US2402965A

US2402965A - Timing device

Info

Publication number: US2402965A
Application number: US411593A
Authority: US
Inventors: Carl S Hornberger
Original assignee: Central Scientific Co
Current assignee: Central Scientific Co
Priority date: 1941-09-19
Filing date: 1941-09-19
Publication date: 1946-07-02
Anticipated expiration: 1963-07-02

Description

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Patented July 2, 1946 UNITED ire/"v i 11 STATES PATENT OFFICE TIMING DEVICE Carl S. Hornberger, Glen Ellyn, Ill., assignor to Central Scientific Company, a corporation of Illinois Application September 19, 1941, Serial No. 411,593

15 Claims. 1

There are many uses for a timing device that will operate an associated mechanism or circuit at regularly timed intervals, particularly when the time intervals may be adjusted over a fairly wide range. One such use is in connection with aerial photography, where it is desirable to take pictures at regular intervals to obtain photographic coverage of a particular area. Obviously the frequency at which the camera shutter must be opened to insure complete coverage of the area being photographed depends upon the elevation of the plane and its ground speed; and experience has shown that a minimum of two seconds and a maximum of one hundred and forty seconds covers the range of adjustability required for ordinary working conditions in this field.

It is also desirable to have the camera interval control such that a picture may be made at any time, even if the normal time interval has not elapsed, should the photographer see a particular terrain that he especially wanted to photograph; and preferably interruption of the regular time required for the taking of a special picture should start a new sequence of exposures at regular intervals after the special picture.

The present invention provides such a device, and one which is of reasonably light weight and small size.

Additional advantages and objects of the invention will be apparent from the following description. and from the drawings, in which Fig. 1 is a perspective view partially exploded, partially in section, somewhat diagrammatic, and with parts omitted, showing the preferred form of the invention which has been chosen for illustration;

Fig. 2 is a perspective view showing the far side of the interceptor arm shown in Fig. 1;

Fig. 3 is a front view, partly broken away, of the device illustrated in Fig. 1, showing especially the front of its case;

Fig. 4 is a hoizontal sectional view taken approximately on the line 4-4 of Fig. 3;

Fig. 5 is a fragmentary detail view of the periphery of the constantly driven wheel and the intermittently driven timing finger engaged therewith;

Fig. 6 is a corresponding sectional view taken approximately on the line 66 of Fig. 5;

Fig. '7 is a vertical sectional view taken approximately on the line 'l-l of Fig. 4;

Fig. 8 is a horizontal sectional view taken approximately on the line 8-8 of Fig. 3;

Fig. 9 is a fragmentary view corresponding to a portion of Fig. 8, but showing the handle pressed in for setting the time interval.

Fig. 10 is a rear perspective view of the rotatable adjustable stop unit;

Fig. 11 is a vertical sectional view taken approximately on the line llll of Fig. 3;

Fig. 12 is a fragmentary view corresponding to Fig. 11, but showing the yoke in the actuated position for causing the return of the timer finger;

Fig. 13 is a fragmentary view corresponding to Fig. 11, but showing the handle pressed in for setting the time interval;

Figs. 14, 15 and 16 are vertical sectional views taken, respectively, approximately on the lines l4-M, |5--|5 and iii-l6 of Fig.3;

Fig. 17 is a fragmentary sectional view taken approximately on the line l'|l'l of Fig. 7;

Fig. 18 is a fragmentary sectional view corresponding to Fig. 17, but showing the parts in actuated position;

Fig. 19 is a vertical sectional view taken approximately on the line l9l9 of Fig. 11;

Fig. 20 is a view corresponding to Fig. 19, but showing the parts in the extreme position toward which they are shifted by the timing finger;

Fig. 21 is a top (inside) View of the connecting box taken approximately on the line 2l-2I of Fig. 3; and

Fig. 22 is a circuit diagram of the device, connected for use with a signal lamp and a camera which may be operated thereby.

Although only one form of the invention has been chosen for illustration, and it has been illustrated in considerable detail to comply fully with R. S. 4888, it will be understood that other forms utilizing the invention will be apparent to or devised by those skilled in the art, and the claims are to be interpreted as broadly as permitted by the prior art.

General organization and operation One of the most important uses of the timing device of this invention is to control (electrically) the shutter and rewind mechanism of the camera ll (Fig. 22) to take a series of pictures at accurately timed intervals, preferably illuminating a signal lamp l2 at a predetermined time before the taking of each picture. The general organization and operation of the timing device can best be described with reference to Fig. 1, where a switch i3 is diagrammatically illustrated for operating the camera, or other device, and a switch It is diagrammatically illustrated for connecting the signal lamp.

To start the apparatus a start button I6 is pressed which trips toggle switch I! to connect a constant speed motor l8 through a source of power. The constant speed motor |8 constantly drives a worm |9 and an actuator or crank disc 2|. The worm l9 constantly meshes with and drives a worm wheel 22. One convenient speed for the worm |9 and disc 2| is one revolution per second, in which case the slow moving worm wheel 22 will move one tooth per second,

The worm wheel 22 may be provided with teeth 23 on its face, adapted to drive a timing finger 24, both the worm wheel 22 and the finger 24 being mounted to rotate on a fixed shaft 26.

When the start button I6 is pressed, a yoke 28 is pivoted about the axis of its mounting pivots 29, and a clutch finger 3|, rigidly carried by yoke 28, slides the timing finger 24 longitudinally of the shaft 26 so as to release it from teeth 23. Upon its release, spring 32 causes it to rotate in a clockwise direction, as seen in Fig. 1, until it comes to rest against an adjustably positioned stop 33. Upon releasing the starting button l6 the yoke 28 will be actuated by spring |4| unless it is momentarily delayed b latch 48, which is raised each second by crank pin 44. Upon actuation of yoke 28, clutch finger 3| presses timing finger 24 into engagement with teeth 23, and the timing movement of timing finger 24, under influence of worm wheel 22, begins.

Shortly after the timing finger 24 reaches the position shown in Fig. 1, it slides under the camshaped end 36 of pivoted lever 31, which operates switch M to illuminate the signal lamp l2 of Fig. 22. Shortly thereafter the timer finger 24 strikes interceptor pin 38 and pushes it to the left. The interceptor pin is thus pressed against a lostmotion extension 39 of interceptor arm 4|, The interceptor arm 4| pivots on a pin 42 carried by the yoke 28. Ideally the interceptor arm 4| and its extension 39 operate as a unit, and they may jointly, therefore, be considered the interceptor arm.

The interceptor pin 38 rocks the interceptor arm 4| to press the interceptor block 43, at the bottom thereof, into the path of crank pin 44 on crank disc 2|, and, more specifically, between the pin 44 and the lower extension 46 of yoke 28. As the crank pi'n rotates it presses block 43 and yoke extension 46 ahead of it, thus rocking the yoke 28 about its support member 29 as said yoke was rocked by original depression of start button l6 (Fig, 15). This again shifts timing finger 24 longitudinally of the shaft 26, so that it snaps back to the stop 33. Rocking yoke 28 also closes switch I3 so as to actuate the camera or other controlled equipment.

A latch 48 holds the yoke in the position to which it has been rocked, until the latch is released by pin 49 on a subsequent revolution of crank disc 2| (Fig. 14), thus allowing plenty of time for the timing finger 24 to come to rest against the stop 33. Upon release of the latch 48 the yoke 28 is free to return to its normal position, and spring 32 presses timing finger 24 into teeth 23 to begin another timing movement. At the same time the switch I3 is actuated a counter is preferably also actuated to indicate the number of film areas that have been exposed.

The position of the return stop 33 determines the length of the path which the timing finger 24 must follow before it actuates the interceptor pin 38 to produce an actuation of the camera. The position of the return stop 33, and hence the length of time of the interval, may be adjusted by a handle 52 with which dial 53 rotates. Pressing the handle inwardly on shaft 26 releases teeth 54 from a toothed lock block 56. The dial 53 may now be turned by handle 52, and through pins 51 it also turns the stop assembly 58 of which stop 33 is a portion. In order that the setting movement of stop 33 will never be blocked by timing finger 24, this timing finger is declutched from the teeth 23 upon pressing handle 52 inwardly, the declutching being accomplished by pins 59 and clutch fingers or rock levers 6|.

The use of the slow moving wheel 22 permits the provision of a time interval of over two minutes, even though the equipment can be housed in a small space. When a long time interval is being used, it is sometimes desirable to take an especially important picture without waiting for the end of the normal time interval. According to the present invention this can be accomplished by the simple expedient of pressing the start button l6, and this automatically starts a new series of intervals beginning with the special picture. This follows from the fact that pressing start button |6 rocks yoke 28 and not thus only closes camera control switch l3 but also declutches timing finger 24 so that it snaps back to the stop 33.

At the end of the series of pictures it is merely necessary to press stop button 63, which turns off the toggle switch I! and stops the motor l8.

The various details of the illustrated form of the invention may be sufficiently clear from the foregoing general description and from the drawings. It is desirable, however, to point out certain special features.

The motor I8 may be any suitable constant speed motor, and may include any suitable regulator for keeping its speed constant. For example, it may comprise a Dumore" /5 H. P. motor, series wound, with a governor arranged to shunt out a series resistance whenever the speed falls below a predetermined value, the constants being such that with the resistance the motor will slow down to said value. For aircraft work it will usually be a twenty-four volt D. C. motor, but it may be designed for other voltages if desired. A motor which has been found satisfactory is one having 2400 R. P. M. and provided with reduction gearing 66, having a 40 to 1 ratio, so that the drive shaft 61 rotates at the speed of one revolution per second. The drive shaft may have any convenient speed, higher speeds permitting intervals of any desired shortness. The motor is secured to and removable with end plate 68 (Fig. 4) of the housing, the drive shaft 61 having a telescoping connection with shaft 69.

Constantly driven shaft As best seen in Fig. 19, a shaft 69 is driven by the drive shaft (.7 through a pin 1|, carried by shaft 69 and riding in slots in drive shaft 61. The shaft 69 fitsloosely in the hollow end of drive shaft 6'1, so that the pin and slot connection serves as a universal joint. A sleeve of rubber or other silencing and resilient material, 12, may be carried by shaft 69 to prevent rattle. The shaft 69 is joumaled in bearing arms 13, cast integrally on the rear casting 14 of the frame or housing. A collar 15 on the end of shaft 69 fitting within drive shaft 61, hub 16 of crank disc 2|, and worm l9 are fast on shaft 69. A sleeve 11 may be provided on shaft 69, having a drive fit with the shaft, and forming a thrust bearing against the right-hand bearing arm 13 in Fig. 19,

the thrust on shaft 69 as a reaction to driving wheel 22 being to the right in this figure. Collared bearing bushings 18 may be provided in bearing arms I3.

Slow moving wheel The slow moving worm wheel 22 is carried by a stationary shaft 26, which, as best seen in Fig. 8, is carried by the back casting 14, being secured thereto by nut I9 which draws a shoulder 8| on the shaft against a bearing sleeve 82, which in turn has an accurately machined shoulder bearing against the rear casting I4 and an accurately machined fiange 83 spaced from the rear casting I4 to receive the bearing hub of slow moving worm wheel 22. The worm wheel 22 is not only provided with worm-shaped teeth on the periphery thereof for engaging worm I9, but it is also provided with radial teeth 23 for engagement with timing finger.24. Since these teeth only drive the timing finger in one direction it is preferred that they be ratchet-shaped to provide adequate driving strength with close spacing to facilitate the entry of the timing finger into engagement therewith. The teeth may be spaced at any desired intervals, corresponding to one or more revolutions of worm I9.

The size chosen for the worm wheel will depend upon the range desired for the timing interval. In the illustrated form the worm wheel has 160 teeth, and since the timing finger can make nearly a complete revolution with the extreme setting of the stop 33, an interval corresponding to at least 140 seconds may be provided.

Timing finger assembly The timing finger 24 is carried by a collar 86 (Fig. 11), being secured thereto in any desired manner as by welding. The collar 86 may have a pressed fit on clutch sleeve 81, which is rotatable and slidable on shaft 26. The clutch sleeve 81 is provided with an annular groove 88, in which clutch finger 3| rides. Sleeve 81 may be urged toward slow moving wheel 22 either by spring 32 or by finger 3I, or by both. Wear can be prevented by relying entirely on spring 32 and having the clutch finger out of contact with the walls of groove 88, but with slow moving parts the wear is negligible. The sleeve 81 is urged in a clockwise direction (as seen in Fig. 1) by the spring 32, one end of which engages sleeve 81 and the other end of which engages a flange formed on collar 89, by which the stop member 33 is carried. The sleeve 81 is provided with flange 9|, which is engaged by the second clutch fingers or rock levers 6|.

It will be observed that the timing finger assembly, including the finger 24 and the sleeve 81, has very low moment of inertia. Except for the slim timing finger 24 all of the weight is concentrated close to the axis. Accordingly, it will respond quickly to the influence of spring 32, and even if it has nearly a full re )lution to move it will traverse the angle quickly and yet this will not cause the timing stop finger to strike the stop 33 with a very heavy blow. The spring 32 can be quite light and still move the timing finger 24 with a quick snap. Finger 24 and collar 86 are preferably made of steel.

When the stop 33 is set for short intervals, timing finger 24 will strike cam 36 from the side instead of from underneath. So that the warning signal will be given even under these circumstances, the meeting portions of finger 24 and cam 36 are preferably beveled at about 45 and 6 the timing finger 24 will push cam 36 up as it is pressed in by clutch finger 3 I.

The shape of the end of the timing finger 24 is preferably best seen in Figs. 11 and 12. It is notched, as at 92, so as to clear the worm I9. If preferable, the parts could be so shaped and proportioned that when the clutch sleeve 81 is slid to its extreme disengaged position the finger 24 will still be in position to actuate the lever 31. The advantage of this is that with a setting of, say, two seconds the timing finger 24 will stay under cam 36 at all times, and therefore the Warning signal will remain lit. However, if it were found more desirable the parts could be positioned so that the timing finger 24 would strike the side of cam 36, with the engaging faces perpendicular to the movement, so that with the short intervals the warning lamp would never be lit. In this event the interceptor pin 38 would be in such position that it would be struck by the timing finger 24, even though the latter were resting against the side of cam 36, and furthermore, the cam 36 should not hold the timing finger 24 entirely out of engagement with the teeth 23 of the slow moving wheel.

It may be noted incidentally that the edge of the timing finger 24 engaging teeth 23 is preferably tapered, on the side which does not contact the flat face of the teeth 23, so as to correspond to the shape of the space between the teeth and to facilitate entry of the timing finger into the teeth.

Adjustable stop assembly The stop assembly 58 is rotatably carried by shaft 26 by means of sleeve 94, clearly seen in any of Figs. 8, 9, 11 or 13. This sleeve may comprise an integral part of the stop assembly, which may desirably be cast of brass or bronze. This sleeve is preferably provided with a steel insert 96 (Fig. 11), having a pressed fit therein, or otherwise secured thereto for forming an end thrust bearing against the shoulder 97 of shaft 26. The stop assembly 58 is urged against the shoulder 91 by a spring 98, which bears at one end against the collar 89 of stop assembly 58 and at the other end against flan e 99 of the handle assembly, thus thrusting the handle assembly against collar IOI, secured on the end of shaft 26. The collar IOI may be secured in any convenient manner, as by a cotter pin. The clutch finger 6| or the rockers of which they form a part, are pivotally mounted in slots I03 formed between lugs I04 cast on the stop assembly 58, suitable bearing pins being secured in these lugs and passing through the rocker members.

As seen best in Figs. 10 and 11, the face of the stop 33, which is struck by timing finger 24, may be provided with a silencing and wear-preventing pad I05, which may desirably be rep-laceably secured by screws, as clearly seen in Fig. 10. The pad may be made of a tough rubber or other suitable material, cork at present being preferred,

Handle assembly The handle 52 is preferably carried by a cupshaped cover 166, which is secured by screws I01 to a gear lock disc I08, as seen best in Figs. 11 and 13. The lock disc I08 may be riveted or otherwise secured to flange 98, forming an integral part of sleeve I89, which has a sliding engagement with sleeve 84 forming a part of the stop assembly. A constant angular relationship is maintained between the stop assembly 58 and handle 52 by means of rivet pins III, secured, by upsetting, to a ring I I2 forming an integral part HUUE 7 of the stop assembly 58. Lock disc I08 is provided with apertures having a smooth sliding fit with pins l I I.

As seen best in Figs. 8 and 9, the lock disc I08 is provided with clutch rods II4, which are secured to the disc I88 by upsetting and which slide through bosses IIB integral with ring II 2 and stop assembly 58. For declutching the timing finger 24 these rods II4 could bear directly against lugs IlI formed at the other end of the rocker levers from the clutch fingers 6I. It is preferred to maintain the parts in contact by resilient links II8, each linked through a hole in rod H4 and a hole in lug IN. This will draw the links back to such a position that the clutch fingers 6| are normally out of contact with flange 9|.

Dial

If the dial I2I moved inwardly when the handle 52 were pressed inwardly, it would be hard to read accurately in one position or the other. According to the present invention, the dial is secured to spacing rivets I I I which, being secured to the ring I I2, rotate but do not move longitudinally of shaft 26. The pointer or other reference marking to which the calibrations of the dial I2I are related may be borne by or depressed in the front plate I22. This plate is preferably flush with dial I2I so as to make the reading of the dial setting as easy as possible.

Any suitable means may be provided for looking the handle and stop assembly in position. It should be sufficiently sturdy so that it will always be dependable and will not be shifted under repeated blows from the stop finger 24, and it should require moving the handle far enough to declutch the timing finger 24 before rotating the stop. Both objects are accomplished by providing the lock disc I08 with gear teeth on the periphery thereof, and providing one or more gear lock blocks 56, secured accurately in recesses in the front of the casting I26. The teeth of disc I08 normally mesh with the teeth of gear lock blocks 56, but upon thrusting handle 52 inwardly the disc I08 moves inwardly to a position where, as seen in Fig. 13, it is clear of the gear lock blocks 56. The angular spacing and positioning of the teeth on handle disc I08 should correspond to the teeth 23 on slow moving wheel 22, so that when latch 48 is released automatically the finger 24, resting against stop 33, will be in a position to mesh with any one of teeth 23, which will give an interval of the number of seconds indicated by the dial I2I.

Yoke

As seen in Figs. '7, 14 and 16, the pivots for yoke 28 are formed by a shaft 29, which extends through brackets I3I extending forwardly from rear casting I4 and preferably cast integral therewith. The shaft may be secured in position in any desired manner, as by having a driven fit with the brackets I3I or by a setscrew either in the brackets I3I or in the yoke 28.

The general shape of the yoke is best seen in Fig. 1. It may be cast of any suitable material, brass being preferred to aluminum, however, because of better wear and warp resistance characteristics. The details of its shape are perhaps better seen from Figs. 7, 15 and 16. The declutching finger 3| may be rigidly secured thereto, as seen in Fig. '7, and is preferably made of steel. At one end a pin I34 may be secured to the yoke 28 for actuation by the starting rocker I36, which is pivotally mounted on a bracket I31 8 extending forwardly from rear casting I4 and preferably integral therewith. The pin I34 and toggle lever of switch I! are preferably spaced apart vertically so that they will not conflict with one another.

As best seen in Fig. 15, the yoke 28 is provided with a flat spring I39 for actuating switch I3. The yoke 28 is constantly urged by spring I4I toward the position shown in Fig. 15, in which position it leaves the timing finger 24 engaged in teeth 23. The spring I4I engages at one end with a hook carried by yoke 28, and at the other end in an aperture formed in plate I42, as seen best in Figs. 14 and 7. The plate I42 is secured to one of the brackets I3I and to one of the bearing lugs I3, as seen best in these same figures. This same plate is utilized for mounting the counter 5|, switch I3, and latch 48, thus making possible the removal of side plate I44 without disturbing any of the working parts.

At the lower left hand end, as seen in Figs. 1 and 7, the yoke 28 carries a pin I48, which may desirably be square in cross-section either through its entire length or through the portion thereof engaging latch 48.

The biased movement of the yoke 28 is preferably limited by a stop pillar I5I, seen best in. Figs. 14 and 15. By virtue of the location of the stop pillar as far from the pivotal axis 29 as possible the stop pillars I5I may be cast accurately enough so very little machining is necessary in order to properly determine the position of rest of the yoke 28.

Interceptor pin The mounting of the interceptor pin is probably best seen in Fig. 4. It is simply slid through apertures in arms I53 and I54 of the left-hand bracket I3I. The aperture in the arm I53 is smaller than that in arm I54, and the two parts of the pin 38 are of corresponding size, as seen in Fig. 4, so that inward movement of the pin is limited, the pin being normally urged inwardly by the interceptor arm 4I or the extension 39 thereof, under influence of spring I63.

Reliably constant return interval In order to obtain the utmost accuracy it is desirable that the time interval allowed for the return or snap back of timing finger 24 be constant and long enough to provide plenty of time for its return under the most extreme conditions. This is accomplished with the aid of latch 48 and by a novel expedient which prevents its being unlatched on the revolution of crank disc 2I, during which it is latched. Crank pin 44 is provided with a flange I56. As seen best in Fig. 18, this flange projects beyond interceptor block 43 to prevent the interceptor arm from springing out of engagement with crank pin 44. The flange I56 is so designed that it assumes this retaining position before pin 44 engages block 43 to shift the block. Other .Jise, as soon as the block was shifted enough to disengage timing finger 24 from teeth 23 the timing finger would snap back part way, and as soon as it was snapped part way, whether all the way or not, the interceptor block 43 would be free to spring out of engagement with crank pin 44.

Flange I56 is also so designed as to hold inter ceptor block 43 in its active position, as seen in Fig. 14, until after the release pin 49 has passed out from under latch lever 48 as seen in Fig. 14. It follows that when the flange I55 moves off of interceptor block 43 the interceptor arm 4| will be pivoted about the pivot 42 by its return spring I63, but the yoke 28 remains latched in its actuated position by virtue of the fact that pin I48 is still engaged in the notch of latch lever 48. Not until the end of the revolution thus started will pin 49 lift latch lever 48 to release the yoke 28. In the meantime the timing finger 24 will have had plenty of time to be snapped back to the stop 33, even if the latter is in the most remote position, and to come to rest thereagainst in spite of any possible bouncing. As a matter of fact, the momentum of the parts is so light that there probably will be no appreciable bouncing.

It may be noted that the latch lever 48 is urged toward latching position by a spring I62 surrounding the pivotal pin for latch 48, and having one end engaging the latch and the other end engaging the plate I42. The pivotal pin is secured to plate I42 by upsetting.

When the latch 48 is raised by pin 49 the yoke 28 will be returned to its normal position by return spring MI, and timing finger 24 will be shifted back into engagement with the proper tooth 23. One second of the time interval having elapsed at this time since the last actuation of switch I3, the proper tooth for the timing finger 24 to engage is a tooth which is one tooth closer to the position in which it produces actuation of the yoke than the number of seconds in the desired time interval. In other words, the dial I2I is calibrated to indicate one second more than the number of teeth between the engagement point of timing finger 24 for which stop 33 is set and the disengagement point. Hence, the dial indicates the correct interval, since the interval is the time traversed by the timing finger 24 in its timing movement plus one second. The reference to one second here is not exact, since the exact portion of the total cycle which is allowed for return of timing finger and the shifting engagement thereof will depend on the exact relationship of the pin 49, the pin 44, and other parts. Another advantage of the long retention period is that it adds one second to the maximum length of interval that can be obtained by a given worm wheel 22. It also holds switch I3 closed long enough to ensure operation of the camera.

The actuation of the camera occurs when the relatively fast moving pin 44 reaches a given point in its cycle and hence the timing is quite exact, once the motor gets up to its governed speed. This may take a few seconds, and so the start button should be pushed a few seconds before the mapping begins. It may be pushed again to start the cycle at the right time for mapping, and, if it is held depressed, only one film area will have been wasted, since holding the. start button depressed holds timing finger 24 declutched.

Interceptor arm For proper coaction between the interceptor block 43 and pin 44, pin 44 should completely miss the coacting edge of interceptor block 43 on one revolution, while on the next revolution flange I56 should extend beyond or hook over the interceptor block 43. Since the movement of interceptor block 43 by interceptor pin 38 and slow moving time finger 24 will be a rather slow movement, it is preferred that pressure of the interceptor block 43 on the end of pin 44 be avoided by cutting away the adjacent face of the interceptor block 43 at I64, as seen best in Figs. 2 and 4 17. The outer face of interceptor block 43 also 10 slopes so as to provide a relatively thin lower portion of interceptor block 43, so that the flange I56 will hook around interceptor block 43 satisfactorily.

The proper timing of the movement of interceptor block 43 will depend upon the length of interceptor pin 38, which must be such as to get the lower portion of interceptor block safely beyond (inwardly of) the orbit of the flange I56, while keeping it out of the orbit of the flange I56 on the preceding turn of pin 44.

It is not essential that the timing be such that interceptor block 43 never presses its inner face against any non-yielding member, because the interceptor arm 4| is constructed in such a manner that it will yield, if necessary. The main portion of the arm H has an extension member 39, secured thereon by a loose rocking type of hinge I66, the two parts being held in place at this point by a loose pin I61. Normally the parts are held in fixed relationship by pressure of a spring I68, which presses bar 39 against the interceptor bar 4| at both ends. The spring I68 bears against a disk I69, which may be carried by a pin I1I secured to the main bar M and to the disk by upsetting. The spring I68 is in the nature of a relief spring, so that if the timing of the parts is not exactly right and interceptor block 43 is pressed inwardly too soon against the head of pin 44, the extension 39 will yield and permit the interceptor pin 38 to be moved by timing finger 24 without causing any damage. This incidentally operates to cook the interceptor arm, so that as soon as the pin 44 passes out from under it the tension of spring I68 will snap the interceptor block 43 into its active position.

If anything should go wrong, and the timing finger 24 should not be released from teeth 23 when it should be, the relief spring I68, together with a safety cam plate I13, will cooperate to prevent damage. As seen best in Figs. 4 and 11, the cam plate I13 15 positioned and shaped so that it will be engaged by the timing finger 24 as soon as the timing finger has passed its normal point of disengagement, It will then ride out on the safety cam plate I13 until the latter has pressed it out of engagement with the teeth 23. In the meantime the release spring I68 will have permitted the extension 39 to move with lost motion, without injuring any parts.

Counter The counter 5 I, which may be a Veeder counter, is carried by plate I42, and is preferably provided with a reset knob I16 on the outside of end plate I 44. The counter may be actuated through its lever I11, which, as seen in Figs. '1 and 14, is to the right of the plate I42. The lever I11 is actuated by crank arm I18 fast on pin I19, journaled in plate I42, and bearing fast thereon crank arm I 8| provided with a lug I82 adapted to engage the yoke 28 to be actuated thereby.

Circuit The circuit of the present invention as applied to a camera is illustrated in Fig. 22. From battery I83 wires I84 and I85 lead to the terminals of plug I86, from which wire I85 is connected to toggle switch I1. When the toggle switch I1 is turned on, the wire I85 is connected to motor I8 and to switches I3 and I4. A resistance I88 is connected in the motor circuit, together with means, such as governor controlled contacts (not illustrated) for intermittently shunting out the resistance I88 with condenser I89 across the con- 11 tacts. When the switch I4 is actuated, it closes a circuit, clearly seen in Fig. 22, from battery I83 through switch I! to lamp I2. When switch I3 is closed it closes a similar circuit to the camera II for actuating the shutter and rewind mechanism to camera.

The switches I3 and I4 may be of any suitable form, those known as the micro switches (made by Micro Switch Corporation) being preferred because of their ability to carry and interrupt the necessary current load, although having an extremely small throw and requiring only a very slight actuating force.

Casing As already mentioned, the casing for the device preferably includes a back casting I4 and a front casting I26. These castings are probably best seen in Fig. 15, which also shows the manner of securing the two castings together by means of screws I9I. The front and back portions of the two castings are preferably spaced apart by corner pillars I92 adjacent the screws I9I. The four side plates and the front plate may be secured to the castings by screws so as to be readily removable. The bottom plate I41 may be clamped to the casting by junction box I94. which in turn is secured to the casting by screws I96. The junction box preferably includes plugin facilities for the camera and battery, and for the signal lamp, and, as seen in Fig. 21, may also include condenser I89 and governor resistance I88. The governor resistance I88 should be ventilated, and is therefore preferably in a separate compartment, which has openings I91 there through for ventilation, a dividing wall I98 protecting the other parts from dust or other foreign matter.

The governor is located outside of the housing, under a removable cap on the motor, for ready accessibility.

The push buttons are mounted in the front casting, in a manner clearly seen in the drawings, especially Fig. 16. The front and back castings are desirably aluminum for lightness.

Withstanding wide temperature range For use in aerial photography the device should be capable of operating satisfactorily through a temperature range of -40 F. to 110 F. Although an accuracy of is considered sufficient. the illustrated form of the invention has an accuracy of of 1% throughout this range. In obtaining this accuracy through such a wide range, care must be taken with respect to the bearings and lubrication. In general, all bearings must have generous clearance so that they will not become too tight under any temperature conditions or even under fairly rapid changes of temperature within the range in question. The motor shaft, of course, should not have excessive clearance and is preferably mounted in ball bearings which should be lubricated with a small quantity of light oil which will not become too stiff at 40 F. The bearings for the parts moving constantly, particularly for the gears, the shaft 69 and the slow moving wheel 22, may desirably be Oilite bushings, each having a driven fit with the part in which it is mounted. The speed reduction gears in the gear reduction box 66 are preferably made of the material known as Synthane (a synthetic resinous material including graphite).

Another factor which may contribute to uniform accuracy is the mounting of the return spring 32 in such manner that its tension is always substantially the same when the stop finger 3I rests against stop 33. There are no positional variations which might sometimes be cumulative with respect to slight temperature variations. This permits the return tension to be fairly low when the finger is against the stop and to be increased substantially as the finger moves further and further from the stop, so that the further it is away the more quickly it starts back.

From the foregoing it is seen that a timing device is provided which is thoroughly dependable and has the extreme accuracy of a precision instrument; which is easy to set; which is entirely accurate for all settings; which can be operated at any time by hand without any time lag, such as would result from indirect operation, and which, after being operated by hand, begins a new series of intervals from the hand operation. In spite of compactness the unit has a wid range of intervals, the illustrated form having a range of from two seconds to one hundred and forty seconds. As a matter of fact, it could have a cycle of one second if the structure were arranged to hold the timing finger 24 in its most advanced position and latch 48 were omitted, but this has not been found necessary for applicant's purposes.

The illustrated form of unit, because of its operating characteristics, its dependability, its compactness and its light weight (about eight pounds), is especially suitable for aerial photography, but the invention could be used for many other purposes, even in its illustrated form. For some purposes different speeds of shaft 69 might be desired, and many other changes might be desirable for special purposes, or to utilize the invention in different designs of apparatus. Among the many other uses are those in connection with timing traffic signals, or other signals, telephone circuits, welding machines, and various automatic machine tools. For some of these purposes the switch I4 would be omitted or would actuate some controlled means other than the warning lamp, and the cam 36 could be positioned to actuate the switch I 4 at any portion of the interval.

I claim as my invention:

1. A timing device including a constantly driven member, a timing member adapted to be engaged therewith approximately at one end of the interval and disengaged therefrom approximately at the other end and to be driven thereby constantly between said engagement and disengagement, means rendered effective when the timing member is driven to a predetermined position by the constantly driven member for releasing the timing member therefrom and causing it to return to a starting position, controlled means operated at a predetermined position in the cycle of the timing member, characterized by the provision of a member moving faster than the con-' stantly driven member, and means controller'- thereby for timing the actuation of the controlled means and for timing the engagement between the timing member and the constantly driven member after the return of the constantly driven member to its starting position.

2. A timing device including a timing member, means for driving the timing member uniformly, pivoted means, means for causing said pivoted means to be pivoted when the timing member is driven to a predetermined position and for positively holding it in the actuated position a predetermined length of time, means disconnecting said timing member from the driving means in response to pivoting of the pivoted means, and controlled means actuated by the pivoted means.

3. A timing device including a constantly driven member, a timing membe shiftable to be engaged with or disengaged from the constantly driven member, a separately pivoted yoke adapted to disengage the timing member when it is shifted to an actuated position, means for pivoting the yoke when the timing member reaches a predetermined position, and controlled means actuated in conjunction with movement of the oke.

y 4. A timing device including a hooked actuator moving in constant cycles, interceptor means movable into the path of the hooked actuator at the end of an interval, means operated by the actuator and interceptor means for starting the timing of a new interval, the operation requiring said interceptor means to pass behind the hook of the actuator during one cycle of the actuator, and means for moving the interceptor means into aid path; characterized by the provision of a relief spring in the means for moving the interceptor means, permitting the interceptor means to be yieldably pressed against the actuator so that it will snap into place during a short portion of the actuator cycle when the actuator moves out of the path of the interceptor means.

5. A timing device including a hooked actuator moving in constant cycles, interceptor means movable into the path of the hooked actuator at the end of an interval, mean operated by the actuator and interceptor means for starting the timing of a new interval, the operation requiring said interceptor means to pass behind the hook of the actuator during one cycle of the actuator, and means for moving the interceptor means into said path; characterized by the shaping of the interceptor means with the point thereof closest to the actuator on the receding movement thereof closer than the thickness of the metal forming the interceptor means to the plane parallel to the movement of the actuator and passing through the point of the interceptor means which will be first telescoped by the hook whereby the hook may at least approximately clear the interceptor means on its receding stroke and still hook over the interceptor means on its engaging stroke, with only slight intervening movement of the interceptor means.

6. A timing device including a constantly rotating shaft, fast moving and slow moving members driven thereby, the slow moving member being in the form of a wheel, a timing member removably engaged with said wheel and rotatable about the axis of the wheel, control means and means rendering said fast moving member operative to operate the control means when the timing member reaches a predetermined position and to release the timing member from the wheel, means for causing the timing member to return to a starting stop, and means to set the starting stop at a variety of positions around the wheel the farthest of which will permit the timing member to travel at least three-fourths of a revolution.

7. A timing device including a constantly rotating shaft, fast moving and slow moving member driven thereby, the slow moving member being in the form of a wheel, a timing member removably engaged with said wheel and rotatable about the axis of the wheel, control means and means rendering said fast moving member operative to operate the control means when the timing member reaches a predetermined position and to release the timing member from the wheel, and means for causing the timing member to return to a starting stop; the position of the starting stop, at times at least, being angularly spaced from said predetermined position by at least three-fourths of a revolution of the wheel.

8. A timing device including a constantly rotating shaft, fast moving and slow moving members driven thereby, the slow moving member being in the form of a wheel, a timing member removably engaged with said wheel and rotatable about the axis of the wheel, control means and means rendering said fast movin member operative to operate the control means when the timing member reaches a predetermined position and to release the timing member from the wheel, and means for causing the timing member to return to a starting stop.

9. A timing device for timing a series of contiguous intervals including a member driven constantly throughout th series, a timing member adapted to be engaged therewith and disengaged therefrom, a return spring urging the timing member in the direction opposite to the movement of the constantly rotating member, stop means for limiting the return movement of the timing member and means automatically causing the timing member to be reengaged with the constantly driven member to begin another timing movement, said timing member consisting of a sleeve close to the axis of rotation and a slender finger extending therefrom whereby its moment of inertia is low,

10. A timing device including a motor, a motor control circuit, a constantly moving member driven by the motor, a timing finger adapted to be shifted to a timing position in which it is driven by the constantly moving member and to a disengaged position, a yoke adapted to shift the timing member from a driven position to a disengaged position, controlled means actuated by the yoke, a push button adapted to actuate the yoke, and a motor switch in the motor control circuit adapted to be turned on by the push button upon actuating the yoke if the motor switch is not already on. said yoke being actuatable by the push button even if the motor switch is already on.

11. A timing device including a constantly driven wheel, a shaft positioned coaxially with the wheel, a timing member rotatably and slidably mounted on the shaft adapted to engage and be disengaged from the wheel, means urging the timing member in the direction opposite to the rotation of the wheel, stop means against which said timing member is urged when disengaged, said stop means being rotatably mounted on the shaft, and handle means rotatably and slidably mouifted on the shaft and adapted to disengage the t ming member by sliding movement and to rotate the stop means by rotative movement.

12. A timing device including a constantly driven wheel, a shaft positioned coaxially with the wheel, a timing member rotatably and slid ably mounted on the shaft adapted to engage and be disengaged from the wheel, means urging the timing member in the direction opposite to the rotation of the Wheel, stop means against which said timing member is urged when disengaged, said stop means being rotatably mounted on the shaft, handle means rotatably and slidably mounted on the shaft and adapted to disengage the timing member by sliding movement and to rotate the stop means by rotative movement, and lock means preventing rotation of said handle means and stop means except upon a sliding movement of the handle means disengaging the timing member.

13. A timing device including a constantly driven wheel, a shaft positioned coaxially with the wheel, a timing member rotatably and slidably mounted on the shaft adapted to engage and be disengaged from the wheel, means urging the timing member in the direction opposite to the rotation of the wheel, stop means against which said timing member is urged when disengaged, said stop means being rotatably mounted on the shaft, handle means rotatably and slidably mounted on the shaft and adapted to disengage the timing member by sliding movement, lock means preventing rotation of said handle means and stop means except upon a sliding movement of the handle means disengaging the timing member, and an indicator carried by the stop means and rotatable with it in a position substantially flush with a cooperating indicator, regardless of sliding movement of the handle means.

14. A precision instrument including a rotatably adjustable member, handle means carried thereby and axially shiftable with respect thereto, a casing enclosing the adjustable member, a gear lock ring carried by the handle means, a gear lock block carried by the casing, and an indicator shield concealing the gear ring carried by the adjustable member and positioned substantially flush with a cooperating indicator associated with the casing, regardless of the axial movement of the handle means.

15. A gauging device including a drive shaft, a gauge member driven in predetermined relation to the rotation of said shaft, a latch adapted to maintain said gauge member disengaged, an actuating pin carried by the shaft, interceptor means moved by the gauge member into the path of the pin and cooperating with it to disengage the gauge member, return means urging the interceptor means out of said path, temporary retaining means associated With said pin for retaining the interceptor means in operative position, and release means shifting said latch to a release position and allowing it to return to a latching position while the temporary retaining means is in a retaining position during each revolution of the shaft whereby the temporary retaining means retains the interceptor means in operative position during a first revolution until after the latch is returned to its latching position, and on a subsequent revolution the release means releases the latch to cause reengagement of the gauge member.

CARL S. HORNBERGER.