US3156851A

US3156851A - Timing mechanism

Info

Publication number: US3156851A
Application number: US210271A
Authority: US
Inventors: William C Monday
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-07-16
Filing date: 1962-07-16
Publication date: 1964-11-10
Anticipated expiration: 1981-11-10

Description

Nov. 10, 1964 w. c. MONDAY TIMING MECHANISM 4 Sheets-Sheet 1 Filed July 16, 1962 INVENTOR. William 6. Monday Nov. 10, 1964 w. c. MONDAY 3,156,351

TIMING MECHANISM Filed July 16, 1962 4 Sheets-Sheet 2 IN V EN TOR.

William 6. Monday BY A fforney Nov. 10, 1964 w. c. MONDAY 3,156,351

TIMING MECHANISM Filed July 16, 1962 4 Sheets-Sheet 3 IN V EN To R. William C. Manda) Affa y Nov. 10, 1964 w. c. MONDAY 3,156,851

TIMING MECHANISM Filed July 16, 1962 4 Sheets-Sheet 4 c- /6 T as c\ I [76 X Normal/y 2 7.9L. Z? Otf Load I Power 1 J\) Power 4: I (S -23 Normal/y 89b p54 0n Load I Operating \f2/ 1 L Power l Channel I Normal/y c 36 0n Load v 8 83 -I 82 x) 79 ower 20 Normal/y O\) Power 76 I 89b 2; Operating I 2/ Power Channel I Fig 4 INVEN TOR.

William 6. Mon do y M Q. Attorney United States Patent 3,156,851 TIMING ltlECHANlSM Willi m C. Monday, Albuquerque, N. Mere, assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Filed .luly 16, 1962, Ser. No. 210,271 8 Claims. (Cl. 317-157) The present invention relates generally to timing means, and more particularly to a timing mechanism capable of elfecting multiple switch actuations at or near the end of a pre-set period of time.

In the prior art, for example, in connection with missile propulsion or control systems, there has existed for some time a problem of providing a relatively simple and highly accurate timing mechanism capable of being operated for various settable time periods with multiple switch actuations at the end of the set time. This problem has been further complicated by the fact that in many instances actuation of the multiple switches should be spaced apart from each other by a predetermined period of time. For example, it is often desirable in the propellant supplying system of a rocket motor to have the fuel enter the combustion zone immediately before the admission of the oxidizer or, when pressurizing the propellant tanks, to permit the pressurizing medium to pressurize the tanks for a given time prior to the opening of the valve for admitting the propellant to the combustion zone.

The present invention aims to overcome problems or difiiculties such as the above by providing new and improved means of relatively simple and inexpensive construction which is adapted to provide a timing operation capable of being readily pre-set to function by actuating switches at the end of any preselected time period chosen from a wide range of possible time settings. The invention further contemplates the provision of means for providing spaced apart switch actuations at preselected time intervals near or at the end of the timing cycle.

An object of the present invention is to provide a new and improved timing mechanism capable of being preset to operate for a given time period with multiple switch actuations near or at the end of the set time.

Another object of the present invention is to provide a new and improved timing mechanism of relatively simple and inexpensive construction.

Another object of the present invention is to provide a double trip element arrangement and a differential gearing assembly for attaining the desired timing period.

A further object of the present invention is to provide reset means for returning the timing mechanism to a zero or initial setting upon completion of the switch actua tions.

A still further object of the present invention is to provide a timing system with a pair of internally coupled timing devices for providing back-up means.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes of illustration and description. The preferred embodiment illustrated is not intended to be exhaustive nor to limit the invention to the precise form disclosed. It is chosen and described in order to best explain the principles of the invention and their application in practical use to thereby enable others skilled in the art to best utilize the invention in various embodiice ments and modifications as are best adapted to the particular use contemplated.

In the accompanying drawings:

FIG. 1 is a top plan view of a timer housing containing a pair of internally coupled timing channels of the present invention with the electrical circuit removed from one of the timing channels for clarity of illustration;

' FIG. 2 is an exploded schematic perspective view, partly cut away, of the gearing arrangement in the timing mechanism of the present invention, with the time setting means shown positioned above the gear train for clarity of illustration;

FlG. 3a is an end view of the present device illustrating the trip element configurations, the trip element follower, and the microswitch arrangement with the trip element follower engaging a non-microswitch opening portion of the intermediate trip element;

FIG. 3b is a view similar to the view in FIG. 3a, but illustrating the trip element follower engaging the first step in the intermediate trip element for opening the contacts on a first set of microswitches;

FIG. 3c is a view similar to the View in FIG. 3a, but illustrating the trip element follower engaging the third step of the intermediate trip element for closing a third set of microswitches;

FIG. 4 shows a diagrammatic representation of an electrical circuit that may be utilized to internally couple a pair of timing channels of the present invention;

FIG. 5a is a plan view of a reset microswitch and actuating sprocket showing the microswitch in an open position; and

FIG. 5b is a view similar to FIG. 5a, but showing the microswitch in a closed position.

Described generally, a timing channel or device of the present invention comprises (FIGS. 1 and 2) a substantially constant speed electrical motor 10 including a speed reduction gearing mechanism 11 for rotating an output shaft 12, a gear 13 and a pair of

integral trip elements

15 and 16 at a constant low speed or number of revolutions per minute (r.p.m.). A differential gearing assembly surrounding the output shaft 12 is driven by the output shaft gear 13 for turning a trip element 17 at an rpm. substantially less than the rpm. of trip element 15. Trip element 17 may be provided with a single large slot 18 and be attached to the differential gearing mechanism adjacent to trip element A trip element fol lower 25 (FIG. 3) having associated therewith microswitches or other

similar miniature switches

21, 22, 23 is adapted to engage appropriate steps in trip element 15 and slot 13 in trip element 17 when such steps and slot are each in alignment with the trip element follower so as to sequentially actuate the microswitches. An adjustable time setting means indicated generally at 25 (PEG. 2), may be coupled to the differential gearing assembly for initially positioning trip element 17, thus providing a predetermined time period which must elapse before the slot 18 in trip element 17 and the steps in trip element 15 are each in alignment adjacent the trip element follower 28 so as to permit the latter to engage the steps and slot and actuate the microswitches.

Described in greater detail and referring in particular to FIGS. l-3c a pair of timing devices or channels indicated generally at 26 and 27 may be positioned and secured in a housing 28 by any suitable means. Each timing device may comprise a constant speed electrical motor 10 coupled through reduction gearing 11 to an output shaft 12 which has a pair of

trip elements

15 and 16 secured thereto and shown adjacent the distal end thereof. T he motor 16 and the reduction gearing 11 may be of any suitable type, such as, for example, a 28 volt DC. motor operating at 12,600 rpm. and an integral speed 7:? reducing assembly for providing an output shaft speed of two rpm. Both units are manufactured by Globe Manufacturing Company, Dayton, Ohio. Trip element 15, which is normally the larger of the two, may be provided with a plurality of progressively deeper or

deepening steps

30, 311 and 32 respectively, about a portion of its periphery. The circumferential spacing between the respective steps is a feature of the present invention which will be discussed in detail below. Assuming clockwise rotation of the shaft 12, the steps progressively deepen in the opposite or counterclockwise direction so as to permit the incremental engagement of the trip element follower 26 with each step as will be described. While a pair of oppositely disposed timing devices or channels are shown in the housing (FIG. 1) it will be clear that any suitable number and arrangement of timing devices may be used. I

Gear 13, which may be fixed in any suitable manner to the shaft 12 adjacent the reduction gearing ll, drives the ditferential gearing assembly, which may comprise gear train 34, 3 5, 36, 3'7, 3% and 39. Gears 36 and 37 may be integral and along with gear 39, which may be disposed on the inner surface of cup-like member 4%), may be positioned about the shaft 12 with suitable low friction hearing means 41 and t2 placed 'therebetween so as to permit such gears to be freely rotatable on the shaft 12. Positioned about the shaft 12 on low friction bearing means 43 and

intermediate gears

36 and 39 is a selectively rotatable gear housing t4 having a centrally disposed counterbore 45 and a recessed or stepped outer portion 4-5. Gear 38 is adapted to be rotatably attached on a suitable shaft to a sidewall of the housing 44 and be so positioned within the counterbore 4-5 as to permit a portion of the gear 38 to extend outwardly through a slot in the stepped portion 46.

When the gears 37, 33 and 39 are in an operative relationship with each other (FIG. 1), they form a planetary gearing system, i.e., the gear 37 acts as the sun gear and is positioned within the gear housing counterbore 45 where it engages one side of planet gear 33 while the ring gear 39 surrounds the gear housing recess 46 and engages the exposed portion of the gear 33. This planetary gearing system provides for selective rotation of gear housing 44 as will be described below.

The differential gearing assembly provides the gear 39 with a substantial speed reduction in the opposite or counterclockwise direction to that of the output shaft 12. Therefore, trip element 17, which may be provided with a single slot 18 and be integral with the cup-like member dill, rotates in the opposite direction to and at a rate sub stantially slower than trip element 15, thus permitting the selectable actuation of the'microswitches by the trip element follower 2t Any desired number of speed ratios may be used between the oppositely

rotating trip elements

15 and 17, such as, for example, if the shaft 12 has a constant rotational speed of two rpm. and if the speed reduction through the differential gearing assembly rotates the trip element 17 at one-tenth the speed of theshaft 12, then this arrangement, due to the initial trip element settingsand the circumferential displacement and width of slot 1%,

permits a maximum rotation of eight revolutions of trip element 15 before the slot 118 in trip element 17 and the steps ltd-32; are in alignment Where the trip clement follower 20 can engage the steps and the slot. The width of slot 18 may be such that with-the sample ratio the trip element 15 rotates one revolution While trip element 1'7 rotates the portion of a revolution equal to the width of the slot 18. Theahove speed ratio example may provide for eight separate time settings spaced apart from each other by a thirty-second time period.

To provide means for selecting the desired time setting, aselectively adjustable dial mechanism may be coupled to the differential gearing assembly through a'pair of

bevel gears

48 and 49 and gear 50. Gear 59, which engages matching gear teeth on the outermost peripheral portion of the gear housing 44, may then rotate housing 44 in either direction due to the planetary gearing arrangement of gears Iii-3% which permits gear 38 to Walk on gear 37 while rotating gear 39 and trip element 17. The dial mechanism 25'comprises a cover 52 having a small window 53 therein and which may be suitably secured to the housing 28 in any desired location, such as the underside of the housing 28 in FIG. 1. A dial 54 having a selective numerical time scale indicated on its surface and which may be coupled to bevel gear 48 through shaft 56, is placed under the cover 52 so that only one numeral at any given time is visible through the window 53 and that being the numeral indicative of the time setting selected for the microswitch actuation.

To set the timing device for microswitch operation at or near the end of a predetermined timing period, the dial 54 may be rotated until the desired numeral or other time identifying means is visible under the Window 53. The rotary movement of the dial 54 rotates shaft 56 and

bevel gears

48 and 49 which in turn effects the rotary movement of gear housing 4-dcausing the gear 38 to rotate gear 39 and position the trip element slot 1% at such a location with respect to the trip element follower 20 that it takes a time period equal to the preset time period before the slot 18 aligns with the trip element follower 2t) and the steps in trip element 15. The end of the dial shaft 56 adjacent the dial 54 may be provided with a small slot St for accepting the end of a screw driver or the like which may be used to rotate the dial 54 and set the operating period for the timing device.

A detent arrangement comprising a notched wheel 55 secured to the dial shaft 56 and a pair of balls 57 continuously urged inwardly by spring 58 may be used to hold dial shaft 56 against being undesirably rotated out of the preselected time setting once the setting has been selected. Also the detent arrangement facilitates accurate settings of the dial 54 by initially placing the notched wheel on the dial shaft as so that at each indicated time setting the balls 57 will be in the wheel notches.

The trip element follower it as best illustrated in FIGS. 3a3c, comprises a main body portion 60 pivotally mounted on shaft 61 and has a spur or lateral projection 62 adapted to engage the steps Cid-3?; and the slot 18 in

trip elements

15 and 17 respectively, and a pair of micro- 7

switch actuators

64 and 65, one of which may be positioned in a slot 655 while the other may be positioned in an offset rounded portion 63. The riser of each step 3tl-32 may be on an acute angle with step tread for facilitating the engagement of the lateral projection 62. A hclically wound tension spring 67 may have one end secured to themain portion 6t? in such a manner as to continuously urge the trip element follower 24 to pivot about shaft 61 and cause the projection 62 to bear against the peripheral surface of both

trip elements

15 and 17.

Microswitch actuator 64, which comprises a relatively rigid and straight piece of metal, may be afiixed to the main body portion 6@ of the trip element follower by inserting and securing one end of the actuator in the slot 63 provided in the main body portion adjacent the offset portion 63. The outer or the exposed end of actuator 64 may be wider than the end secured Within the slot so as to permit the actuator to close or open the contacts on two pairs of oppositely disposed microswitches 21 and 23 (FIG. 1).

, Microswitch actuator 65, on the other hand, preferably comprises a resilient and curved metal spring member secured at one end in any suitable manner in the offset A portion 63 adjacent to the uppermost part of the main body portion 6t while the other end or the exposed end may be providedwith a small'indenture or the like 69 While the

actuators

64 and 65 are each shown as having widened exposed end portions for simultaneously opening or closing contacts on a pair of microswitches (the purpose of which will be described below) it will be clear that such end portions may be of any desired width as to engage any desired number of microswitch contacts.

When assembling the timing device of the present invention trip elements and 37 should be initially positioned in proper relationship with each other so that the timing period set by the dial is accurate. This correct assembling position may be attained by providing a small notch 7% in the tread of step 32 in trip element 15 and a fiducial mark 71 on the side of trip element 17. Then alignment of the notch 7t) and the mark 7i with the end of the projection 62 (FIG. 3a) will properly position each trip element with the trip element follower fill.

The scale used on the dial 54 may be used for determining the location for the mark "71, or vice versa, since with a known output shaft speed and a given gear ratio in the differential gearing assembly the distance between the mark '71 and the opening to slot 18 is directly proportional to time. Therefore, if it takes, for example, thirty seconds for the trip element It? to rotate from the point adjacent the mark 71 to the opening of slot 18, then the first numeral on the scale may be with each addi tional numeral being a suitable graduation of thirty.

In order to insure that the selected numeral on the dial 54 corresponds to the operating time or" the device, it may be necessary to provide means for preventing complete rotation of the dial, since by rotating the dial 360 or more the slot 18 in trip element 17 may be improperly positioned with respect to the projection 62 on the trip element follower 2% so as to render the timing device inaccurate. may be attained by providing the dial 54 with a raised wedge shaped portion 72 at the point of initial setting and the cover 52 with an inwardly extending pin or the like (not shown) adjacent to and engaging one side of the wedge when the latter is in its initial position. Thus, the

ial 54 may be rotated in only one direction at the outset, but once moved away from its initial position it may then be rotated in either direction to attain the desired setting. However, in no instance may the dial 54 be rotated a complete revolution or 360 so as to improperly position the trip element notch it; with respect to the dial 54.

A second channel 27 or back-up timing device, which may be placed in housing 23 alongside of the first channel 26 (PEG. 1) may be constructed similarly to the first channel and be provided with the same speed ratios and trip element configurations. Each channel may then be mechanically coupled to the same time setting means 25 so that the timing period selected by moving the dial 54 positions the trip elements of each channel to simultaneously align with its trip element follower projection at the end of the tirm'ng period. To couple the second channel 27 to the time settin means, an additional bevel gear 74, which functions in the same manner as bevel gear 49, may be provided in an engaging relationship with the bevel gear 48 on the dial shaft 56.

After the desired time period has been selected on the dial scale and the motor it) of each timing device energized, the trip element 17 may be rotated in a counterclockwise direction by the ditferential gearing assembly and the trip element 15 rotated in a clockwise or opposite direction by the shaft 12. These oppositely rotating trip elements cause the slot 18 in the trip element 17 and the steps in trip element 15 to move in opposite directions and eventually into alignment with each other adjacent the projection 62 on the trip element follower 2%. Thus, when the slot lid is in registry with the projection 62 and the steps of the faster rotating trip element 15 move into alignment with the slot 13, the projection pivots about the trip element shaft 61 under the influence of the Prevention of such undesirable dial rotation spring 67 and engages the first step 30 in trip element 15 (FIG. 3b). This pivoting movement of the trip element follower Ztl lifts the actuator 64 and opens a first pair of contacts on microswitches 21 (FIG. 1) for controlling the operation of an external circuit. Microswitches 22 remain closed at the end of the first trip element pivoting movement since the resilient actuator is not lifted from the contacts but merely springs into the offset rounded portion 63 of the trip element follower. As the trip element 15 continues to rotate, the trip element follower projection 62 moves along the step 30 a predetermined length until step 31 aligns with the projection 62 which then permits the trip element follower 20 to further pivot (not shown) and lift actuator 65 off the con tacts of microswitches 22, thus controlling the operation of a second external circuit. When the trip element 15 has rotated sufficiently to move step 32 into alignment with the trip element follower projection 62 (FIG. 30), the trip element follower 20 again pivots and moves the actuator 64 against the contacts of the microswitches 23, closing the latter and effecting the operation of an additional external circuit. The closing of the contacts on microswitches 23 may indicate the lapse of the time period selected by the dial setting or, alternatively, the opening of the first set of microswitch contacts 21 may indicate the end of the selected time period with the actuation of

microswitches

22 and 23 occurring a predetermined time thereafter.

The tread lengths of

steps

30 and 31 are each directly proportional to time and may thus be of any desired length necessary to establish a suitable time lag between the consecutive actuations of the microswitches.

Normally after the actuation of microswitches 23 the need for the timing mechanism is ended and the circuit to the motor ltl may be opened by the microswitches 23 or in any other desired manner to stop the timing operation so as to leave the trip element projection 62 within step 32 and the microswitches 23 in a closed condition.

When providing a timing device with a back-up system or a second timing device, as shown in FIG. 1, it may be desirable to internally couple the timer operating circuits and the microswitch circuits so that if one timer fails in its intended function due to some unforeseen condition or if one timer is hindered in its timing cycle, then the other timer may complete the timing cycle and operate the microswitches. It may also be desirable to internally couple both the timer motor operating circuits so that the completion of the timing cycle by one timing device simultaneously opens the circuits to both timer motors.

FIG. 4- schematically illustrates how a pair of separate timing devices may be internally coupled so that the circuits of one timing device are capable of being opened or closed by the other timing device. Various components of channels I and II are designated by numerals similar to the numerals used in FIGS. l-3c to indicate like components. The Wiring diagram shows a duplicatron of external loads or circuits for each timing device, thus providing back-up circuits for external use. However, in event only a single set of external circuits is desired for the timing mechanism the wiring and microswitches associated with the external back-up circuit may be omitted, thus omitting one microswitch of each pair of microswitches 21-23.

resser the trip element 15 moves the switch 6d into engagement with switches 23 and closes the circuit from power source 89a to loads 76 of both channels. Thus, as above described, the back-up system including the internally coupled circuits provides a fail-safe timing mechanism capable of performing its intended function through the operation of either timing channel.

Upon completion of the timing operation, it may be desired to reuse the timing mechanism in a subsequent operation and in order to do so the cams should be returned to their original positions. To accomplish this a reset system may be used such as, for example, one comprising a first reset m'icroswitch '78 having a spring loaded actuator '79 and positioned adjacent trip element lie so as to permit the actuator 79 to engage notch 55% in trip element 16 and open the microswitch contact (FIG. 3a). A second reset microswitch 82 may be positioned adjacent to gear 36 of the differential gearing system and be provided with a spring loaded actuator 83. A pair of dowels or pins 84- (one not shown) extend from the side wall of gear 36 and are circumferentially spaced 180 apart from each other. Each of these pins $4 is adapted to engage any of a plurality of notches d5 a sprocket 86 (FIG. So) as the gear 36 rotates. The sprocket, which may be rotatably mounted in any suitable manner upon the timing device, in turn engages the actuator 83 for controlling the operation of the microswitch. A single enlarged notch 83 in the sprocket 86 is adapted to 'e eive the actuator 83 and open the microswitch contact (FIG. So) while the other notches 85 are to ll f h actuator acceptance, thus permitting microswitch' 053511- 111g at only one position on the sprocket 86 (FIG. 51)). As shown in FIG. 4, the reset microswitches 7t; and 82 are arranged in a parallel circuit between a power source 8912, which may have a manually operated switch 90, and the motor it) of the timing device so that if both

microswitches

78 and 82 are simultaneously opened the circuit between the power source 8% and the motor 16 will be broken.

The operating power for the motors It loads '75, '76, and the reset mechanisms of both channels is preferably obtained from a single power source which for convenience and clarity of description and illustration is shown as rectangles 39, 89a, and $919 in H6. 4. However, if desired, independent power sources may be provided for one or more of the motors, loads, or reset mechanisms.

Gear 36, when using the above described speed ratio for example, may rotate at one-third the speed of trip element 16, thus sprocket 86 with siX notches, including the large notch 88, completes a complete revolution for every three revolutions of the gear 336. Therefore, with th sample speed of trip element 37 being one-tenth the speed of trip element 16, it will complete a full revolution for each full revolution of sprocket 86. When initially setting the timing device during assembly the microswitches 7t and 3t? should each be open as shown in FIGS. 3a and 5a respectively. After the completion of a timing operation, the motor lil may be energized by the power source 8% by closing the switch 96 so as to rotate gear 36 and the trip element 16. When the tripelements l6 and 17 are returned to their preset or initial position, both microswitches 7d and 32 will open to break the power circuit and stop the motor 1d.

When providing a timing device with a reset circuit as above described, the step 32in trip element 15 should gradually slant outwardly towards the trip element p eriphery so as to lift the trip element follower projection 62 out of notch 13 in trip element 1'7. Also, the notch 18 in trip element 17 should be sufiiciently wide as to prevent the trip element 1'7 from engaging the trip element follower Zii before the latter is lifted out of the to the trip element follower means.

ti notch 18, since such engagement maydamage the timing device.

The timing mechanism of the present invention provides numerous advantages over the timers now in use and could be easily adapted to function within many electrical systems where multiple timed switch closures and reliability are desired. By varying the input speed and/ or the gear ratios the maximum operating time may be varied from a few seconds to days with the end time resolution being in the order of four-tenths percent of the total time setting.

As various changes may be made in the form, construction and arrangement of the parts herein without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A device of the character described comprising in combination a' constant speed driving means having a rotatable output shaft extending therefrom, trip element means secured to said shaft, additional trip element means positioned intermediate the first mentioned trip ele ment means and said driving means, means adapted to be driven by said driving means for rotating said additional trip element means in a direction opposite to and at a soced less than said firstmentioned trip element means, switch means disposed adjacent to both of said trip element means, means operatively associated with both of said trip element means for actuating said switch means when both of said trip element means are rotated to have a predetermined positional relationship with each other, and means operatively associated with said additional trip element means for initially positioning the latter.

2. A timing device comprising in combination a contoured pair of oppositely rotating means, drive means for rotating said rotating means at dilierent speeds, a plurality of switch means disposed adjacent to said rotating means, actuating means operatively associated with said rotating means and said switch means for sequentially actuating said switch means in response to predetermined contour alignments between said pair of rotating means with each other and with said actuating means, and means operatively associated with a portion of said drive means for initially position ng one of said rotating means.

3. A timing device of the character described comprising in combination a constant speed drive means having speed reduction means and a rotatable shaft operatively associated therewith, trip element means attached to said shaft having an inwardly disposed notch means in a portion of the peripheral surface thereof, gear means secured to said shaft, a diiierential gearing assembly disposed about said shaft intermediate said trip element means and said gear means and rotated by said gear means, said gearing assembly being provided with bearing means for free rotation on said shaft, additional trip element means having a slot in the peripheral surface thereof and rotatably positioned on said shaft adjacent to said first mentioned trip element means and adapte to be rotated by said gearing assembly in a direction opposite to the first mentioned trip element means, trip element follower means operatively associated with both of said trip element means, switch means positioned adjacent to said trip element follower means and adapted.

to'be actuatcd'by said trip element follower means when the slot and notch means of both trip element means are rota-ted into alignment with the trip element follower means and receive the latter, and dial means operatively attached to the differential gearing assembly for initially positioning the additional trip element means with respect 4. The device claimed in claim 3 means in the first mentioned trip element means comprises a plurality of progressively deepening stepped portions wherein the notch with each stepped portion being of predetermined length, and wherein said switch means comprises a plurality of microswitches adapted to be sequentially actuated by the trip element follower means as the latter sequentially engages the stepped portions.

5. The device claimed in claim 4 wherein the trip element follower means comprises a main body portion pivotally mounted on a shaft and includes a lateral projection adapted to engage the slot and the stepped portions, a spring means is secured to the body portion for continuously urging the main body portion to pivot and move the projection into the slot and stepped portions, and a pair of microswitch spring loaded actuators is secured to the main body portion.

6. The device claimed in claim 3 wherein said dial means comprises a dial shaft having gear means, a rotatable dial having a timing scale indicated on a surface thereof and aflixed to said shaft, spring loaded detent means is provided on said shaft intermediate said dial and the gear means on the dial shaft for maintaining the dial in a selected timing position, and additional gear means is provided operatively intermediate the gear means on the dial shaft and the differential gearing assembly, the difierential gearing assembly includes planetary gearing which permits the dial means to initially rotate the additional trip element means in either direction while leaving the notched trip element means in a stationary position, and wherein the detent means is adapted to normally secure the palentary gearing from rotation about said rotatable shaft.

7. The device claimed in claim 3 including reset means for returning both trip element means to an initial preselected position, said reset means comprising a further trip element means having a notch therein and secured to the shaft, a microswitch having an actuator adapted to engage the notch of said further trip element means, pin means secured to a gear in the diiferential gearing assembly, a notched sprocket adapted to be rotated by said pin means, a second microswitch having an actuator adapted to engage a notch in said sprocket, and means adapted to effect rotation of said further trip element means and said sprocket until the actuators of each microswitch simultaneously engage the trip element notch and said sprocket notch.

8. A timing apparatus of the character described comprising in combination a housing having a plurality of timing devices dispcsed therein, each device including a pair of counter-rotating means, one of which rotates at a speed slower than the other, switch means operatively associated with each pair of counter-rotating means and adpated to be actuated thereby, means common to said devices for initially positioning one of said counterrotating means of each device with respect to the other counter-rotating means of the same device, and circuit means interconnecting the switch means of each device, whereby actuation of switch means in one of said devices actua-tes said circuit means.

References Qited in the file of this patent UNETED STATES PATENTS 2,477,953 Berthiez Aug. 2, 1949 2,975,612 Everard Mar. 21, 1961 3,001,036 Everard Sept. 19, 1961 FOREIGN PATENTS 916,883 France Aug. 26, 194-6

Claims

8. A TIMING APPARATUS OF THE CHARACTER DESCRIBED COMPRISING IN COMBINATION A HOUSING HAVING A PLURALITY OF TIMING DEVICES DISPOSED THEREIN, EACH DEVICE INCLUDING A PAIR OF COUNTER-ROTATING MEANS, ONE OF WHICH ROTATES AT A SPEED SLOWER THAN THE OTHER, SWITCH MEANS OPERATIVELY ASSOCIATED WITH EACH PAIR OF COUNTER-ROTATING MEANS AND ADAPTED TO BE ACTUATED THEREBY, MEANS COMMON TO SAID DEVICES FOR INITIALLY POSITIONING ONE OF SAID COUNTER-