US2414467A - Timing device - Google Patents

Description

Jan. 21, 1947. I w. L. HUNT TIHIRG' DEVIfiE am June 29. 1943 3 Shoots-sheaf 1 wzwrmz'm 5a orcomamon OF Jan. 21, 1947. w. L. HUNT 2,414,467

TIMIN'G DEVICE Filed June 29, 1943 3 Sheets-Sheet 2 MOVABLE WITH CHANGE CONDITIONED DEVICE Mentor:

- flaming/z Jan. 21, 1947. w L T 2,414,467

TIMING .DEVICE Filed June 29, 1943 3 Sheets-Sheet 3 MOVABLE WTH CHANGE OF CONDlTlON OF CONDITIONED DEVICE lll lllllllllllll Illllilllilll 'IIIIIIIIIIIIIIIII. 1

.Ziakniorf y lierflalem memes he. 21, 1941 Walter Leslie Hunt, Philadelphia, Pa., assignor to Automatic Temperature Control 00., Inc.,

Philadelphia, Pa., a corporation of Pennsyl- Vania Application June 29, 1943, Serial No. 492,674

13 Claims. (01.161-1) This invention relates to timing devices, and particularly to variable timers either of stop or repeat cycles.

In the art of timers, which has been-very well explored in the past by various inventors and manufacturers, timing devices of great accuracy and of relative flexibility have been developed, whereby timed intervals of long or short duration have been manifested by electric circuit controlling functions or the like, but so far as known in every case, the variation in the timed interval has been a pre-set manual functioning, as a necessary preliminary or prerequisite to initiation of the step, operation, or -method to. be timed. If through some change in. variable condition in the processing step or in the material being workedmr the like, the manually pre-set timing becomes incorrect, it is too late, according to present timing systems, to change the timed interval or predetermined cycle. In other words, previou timing methods made the processing step dependent upon a predetermined manually set timed interval, whereas the timed interval should be a mere function of the actual specific processing step in progress, as modified by the attributes or condition of the work involved.

It is among the objects of this invention: to provide a timing system coupled with a device vice; to improve the art of timers; to provide a novel form of timer: to provide an electronic susceptible to variations in condition whereby the timer of accuracy and ease of operation; to provide an electronically sensitive timer which is variable in setting through either manual or anatively coupled with a conditioned device for an tomatically predetermining the timed interval as a function of condition of the device, which may be either electrically or mechanically coupled and in which the timing-interval producer may be to any device of variable condition; and other obiects and advantages will become more evident as the description proceeds. In the accompanying drawings forming part oi. this description:

Fig.1 represents a diagrammatic illustration of tomatic means; to provide a variable timer opera novel form of electronically controlled timerhaving a repeat cycle according to one form of the invention;

Fig. 2 represents a diagrammatic perspective of a specific application oi. a form of invention to a variable weight condition;

Fig. 3 represents a somewhat diagrammatic fragmentary front elevation of a mechanically controlled timer, representing a modification of the invention;

Fig. 4 represents adiagrammatic section partially in full lines of the mechanically controlled timer of Fig. 3.

Fig. 5 represents a diagram of a purely electronic timer of a stop cycle type according to a further modified form of invention;

Fig. 6 represents a fragmentary diagrammatic elevation of a governor controlled slidewire;

Fig. 7 represents a fragmentary diagrammatic section of a flow meter having an inductive coupling as the control of the bridge circuit; I

Fig. 8 represents a fragmentary diagrammatic section through a conditioned device with an expansion controlled element for varying the bridge circuit.

In a simple but preferred embodiment of the invention, a bridge circuit is provided, the respective actuating and actuated components of which may be widely spaced and respectively may be located in juxtaposition to the instrumentalities which control the actuating component and those which at a remotely different point are to be con Y the actuating condition-responsive element and ar mechanically or electrically coupled thereto so that the relative position of the arm and slidewire is a direct function of the instantaneous condition of a conditioned device or unit. In the purely illustrative form of device shown in Fig. 2, slidewire arm I5 is directly coupled with a weighing scale, to be described, to position the slidewire as a function of the particular load on the scale. However embodied. it is the controlling iactor of the timer, and is susceptible to variations in setting as functions of the variations or fluctuations of any condition of a device, whether the con-.

I ditions are of speed, in which the slidewire arm and slidewire are relatively adjusted by a governor or the like as indicated in Fig. 6, or of humidity, pressure, temperature, linear dimensions, however varied, 'su h aslength, height, width, orof motor 85, through common return 31 to the line L2. The line 40 intersects'at A3 a relay coil connection 44 leading to the plate 45 of the tube after passing through relay coil 28,

hardness, or deflection, or weight, or flow, as indicated in Fig. 7, or any other condition.

The bridge circuit is energized by the secondary I! of a transformer 18, the primary it or which is connected across the A. C. powerlines, respectively Li and L2. of the timing instrument has a limited extent defined by the starting point'for each timing cycle designated as Min" at 2B, and having a maximum limit designated by 28, toward which each timed cycle starts,.but which is only attained if the predetermined timed interval requires such a maximumrange of movement. The actuated slidewire pointer or arm 22, pivoted on a transverse axis 23, is shown, in a purely illustrative position, as slightly off the min or starting point 20, and is in electrical connection with the actuating slidewire arm or pointer it through the primary 24 or an input transformer 25. It will be understood that there will always be a current flowing through the primary 2% so long as the'a'rms I5 and 22 occupy disproportionate settings on their respective slidewires, and that balance and termination of the'iiow only occurs when the pointer 22 has been moved, illus The actuated slidewire l3 tube 21, which controls the energization of the relay coil 28 and therefore both of the switch members-29 and 33., .The upper switch member 29;;controls the particular desired loads by means of a common terminal 30 and the alternate Poles 3] l and 32 of the load circuits, which are not shown in detail as any desired instrumentality or iris ntaiities are to be controlled by these load circuits. The lower switch member 33, in

the dropped out condition (shown). closes theline from power lead Li, switch 33, through pole terminal 36, through the in" running field 35 of the synchronous reversible motor 35, and through the common return 31 to line L2. The circuit throughv the ,out running field 39 of motor 36 will be described later herein. The output shaft of the-reversible synchronous motor 36, after passingthrough suitable reduction gears or the like (not shown) drives the actuated slide- ,wire arm 22 on axis 23,111 one direction or the otherrelative to slide'wire l8, and the energizetion of the field so drives the arm 22 from wherof slidewire [3,3, special limit switch 38 is provided, onejside of which connects with power line Lij,..and "the other sideofjwhich connects through ailine' lli to theupper pole of the.

lower switch ofthe relay, and through a line 42 through the out" running field 39 of the As the start of a timing cycle is always from the point min'i at 20 on the slidewire l3, the actual initiation of the cycle isat the instant that the switch 38 is made by the pointer or arm 22. At'this juncture of course the actuating pointer or arm l5 has been moved relative to slidewire in either automatically as a function of the instantaneous value of a particular condition of the conditioned device with which the timer is in operative association, or, in the broader aspects of the invention, by a manual setting of the actuating pointer and slidewire. With the pointer 15 at some condition-functional position relative to its slidewire, say to the position indicated in Fig. l, and with the'actuated slidewire pointer 22 at min setting, it willbe clear that the flow across the bridge and through the primary 24 will bea maximum, so that ii the plate circuit were closed, it too would be at a maximum. The closing or the switch 38 actually closes the plate circuit so that it flows from line Li, switch 38, connectors so, 54, relay coil 28, plate 45, cathode connector cc, to the other power line L2. Thus, the closing of the switch 38 instantaneously energizes the relay coil 28 which snaps in, and the lower switch member 32 thereof successively breaks the circuit through the "in field 35 of the motor 36 by leaving pole 36, and then makes the circuit through the out field 39 of the motor by engagingpole 4|. The power circuit through the "ou field will be clear, as with the relay in the circuit is from line LI, connector 48 and 41, switch 33, pole or contact M, connector 42, out

field 39 of the motor, through the common return 31 to the line L2. It is to be noted that the completion of the power circuit through the out field or he motor pursuant to movement of the relay in, is accompanied by a continuation of the established plate circuit holding the relay in," because the plate circuitis then from the line Ll through the filament connection 68 and connector 61 to switch 33, contact 4!, connector to, relay coil 28, plate 65, through the cathode connector 26 to the line L2. Thus, the relay is held in by the energization of the coil 28 as long as any current flows across the bridge through the more or less slight modification of the position of pointer 22 because of the existence or resistance it in side connector H of the bridge circuit, the progress from maximum current flow tion of the flow through coil 26 represents a timed interval comprising one-half of the total cycle of the timer.

If it be assumed that the condition of the device controlling the actuating pointer was such for instance, that a timed interval of twenty minutes was indicated, then the motor 35 will run for twenty minutes, in a purely illustrative case, from the time that the switch 38 isfirst closed, until the motor has moved 'thepointer 22 successively of! from switch 38, permitting the latter to open, and onwardly in its "out movement or stroke until the pointer has been moved to a point on its range between "min" at .29 and "max" at 2: respectively, at which the 1 running of the motor, and one-hali'of the cycle is completed, with the pointer 22 in the line position.

By the dropping out of the relay controlled by the coil 28, the dropping oi the switch 33 from contact or pole 4|, synchronously and substantially' simultaneously engages the switch 83 dotted electrically with the lower pole or contact it.

This closes a circuit through the in field 35 of the motor, starting the second timed half cycle of running of the motor 35, which is only terminated after twenty minutes of running time (illustratlvely as before) by the attainment by the pointed 22 of th "min position at Ell, accompanied by the closing of the special limit switch 38. This circuit, as should. be clear, is

1 from line Ll, connector 48, conn ctor di, switch .33, contact 34, through in field at of the motor 36, through common return 31 to the line L2.

Obviously, in the circuit thus far described, the system gives a, repeat cycle, which continues to repeat. until interrupted in a suitable manner. In order to insure a continuanc of the repeated cycles, even during the time when the actuating arm or pointer I is at the zero end of its scale or range, adjacent to the side'leg H of the bridge circuit, the preferably small resistance is is provided, which is such as to maintain a degree of unbalance in the bridge circuit so as to cause a timing cycle of operations of the actuated pointer 22, even when there is no actual timing cycle indicated by the conditions. Obviously,

, tloning as in ordinary timers. Thus, it is coatempiated that the actuating slidewire ill and its pointer I5 may be relatively moved or have their resistances varied by manual settings. It is also contemplated that the relative position or electrical value of the slidewire arm l5 and the slidewire ill may be accomplished as either a mechanical or electrical follow-up" of any other form 0! angular motion, or as functions of the motion or the acceleration thereof, or as more changes in electrical characteristics, or as a direct coupling to the condition--responsi 1e member itself.

In the device shown illustratlvely in Fig. 2, a rail an is provided leading over a furnace 51 in which the contents of a scoop 52 are to be heat treated for a time directly proportional to the weight of the contents 53. A scale Ed is provided leading to a supporting rollingdcvlce 55 on the track '50. The'weight oi the particular load 53 :of the material is registered or indicated by the pointer 56 on the dial" 51. Let it be assumed that the pointer to is coupled mechanlcally. or electrically if desired, to the controlling slidewire pointer or arm is so that the adjustment of the controlling slide-wire arm is a direct function of the particular load 53 in the scoop. The timing cycle thus established is used to time the duration of exposure of the scoop and its contents to the heat of the furnace, and perfect heating is secured, as should be clear.

In the type of device discussed heretofore, a

. preferred and novel electronically controlled circuit has been disclosed, but in the broad aspects of this invention, the results can be approximated by certain mechanical timing assemblies, for which in a purely illustrative fashion reference may be had to Figs. 3 and 4 herein. In a Patent No. 1,978,947, issued to J chanson et al. on October 30, 1934, there was disclosed an electrically actuated time-controlled circuit-controller, in which there were two variables as to which timed conthis small timed cycle may be of very short dura- 'tion compared to the entire range available from the particular system, and simply insuresthat the repeat cycles do not come to a complete termination, so that a further change of condition will find the timer set and operating.

Of course, it will be evident in the form of invention thus far described, that the gearing and synchronism of the motor will be such that there will be a continuous repeat cycle each comprising a stroke or running out, followed by an identical but opposite stroke or running in,"

with the time duration of both being the same so long as conditions remain the same. In other words, there are preferably always two identically timed strokes in a cycle. The cycle can be conat the end of the cycle. Similarly, it will be evident that for one-half of the complete cycle the relay will beheld in, while for the identical complemental half, the relay will be dropped out, The provision of the upper switch member 29 will permit the establishment of twoidentically timed circuit controlling functions during each cycle.

It will be clear that although in the preferred form of the invention the actuating arm IS on slidewire in is adjusted as an automatic function of a change in condition of some conditioned device with which it is operatively associated, it will be understod that in the broadest aspects of the invention, the particulartiming derived from tinuous as described, or can be caused to stop invention in this field and has been a highly successful development in the industry. It was a feature of one form of this invention that all controls were disposed in concentric relation about a common dial, and that there were manually settable devices moving about the common axis normal to the dial face, by which an arm, driven by a reversible synchronous motor, moved between a fixed contact and a variably positioned contact in a dial-sweeping timed motion, and so arranged that contact with the adjustably positioned contact reversed the motor to reverse the sweep of the arm toward the fixed contact. Additional concentric means was provided to control the duration of a circuit that was made at each end of the stroke of the motor driven arm. The disclosure of that patent has been skeletonized for inclusion herein by omitting certain portions which are inferentialiy included, in order to show, illustratively, the modifications by which the obiects or this invention can be carried out in amore or less mechanical timer, as distinguished from the electronic timer of the earlier figures. As that timer has been developed in earlier embodiments. the timing cycle was a. function of a manual presetting.

Referring to the two figures mentioned, a dial till is provided, if, this should be necessary in an automatically functioning device, with. a concentric axial aperture oi, through which extends the tubular driveshait 62, driven by the roversible synchronous motor 53, through a lost motion connection at. An insulating bushing 65 has change as against which the. adjustable time controlling arm 6'! is pressed, and is disposed behind the dial to. The controlling arm El is integralwith or keyed to a pinion gear so so that they turn together, and if desired, an electrical N anism, such iorinsta'nce as them-metallic therconductor disc it, having a soldering terminal j.

H, is disposed upon the bushing 85 in intimate electrical contact with the pinion gear as and contact arm ill. An insulating disc 12 is provided for lateral abutment against-the connector lo and is pushed thereagainst to furnish a frictional resistance to movement by a compression spring 113'. engaging between the abutting disc 72 and a fixed supporting hearing it. The front of the dial Ed is overhung by a contact-making element is positionable at any desired setting angularly about the dial variable in setting as the actuated pinion gear is turned, as will be explained. The protruding frontal portion of the tubular shaft 62 carries the dial sweeping arm id, in electrical connection with the shaft, and one line from the power circuit extends through the support M and through the tubular shaft 62 to the contact of'the sweep arm it. A fixed contact ii is dis posed at the zero, minimum or starting point of the dial, for instance, in position to be energized by the sweep arm it at the lower end or com clusion of its stroke in the second half of its two= part cycle, and contact to wherever it happens to be located as a result of a given response to a condition, is arranged to be energized at the upper end of its stroke.

A beam til is provided, which, diagratically, represents an element which ismovab-le as a function of the variation in a given condition of a conditioned device including any of the conditions to which the electronically controlled circuit is responsive as described 01' Fig, l. The

. beam. at by any desired condition is caused to sttain a certain position vertically on its range by acres controlled in its movement on the voltage divider, by any suitable condition-responsive mechrnally responsive element H2. The pointer HI oi the voltage divider H0 leads through a resistance lid to a time-adiustable bleed circuit H5, shunting a condenser H5 and leading to a grid lid in a triode ill. The plate lid of the tube leads through a relay 120 to line Ll. The cathode i2i leads to line L2 while being heated by filament 922 as is usual. The time adjustment lI-i is adjustable to vary the rate of bleed or discharge, and a line i23, containing switch I26, extends between line L2 and the condenser end of resistance H3, as at I25, It will be understood that as the voltage divider is-actuated in accordance with a given variable condition, the arm Hi the value of the'condition, and this value is represented by the position of the rack 85 and the angular position of pinion gear 68 permanently in mesh therewith and moved thereby. Thus, the

' position of the time control arm 61 relative to the fixed contact member ll, as affecting the time during which the sweep arm is is traversing the dial face between contacts, is a direct function of the instantaneous value of the condition shooting the beam and rack setting. It will be understood that all reversing functions, circuit controlling functions and the like set up in the said patent to Johanson et al., will be present in the full description of Figs. 3 and but are only thereof is swung either toward line L2 or line Li. It will be clear that if it reaches point H6 presses a maximum charge on the condenser, as

will be clear.

With a given condition of the device associated with condition-responsive element H2, and the arm iii appropriately adjusted as a function thereof, the condenser is charged and remains appropriately charged and the tube remains conductive so long as switch lZ-l is open. As soon as switch its is closed, a timed interval is be gun which maintains during the discharge of the condenser through the timed bleed shunt during which the tube is hau -conductive. The discharge actuates the grid lid and causes plate current to cease flowing and relay i2li drops out from the normal non-timing position shown in Fig. 5'. To secure a controlling function, the relay controls a switch member I28 which from its engagement with upper contact or pole I30, with whatever circuits, if any, this may control, the switch member H8 is dropped into engagement with lower pole l3i to control a timed circuit which lasts until the condenser has been discharged and the plate current builds up and the relay pulls in. It will be clear that a variable timing is secured, due to the variable charging of the condenser, in turn due to variation in the position ofpointer ill relative to the resistance in voltage divider Ho. The variable timing is also aflected by the adjustment of the timing adjuster i it governing the rate of bleed, as will however. that if desired, the condition-response may be made efiective upon the adjustment 4 for varying the timed interval with a fixed and constant charge on the condenser.

It has been made clear that the source ofjthc controlling moment may be any conditioned de-,

preferred in a repeat cycle timer, although ob- I viously other forms of" systems could be availed of for this purpose. Obviously also a single stop half cycle we complete stop cycle could be secured from the motor devices thus far disclosed. Within the purview of this invention, however, is the purely electronic timer device of Fig. 5..

Referring to Fig. 5, there is disclosed the power iinesLi and L2, having a voltage'divider convice, and that it is not necessary, with most forms of the inventioh, that the timing assemblyand its control andcontrolled circuit'sfbelocated, in adjacency to the conditioned device, as it is merely a matter of length of electrical connectors to separate the actuating and actuated slidewire assemblies in an operative bridge circuiti'with,

part close to the conditioned device and part-re,- motetherefrom; I i

As a purely illustrative form of device caused to function, by speed or relativespeed, the" dia grammatic device of Fig. 6 may be considered typical.

81 and resistance or slidewire 38 are the exact counterparts oi the actuating slidewire arm I! and slidewire it of the bridge circuit of Fig. 1, and iunction the same.

It will be clear that in the creation of a bridge circuit it is not necessary that the control he by variable resistances, as variable inductances or the like may also be used'with similar results.

A diagrammatic illustration of this sort of circuit is disclosed in Fig. 7. In this typical installation, the conditioned device comprises a flow meter casing 99, through which fluid flows between inlet iii and exit 92, and the float .element 93 supports the floating core 95 through a rod 9d, and the core is movable with relation to in the. inductance coil 96 having a center tap 9! connecting with the actuated slidewire arm 22 of the bridge circuit slidewire is through the primary 2%, as in Fig. 1, and the ends of the inductance coil connect with the slidewire it by side legs ii and id as will be clear. The variation in inductance of the actuator core t5 and inductance t8 causes unbalance of the bridge circuit, requiring movement, in timed relation, of the slide wire arm 22 to balance the circuit, just as inFlg. 1.

As a further illustration of an operative assembly of elements within the purview or the invention, reference may be made to the disclosure of Fig. 8, in which a conditioned device is llustrated in fragmental form at Hill. A slidewire or the like lill is provided which is identical in functioning to slidewire Id of Fig. l, a pointer I82 is identical to actuating pointer it of Fig. 1, and is either suitably pivoted for movement (not shown), or may be carried bodily for movement on the free end of a bellows 863. The latter is in aclosed tubular line- Hi l extending to the sealed bulbous element I05, and the state of compression or expansion of the bellows is a funcwhether accomplished by movement or by purely tion of the internal pressure in the entire bellows system. Normally, with the device illustrated.

the condition in or of the'device ice to which the bellows will respond will be temperature, but it may equally well be pressure. Any such assembly or combinations of assemblies of elements to control the actuator of the timer may be resorted to in accordance with the desired-conditions.

It is an important phase of the invention, that I the entire assembly of the timing circuit and re- 'due course, a controlling assembly of slidewire i0 and arm l5 can subsequently be operatively connected when the particular controlling actuating assembly necessary for a given installation,

, whether close to or remote from the conditioned device, and whether it comprises a variable resistl0 ance, inductance, or any other type of bridge-circult controlling electrical assembly is provided. This universality of use is characteristic not only of the disclosure of Fig. l, but also of the electronic timer assembly of Fig. 5.

It'will be clear that it makes no diflerence electrical activity. e

The great range of usefulness and theiull list oi advantages attaching to the invention herein, as well as the fact that the form of invention disclosed herein are purely illustrative are not limitative, will be evident, and any change of form or modifications to accord with dcsirements for other exemplifications or the invention are to be construed as within the purview of this invention and the scope oi the attached claims, unless'the latter should be otherwise limited.

Having thus described my invention, I claim:

1. A timing" device comprising means automatically movable pursuant to a change of condition of a conditioned device, a timing device having a cycle oi operations of variable total length, and means varying the cycle in its total length as a function of the change of condition of said conditioned device.

2. A timing device comprising means automatically movable pursuant to a change of condition of a conditioned device, a timing system comprising a reversible synchronous motor having cycles of varying length each comprised of a stroke out and an equal return stroke in, and means operatively associating the said means with the device to vary the duration of the stroke out and therefore of the duration of the return stroke in as a function of the condition of the conditioned device. I

3. A timing system which comprises in combination a device 01' variable condition, means of variable setting, means coupling the device and means in automatic driving relation to vary automatically said setting with aid condition, and

'a timing device establishing a timing interval as a function of such setting.

4. A timing system comprising a unitary structure comprising a thermionic circuit, a relay in the plate output circuit, a reversible motor driving in a cons ant repeat cycle of movement, a slidewire of a bridge circuit, and a slidewire arm for the said slidewire in driven relation to the motor to secure a sweep of the arm relative to the said slidewire, with a connection controlled by the slidewire arm for controlling the thermionic circuit, so arranged that a complemental electrical unit of variable value can be subsequently attached to the unit to com lete the bridge circuit and the control circuit to the thermionic system, and so that the change or value can be automatically effective upon the said complemental portion of'the bridge circuit to control the timed output of the relay as a function or the change in value. Y

5. A timingdevice comprising means of variable electrlcal effectiveness automatically actuataerator cated by the system, movable means arranged for operative association with a conditioned dc vice the condition oi which is variable relative to a predetermined condition and movable automatically as the condition of said device varies, and means coupling the movable means and the adjustable means for synchronous operation whereby the duration or the timed interval of the sys tem is varied as a function of the condition of said device.

' 7; A timing system comprising in combination a conditioned device subject to change of condition relative to a predetermined condition, a, timing device operative to indicate a timed interval, means in the timing device for varying the duration of the timed interval, and means automatically responsive to changes in condition of the conditioned device to synchronously actuate the means in the timing device to effect a timed interval which is a function of the deviation of instantaneous condition of said conditioned device from said predetermined condition.

8. A timing system having a first and a second slidewire, pointers for the respective 'slidewire and relatively adjustable thereon between a fixed minimum point and a variable maximum point, a transformer having a primary in circuit with the resnective pointers iorthe respective slidewires and arranged to energize the. primary in accordance with the unbalance oi the bridge circuit, means comprising an electronic circuit including the secondary of said transformer, a thermionic tube in the electronic circuit, a double throw relayha'ving an actuating coil inthe output circuit of said tube, a motor having forward and reversing fields and the armature of which is in driving engagement with the pointer of said second mentioned 'slidewire in both directions of running controlled by said respective fields, an electrical networlsincluding the contacts of the relay and the respective fields of the motor and so arranged that when the actuating coil of the relay is energized a circuit is closed through the forward field of the motor and when'deenergized a, circuit is closed through the reversing field of the motor, means for relatively adjusting the pointer on the-first mentioned slidewire between the minimum and maximum points thereon to neously opens the circuit through the forward held of the motor and closes a circuit tmoush the reversing field thereof and the pointer of the second slidewire is movedin a timed interval complemental oi the first relatively to the second slidewire until it again attains its initial minimum position, and means for indicating the total time interval comprised of the forward stroke and the complemental reverse stroke of the pointer for the second slidewire as the timed interval of the timing system. I i

9. A timing system as recited in claim d, char-- acterized by the provision oi supplemental switch means for energizing the coil of the relay to re verse the direction of running of the motor when the pointer oi the second slidewire reaches its minimum point in the reversed running of the motor, for initiating a repetition oi? the timing running of the motor forward and reverse in a repetition of said total timing interval.

1.0. In a timing apparatus arranged for opera;- tive association with a source of electric poten tiai. a bridg circuit comprising a pair oi no-- tentiorneters connected in parallel acrom such source when ogeratively associated therewith and each having a contact adiustahle thereover, a

bridge output circuit connected between said ad '1 ,iustable contacts whereby voltage from such oneratively associated source is impressed across said output only when said contacts are not simition to oscillate said motor=driven contact at a constant speed between a predetermined initial position and the position of zero bridge circuit output as determined by the position of said arbitrarily adjustable contact, whereby the position establish a timing interval when the slidewire I until the pointer of the second slide'wire has moved iromits minimum point relatively on the slidewire to a point atwhich the bridge circuit is balanced and the actuating coil or the relay is deenergized, and which substantially instantaof the latter determined the time said motor opcrates in each directionin each cycle oi its oscillatory motion.

11. In a timing apparatus as recited in claim 10, said network including a working circuit, and means in said network for automatically controlling said working circuit as a function of the time of running of the motor in one direction 12. In a timing apparatus as recited in claim 10, means in said network ior automatically reversing said motor to initiate a repeat cycle of running to oscillate said motor-driven contact between its said predetermined position and the position of zero bridge circuit.

13. In a timing apparatus as recited in claim wamm was none.

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