US1759996A

US1759996A - System for alternately recording and controlling

Info

Publication number: US1759996A
Application number: US134427A
Authority: US
Inventors: Henry C Parker
Original assignee: Leeds and Northrup Co
Current assignee: Leeds and Northrup Co
Priority date: 1926-09-09
Filing date: 1926-09-09
Publication date: 1930-05-27
Anticipated expiration: 1947-05-27

Description

H. C. PARKER SYSTEM FOR ALTERNATELY RECORDING AND CONTROLLING Filed Sept. 9. 1926 4 Sheets-Sheet 1 7/70/22" IIMMZ I N V EN TOR. 7 emu I ATTORNEY.

May 27, 1930. H. c PARKER 1, 9

SYSTEM FOR ALTERNATELY RECORDING AND CONTROLLING Filed s t. 9, 1926 4 Sheets- Sheet 2 '1 uuuuuunnunnn eooooooooooe a. N INVENTOR.

By 7 A mdw 2 ATTORNEY.

H. C. PARKER Mai 27, 1930.

SYSTEM FOR ALTERNATELY RECORDING AND CONTROLLING Filed Sept. 9, 1926 4 Sheets-Sheet 5 IN VEN TOR.

% WM'ED K; ATTORNEY.

May 27, 1930. H. c. PARKER 1,759,995

I SYSTEM FOR ALTERNATELY RECORDING AND CONTROLLING Filed Sept. 9, 1926 4 Sheets-Sheet 4 N Y fi I N VEN TOR BY 1% a GMQ,

762. ATTORNEY.

Patented May 27, 1930 UNITED STATES PATENT OFFICE HENRY O. PARKER, OF PHILADELPHIA, PENNSYLVANIA, AS SIGNOR TO LEEDS & NOR- THRUP COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PENN- SYLVANIA SYSTEM FOR ALTERNATELY RECORDING AND CONTROLLING Application filed September 9, 1926. Serial No. 134,427.

a My invention relates to a system for alternately recording and controlling the magnitudes of a condition, suchas the electro-motiveforce, impedance, ion concentration. or

'5 conductivity of an electrolyte, temperature,.

etc. i In accordance with my invention, periods for recording and controlling, of any suitable relative lengtl s,alternate with each other. During a recording period, the varying magnitude of the condition is recorded, andduring a control period there i's'substituted for the ion concentration cell, conductivity cell,

resistance, impedance or othenmeans for exhibiting "varlat ons of the magnitude 1nvolved, another device, as a source of electro-.

for the control to take effect; and more particularly in accordance with my invention, this time lag, which is constant after having once been empirically determined, is equal to the sum of the recording and control periods, and the control period is preferably a small fraction of the recording period.

Further in accordance with my invention, the change in the rate of application of the agent which effects change in magnitude of the condition is proportional to the difference between the actual magnitude of the condition and the desired magnitude of the condition at the time of inception of the control or change in rate of application of the agent; and more particularly in accordis effected by limiting the deflections of a galvanometer, which controls the control mechanism, to substantially constant magnitudes which are independent of the extent of departure of the actual magnitude of the ance with my invention, this proportionality condition from the desired magnitude, but the duration of the deflection is dependent upon the aforesaid departure of the actual from the desired magnitude of condition.

My invention resides in a method and apparatus of the character hereinafter described.

Foran understanding of my method, and for an illustration of some of the various forms my apparatus may take, reference is made to the accompanying drawings, in which:

Fig. 1 is a diagrammatic View of one of the circuit arrangements utilized in accordance with my invention.

Fig. 2 is a perspective view of recording and control mechanism embodying my invent1on.

Fig. 3 is a fragmentary elevational view of switches and their actuating or control mechanism.

Fig. 4 is a sectional view, partly in elevation, of a control valve.

-Fig. 5 is a sectional view, partly in elevation, on the line 55 of F ig. 4.

Fig. 6 is a fragmentary sectional View taken'onthe line 66 of Fig. 5.

Fig. 7 is an elevational view, partly in section, of a modified form of valve structure.

Fig. 8 is a fragmentary elevational view, on enlarged scale, of a portion of the recording and control mechanism.

Fig. 9 isa top plan- View of the structure shown in Fig. 8.

Fig. 10 is a fragmentary sectional View on the line 1010 of Fig. 8.

Fig. 11 is a perspective view of an adjustable abutment.

Fig. 12 is a diagrammatic View of a modified circuit arrangement utilizable in accordance with my invention.

Fig. 13 is a fragmentary View, partly in section, of structure utilizable in temperature control in accordance with my system.

Fig. 14 is a diagram of a complete cycle of control illustrating alternate recording and control periods.

In Fig. 1 there is illustrated diagrammatically a system for applying to water, for example, Whose rate of flow may vary, another material, such as acid, to procure a product comprising a mixture of water and acid in predetermined proportions, or having a predetermined ion concentration.

The condition whose magnitude varies is,

for example, the hydrogen ion concentration of the mixture, and the agent applied at progressively varying rate for maintaining a desired hydrogen ion concentration is the aforesaid acid. The magnitude of the ion concentration is represented by an electromotive-force produced by a hydrogen ion cell which is a source of variable electro-motiveforce included in a balancing circuit, such as a potentiometer circuit, including a galvanometer whose deflections control suitable mechanism for in turn controlling a valve upon whose extent of opening depends the rate of application of the acid. It will, therefore, be understood that Fig. 1 represents not only a preferred application of my invention, but also generically the application of any suitable agent for varying the magnitude of any condition during periods which alternate with periods for recording the variations in magnitude of the condition.

Briefly, in Fig. 1, water (which term includes generically any other material) is delivered through the pipe W, controllable by the manually operable valve '0, into the mixing tank T, into which is delivered acid (which term includes generically any other suitable material or agent) through the pipe A controllable by the manually operable valve 42 and by the control valve V operable in opposite directions by the reversible electric motor N during the hereinafter described control periods. The mixture is discharged to any suitable region or point of use through the pipe D, controllable by the manually operated valve Q2 A continuous sample or side stream of the 4 resultant mixture is conducted through the pipe d, controllable by the manually operable valve '0 to and through the cell H, from which it is discharged through the tube (Z The cell H may be a hydrogen ion cell of any suitable character, to whose positive and negative electrodes are connected, respectively, the conductors p and n. The cell H constitutes a source of electro-motive-force, vary ing in magnitude with variations in magnitude of the condition to be controlled, in a potentiometer circuit P with which co-acts the galvanometer G having, as indicated in Fig. 2, the needle or pointer 19 actuated by the movable or deflecting system or coil 20 for controlling the mechanism which alternately operates as a recorder and a controller. Both the recording and controlling operations are effected by and in accordance with the angular movements of the shaft 10. For recording, the shaft 10 controls movement of the marker or pen B transversely of the continuously moving record sheet or paper S. For controlling, the shaft 10 rotates the disk G carrying the contacts wand b,

which, in cooperation with the stationary or adjustable contact 0, control the aforesaid valve-actuating motor N.

The control and recording mechanism may be of any suitable character, and may, for example, and preferably, be generally of the character disclosed in prior Letters Patent to Leeds No. 1,125,699, January 19, 1915.

Briefly, this mechanism, Fig. 2, comprises the electric motor M whose shaft 1 drives at substantially constant speed the Worm 2 meshing with and driving the gear 3 secured upon and driving the shaft 1. Pivoted upon a horizontal axis adjacent its upper end is a lever 5, upon which there is pivoted on a horizontal axis the arm 6, on each end of which is a shoe of cork or the like frictionally engaging the rim 8 of the clutch disk 9 secured upon the aforesaid shaft 10. Secured upon the shaft l is a cam 11, which periodically engages the lever 5 and moves it outwardly away from the disk 9 in opposition to a spring, not shown, thereby lifting shoes 7 free from the rim 8, the spring returning the shoes into engagement with the rim after predetermined rotation of the cam 11. Upon the shaft 4 is secured asecond cam 12 which, after cam 11 has lifted the shoes 7 from rim 8, actuates the end of finger 13 on the lower end of arm 14 secured at its upper end to the member 15 pivoted at 16. Upon the frame 15 is secured the member 17, whose upper edge 18 is inclined and increases in height from the center toward each side. Disposed immediately above the edge 18 is the aforesaid needle or pointer 19 of the galvanometer Gr. Deflections of the needle 19 are limited by the abutments 15 Figs. 2, 8, 9, 10 and 11, disposed on opposite sides of the needle 19 and secured to the member 15 by screws 15 extending through slots 15 in the lugs 15,

to which the abutments 15 are secured or with which they are integral. These limiting lugs 15 have a purpose and function hereinafter referred to.

Directly above the needle 19 and beneath which it normally freely swings are the edges 21, preferably. straight and horizontal, on the lower sides of the

members

22, 22, pivoted at 23, 23 and extending toward each other, leaving a gap of sufficient width between their inner nds to allow the free entry of the needle 19 when in balanced, Zero or mid position. The needle 19 normally swings freely between the edge 18 of member 17 and the lower edges 21 of the members 22. Upon the members 22 are the downwardly extending

arms

24, 2 1, drawn toward each other by the spring 25. Attached to the lower end of lever 5 is the triangular plate 26 carrying the pins 27 and 28, with which co-act the lower ends of the fingers 24:. At opposite ends of the arm 6' are the ears or lugs 29, 29, adaptedto be engaged by the

cams

30, 30, similarly shaped and similarly positioned and secured upon the shaft 4.

As well understood, the deflections of the galvanometer needle 19 cause rotations of the shaft 10 to extents and in directions proportional to or dependent upon the extents and directions of deflections of the needle 19; by application of the deflection-restricting lugs 15, however, the movements of the shaft 10 are substantially equal so long as the needle 19 is in engagement with either lug 15, but the direction of movement of the shaft 10 still depends upon the direction of deflection of the needle 19.

Secured upon the shaft 10 is the aforementioned disk G, whose angular position upon the shaft 10 is adjustable by means of the set screw 31 threaded through the hub 32 of the disk C, thereby determining the position of the gap between the motor control contacts a and Z) with respect to the contact a, mounted on arm 47.

Upon the shaft 10 is secured the grooved pulley 33, around which passes the cord 34, passing over idler wheels 35, for moving the aforesaid marker on pen B transversely of the record sheet S, which latter is stored upon a roll 36 and passes over the sprocket roll 37 driven through suitable gearing from the shaft 4.

Upon the disk E, which is secured upon the shaft 10 in any suitable angular adjustment thereon by the screw 38, is the resistance R, with which co-acts the stationary contact 39 to constitute a slide wire resistance of the aforementioned potentiometer P, Fig. 1. Secured upon the shaft 40 is the adjustably mounted and manually operable dial or knob 41, bearing suitable graduations in any suitable units, as electro-motive-force, for the system of Fig. 1. WVith the markings upon the member 41 co-acts the stationary index 42, whereby the member 41 and shaft 40 may be rotated to or set in any predetermined position corresponding with the desired magnitude of the condition to be controlled. Upon the shaft 40 is adjustably secured a disk F, upon which is disposed the resistance R with which co-acts the stationary contact 43 to constitute a second slide wire of the potentiometer P, of which the resistances R and R are in parallel with each other. Upon the shaft 40 is secured the gear 44, meshing with the gear 45 loosely bearing upon the shaft 10 and carrying the bracket 46, preferably of insulating material, upon which is secured the conducting arm 47 which carries the aforesaid motor-control contact a co-acting with the contacts a and 5 upon the disk C.

The dial 41 and slide wire resistance R. are so mounted that when the contact 43, operating on slide wire R is at the same potential as that of the contact 39, operating on slide wire R, the index 42 points to a potential value on dial 41 which corresponds to the potential indicated on the recorder scale. When this adjustment is made, the disk C, mounted upon the shaft 10, is simultaneously adjusted so that the contact 0 falls midway between the contacts a and Z).

Reverting to Fig. 1, the contact 0 connects through the switch I, when closed, with the conductor 48 of a current supply circuit, for example, of the direct current type, whose other conductor 49 connects with one terminal of the armature 5O ofthe reversible motor N, having the two

field windings

51 and 52 brought into series with the armature 50, respectively, through the contacts a and Z; for effecting rotation of the motor shaft 53 in the one direction or the other. The shaft 53, through suitable reducing gearing, ro-

tates the stem 54 of the valve V.

The potentiometer P comprises the aforesaid slide wire R through which current of predetermined magnitude from the battery 6, as determined by the rheostat f, is passed.

During the recording period the contact 39, bearing upon the resistance R, is connected through the switch J with one terminal, as the positive, of the cell H through the conductor 19, and the negative terminal, for example, through the conductor a, connects to the galvanometer G and thence through the switch L, when in its upper position, and thence through the switch K, when in its upper position, with one terminal of the resistance 9 in series with the aforesaid resistance R. During the recording period the contact 43 of the slide wire R on disk F, is out of circuit, and the system comprises then a simple potentiometer system producing upon the sheet S by the marker B a record of the potential differences across the electrodes of the cell H depending in turn upon the variations in the hydrogen ion concentration in the mixture of acid and water discharged through the pipe D.

The switch L, Fig. 1, is shown also in Figs. 2 and 3 as actuated or controlled by the cam 55 engaged by the cam follower 56 carried upon the switch blade L. The face of the cam 55 is of such angular extent and so positioned upon the shaft 4 that the switch L is in its lower position, Fig. 1, during each period that the galvanometer needle 19 is held or clamped between the

members

17 and 22, thereby opening the circuit of the cell H, preventing useless withdrawal of current therefrom during the periods in which the galvanometer needle is retrained by the clamping members, and thereby reducing the amount of polarization which takes place in the cell H due to withdrawal of current therefrom while its circuit is closed. When the switch L is is in its lower position, opening the circuit of the cell H, it shunts the galvanometer Gr through the resistance h,

which may be of suitable magnitude for damping oscillations of the galvanometer upon release of its needle and before the circuit of the cell H is again closed by the switch L at its upper position.

The switches I, J and K are mechanically connected by an insulating member 57, Figs. 2 and 3, constituting a follower for the cam 58 secured upon the shaft 59 driven through reducing gearing 60, 61 by the shaft 4. The relatively slow speed of rotation of the shaft 59 introduces a time lag, effecting delay of ac tion of the switching mechanism by the cam 58 for a period which is the sum of the control and recording periods. The control period is preferably the shorter, and may be of the order of one-eighth the duration of the recording period. This ratio of the recording and control periods is determined by the contour of the cam 58, which, when the follower 57 is upon the cam surface of larger diameter, holds the switches I, J and K closed in the positions indicated in Fig. 1 for recording. WVhen the follower 57 passes off on to the cam surface of lesser diameter, a control cycle or period is instituted, and the switches I, J and K move against their lower contacts, Fig. 1.

During a control period, the switch I, in effect a motor control switch, is brought into communication with the control contact 0, to permit the contacts a and b to cause rotation of the motor N in the one direction or the other. Similarly, during a control period, one terminal of the galvanometer G communicates through the switch J with the contact 39 in engagement with the potentiometer resistance R, and the other terminal of the galvanometer connects through the periodically actuated switch L and the switch K with the contact 43 in engagement with the second slide wire resistance R This shifting of the switches J and K into engagement with their lower contacts, Fig. 1, in effect cuts out for the control period, during which polarization ceases, the source of electro-motive-force or cell H, and connects the galvanometer G, through a suitable resistance 2', across the

contacts

39 and 43, substituting-for the electro-motive-force of the cell H, or generically for the electrical effect representative of the changes of the magnitude of the condition involved, a potential difference between points on the slide wires R and R determined by the manual setting of the disk F, Fig. 2. In this way there is in effect substituted for the electro-motiveforce of the cell H an auxiliary electro-motive-force, whose value is equal to or representative of the voltage across the terminals of the device H corresponding with or representative of the desired magnitude of the condition.

By adjusting the knob or dial 41 to position corresponding with the desired magnitude of the condition to be controlled, there is in effect set up in the potentiometer circuit a reference voltage, corresponding to the desired magnitude of the condition, and the control is then effected with regard to the manually selected electro-motive-force representing the desired magnitude.

If at the beginning of a control period the ion concentration of the mixture discharged through the pipe D is at the desired magnitude, the control mechanism will not operate, because the contact 39 will have been moved along the slide wire R during the preceding recording period to a point corresponding with the desired magnitude, and in so doing the disk C, mounted on the same shaft 10, will have rotated to such a position that the contact 0 is midway between the contactsa and b. The motor circuit is, therefore, broken at this point; and there will therefore be no difference of potential between the

contacts

39 and 43. If, on the other hand, at the beginning of a control period, that is, at the end of a recording period, the ion concentration is at some other than the desired magnitude, the shaft 10 of the structure shown in Fig. 2 will have rotated the resistance R with respect to the contact 39, in producing the record up to the end of the recording period, to such a position that there is then a difference of potential between the

contacts

39 and 43 representative of the departure of the then magnitude of ion concentration from the desired magnitude. During the rotation of the shaft 10, the disk 0 becomes rotated in respect to contact 0, thereby causing engagement of contact 0 with contact a; or 6 -ac cording to whether the magnitude being measured is below or above the desired value. WVhen the key I, Fig. 1, is then closed at the start of a control cycle, the motor circuit is completed and the valve V starts opening or closing according to whether the magnitude is above or below the desired value. At the same time the recorder starts to balance at the potential represented by the setting of dial 41, Fig. 2, and hence the shaft 10 start-s to rotate in such a direction as is required to place contact 0 midway between contacts a and Z). As soon as the contact 0 disengages from contacts a or b, the motor circuit is broken. In this manner the angular displacement of the valve V is proportional to the time required for the recorder to come to balance at the potential-.

of rotation in the same direction, the number of these movements depending upon the duration of the deflection of the needle 19, which duration is dependent upon or proportional to the magnitude of the departure at the beginning of the control cycle of the actual from the desired ion concentration of the material in the discharge line D. The limitation of the deflection of the needle 19 by the abutment structure 15 increases the time for moving the resistance R with respect to its contact 39 through a given or unit angle. There is accordingly effected an increase of opening of the valve V for a given displacement or departure of the ion concentration from the desired magnitude. lVith the valve-actuating motor N operating at a substantially constant speed and with a given gear ratio between the motor shaft and the valve stem 54, the limitation of the deflection of the needle 19 by the abutment structure 15 has the effect that for a given displacement or departure from the desired concentration the motor is caused to operate for a longer period. For example, adjustment of the abutments 15 towards the zero or null position of the needle to half distance requires the valve-actuating motor N to run twice as long, so effecting twice the change in the extent of rotation of valve V.

The valve V is not actuated from closed position to open, or vice versa, but its aperture or opening is progressively or gradually changed by rotation of the stem 54. This is effected by structure of any suitable character, an example of which is illustrated in Figs. 4, 5 and 6, in which the plug 54*, ro-. tated by the stem 54, is provided with a'wall 54 having a series of ports or holes 54 disposed in a suitably curved path, whereby the rate of change of effective valve opening gradually varies with rotation of the plug 54 about its axis. 4

In Fig. 7 a generally equivalent arrangement is shown wherein in the plug 54 there is provided a tapered opening 54 producing generally similar effect to that described in connection with Figs. 4 and 5.

The operation as above described effects a control of the rate of application of the agent, causing change in the magnitude of the condition involved, which is proportional to the difference between the desired magnitude of the condition and the actual magnitude at the inception of a control period. This proportionality is dependent upon the limitations of the deflections of the galvanometer needle 19 by abutments 15 tosubstantially constant magnitudes which are independent of the extent of the departure of the actual from the desired magnitude of the condition, but the duration of the deflection of the needle 19 is dependent upon the magnitude of that departure, and so keeps the valve-actuating motor N in operation and varies the opening of the valve V for a period which is dependent upon the departure of the actual from the desired magnitude of the condition.

At the end of a control period, the cam 58 actuates the switches I, J and K. to restore them to their recording position indicated in Fig. 1, whereupon the motor circuit is additionally broken at the switch I, and a record is produced on the sheet S of the variations in the magnitude of the ion concentration 00- curring during the recording period.

The gearing 60, 61 drives the cam 58 so slowly that there is effected a time lag to permit the control to take effect, that is, to allow time after change of rate of admixture of acid for the effect of the admixture to make itself felt as regards its influence upon the cell H. This time lag is dependent upon the speed of the motor M and the extent of the reduction of speed effected by the reducing gearing intermediate the motor shaft and the shaft 59. The time lag is accordingly constant, but may be readily adjusted by changing the gear 61. It is equal to the sum of the recording and control periods, and the control period is preferably a small fraction, as, for example, one-eighth of the recording period.

While recording and control of ion concentration have been more specifically re- 5 ferred to above, it will be understood that the there may be mentioned temperature; for example, the temperature within a furnace 0, Fig. 13, produced by combustion of gas delivered through the pipe 62 through the valve V to the burner 63, which latter may be the main burner or an auxiliary burner. A thermocouple Q is disposed within the furnace,

partaking of the temperature thereof. and

producing an electro-motive-force corresponding with the temperature. The thermo-couple Q may be substituted for the cell H in the arrangement of Fig. 1, and the motor N then controls the gas supply valve V.

In Fig. 12 the mixture of acid and water, for example, is again controlled by the valve V. Immersed in the mixture in the tank T are the electrodes and 7c of a conductivity cell, the resistance between the electrodes j and 7c varying with changes in concentration of the acid in the mixture. The cell is included in one arm of a Wheatstone bridge, in two R, mounted upon the disk E of Fig. 2. With the resistance 69 becomesthe source of alternating current in the second conjugate conductor 71 connected between the conjugate points 7 2 and 7 3 of the Wheatstone bridge. During a recording period, in the system of Fig. 12, switches I, J and K are in their upper positions as indicated, and, as indicated in Fig. 2, they are actuated or controlled by the cam 58. In the recording position the switch I is open, thereby preventing energization of the valve-controlling motor N. The switch J is closed against its upper contact, thereby completing the arm of the bridge, containing the resistance 9, between the

points

65 and 72. The switch K in its upper position completes the arm of the bridge, containing the cell j, is, between the

points

65 and 73.

At the end of a recording period the cam 58, Fig. 2, shifts the switches I, J and K into engagement with their lower contacts, the switch I thereby closing the circuit to the motor control contact 0. The switch J now includes between the conjugate point 7 2 and the conjugate point or contact 43 an arm of the bridge including the resistance 1" and a portion of the slide wire R in substitution for the resistance 9. And the switch K includes between the conjugate point 73 and the conjugate point 43 a resistance 8, and a portion of the slide Wire R in substitution for the cell 9', la. Between the arms comprising the resistances r and s is the slide wire resistance R disposed upon the disk F, Fig. 2, and its position with respect to the contact or conjugate point 43 is set or determined by hand, by operation of the dial or knob 41. The position of the contact 43 upon theresistance R is so chosen that the portion= of the resistance R to the right of the conjugate point 43, plus the resistance of s in the same arm, causes the bridge to balance andlh'lence causes contact 39 to occupy the same position on slide wire R as is caused, during the recording period, by the resistance of the 'cell j, 70, when the concentration of the electrolyte in the tank T is of the desired magnitude. 1

At the inception of a control period, therefore, the coil 20 of the galvanometer will deflect only when there is a difference of potential between the conjugate points 39 and 43, and this occurs only when at the end of a recording period the contact 39 is on such point of the resistance R as corresponds with a magnitude of concentration differing from the desired magnitude. During the control period, the apparatus operates as heretofore described in connection with Figs. 1 and 2, causing a control by disk O of the motor N, and in turn of the valve V, and of the application of acid at such rate and for such time as to restore the concentration to or towards the desired magnitude, which, when reached, will cause a balance of the bridge, Zero deflection of the galvanometer coil 20, and the cessation of operation of the motor N, since the contact 0 is again in the position between the two contacts a and b.

The operation during such control period is generally of the character hereinbefore described in connection with Figs. 1 and 2. The time lag is provided, the recording period is relatively longer than the control period, and the abutments 15 again have the same purpose and result.

In the system of Fig. 12 again, periods of recording alternate with those of control, and in shifting from recording to controlling operations there is substituted for the device producing during the recording period an effect representatlve of varlatlons of the magnitude of the condition, another device pro-' ducing an effect representative of the desired magnitude of the condition, and the control effected is proportional to the departure of the actual from the desired magnitude at the inception of the control period.

Fig. 14 illustrates graphically the operation of the mechanism in alternately recording and controlling ion concentration or other condition. Base line XX represents the desired predetermined or standard value with respect to which the condition is to be controlled. Assuming that ordinates above and below the base line represent degrees of high and low concentrations respectively, the action of the control mechanism in moving from X to X results in movement of valve V to a position permitting less flow of acid 7 to the main tank T. It is therefore apparent that change in rate of flow of the agent controlling the concentration depends upon the time required for control disc C to move between positions representative of X and X respectively. When control disc 0 reaches point X it will be in the position indicated in Fig. 1 wherein contact 0 is in neutral position for interrupting the motor circuit.

Thus it will be noted thatthe extent of movement of valve V is not dependent on the length of time switch I is closed, but on the length of time required for contact 0 to reach neutral position on disc 0. By providing adjustable stop members 15" to limit deflections of galvanometer pointer 19, movement of control disc C through clutch member 6 may be effected in steps of different magnitudes. The number of such steps per unit of time remains constant as the speed of motor M is substantially constant, so the time required for contact 0 to reach neutral position may be considered as depending on the magnitude of the individual steps of clutch 6.

When cam 58 has determined the length of the control period, switches J and K operate so as to balance the bridge or potentiometer with reference to the true instead of the desired condition. The clutch will then move pen-controlling disc 33 frompositionY toY and continue recording to point Y when the control period will again take place. There.- upon valve V again closes to an extent dependent on the departure of the condition from its predetermined standard, only in case however that the limits of deflection of pointer 19 are maintained constant.

A suitable ratio between the duration of the recording and control periods may be effected by proper design of cam 58, as previously explained, so that the condition will have sufficient time to vary in response to the control agent between control periods.

As previously brought out, the time lag, which is equivalent to the sum of a control and recording cycle, may be varied by changing gearing 61 which drives switch actuating cam 58. The advantage of changing the time lag is readily apparent where a greater change in rate, for instance, of application of the control agent is desired. In such a case, the relative duration of the recording period could not be appreciably decreased for a given time lag as the full effect of the control agent would not be recorded before the next control cycle began. By extending the time lag however, the control and recording periods may have the same relative duration, while permitting an appreciable change in the rate of application of the control agent.

WVhile there has been specifically described a conductivity cell in an arm of the bridge, it will be understood that any other suitable device for any suitable purpose may be uti lized in lieu thereof. For example, as indi cated in Fig. 13, there may be disposed in the furnace O a thermometer resistance U, which may be utilized in a bridge of the character indicated in Fig. 12 in substitution for the cell 7', is, in which case during the control period the sum of the resistance 8 and that portion of the resistance R to the right of the contact 43 will cause the bridge to balance at a point identical to that caused by the thermometer resistance U at the desired temperature.

l/Vhat I claim is:

1. Thameth gdiwhich comprises producing an effect viiiiying in accordance with variation of the magnitude of a condition, and producing in successive periods a record of variation of the magnitude during said periods, and during shorter periods alternating with said periods controlling the application of an agent for controlling the magnitude of the condition.

2. The method which comprises producing an effect varying in accordance with variation of the magnitude of a condition, producing a record of the variation, substituting for said effect an effect representative of a desired magnitude of the condition, and controlling the application of an agent for varying the magnitude of the condition in accordance with the difference between the magnitudes of said effects.

3. The method which comprises producing an effect varying in accordance with variation of the magnitude of a condition, producing a record of the variation, substituting for said effectan effect representative of a desired magnitude of the condition, and controlling the application of an agent for varying the magnitude of the condition in accordance with the difference between the magni tude of said second named effect and the magnitude of said first named effect at the termination of the recording period.

4. The method which comprises producing an effect varying in accordance with variation of the magnitude of a condition, producing a record of the variation, substituting for said effect an effect representative of a desired magnitude of the condition, controlling the application of an agent for varying the magnitude of the condition in accordance with the difference between the magnitude of said second named effect and the magnitude of said first named effect at the termination of the recording period, alternating the periods of record production and control, and causing the recording periods to vary in duration from the controlling periods.

5. The method which comprises producing an effect varying in accordance with variation of the magnitude of a condition, producing a record of the variation, substituting for said effect an effect representative of a de sired magnitude of the condition, and controlling the application of an agent for varying the magnitude of the condition in proportion to the difference between the magnitude of said second named effect and the magnitude of said first named effect at the termination of the recording period.

6. The method which comprises producing an effect varying in accordance with variation of the magnitude of a condition, producing a record of the variation, substituting f6? said effect an effect representative of a desired ma nitud e pf the cogdition, controlling the application ofan "agent for varying the magnitude of the condition in proportion to the difference between the magnitude of said second named effect and the magnitude of said first named effect at the termination of the recording period, alternating the periods of record production and control, and

causing the recording periods to vary in duration from the controlling periods.

7 In a system of recording and control, a deflecting member, a movable structure the extents and directions of whose movements are controlled by said deflecting member, recording and control structures controlled by said movable structure, and means for controlling said recording and control structures alternately.

S. In a system of recording and control, a deflecting member, a movable structure the extents and directions of whose movements are controlled by said deflecting member, recording and control structures controlled by said movable structure, means for cont-rolling said recording and control structures alt-ernately, and means for causing the periods of control of the recording structure to vary in duration from the periods of control of said control structure.

9. In a system of recording and control, the combination with a galvanometer, of a circuit controlling it in accord with varia tions in magnitude of a condition, a movable structure the extents and directions of whose movements are controlled by said galvanometer, recording and control mechanisms controlled by said movable structure, and means for effecting alternate control of said recording and control mechanisms.

10. In a system of recording and control, the combination with a galvanometer, of a circuit controlling it in accord with variations in magnitude of a condition, a movable structure the extents and directions of whose movements are controlled by said galvanometer, recording and control mechanisms controlled by said movable structure, means for effecting alternate control of said recording and control mechanisms, and means for causing the periods of control of the recording mechanism to vary in duration from the periods of control of said control mechanism.

11. In a system of recording and control, the combination with a galvanometer, of a balancing circuit controlling it, means in said circuit responsive to variation in mag nitude of a condition, a movable structure controlled by said galvanometer, recording mechanism and means for balancing said circuit controlled by said movable structure, means for substituting in said circuit for said first named means means producing an effect representative of a predetermined desired magnitude of the condition, and control mechanism controlled by said movable structure while said last named means is in cir cuit.

12. In a system of recording and control, the combination with a galvanometer, of a balancing circuit controlling it, means in said circuit responsive to variation in magnitude of a condition, a movable structure controlled by said galvanometer, recording mechanism and means for balancing said circuit controlled by said movable structure, means for substituting in said circuit for said first named means means producing an eflect representative of a predetermined desired magnitude of the condition, control mechanism controlled by said movable structure While said. last named means is in circuit, and means for causing the periods of control of the recording mechanism to vary in duration from the periods of control of said control mechanism.

13. The combination with a deflecting member, of a periodically operating member adapted to engage said deflecting member, driving and driven members, means for setting the driving member with respect to the driven member in response to engagement of said deflecting member by said periodically operating member, means for thereafter actuating the driving member to move the driven member, a marker controlled by said driven member, and abutment structure limiting the deflections of said deflecting member to small extents, whereby during the application of deflecting force to said deflecting member said driven member partakesof a series of short movements.

14:- The combination with a deflecting member, of a periodically operating member adapted to engage said deflecting member, driving and driven members, means for setting the driving member with respect to the driven member in response to engagement of said deflecting member by said periodically operating member, means for thereafter actuating the driving member to move the driven member, control mechanism controlled by said driven member, and abutment structure limiting the deflections of said deflecting member to small extents, whereby during the application of deflecting force to said deflecting member said driven member partakes of a series of short movements.

15. The combination with a potentiometer circuit, of a galvanometer controlled thereby, a source of electro-motive-force in said circuit representative of variation of the magnitude of a condition, and means controlling said condition comprising means for substituting for said source a second source of electro-motive-force of fixed magnitude whose magnitude represents a predetermined magnitude of the condition.

16. The combination with a potentiometer circuit, of a galvanometer controlled thereby, a cell in said circuit producing an electro-motive-:torce varying with variation of magnitude of ion concentration, and means controlling said condition comprising means for substituting for said cell a source of electro-motive-force of fixed magnitude representative of a predetermined magnitude of the ion concentration.

17. In a control system the combination with a Wheatstone bridge, of a galvanometer deflecting when said bridge is unbalanced, an impedance in an arm of said bridge varying in magnitude in accordance with variation in magnitude of a condition to be controlled, and means controlling said condition comprising means for substituting for said impedance an impedance of fixed magnitude representing a predetermined magnitude of the condition.

18. In a control and recording system the combination with a WVheatstone bridge, of a galvanometer deflecting when said bridge is unbalanced, a conductivity cell in an arm of said bridge varying in resistance with variation of composition of an electrolyte, and means controlling said condition comprising means for substituting for said cell an impedance of flxed magnitude representative of a predetermined composition of said electrolyte.

19. The combination with a balancing circuit, of a galvanometer controlled thereby,

. means in said circuit for producing an effect representative of the variation of magnitude of a condltlon, means for substituting there- 'for means producing a like effect representative of a predetermined magnitude of the condition, and recording and control mechanisms alternately controlled by said galvanometer to respectively record variations in the magnitude of the condition and to vary said magnitude.

20. The combination with a potentiometer circuit, of a valvanometer controlled thereby, a source of electro-motive-force in said circuit representative of variations of the magnitude of a condition, means for substituting for said source a second source of electro-motiveforce whose magnitude represents a predetermined magnitude of the condition, and recording and control mechanisms alternately controlled by said galvanometer to respectively record variations in the magnitude of the condition and to vary said magnitude.

21. The combination with a potentiometer circuit, of a galvanometer controlled thereby, a cell in said circuit producing an electro motive-force varying with variation of magnitude of ion concentration, means for substituting for said cell a source of electromotive-force of fixed magnitude representative of a predetermined magnitude of the ion concentration, and recording and control mechanisms alternately controlled by said galvanometer to respectively record variations in the magnitude of the ion concentration and to vary the ion concentration.

22. The combination with a Wheatstone bridge, of a galvanometer deflecting when said bridge is unbalanced, an impedance in an arm of said bridge varying in magnitude in accordance with variation in magnitude of a condition, means for substituting for said bridge is unbalanced, a conductivity cell in an arm of said bridge varying in resistance with variation of composition of an electrolyte, means for substituting for said cell an impedance of fixed magnitude representative of a predetermined composition of said electrolyte, and recording and control mechanisms alternately controlled by said galvanometer to respectively record variations in the composition of said electrolyte and to vary the composition of said electrolyte.

24. The combination with a galvanometer, of movable structure whose movements are controlled by said galvanometer, a control circuit, relatively movable contacts controlling said circuit, one of said contacts moving in unison with said movable structure, an electrical device afi'ecting deflection of said galvanometer, and means independent of said movable structure for adjusting said device and another of said contacts in unison.

25. The combination with a balancing circuit, of a galvanometer controlled thereby, movable structure controlled by said galvanometer, electrical means in said circuit adjusted by said movable structure to rebalance said circuit, a control circuit, contacts controlling said control circuit, one of said contacts moved by said movable structure, electrical means operatively related to said circuit for aflecting the deflection of said galvanometer, and means for adjusting said last named means and another of said contacts in unison.

26. methodof c ontrolnfor a physical, 11o

chemical,*""tliermal"or electrical condition", which consists of balancing an electro-motive-force representative of said condition against an electro-motive-force representative of a predetermined or desired condition for determining the degree of departure from the same, and v arying by steps the appllcationgjj an agent ,oiireagent for correcting said ndition, the rate of change of said application b e ng proportional to the degree of 1 departure of said condition from its predetermined standard at the beginning of said control.

27. In a system for eflecting control of a condition with respect to a predetermined standard, electrical balancing means adapted to balance at positions representative of the actual and desired conditions respectively, and mechanism controlled thereby for varying the application of an agent for correcting said condition at a rate which is proportional to the time required for said balancing means to move from a balance representative of the actual condition to a balance representative of the desired or standard condition.

28. A system for eflecting control of a condition with respect to a predetermined standard comprising electrical balancing means responsive to forces representative of the actual condition and its desired or predetermined standard respectively, mechanism controlled thereby for varying the rate of application of an agent or reagent for correcting said condition, said rate of variation being proportional to the degree of departure of said condition from its predetermined standard at the beginning of said control.

29. A system for effecting control of ion concentration of a solutionwith respect to a predetermined standard comprising electrical balancing circuit, a deflecting member responsive to conditions within said circuit representative of variations of said concentration from its predetermined standard, a

control member movable through equal steps in response to deflections of said deflecting member, and means governed by said control member during a control period for varying flow or addition of a reagent for correcting said concentration at a rate which is proporboth actual and desired states ofa condition under control, means for effecting control of said condition while said mechanism is responsive to the desired state alternating with means for recording while said mechanism is responsive to the actual state of said condition, means for maintaining a predetermined ratio between the duration of said control and recording cycles, and means for varying the time lag of said system by varying the period representative of the summation of a recording and control cycle.

33. A system for effecting control of a condition with respect to a predetermined standard comprising electrical balancing means, mechanism periodically controlled thereby for efl'ecting control of said condition by varying the rate of application of an agent or reagent at a rate which is proportional to the duration of said control period, means actuated in alternation with said mechanism for recording said condition, and means for varying the combined duration of a recording and control cycle, thereby varying the time lag of said system.

HENRY C. PARKER.

tional to the extent of movement of said control member during said period.

30. In a system for effecting control of a condition with respect to a predetermined standard, the combination with a balancing circuit, a deflecting member responsive to conditions therein, a member for controlling the rate of application of a control agent movable in direction and degree in accordance with the deflection of said first-named memher, and adjustable means for limiting the deflection of said first-named member within variable limits whereby said: control agent may be applied over a variable period of time for a given departure of said condition from its normal standard.

31. In a system for eflecting control of a condition with respect to a predetermined standard, the combination with a balancing circuit, a deflecting member responsive to conditions therein, a member for controlling the rate of application of a control agent movable in direction and degree in accordance with the deflection of said first-named member, and adjustable means for limiting the