US2113069A - Indicating, recording, and/or controlling apparatus - Google Patents

Description

A ril 5, 1938.. R. w. oss ET AL INDICATING, RECORDING AND/OR CONTROLLING APPARATUS Filed April 18, 1936 7 Shets-Sheet 1 ,INVENTORS Raymond W. Ross 5 0rd. H..Seber/k1gen,deceu:d Sophie Seberhaqen, 'execuirix by Mar! WM ATTORNEY April 5, 1938. R. w. R088 ET AL 2,113,069

INDICATING, RECORDING, AND/OR CONTROLLING APPARATUS Filed April 18, 1936 7 Sheets-Sheet 2 8 O a O r aka-VF o \M v m o mwhwmwm e Q Q INVENTORS Raymond M Ross Sigurd H- Seberhagen, deceased Sophie Seber'hagen, execuir'ix Br W a, waif ATTORNEY.

A ril 5, 1938. R. w. R055 ET AL 2,113,069

INDICATING, RECORDING, AND/OR CONTROLLING APPARATUS Filed April 18, 1936 7 Shets-Sheet s IN EN ORS Raymond W. Ross SLgur'd H. Seberhagen deceased Sophie Seberhaqen, executrix ATTORNEY.

'Aprii 5, 1938.

R. W. ROSS AL INDICATING, RECORDING, AND/OR CONTROLLING APPARATUS 7 Sheets-Sheet 4 Filed April 18,- 1956 INVENTORS Raymond W- Rgss Sigurd. H. .Seberhaqemdecanm Sophia Seberhagemexecutm'x 9 W 1.03m

ATTORNEY.

April 5, 1938 I R. WJROSS ET AL 2,113,069

INDICATING, RECORDING, AND/0R CONTROLLING APPARATUS- Filed April 18, 1936 7 Sheets-Sheet 5 JZL INVENTORS Raymond W. Ross Sigurd H. Serbsvhagerwleceased Sophie Seber'hdgcn,cxecvtrix Mica-7a.;

ATTORNEY.

April 5, 1938. w; R055 ET AL INDICATING, RECORDING, AND/OR CONTROLLING APPARATUS Filed April 18, 1936 7 She ets-Sheet 6 m. mu S m & m N Tsw Nu Ra W 3 N.WS.M I M w J. m wh B ygp a O RS5 ATTORNEY.

A ril 5, 1938. R. w. R055 El AL 2,113,069

INDICATING RECORDING, AND/OR CONTROLLING APPARATUS Filed April 1a, 1956 7 Sheets-Sheet v FIGIBA INVENTORS Raymqnd M Ross Scgurd H. Seber'hagemdermsed Sophie Sebrhaqemexecvtrlx 7 Mwkflu ATTORNEY.

named A s, was

I INDIOA'IING,

ll. Pa by Sophisdelphia, Pass-signer Ecol-DING, AND/OI GON- m TUB ,mcuirhl'hilatolieadsandNorthi-up company, Philadelphia, Pa-,a corporation of was... in is, me. Serial No. 15,208

This invention relates to exhibiting instruments and apparatus for indicating, recording, controlling or otherwise measuring the magnitude of any predetermined condition; and more particularly to an apparatus for use in connection with a measuring circuit and including means for intermittently rebalancing the same, of such type, for example, as shown and described in United States Letters Patent No. 1,935,732, granted November 21, 1938, upon the application of L. Y. Squibb.

This application is a continuation-in-part of 1 copending application Serial No. 2,972, filed January 22, 1935, for Indicating, recording and/or controlling apparatus. a

While this invention is of general application, it is particularly suitable for application to multiple-record indicating, recording and/or measuring apparatus for use in connection with a measuring circuit and including means for periodically recalibrating the measuring circuit; this invention relates further to the several component operating mechanisms of such an apparatus by means of which the various portions thereof are maintained insynchronism and the phase therebetween accurately adjusted, thus avoiding interference of the separate mechanisms or misleading or irregular records or indications.

More specifically, this invention comprises indicating, recording, controlling and/or measuring apparatus including a primary member movable in response to the magnitude of a condition under measurement, as determined by a measuring circuit; a continuously operated driving element or power mechanism, and a mechanical relay apparatus controlled'by the primary movable member and operating periodically to rebalance the measuring circuit, control and operate the indicating and recording unit assembly. 'I'he apparatus includes also a recalibrating mechanism operated by the drivingelement effective periodically to recalibrate the measuring circuit to compensate for variations in any electrical condition of the source of power for the measuring circuit, and means for synchronizing, and accurately controlling the phase relationship between, the mechanical relay apparatus and the recalibrating mechanism.

In case'this invention is applied to a printing recorder, as contrasted to a continuous curve drawing recorder, the marker or printing element or assembly is operated by the driving element and is interlocked with the calibrating operating mechanism to prevent operation of the marker during a recalibrating cycle; and there is provided also means for synchronizing, and accurately determining the phase relation between, the marker operating mechanism and the mechanical relay apparatus. In case this invention is applied to a multiple-record indicating, recording or measuring apparatus; that is, ap- "paratus for measuring a plurality of similar or different conditions at the same or different points or locations, it includes also means rendered inoperative during a recalibrating cycle, for successively advancing the marking element or assembly, preferably in step-by-step motion, and for simultaneously changing the circuit connections of the measuring circuit successivelyto respond to a plurality of predetermined conditions in a definite sequence, and the apparatus includes also mechanism for synchronizing, and accurately determining the phase relation between, the operating mechanism for advancing the marking element and operating the circuit controller and the mechanical relay apparatus.

This invention comprises also improved and simplified sub combinations or component mechanisms of a combined indicating, recording and/or measuring apparatus of the type Just described by means of which a high degree of accuracy and reliability of operation is attained.

A further feature of this invention comprises an improved recording element assembly particularly suitable for use in the combined apparatus described above, and also an improved universal single or multiple point recorder element assembly, and to new and improved inking devices particularly useful in connection with such recorder element assembly.

The term "measure is used herein to connote any indication, recording, controlling or other eifect which is derived from and constitutes a measure of a given primary condition.

For a better understanding of this invention, together with other and further features thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the drawings,-1"ig. l is a view in rear elevation, of a combined indicating-recording apparatus embodying our invention;

Fig. 2 is a front elevation, partly broken away, of the apparatus of Fig. 1;

Fig. 3 is a top plan view of the apparatus of Fig. l; a M

Fig. 4 is a cross-sectionalview of the recorder element assembly shown in lfigs. 1 through 3;

Fig. 7a is a detail of an operating cam of the mechanism of Fig. 7;

Fig. 8 is a schematic circuit diagram of a measuring circuit and its associated elements with elements corresponding to those shown in the preceding figures identified by like reference characters. A

Fig. 9 is a cross-sectional view of the current calibrating operating mechanism along the lines 99 of Fig. 3; 7

Figs. 10 and 11 are, respectively, front and side elevations of a modified form of inking device;

Fig. 12 is an exploded perspective view of selected parts of the mechanism of Figs. 1-9, particularly the calibrating mechanism, the printing mechanism, and associated drive shafts, timing gears and operating cams;

Fig. 12A is a side elevation of one of the discs of Fig. 12 together with a part of its associated follower;

Fig. 13 is a perspective view of a modified form of mechanism suitable for the control of the printing or recording mechanism; and

Fig. 13A is a fragmentary end elevation of Fig. 13. v

It is believed a clear understanding of the arrangement and operation of the various parts of the apparatus will be best understood from a complete description of the operation of the apparatus as a whole, and therefore the construction and arrangement of certain of the mechanisms or component parts of the apparatus by themselves will be first'described in detail.

Referring now more particularly to Figs. 1, 2,

I and 3 of the drawings, there is shown one embodiment of this invention comprising indicating, recording and/or controlling apparatus operable in response to changes or variations inimagnitude of any desired condition as indicated by a galvanometer G, provided with a pointer or defleeting element Ill. The several indicating, recording and/or controlling elements or mechanisms to be described hereinafter may be operated in accordance with deflections of the pointer l through any suitable mechanical relay apparatus, although there has been illustrated, by way of example, a particular mechanical relay apparatus, similar to that described and claimed in U. S. Letters Patent No. 1,935,732, granted November 21, 1933, upon the application of L. Y. Squibb.

In brief, the mechanical relay apparatus comprises a pairlof clamping members or bars ll between which the pointer ID of the galvanometer G normally freely deflects. One of the members II is periodically moved toward engagement with each other, and with the pointer ID by means of linkage elements (not shown) and a cam l2 continuously rotated by a power shaft l3 driven by a motor M through a worm l4 and a worm wheel M. There are also provided a pair of scissors-like pointer engaging arms or feelers l5 pivoted respectively at l5a on a plate 9 (shown in dotted outline for the sake of clarity) and biased into engagement with each other by a suitable spring 16. The plate 9 is pivoted at its upper end from the frame of the apparatus and about an axis parallel to the plane of the paper, as viewed in Fig. 1. Secured to the arms l5 are the cam followers lib, which ride on the cam surfaces l2b of the cam element I2, the arms being thereby separated to disengage the pointer 10 for a predetermined portion of each rotation .of the shaft l3.

Also pivoted on the plate 9 at 11a is a clutch arm I! having a pin llb adjustably securedin a slot of an upstanding arm He. The pin "b is disposed between the lower portions of the arms or feelers l5 and is adapted to be engaged thereby when the scissors are closed by the biasing spring l6 after release by the cam l2. The outer ends of the clutch arm I! are provided with clutch surfaces or shoes (not shown) cooperating with a clutch rim l8a of a clutch disc l8. The outer ends of the clutch arm II are provvided also with cam surfaces or followers lld disposed in the path of rotation of a pair of cams l9, driven by the shaft I3. The clutch disc I8 is rigidly secured to a shaft 20 (Figs. 2, 3) journaled in the frame of the apparatus The manner in which the above described apparatus operates periodically to rotate the shaft 20 through an angle dependent upon and constituting a measure of the deflection of the pointer III of the galvanometer G is set forth in detail in the above entitled Squibb patent. In brief, assuming the parts to occupy the positions indicated in Fig. 1, the galvanometer pointer I0 is free to deflect in response to variations in magnitude of the condition to be measured or controlled. At a predetermined point in a cycle of rotation of the shaft I3, as determined by the cam 12, the pointer III in its deflected position is clamped between the bars ll. Substantially immediately upon the clamping of the pointer I by the bars II, the cam followers lib ride oil! the cam surfaces 12b and release the arms or feelers l5, which move toward engagement with each other under the influence of the biasing spring l6. In case the pointer III has previously been deflected in response to a change in magnitude of the condition to be measured, one of the feelers IE will engage the pointer before the other, which latter then moves beyond its central or neutral position until it deflects the clutch arm I! an amount corresponding to the deflection of pointer l0. More specifically, the plate 8, prior to release of the feelers, has been moved by the cam l2 about its pivot to disengage the clutch arm II from the clutch disc l8 so that the arm I! is free to move. The lower arm of that one of the feelers l5, which has moved beyond its neutral position as aforesaid, engages the pin I lb secured to the arm l1, and rotates it, about its pivot l'la through an angle proportional to the deflection of the pointer l0; thereafter the cam l2 releases the plate 9 and the arm I! in its new position is returned into drivlng engagement with the clutch disc I 8a. One of rotating cams I 9 then engages its associated cam follower "d, which has been deflected upwardly into its path of rotation by angular movement of arm l1, and; during continued rotation of the cam, returns the clutch arm I! to its normal or horizontal position, at the same time driving the clutch disc ll through an equal angle.

The clutch disc I8 is secured to a shaft 20 journaled in the frame of the apparatus, the angular movement of the shaft being utilized to drive the indicating, recording and/or controlling elements of the apparatus. For example, an insulating disc 2|, Fig. 2, secured to the shaft 20 may carry a potentiometer Mil cooperating with a stationary adjustable contact 2). and this 'slidewire or potentiometer may-preferably be ina pulley 22 cooperating with a cord or endless belt 23, Fig. l, passing over idler pulleys 25 and attached by screw clamps 25b to a carriage 25 carrying the indicating and recording elements. As shown more clearly in-Figs. 4, 6, 7, 12, and 13, the carriage" comprises a substantiallyboxlike frame, open at top and bottom, and suitably fabricated from sheet metal. Disposed within the carriage-frame 25 is a driving gear 25 secured on a sleeve 21 journaled in the ends of the frame 25. The respective ends of the sleeve 21 are of reduced diameter and pass respectively through corresponding openings in the ends of the frame 25, Figs. 3, 5, and 12, the shoulders 21s bearing against the inner sides of the ends of the frame to insure lateral movement of the sleeve 21 and carriage as a unit and to permit rotation of gear 25 independently of the carriage 25. A driving connection between the sleeve 21 and shaft 28 is provided by a longitudinal slot or keyway 23a in which is disposed a key interconnecting the shaft and the sleeve 21. As shown more clearly in Fig. 5, a cylindrical key 21a is secured within the sleeve 21 by a set screw 21b, the key 21a sliding with minimum friction in the slot 28a of the shaft 23. Projecting from the carriage 25 are a pair of arms 25a which slidably engage a guide shaft or rod 23 to prevent rotation of the carriage 25 about the shaft 23.

A second box like frame, Fig. 6, having upstanding ears or lugs 30a is pivotally. supported from the frame 25 by means of pivot pins 30!) passing through apertures of the frame 25 and the upstanding lugs 30a. Journaled between the side bars of the frame 30 and extending at right angles to shaft 23 is a shaft 3| upon which is secured a helical driven gear 33, Fig. 4, meshing with driving gear 25 substantially in a line passing through the axis of the pivots 33b. Also secured to the shaft 3| is a recorder device or printwheel 32 provided with a plurality of printing characters or like marking elements, and an index plate 34. From the front end of the frame 33 or, as viewed in Figs. 4, 5, and 'l, at the left end thereof, there extends a U-shaped member, one arm 35 of which constitutes an indicator which cooperates with a stationary scale 36. Depending from the carriage-frame 25 is a V-shaped plate or arm 31 (Figs. 1, 4, 6, and '7) having a pin 38 in its lower extremity disposed to engage peripheral recesses in the index plate 34, as described more fully hereinafter.

A second V-shaped plate or bracket 33 extends upwardly from the forward side bar of the frame 25 and may be integral therewith or, as illustrated in Fig. 4, may be adjustably secured by a screw or nut and bolt 40 passing through a slot in the bar of the frame 25 and a hole in the bracket 33, or vice versa. The bracket 39 preferably extends upwardly at an angle of approximately and journaled therein is a stub shaft 4| upon which is secured a helical gear 42 also meshing with the driving gear 26. A second stub shaft 43 is provided with a threaded extension 53a engaging a threaded recess in the shaft ll and forms an extension thereof. The shaft 43 is provided with a knurled end 4317 to facilitate engagement and disengagement between the shafts II and 43. a

' preferably proportioned to fit closely within the recesses a and a retaining dmc or plate 45 is secured to the face of the disc 44 by screws a additionally to retain the inking pads b in the disc 44. The inking drum 44 is loosely- Journaled on the shaft 43 and, in order to secure proper synchronization between the drum 44 and the printwheel 32, an arm 45 is secured'to and projects from the stub shaft ll and engages in a recess c of the drum 44 forming a driving engagement therewith.

In order to tilt or oscillate the frame 30, in which is mounted the printwheel 32, to bring the latter into engagement with the record chart, the frame 30 is provided with an extension or arm 30c terminating ina cylindrical guide element 30d disposed in a key'or slot 230 in the shaft 23. Movement of the shaft 29 in a clockwise direction (Fig. 4) thereby tilts the frame 30 and the printwheel 32 until the latter engages and registers a distinctive character upon the record chart.

In certain instances, as for example, when the printwheel 32 is provided with a plurality of distinctive record characters, a single color inking pad sufflces. In Fig. 6 is shown a modified assembly in which the bracket 39, of Fig. 4, supporting the inking pad drum 44 is replaced by a bracket 41. The bracket 41 terminates in a holder "a in which is mounted an ink pad 41b registering and cooperating with the several record characters of the printwheel 32. The bracket 41 is secured to the frame 25 by suitable screws or bolts 4|! and is preferably interchangeable with the bracket 39, so that either may be replaced by the other simply by releasing the screws or bolts 40.

The printwheel 32 may register its record upon any suitable record chart driven by any wellknown mechanism. By way of example only, there is shown (Figs. 1, 2, 3, and 7) a continuous strip chart which, as supplied from a feed roll (not shown), passes over a chart drum or driving roll 5| and thence over a backing plate 52, during which passage the record may be viewed by an observer. By mounting the printwheel 32 with its axis normal to the face of the chart and arranging the characters along a beveled edge thereof the printed record is visible from the front of the instrument as soon as the printwheel is returned to its normal position as shown in Fig. 2 and described with greater particularity hereinafter. Mounted on the main power shaft I3 is a worm 53 (Fig. '7) engaging a worm wheel 54 mounted upon and driving a shaft 55 which, through gearing 56, drives a shaft 51 on which is secured a worm 58 registering with a worm wheel 53 secured to the shaft 60 of the chart drum 5!. Consequently the chart 50 is continuously driven at low speed from the power shaft l3.

While the printwheel 32 may be advanced stepby-step by any well-known mechanism to bring in succession its characters into printing positions, it is advantageous to use in accordance with the present invention a mechanism which not only advances the printwheel but also serves periodically to oscillate or tilt the printwheel 32 into momentary engagement or registration with and a double -armed member or bell crank 62 independently movable with respect to but journaled on the shaft 28 and on one arm of which is pivotally mounted a ratchet pawl 88 biased into engagement with the wheel Si by means of a spring 88a. There is also provided a locking ratchet pawl 84 mounted on a stationary pivot and biased into engagement with the ratchet wheel Si by a spring 84a, thereby preventing reverse rotation of the ratchet wheel 8i. Referring to Fig. 7, the other arm of the bell crank 82 is provided with a slot 620. in which slides a pin 68 adjustably secured in a slot 86a of one arm of a second bell crank 88. The other arm of the bell crank 88 is operated'by a mechanism comprising a link 81 and an arm-88 pivoted intermediate its ends on a fixed pivot pin 88a. The link 81 is connected to the end of the arm of the bell crank 88 by a pivot pin 8111, while in its other end is provided a slot 81b in which is adiustably secured a pin 88 journaled in the end of the arm 88. A biasing spring Iii attached to the upper portion of the arm 88 tends to rotate it in a counter-clockwise direction, thus moving the bell crank 82 also in a counter-clockwise direction to advance the ratchet pawl 88 with respect to ratchet wheel 8i so that, upon subsequent return of the operating mechanism to the position shown in Fig. 7, the ratchet wheel 8i will be advanced through a predetermined angle or step. An adjustable stop ii is provided to limit the throw of the operating arm 68 under the influence of the spring 10.

The operating mechanism above described is normally restrained in a position shown in Fig. 7 by means of a cam follower, shown as a projection or pin 12 (Fig. 12) extending from the lower arm of the member 88 and riding on the face of a cam or disc 13 provided with a single peripheral notch or recess 13a (Figs. 1, 2, and 7a). The disc '13 is driven by a worm wheel I4 engaging the worm 58 driven by the main power shaft i3. Therefore, once each predetermined number of revolutions of the shaft ii, the pin 12 registers with the recess 13a, permitting the arm 88 to move in a counter-clockwise direction under the influence of the spring iii.

It is highly desirable that the print wheel 82 shall be prevented from registering with the record chart" during that portion of the cycle in which the clutch arm il (Fig. 1) engages the clutch disc i8, since a rotation of the disc l8 might produce a transverse movement of the printwheel carriage during the printing operation and smear or blur the record chart. The timing of the registration of the printwheel 32 with the record chart 5i with respect to the cycle of operation of the mechanical relay apparatus described above is obtained by means of a cam I8 (Fig. 7) mounted on the shaft i8 and provided with a single recess 160 with which cooperates a projection or pin 15 (Fig. 3) adjustably secured in the lower end of the arm 68. It is clear that the cam 18 operates at a speed of a lower order of magnitude than that of the cam 18. Thus, the pin 12 and the disc 13 determine the frequency of registration of the printwheel 82 with the record chart II, as determined by the gear ratio between the worm 88 and worm wheel 18, while the pin 18 and the cam 16 accurately time or phase the registration of-the print wheel with respect to the angular position of shaft i3 and its cam i2, or with respect to a desired portion of the cycle of operation of the mechanical relay apparatus. Both the disc 18 and the cam 18 are adjustable with respect to their respective shafts Ila and II, to insure proper phasing with respect to the mechanical relay.

It is often desirable automatically to switch the circuit of the galvanometer G between several measuring circuits simultaneously with the suc cessive step-by-step movement of the printwheel 82 and the inking drum 88. To this end, the shaft 28 which imparts the step-by-step movement to the printwheel 22 and the inking drum 44 carries a gear 'i'i which, through an intermediate idling gear 18, drives a gear 19 attached to a shaft 80. Upon the shaft (Fig. 1) is mounted a bevel gear 8i cooperating with a sec ond bevel gear 82 secured on the shaft 83, on the lower end of which is attached a rotatable brush member 84. The member 84 cooperates with the stationary member 85 carrying a plurality of segmental annular contact members 85a. The selector switch comprising members 84 and 85 is preferably enclosed within a casing 81 which may contain oil or other suitable lubricating medium.

The operation of the above described automatic multiple-record indicating and recording apparatus will be understood more clearly by now referring to Fig. 8 in which is shown a schematic diagram of a system, including certain of the several elements thus far described, for successively measuring the magnitudes of a plurality of conditions at the same or different locations, for example, the temperatures at a plurality of points or locations; in one specific example which has operated satisfactorily, 16 points. Thus, by multiple-point recording and/or indicating means, reference is made to provisions for utilizing the same instrumentality for successively measuring and/or recording conditions as measured at a plurality of points by condition-responsive means individual to each point or location. In Fig. 8 it is seen that the measuring circuit includes a potentiometer comprising a slidewire or adjustable resistance 2ia having an adjustable contact 2 I b connected in series with fixed resistors 81a and 88 and energized from a source of current, such as a battery 89, through a callbrating resistance 90 provided with an adjustable contact 90a. The galvanometer G is connected in circuit successively with one of several thermocouples 92 or other primary condition-responsive elements through a two-position switch 9i, when in its left-hand position, as seen in Fig. 8, and in series with that portion of the potentiometer 81a'-2ia88 comprising the resistance 81a and the left-hand portion of the slidewire 2 la.

It is now believed that a comprehensive understanding of the invention, including the construction; arrangement and operation of the apparatus, will be facilitated by a description of the operation of the organization as a whole. To this end it will be assumed that the movable element of the selector switch has just been moved to the position shown in Fig. 8 of the drawings, in which it completes the circuit through one of the several thermocouples 92. If the temperature as measured by the particular thermocouple 92 is different from that indicated by the preceding thermocouple and with which the setting of the adjustable contact 2i b of the slidewire 2ia corresponds, an unbalance voltage will appear in the circuit of the galvanometer G which will deflect its pointer i0. When the pointer i0 is thus deflected, a motion will be imparted to the shaft 20, Figs. 2 and 3, carrying the slidewire 2ia which, within predetermined limits, is representive of,

wire 2 a will be moved in a sense which will tend to rebalance the measuring circuit of Fig. 8.

In case the initial movement of slidewire 2l'a is insuflicient or over-suflicient to rebalance the measuring network, the mechanical relay apparatus repeats its cycle of operation again to adjust the potentiometer slidewire 2|a to rebalance the measuring circuit. The relay apparatus, before printing, may operate for a predetermined number of revolutions of the shaft I3, such as 24, which is suificient to insure a complete balancing of the measuring circuit of Fig. 8

even under extreme changes in electromotive force between successive thermocouples occasioned by widely varying temperatures at the difierent measuring points.

Simultaneously with movement of the slidewire 2|a the carriage and associated elements are, by the driving pulley 22 and the endless belt 23, moved across the chart 5|. The position of 25 the indicator 35 with reference to the scale 36 (Fig. 2) is a measure of the magnitude of the condition under measurement. As .soon as the potentiometer circuit is rebalanced a direct reading may be taken which will correspond with 3 great precision to the magnitude of the condition under measurement.

After a predetermined number of cycles of operaticn of the mechanical relayapparatus, corresponding to the number of rotations of shaft I3 35 as determined by the ratio of the worm 53 and the 40 or recess 13a of the disc preparatory to the printing or recording operation.

Just prior to registration of recess 13a and pin 12, an effective inking of the uppermost marking element of the printing wheel 32 is 45 accomplished by means of a raised or punched out portion 13b (Figs. 7a and 12A) corresponding with the leading end of the notch or recess 13a of the disc I3. Thus as the raised portion 13b is moved into engagement with the pin 12, a

50 slight clockwise movement is imparted to the arm 68 which movement is transmitted through link 61, bell crank 66, shaft 29 and extension 330 to rotate the uppermost character of print wheel 32 into firm engagement with the corresponding 55 one of the inking pads 44b carried by the disc 44. A slight-additional movement of the disc 13 releases arm 68 which then moves through a sinall angle in a counterclockwise direction to its original position. By this means an effective 60 inking of the several marking elements of the disc or print wheel 32 is accomplished, at the same time avoiding the continuous pressure between the print wheel 32 and the disc 44 which "would result in increased friction or possible 65 binding of the elements of the recorder assembly.

As stated above, for the printing operation the release of the operating arm 58 is accurately timed, with reference to the operating cycle of the relay mechanism, by the cam I6 and the aux- 0 iliary pin 15. Thus, immediately after the cam 12 disengages the clutch arm l1 from the disc l3 the cam 16 is arranged to move its recess 16a into registration with the pin 15 carried by the arm 88. This arm is thereby released for 15 movement in a counter-clockwise direction under the influence of the operating spring ll. As the arm 53 moves, the pins or followers 12 and I5 respectively enter recesses 13a and 16a and thebell crank 66, now rotated by operating arm 58 and link 51 in a clockwise direction, drives, in a clockwise direction, the shaft 23 which in turn moves the print wheel supporting frame pivoted at 30b through a corresponding angle in a counter-clockwise direction, the movement being suilicient to insure registration of the print wheel 32 with the record chart 5|. The duration of the time the print wheel 32 is in engagement with the chart 5| is determined by the size or extent of the recess 15a of the cam I6. Since the chart is continuously driven from the main shaft I3 the recess 16a has a configuration such that the print wheel 32 moves rapidly into and out of engagement with the chart thereby to prevent blurring or smearing and to insure a single imprint of the record mark or indicia by the print wheel 32 upon the record chart.

It may here be observed that the axis of the print wheel 32 is normal to the plane of the face of the chart 5| (Fig. 2) and that during the printing operation the print wheel or disc 32 registers with the chart forwardly and substantially below the top of the chart drum. In consequence, as soon as the print wheel 32 is returned to its normal position and out of engagement with the chart 5|, the record left thereon is immediately and readily visible from the front of the apparatus, as shown in Fig. 2.

Simultaneously with the printing operation, the bell crank 62, is by clockwise movement of bell crank 66 rotated in a counter-clockwise direction, the ratchet orpawl 63 merely sliding over one tooth of the ratchet wheel 6|, which is locked against rotation in this direction by the locking ratchet pawl 64. However. as the arm 58 is returned to the position shown in Fig. 7 by the cam 16 operating on the pin 15, the shaft 29 is again rotated to the position shown in Fig. '7, returning the print wheel 32 to its normal position. During this return motion, the bell crank 62 is rotated in a clockwise direction and drives the shaft 28 through a similar angle by means of the ratchet pawl 63. This rotation of the shaft 28 is adjusted by means of the adjustable pins 55 and 69 to correspond exactly to the angle between adjacent record characters or marking elements on the periphery of the print wheel 32. The shaft 28 through the helical gears 26, 33 and 42 drives the print wheel 32 and the inking drum 44 through corresponding angles, so that the print wheel 32 is in position to register the condition at a succeeding location or point under measurement in response to a change in circuit connections as is presently to be described.

As mentioned above, the spiral gear 33 meshes with spiral gear 26 on the pivotal axis through screws 30!). This is done in order to prevent rotation of the print wheel upon its movement into engagement with the chart.

In order substantially to eliminate errors in the registration of the print wheel 32 on the record chart 5|, due to any lost motion in the driving mechanism between the shaft l3 and the print wheel 32, an index plate 34 is carried by the same shaft as the print wheel 32 and is rigidly secured thereto. This index plate 34, upon depression of the print wheel 32 as described above, engages a projecting pin 38 on the depending stirrup or bracket 31 secured to the frame 25 of the indicating and recording element assembly, and guides the print wheel during printing.

The peripheral notches or indentations of the index plate 84 are in exact angular alignment with the record characters or printing elements of the print wheel 82 so that the angular position of the print wheel 82 is accurately determined for each printing registration, thereby insuring that each character is moved flat against the chart III. A further important function is to prevent rotation of the print wheel 82 and to prevent lateral displacement of the record which might otherwise result. In this manner, all records are accurate to within one-quarter of a per cent and no inaccuracies are introduced by lateral displacement of the printed record.

In brief then, the galvanometer G is automatically and successively connected in circuit with the several thermocouples 82 and, after each such number of cycles of operation of the mechanical relay apparatus sufficient to insure the rebalancing of the measuring circuit, the recording mechanism, which has been moved to a new position with respect to the chart, is automatically operated to register an indication on the record chart of the magnitude of the condition existing at the particular point under measurement and the indicator 85 indicates this value on the cooperating scale 88. Thereafter, the galvanometer is successively connected in circuit with the other thermocouples and the above described cycle of operation is repeated; For each point, the indicator and recorder element assembly is moved transversely of the scale 88 (Figs. 2, 3. 4, 6, and 7) and the record chart 58, so that the indicator 85 will indicate on the scale 88 the magnitude of the condition existing at the point of the measurement; this magnitude may be registered on the record chart graduated as the scale 88 by means of the impression left by print wheel 82. At the same time a numeral 82a on the front face of the print wheel 82, appearing through the opening in themask 821), indicates the number of the control point at which the measurement is being taken. Preferably a corresponding numeral is printed on the chart by the print wheel 82..

It will be noted also that the connection of the galvanometer successively into the several thermocouple circuits is automatically synchronized with the step-by-step movement of the print wheel 82 and the inking drum 44 through the gearing TI'I8'I8-8I--82, described above.

It is well understood that the voltage of a battery, such, for example, as that utilized to energize the potentiometer measuring circuit of Fig. 8, varies appreciably with time, and that the accuracy of measurement, as determined by the above described apparatus, depends upon the constancy of current to the slidewire 2Ia; that is, the constancy of the terminal voltage of the battery 88. In order to compensate for variations in voltage of such a battery, it is desirable periodically to recalibrate or restandardize the measuring circuit by substituting therein a standard electrical unit, preferably an auxiliary standard cell or source developing a constant or standard electromotivei'orce. For example, referring to Fig. 8, if the switch 8| be operated to its right-hand position, the galvanometer G will be connected directly across the potentiometer circuit in series with a standard cell 8 supplying such an electromotive force. Under normal conditions, the voltage of the standard cell 8 just balances that across the potentiometer comprising the resistances 81a and 88 and the slidewire 2Ia. If, however, the voltage of the battery 88 has changed, the measuring circuit will no longer be balanced. It may be restored to balance by varying any desired electrical condition or constant of the measuring circuit, for example, by adjusting the contact 88a of the calibrating resistance 88.

It is desirable to effect this restandardization or recalibration automatically and periodically, for example, every half or three-quarters of an hour, corresponding to a predetermined higher number of revolutions of shaft I8. To this end, there is provided an arm 88 (Figs. 1-3 and 12) pivotally supported at 83a, and periodically re leased to operate, through the auxiliary pivoted arm 84 and projection 8411, the switch 8i above described in connection with Fig. 8. 'Thus, depression or clockwise rotation of the projection or element 84a, Figs. 1 and 12, corresponds to a movement of the switch 8I of Fig. 8 to its righthand position.

The time between successive operations of the arm 88 and of the switch 8I is determined by means of an adjustable rotating cam or disc 85, having a single peripheral notch or recess 85a, driven from the shaft I3 through an intermediate double-worm gear reduction drive. The gear ratio. provided by the aforesaid drive and comprising worm 88 secured to shaft I8, and driving worm wheel 81 on shaft 81b which in turn drives through its associated worm 88a and worm wheel 88 the disc 85, is very high, for example, of the order of 1200 to 1; that is, for twelve hundred revolutions of the shaft I8 the disc 85 completes one revolution. During that revolution the peripheral notch 85a is moved into registration with the projection or cam follower 88b of the arm 88 which is biased for clockwise rotation, as by a spring 83c.

Immediate movement of the arm 83, however, is prevented until the recess I Illa of an adjustable cam MI is moved into registration with an adjustable cam follower or pin I82, Figs. 9 and 12, carried by the arm 88. The delayed movement of arm 88 is for the purpose of preventing operation of the switch 8I until the galvanometer needle or pointer I II is clamped between the bars II, Fig. 1. To this end, the angular position of the cam IIII is predetermined with respect to the shaft I 8 and its cam I2, so that after registration of notch 85a with projection 83b, registration of recess Illa with pin I82 occurs substantially concurrently with, or immediately after, the clamping of pointer III. This phasing or timing is readily accomplished by proper angular adjustment of the shaft 81b and the cam IIII provided for by a split collar 81a, Fig. 3, of worm wheel 81. In consequence, violent swinging or deflection of the galvanometer pointer I II incident to the opening and closing of switch 8| is prevented. Thus the cam 85 and projection 88b determine the frequency of recalibration as determined by the gear ratio of the double-worm drive, while the cam IIII, operating at a substantially higher speed than cam 85, and the projection I82 accurately phase or time the operation of the switch 8| with the aforesaid desired portion of the cycle of operation of the mechanical relay mechanism.

Assuming now that the'galvanometer needle III is clamped into a fixed position by the bars II and that disc 85 and cam IIII occupy positions for recalibration, the arm 99, under the influence of the relatively strong spring 93c. rotates about its pivot 99a in a clockwise direction, rotating with it the arm 94 whose projection 94a operates the switch 9| to establish the recalibration circuitconnections. The aforesaid clockwise rotation of arm 94 increases the tension in a return spring 94!) connected to that arm and to a flxed support as well as the tension in a spring 99b which interconnects one end of an arm 99 and a depending projection 94d of the arm 94. Obviously, the main operating spring 990 is powerful enough to overcome the opposition offered by springs 94b and 99b to movement of arm 93.

The biasing force developed by the spring 9917 however tends to rotate the arm 99, pivoted for independent movement on the shaft 91b, in a clockwise direction thereby to move a clutch disc I99 pivotally supported at I99a on the lower end of the arm 99 into driving engagement with the rim or flange 22a of the pulley 22. Supported on the friction disc I99 is the calibrating resistance 99 shown in Figs. 2 and 12 in the form of a slidewire and automatically adjustable to compensate for deviation from a predetermined value of the voltage of the battery or source of supply 99.

Since, as described above, the switch 9| is operated at the time the pointer I9 is clamped, it is undesirable to operate the friction disc I99 into driving engagement with the pulley 22 until later in the cycle of operation of the mechanical relay; that is, until after the feelers l5, Fig. l, have set the clutch arm I! to correspond with the galvanometer deflection and the cams I 9 have thereafter returned the clutch arm I! to its horizontal or neutral position. Therefore, immediately prior to operation of the switch 9| by arms 93 and 94, a cam I93, adjustably carried on, and driven by the shaft 91b in predetermined phase relation with respect to shaft I3 and its cam I2, and retarded in phase with respect to cam I9I, moves its pointed projection I93a against one end of an arm I94 pivoted intermediate its ends on the frame at Ma. The opposite end of the arm I94 cooperates with the arm 99 to prevent movement thereof, by means of a slot I94?) engaging a pin 99c projecting from the rear of the arm 99 as viewed in Fig. 2 but shown on the front of the arm for convenience in Fig. 12. The pointed projection I93a is by shaft 972) moved clear of the lever I99 immediately after the return of the clutch bar I1 to-its horizontal position. The spring 99b is then effective to rotate the arm 99 until the aforesaid driving connection between clutch disc I99 and pulley 22 is effected.

The calibrating mechanism is now in readiness for recalibration of the measuring system, as the potentiometer circuit of Fig. 8. Since the recalibration of the potentiometer circuit occurs at predetermined time intervals, as determined by the aforesaid double-worm gear drive, and independently of the position of the selector switch 85 or of the printing and/or recording mechanism, successive calibrations may take place with the selector switch in different positions.

Therefore, suitable mechanism is provided to prevent operation of the selector switch 9495 and the printing and/or recording mechanism during the operations constituting the recalibrating cycle. In one form of our invention, this mechanism comprises a disc I91 adjustably supported on a worm wheel I95 by means of screws I9'Ibdriven by a worm I96 secured to the shaft 140, a projection I9Ia on the disc I91 cooperatprojection I'9Im of the disc I97 and the notch 99a of the disc 9!, taken in conjunction with their respective gear ratios from the main shaft I3, is predetermined so that the projection I9la is always moved below or in the path of stop element 99b after notch 99a registers with projection 93b and. before the cam I9 and disc I9 occupy positions for printing and/or recording operations. Therefore, even though the arm 99 is, by disc I9 and cam 19, freed for actuation of the switch 94--95 and the printing and/or recording mechanism, such operation cannot occur until the projection I9Ia moves out of engagement with stop element 991) at which time recalibration has been completed.

Continuing with the. operation of the recallbrating mechanism, shortly after the clamping of the pointer I9 and the deflection of the clutch bar II, the feelers I5 by cam I2 are spread and one of the clamping bars II operated to release the pointer for deflection. The galvanometer pointer then deflects in accordance withany unbalance which may exist due to change in the voltage of battery 99. During the time the needle or pointer I9 is moving to its new position, the clutch arm I I is returned to its neutral or horizontal position and the aforesaid driving connection completed between the rim 22a secured to pulley 22 and the friction disc I99. Thereafter the needle is clamped by bars II in its new position, the feelers again move the clutch arm to an angular position corresponding to the degree of deflection of the galvanometer pointer from its neutral position. The restoring cams I9, after arm I! again engages the clutch disc I9, return arm I! to its horizontal position. In this case the corresponding angular movement of arm IT and clutch disc I9 is by shaft 29 and rim 22a transmitted to the friction disc I99 which moves the slidewire 99 to a new position. The direction of movement of the slidewire is, as referred to the circuit of Fig. 8, in the direction to correct for the extent of deviation in the voltage of battery 89 from its predetermined value.

The foregoing cycle of operations is repeated several times, eight cycles being safely suflicient, to insure that the slidewire 99 is moved accurately and with great precision to a position where the potentiometer voltages as derived from the battery 99 and the standard cell S are in ex act balance. The number of cycles of operation, preferably about eight,- is determined by the shape and extent of the recess I9Ia and its speed as compared to that of the shaft I3. Thus after the shaft I3 has completed eight revolutions, corresponding to the aforesaid eight cycles of operation, the cam I9I occupies a position to initiate counter-clockwise rotation of arm 93. Additional rotation of the cam I9I raises the pin or projection I92 from recess I9la thereby returning the arm 93, against the bias of the main spring 930, to its original position. The arm 94, under influence of the spring 94b, moves with or follows after the arm 93 to release the switch 9I- which is automatically returned to the position shown in Fig. 8, as by resilient members upon which the switch contacts are mounted. In addition to predetermining the number of cycles for recalibrating the circuit, the trailing operating surface of the cam IN is phased or angularly disposed with respect to shaft I9 and cam I2 so that the return ofthe potentiometer system to one of elements 92 occurs during that portion of the mechanicalrelay cycle when the galvanometer pointer is clamped in a fixed position.

The driving connection between the recalibrating slidewire 90 and the rim 22a is broken by reason of the engagement of arm 94 with the adjustable set screw 99d carried by arm 99. Thus as arms 94 and 99 are rotated in a counter-clockwise direction by the spring 94b, the friction disc I and slidewire 90 are returned to their original positions, Figs. 2 and 12.

-The three-part calibrating mechanism comprising arms 93, 94, and 99 together with their associated biasing springs and pivotal mountings is particularly well adapted for the purposes and functions described above.

As explained above, the voltage of the battery 89, with use and over a period of time, gradually decreases in value so that the slidewire 90 during a relatively long period, which may be of the order of six months, will be substantially entirely excluded from the potentiometer circuit. To show the position of the slidewire and generally to indicate the condition of the battery, an index 99f may project from a portion of the frame, or as illustrated, Fig. 2, from the arm or lever 99 and' may cooperate with graduations or an arrow I 0022 marked on the disc Hill. In any event, when the arrow and index are substantially in alignment, all of the slidewire 99 has been excluded from the circuit indicating that no further correction for decreased voltage may be accomplished by the slidewire 90. For continued accuracy a new or re-charged battery must then be included in the circuit, or the supply voltage as applied to the measuring circuit otherwise increased. 1

Continuing with the operation of the apparatus, the projection lil'la of disc I01 frees the arm 68 after the galvanometer is again connected in circuit with one of the condition responsive elements 92 and before the cam or disc 13 and cam- 16 again occupy positions for the printing and/or recording operations. In addition to being phased with respect to disc 95 and cam lill, the projection lll'la, by reason of its angular position and the gear ratio between worm I08 and worm wheel I05, is moved out of registration with stop element 68b after the recess 13a of disc I3 moves beyond projection 12. In this manner the first printing and/or recording operation subsequent to recalibration occurs after substantially the full number of cycles of operation of the mechanical relay, thereby insuring the rebalance of the circuit before printing; that is, recalibration requires eight cycles of operation; twenty-four cycyles are provided between each printing operation. Thus after recalibration the mechanical relay apparatus operates at least sixteen times to insure accurate indication of the magnitude of the condition under measurement. It may here be observed that unbalance of the circuit (Fig. 8) during recalibration is independent of the position of slidewire Ila. Consequently the carriage 25 and frame 30 are moved but a slight amount during recalibration. Moreover, since the switch 84-85 is retained in fixed position during recalibration, the galvanometer is reconnected in circuit with the particular one of elements 92 with which it was connected just prior to initiation of the recallbrating cycle.

If the foregoing provisions were not made, a printing operation might occur during calibration; in that event the resulting record on the chart i would be confusing and of little value. Moreover, there would be lost a record of the condition indicated by one of the elements 92.

In accordance with the present invention, however, the operation of the printing and/or recording mechanism is interrupted until after completion of the calibrating cycle and until after the mechanical relay mechanism has again rebalanced the circuit and moved the carriage 25 and print wheel 32 to a position with respect to the chart which is an accurate indication of the magnitude of the condition under measurement.

In one embodiment of the invention recalibration was provided for each 1200 revolutions of shaft l3, or after each forty-ninth printing operation. Thus with the sixteen control elements 92, it will be seen that each successive recalibration cycle takes place with the selector switch 84-85 one position beyond its preceding position, or angularly displaced from the position corresponding to the preceding rec'alibrating cycle. In this manner maximum average accuracy for all points may be attained, particularly for a case where there is a measurable drift in voltage of the supply between successive recalibrating cycles.

Now that the principles of the present invention are understood, it will be apparent the recalibrating mechanism is applicable to Wheatstone bridge circuits, in which case the slidewire 90 may be included in the ratio arms of the bridge while a standard resistance or impedance device is by switch 9i substituted for one of the elements 92.

From the above, it is seen that there is provided a full automatic indicating, recording and/or controlling apparatus which successively indicates, records. and/or controls in accordance with, the conditions measured at a plurality of points, and which automatically recalibrates or restandardizes the measuring circuit, at the same time avoiding any interference between the operations of the several component mechanisms.

In Figs. 10 and 11 is shown a modified and simplified form of inking device which, in certain instances, may be used in place of the device 44 of Fig. 4. This device comprises essentially a pair of spiders H0 which may be integral with, or firmly secured to, a central hub adapted 5o for mountlng'on the shaft 43, as in the case off j the inking device 44. The several arms i Illa oi/,

the spiders H0 are provided with radial slots I illb. The spiders llll may conveniently be formed of sheet metal so that the slotted /a'r lllla have a substantial resilience. Near "e outer end of each -of the radial slots till i is formed a notch or recess adapted to receive and resiliently retain an arbor Illa of an inking pad III which may be of any suitable shape/t The arbors Illa and the notches in the $10 0b may be of any suitable shape. In ca round inking pads are employed so that their angular relation is unimportant, the arbors Illa may be round, while the shape of the notches is unimportant. However, in case square inking pads are employed, as shown, the arbors Ilia are preferably non-circular and of a configuration complementary to the notches in the slots lillb; for example, as shown, the arbors Ilia may be square, fitting into V-shaped notches in the slots device'of Figsaio and v11 may be used directly rotation. or the outer end of frame-arm in placeof inking devices similar to 44 in the recorderfelement assembly of Fig. 4.

loosely journaled on shaft 30.

In Fig. 13 there is showna modified form of ratchet mechanism which-may replace the cam 13, disc 13, disc -I01-and, their associated driving gears. 'This ratchet' mechanism comprises a U- shaped frameI I5 .loosely journaled on the shaft I II.- A" link III pivotally connected to one frame-' arm II5aat I'II oscillates'theframe II5 under the control of a crank formed by disc I I secured 'toshaft and supporting from its face a pin III pivotally engaging the opposite end of the link I I5. In order to. phase or time the operation of the'print wheel 32 (not shown in this figure) a ratchet wheel I23 issecured upon a sleeve I2I, A cooperating pawl I22, journaled on a-rod or shaft I22a secured between opposite arms of frame H5, is. biased into engagement with the ratchet wheel I20by leaf spring I22b andserves to rotate the ratchet wheel a predetermined amount every time the shaft I3 or pin II 0 completes a revolution. By predetermining the position of a cam I23 carried by the sleeve I2I, it will be apparent that for a given number of revolutions of the shaft I3 the cam I23 will be rotated through 360. Thus this cam is phased, and the ratchet mechanism adjusted, so that just prior to completion,

of the cycle of operations of the mechanical relay for a given control point, a projection I23a of the cam I23 is moved against a lateral projection I250 of a crank arm I25 pivoted from the frame at I26, and thereby rotates the crank arm I25 in a clockwise direction as viewed in Fig.

13, against the bias of a spring I21, and a second spring I20, connected to the frame and to a pin I29 eccentrically mounted on a disc I30 which itself is secured to an operating shaft I3I. The outer or free end of the crank arm I25, being beneath thepin I23, is-etfective to rotate the shaft I3I in a counter-clockwise direction. Rigidly secured to shaft I3I, as by pins I32, is a rod I33 engaged by projections I34 of a frame I35, in which is journaled the print wheel 32 (not shown in Fig. 13). Accordingly, the counterclockwise rotation of shaft I3I rotates the frame I35 in a clockwise direction about pivots'30b to move the print wheel firmly into engagement with the inking disc 44.

As the pawl I22 rotates the ratchet gear I20 and cam I23 an additional distance, a recess I23b is moved into registration with the lateral projection I25a. This recess may be next to the projection I230, orseparated therefrom a slight amount so that as the projection I231: is moved beyond the projection I25a'the springs I21 and I28 are effective to return the respective crank arms I25 and I3I, I33 to their original positions, the print wheel at the same tirfie being moved out of engagement with the inking disc 44. In any event, as soon as the recess I23b registers with the extension I250, the springs I21. and I23 are effective to rotate respectively the crank ing operation occurs'when the frame has been moved substantially to its limit of clockwise Illb is below the projection I250. Accordingly, as the crank arm lll'rotates counter-clockwise,

the projection I254 moves over the upper cam 'to the last-mentioned return movement of cam I23, a second cam I30 carried by sleeve I2I occupies a position such that its recess I35a registers with one pawl I31a of a double-pawl member I31 journaled on rod i224: and biased for clockwise rotation by springs I30. The other pawl I31b of member I31 normally retained in a lifted, ineifective position, upon .-"registration of recess or notch I3 and end I31a, moves downwardly into engagement with one tooth of a ratchet wheel I33 secured to the shaft 80. In consequence, the shaft 00 is rotated, as the print wheel is returned to its original position, an amount suilicient to move the selector switch 34-35 for connection of a different one of the elements 32 in the potentiometer circuit. ratchet wheels, and crank H3, H8 are phased with respect to shaft I3 so that the switch movement is completed while the galvanometer pointer is clamped in a fixed position.

The recalibration cycles are timed and controlled by the disc 05 and cam IOI in the manner described above. However, as soon as the arm 93 is moved downwardly by the spring 530, a cam I40 journaled on shaft 50 is rotated in a counterclockwise direction by a crank journaled in the frame F, one end of which is by link I pivotally secured to arm 33 while its opposite end is by link I42 pivotally secured to the cam I40. By the aforesaid rotation a lower end M of the cam is moved toward or against the projection The I25a to prevent movement thereof even though prevent movement thereof upon registration of pawl I31a with notchv or recess I360. In this manner the operating means for the,selector switch 34-45 and the printing and/or recording mechanism is rendered ineffective during calibration. The timing and phasing in other respects may be and preferably is identical with r the modification of our invention previously described.

While there has been described what at present is considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the invention, and therefore the appended claims cover all such changes and modifications as fall within the spirit and scope of the invention.

What is claimed is:

i. In a self-balancing measuring system including a measuring circuit, a driven member including a circuit adjusting element, a mechanical relay for driving said adjusting element by a plurality of decreasing steps to a circuit rebalancing position and including a control element periodically releasedfor deflection in accordance with the sense and extent of unbalance of said circuit, relay driving means including a driving shaft, means operable by said shaft to release said control element and effect a stepby-step movement of said driven member corresponding to the sense and extent of deflection of said control member, the combination of transfer means periodically operable after completion of a predetermined low number of revolutions of said shaft for subjecting saidcircuit in predetermined sequence to a plurality of conditions, an interlock operable after a predetermined higher number of revolutions for retaining said transfer means in a fixed position irrespective of the completion of said lower number of revolutions, calibrating means, and means operable during only a fraction of said lower numberof revolutions for including said calibrating means in said circuit and for effecting under control of said relay recalibrating adjustment of said circuit, said last-named means thereafter excluding said calibrating means from said circuit whereby said relay during the remaining fraction of said lower number of revolutions rebalancessaid circuit prior to operation of said transfer means.

2. In a self-balancing measuring system including a measuring circuit, a driven member including a circuit adjusting element, a mechanical relay for driving said adjusting element by a plurality of decreasing steps to a circuit rebalancing position and including a control element periodically freed for deflection in accordance with the sense and extent of unbalance of said circuit, relay driving means including a driving shaft, means operable in response to each revolution of said shaft to free said control element and effect a step-by-step movement of said driven member corresponding to the sense and extent of deflection of said control element, the combination of transfer means periodically operable from one to another of a plurality of positions after completion of a predetermined low number of revolutions of said shaft for subjecting said circuit in predetermined sequence to each of a plurality of conditions, calibrating means for said circuit, means operable in timed relation with said transfer means for periodically rendering said calibrating means effective so that each successive operation of said calibrating means occurs for a different position of said transfer means, and means for preventing operation of said transfer means during operation of said calibrating means.

3. In a self-balancing measuring system including a measuring circuit, a source of supply therefor, a primary member movable from a neutral position in accordance with variations in magnitude of a condition under measurement as determined by said measuring "oircuit,-a secondary movable member, means operable by said secondary member to rebalance said circuit, operating means for said secondary member controlled by said primary movable member for periodically actuating said rebalancing means to rebalance said measuring circuit, mechanism for periodically recalibrating said measuring circuit comprising means for adjusting an electrical condition thereof, a standard electrical unit,

circuit controlling means for connecting said standard unit in said measuring circuit in opposition to said source of supply, the combination of a continuously rotating cam provided with a peripheral recess, a cam followernormally bearing upon the face of said cam and biased into said recess, means responsive to theentry of said follower into said recess for actuating said circult controlling means and for effecting an interconnection between said secondary movable member and said adjusting means, and an auxiliary cam for disengaging said followerv from said recess.

4. In a self-balancing measuring system including a measuring circuit, a source of supply therefor, a primary member movable from a neutral position in accordance with variations in magnitude of a condition under measurement as determined by said measuring circuit, a secondary movable member, means operable by said secondary member to rebalance said circuit, operating means controlled by said primary movable member for periodically moving said secondary member to effect said rebalance of said measuring circuit, mechanism for periodically recalibrating said measuring circuit comprising means for adjusting an electrical condition thereof, a standard electrical unit, circuit controlling means for connecting said standard unit in said measuring circuit; the combination of a continuously rotating cam provided with a peripheral recess, a cam follower normally bearing upon the face of said cam and biased into said recess, means responsive to the entry of said follower into said recess for actuating said circuit controlling means and for effecting an interconnection between said secondary movable member and said adjusting means, and additional means operating at a higher speed, and of a different order of magnitude than said cam, for accurately and additionally controlling entry of said follower into said recess.

5. In a self-balancing measuring system including a measuring circuit, a source of supply therefor, a galvanometer connected to measure the unbalance of said circuit, a driven shaft, mechanical relay apparatus, including a continuously rotating driving shaft, for periodically adjusting said driven shaft under control of said galvanometer, and means operated by said driven shaft to rebalance said measuring circuit, mechanism for periodically recalibrating said measuring circuit comprising means for adjusting an electrical condition thereof, a standard electrical unit, circuit controlling means for connecting said standard unit in said measuring circuit, the combination of a rotatable cam, a double-worm gear reduction for driving said cam from said driving shaft, a cam follower, means responsive to movement of said follower relative to said cam to actuate said circuit controlling means and to effect an interconnection between said driven shaft and said adjusting means, a second cam driven by the first worm Wheel of said gear reduction, and a follower for said second cam acting conjointly with said first follower accurately to phase the operation of said actuating means with respect to the cycle of operation of said mechanical relay apparatus.

6. In a self-balancing measuring system including a measuring circuit, a source of supply therefor, a primary member movable from a neutral position in accordance with variations in magnitude of a condition under measurement as determined by said measuring circuit, a secondary movable member, means operable by said secondary member for rebalancing said measuring circuit, operating means controlled by said primary movable member for periodically actuating said rebalancing means to rebalance said measuring circuit, mechanism for periodically recalibrating said measuring circuit comprising means for adjusting an electrical condition therea means .m '-=uouslyotatingncamprovide'd with a'peripheral recess, a follower-normally; bearing upon the face of said; cam biased into said recess, .means'responsive to entry'of. saidfollower into or. a man-d. electrical unit}: circuit controlling n'gi-c'ircui't, the. combination of a lcontinsaid 'recess for actuating said circuit controlling means and for effecting. an interconnection be- .tween, said secondary; movable member and said adjusting'meansra second cam rotating con-- vtinuously at'a speedfv'ery much higher than said 'flrst mentioned cam, and a cam follower for said second cam actingconjointly withsaid first follower accurately totime the operation of said actuating means;

'1. In aself-Qbalancing' measuring system in-v cluding a measuring circuit, a galvanometer connected to measure the unbalance of said circuit,

, a driven shaft, mechanical relay apparatus, in-

cluding a continuously rotating driving shaft, for periodically adjusting said driven shaft under control of said galvanometer, and means operatedby said'driven shaft to rebalance said measuring circuit, and mechanism operable by, said relay apparatus for periodically recalibrating said measuring circuit including means for adjusting an electrical condition thereof, the combination of a rotatable cam, a double-worm gear reduction for driving said cam from said driving shaft, a cam follower, means controlled by said follower to effect an interconnection between said driven shaft and said adjusting means, a second cam driven by the intermediate worm wheel of said gear reduction, and a follower for said second cam acting conjointly with said first follower accurately to phase the operation of said interconnecting means with respect to the cycle of operation of said mechanical relay apparatus.

8. In a self-balancing measuring system including a measuring circuit, a primary member movable from a neutral position in accordance with variations in magnitude of a condition under measurement as determined by said measuring circuit, a secondary rotatable structure including means for rebalancing said circuit, and operating means controlled by said primary movable member for operating periodically said secondary structure to rebalance said measuring circuit, mechanism for periodically recalibrating said measuring circuit, circuit controlling means for completing connections for said recalibration of said measuring ,circuit, and a rotatable adjustable impedance interconnected with said measuring circuit, the combination of a support for said impedance pivoted aboutan axis parallel to said rotatable structure, and means operating intermittently to actuate said circuit controlling means and to move said support about its pivot to effect a driving engagement between said rotatable structure and said rotatable impedance.

9. In a self-balancing measuring system including a measuring circuit, a primary member movable from a neutral position in accordance with variations in magnitude of a ctmdition under measurement as determined by said measuring circuit, including means for rebalancing said circuit, a secondary rotatable structure, means con-o.

trolled by said primary movable member for periodically actuating said secondary structure to rebalance said measuring circuit, mechanism for periodically recalibrating said measuring circuit, circuit controlling means for completing recalibrating connections for said measuring cirfor connecting saidrstandard unit in said and biased for movement about its pivotal axis to eflect a driving engagement between said rotatable structure and said rotatable impedance,

, a oontinuouslyrotating cam, and means includa ing, a cam follower'normally restraining said pivoted support from movement about its pivotal 1o axis but intermittently releasing the same for recalibration of said measuring circuit.

10. In a self-balancing measuring system including a measuring circuit, a primary member movable from a neutral position in accordance with variations in magnitude of a condition under measurement as determined by said measuring circuit, a secondary movable member, circuitrebalancing means operable thereby, operating means controlled by said primary movable member for periodically operating said secondary member to rebalance said measuring circuit, mechanism for periodically recalibrating said measuring circuit and including means for adjusting an electrical condition thereof, circuit controlling means for completing recalibration connections for said measuring circuit, the combination of a continuously rotating cam, a cam follower, means controlled by said follower to actuate said circuit controlling means, other means also controlled by said follower to effect an interconnection between said secondary movable member and said adjusting means, a second cam rotatable with said first cam but having an operating element retarded in phase with respect 5 to that of said first-named cam, and a follower for said second cam controlling said interconnecting means conjointly with said first-named cam and follower.

11. In a self-balancing measuring system including a measuring circuit, a primary member movable from a neutral position in accordance with variations in magnitude of a condition under measurement as determined by said measuring circuit, a secondary movable structure including means for rebalancing said circuit, means controlled by said primary movable member for periodically operating said secondary structure to rebalancc said measuring circuit, mechanism for periodically recalibrating said measuring circuit including means for adjusting an electrical condition thereof, circuit controlling means for completing recalibrating connections for said measuring circuit, the combination of a pivotally mounted member biased to move about its pivot and to actuate said circuit controlling means, an auxiliary pivotally mounted member biased to -move about its pivot and to effect an interconnection between said secondary movable structure and said adjusting means but normally restrained by said first-named pivotally mounted member, a continuously rotating cam, means including a cam follower therefor normally restraining said first-named pivotally mounted member from motion about its pivot and timing its operation, a second cam rotating with said first-named cam but having an operating element retarded in phase with respect thereto, and

a follower for said second cam normally restraining said auxiliary pivotally mounted member from motion about its pivot and timing its operation with respect to that of said first-named pivotally mounted member.

12. A multiple-point measuring apparatus comprising a rotatable structure provided with a 15 plurality of spaced peripheral marking elements, a pivotal support for said rotatable structure, means for carrying a record chart, means supporting said structure and its support for displacement across said chart,.actuating mechanism effective upon each operation thereof to oscillate said support to bring said structure into registration .with said record chart and including a. ratchet and pawl mechanism operable concurrently with oscillation of said structure into and out of registration with said chart for rotate ing said structure through an angle equal to the angular spacing of said marking elements, a continuously rotating shaft, a cam operated by said shaft, and a cam follower therefor periodically operating said actuating mechanism.

13. A multiple-point measuring apparatus comprising a rotatable structure provided with a plurality of spaced peripheral marking elements, a pivotal support for said rotatable structure, a shaft connected to rotate said structure and along which said support is slidable, means for carrying a record chart, an oscillatable member having a sliding engagement with said support, actuating mechanism-including a crank secured to said oscillatable member to bring said rotatable structure into registration with said record chart and a ratchet and pawl mechanism respectively secured to and supported by said shaft to rotate said structure step-by-step, a continuously rotating shaft, a cam operated by said continuously rotating shaft, and a cam follower therefor connected to operate said actuating mechanism.

14. In a multiple-point measuring apparatus comprising a rotatable structure provided with a plurality of spaced peripheral marking elements, a shaft connected to rotate said structure, a carriage slidable along said shaft, means for carrying a record chart, the combination of a support for said rotatable structure pivotally supported from said carriage, an oscillatable shaft having a longitudinal slot, said carriage having an element engaging'said oscillating shaft to prevent rotation of said carriage and said support having an element engaging said slot, actuating mechanism including a crank arm secured to said oscillatable shaft to effect registration between said chart and said structure and a ratchet and pawl mechanism connected to said first-named shaft to effect step-by-step rotation thereof, a continuously rotating shaft and means operated by said continuously rotating shaft for periodically operating said actuating mechanism.

15. In a multiple-point measuring apparatus comprising a rotatable structure provided with a plurality of spaced peripheral marking elements, means for carrying a record chart, means for moving said structure with respect to said chart, the combination of an actuating mechanism effective upon each operation thereof to bring said rotatable structure into registration with said record chart and to rotate said structure through an angle equal to the angular spacing of said marking elements, said mechanism a record chart, means for moving said structure with respect to said chart, the combination of an actuating mechanism effective upon each operation thereof to bring said rotatable structure into registration with said record chart and to rotate said structure through an angle equal to the angular spacing of said marking elements, said mechanism including a pivoted lever biased to an operating position, a continuously rotating cam, a cam follower therefor periodically operating said actuating mechanism, a second cam rotating continuously at a speed very much higher than, said first-named cam, and a cam follower for said second cam acting conjointly with said first follower accurately to time the operation of said actuating mechanism.

17. In a mechanical relay operated multiplepoint self-=balancing measuring system, including a continuously rotating driving shaft, a rotatable structure provided with a plurality of spaced peripheral marking elements, means for carrying a record chart, and means operated by said driven shaft to move said structure with respect to said chart, the combination of an actuating mechanism effective upon each operation thereof to bring said rotatable structure into registration with said record chart and to rotate said structure through an angle equal to the angular spacing of said marking elements, a rotatable cam operated by said driving shaft but at a reduced speed, a cam follower therefor controlling the operation of said actuating mechanism, a second cam operated by said driving shaft at a speed of a higher order of magnitude than said first cam, and a follower for said second cam acting conjointly with said first follower accurately to phase the operation of said actuating mechanism with respect to the cycle of operation of the mechanical relay.

18. In a mechanical relay operated multiplepoint self-balancing measuring system, including a continuously rotating driving shaft, a rotatable structure provided with a plurality of spaced peripheral marking elements, means for carrying a record chart, means for displacing said structure across the chart, the combination of an actuating mechanism effective upon each operation thereof to bring said rotatable structure into registration with said record chart and to rotate said structure through an angle equal to the angular spacing of said marking elements, a rotatable cam, a worm and worm wheel for driving said cam from said driving shaft, a cam follower therefor controlling the operation of said actuating mechanism, a second cam secured to and rotatable with said driving shaft, and a cam follower for said second cam acting conjointly with said first follower accurately to phase the operation of said actuating mechanism with respect to the cycle of operation of the mechanical relay.

19. In a multiple-point recorder having a rotatable structure provided with a plurality of peripherally spaced marking elements, the combination of a shaft, a carriage slidably supported on said shaft, a frame pivotally mounted from said carriage and having provisions for rotatably supporting said structure, adriving gear rotatable with said shaft and slidable with said carriage a cooperating driven gear journaled in said frame and meshing with said driving gear substantially at the pivotal axis of said frame for rotating said structure, an elongated member disposed parallel to said shaft, said frame having at least one extension cooperating with said member to predetermine the position of said frame,

-ing said print wheel and said structure in synmeans for moving said member and by said at least one extension to rotate therewith said frame from said predetermined. position, and ratchet means supported by said shaft and operable only upon return movement of said frame to said predetermined position for rotating said shaft an amount suflicient to drive said structure an amount equal to the angular displacement between said marking elements.

20. In a multiple-point recorder having a chart-support, a carriage, means mounting said carriage for transverse movement across the chart, a frame pivotally mounted from said carriage, a print wheel journaled in said frame with its axis of rotation normal to the chart, said print wheel having a plurality of angularly disposed marking elements disposed on a beveled face thereof, and means for actuating said frame to move a selected one of said elements into and out of printing engagement with the chart.

21. In a multiple-point recorder having a chart-roll disposed adjacent the front thereof, a carriage, means mounting said carriage for transverse movement across the chart, a frame pivotally mounted from said carriage, a print wheel journaled in said frame with its axis of rotation normal to the chart and normal to the pivotal axis of said frame, and means cooperating with said frame for normally retaining said print wheel in a non-printing position, for bodily moving said print wheel downwardly therefrom to a position substantially below the top of and in front of said roll to print on the-chart a record, and for returning said wheel to said non-printing position to render immediately visible on said chart said printed record.

22. In a multiple-point recorder having a multiple point recording element assembly comprising a rotatable structure provided with a plurality of spaced peripheral marking elements, the combination of a carriage, a support for said structure pivotally mounted from said carriage, a driving gear journaled in fixed position with respect to said carriage, and a driven gear journaled in said support for rotating said structure and meshing with said driving gear substantially at the pivotal axis of said support.

23. In a multiple-point recorder including a rotatable structure provided with a plurality of spaced peripheral marking elements, the combination of a carriage, a support for said structure pivotally mounted from said carriage, an inking device supported from said carriage for cooperation with said rotatable structure, and means for moving said support about its pivot to effect a registration of one of said marking elements with a record chart and to effect engagement and disengagement of one of said elements with said inking device.

24. In a multiple-point recorder including a recording elementassembly comprising a rotatable print wheel provided with a plurality of spaced peripheral marking elements, the combination of a carriage, a support for said print wheel pivotally mounted from. said carriage, a rotatable structure provided with a plurality of inking pads similar in number and spacing to said marking elements, said structure being pivotally supported from said carriage in cooperative relation with said marking elements, means for pivotally moving said support to effect engagement and-disengagement of said inking pads and marking elements and to eifect registration of the latter with a record chart, and means for rotatchronism.

25. In an instrument having a member movable in accordance with unbalance of a balanceable network, the combination of a calibrating impedance for said network; an arm supporting said impedance for movement into and out of driving engagement with said member, an actuating arm normally biasing said supporting arm to a position to retain said impedance out of engagement with said member, a calibrating switch for said network operatively. associated with said arm, a control member biased towards said actuating arm with sufflcient force to operate said switch, and releasable means for retaining said control member in a position ineffective to cause said operation of said switch.

26. In an instrument having a member movable in accordance with unbalance of a balanceable network, the combination of a three-part calibrating device, onepart comprising a pivoted switch-actuating arm, a second part comprising a pivoted support for an impedance device, and the third part comprising a control arm pivoted about the same axis as said first part for moving said first part, a spring interconnecting said first and second parts, a second spring biasing said first part into engagement with said second part, and a third spring for moving against the bias of said first and second springs said first and third parts into switch operating positions,- and means for successively releasing and thereafter moving out of said switch operating position said third part.

27. In an instrument having a member movable in accordance with unbalance of a balanceable network, the combination of an adjustable impedance, an arm supporting said impedance for movement into and out of driving engagement with said member, a switch for completing a circuit including said impedance, an actuating arm for said switch normally engaging said supporting arm to retain it in a position with said impedance out of said engagement with said member, a control member biased toward said actuating arm with sufficient force to operate said switch, releasable means for retaining said control member in a position ineil'ective to cause operation of said switch actuating arm, said control member upon release thereof operating said actuating arm to actuate said switch, and means for retaining said supporting arm in a position with its said impedance out of said driving engagement for a time interval after operation of said switch by said actuating arm.

28. In an instrument having a member movable in accordance with unbalance of a balanceable network, the combination of an adjustable impedance, an arm supporting said impedance for movement into and out of driving engagement with said member, a switch for completing a circuit including said impedance, an actuating arm for said switch biased to a first switch-operating position and normally engaging said supporting arm to retain said impedance out of said driving engagement, a control member biased for movement into engagement with said actuating arm with suflicient force to move said arm against its bias to a second switch-operating position, afirst cam releasably retaining said control member in a position to prevent operation of said switch to its second position, a second cam releasably retaining said supporting arm and its impedance out of said driving engagement, means for driving said cams with said second

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