve in the said first named direction to anticipate a temperature lag when the temperature moves towards the said predetermined temperature.

6. The combination of a furnace having a fuel supply controlled by a valve for mamtaining a predetermined temperature within the furnace, means for operatlng the valve to vary the fuel supply in response to temperature changes within the furnace, means for automatically operating said valve to check the variation in the fuel supply when the said temperature change has been checked and the temperature returns to the predetermined temperature, a device tending to premature operation of the valve to again vary the fuel sup 1y to anticipate a lag in the said return of t e temperature and means neutralizing the operations of said device if they tend to o erate the valve within a time lag perlod o the furnace after the said 7 changes in temperature have been checked.

CHRISTIAN WILHJ ELM.

the furnace, means for opening said valve to

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