Digital timer and method of operating such
REFERENCE TO RELATED APPLICATION 
     This application is a division of parent application Ser. No. 464,255 filed Apr. 25, 1974, which is specifically incorporated by reference herein and which issued into U.S. Pat. No. 3,898,792 on Aug. 12, 1975. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention is related in general to digital timers and in particular to means for effecting operation of the digital timer. 
     In the past, various types of digital timers were provided with counting or time indicating wheels or drums which were drivingly interconnected by various means, such as a geneva or mutilated gear, to indicate at least hours, tens-of-minutes, and minutes viewable through windows or the like provided at predetermined positions with respect to the drums. In many of the past digital timers, a synchronous timing motor was drivingly interconnected with the minute drum (or a second indicating drum) to effect the digital time indicating function of the drums. In addition, various means for manually resetting the drums to indicate a selected digital time were also provided in some of the past digital times. The past digital timers were of various constructions and sizes, and one criteria was to miniaturize or make the digital timer as small as possible since, in many installations therefor, space was at a premium. One of the disadvantageous or undesirable features of at least some of the past digital timers was that if the operator or user did not make the exact correct time setting of the time indicating drums, the digits thereon would not index into their respective digital time viewing windows accurately. Another disadvantageous or undesirable feature of some of the past digital timers was that due to gear backlash in the gear train or the like for driving the time indicating drums, the operator or user may have set the digital time accurately but lag in the gear train produced inaccurate positioning of the digits on the time indicating drum at the respective windows thereof. Yet another disadvantageous or undesirable feature of some of the past digital timers was that they were inordinately large with respect to the relatively small operating spaces provided therefor in some of the current miniaturized assembly or manufacturing applications for such digital timers. 
     SUMMARY OF THE INVENTION 
     Among the several objects of the present invention may be noted the provision of a digital timer and a method of operating a digital timer which overcome the aforementioned disadvantageous or undesirable features, as well as others, with respect to the past digital timers; the provision of such digital timer and method in which a digital time indicating means is generally maintained against slippage from a respective time indicating position thereof at a selected location in the timer by means associated with means for driving the indicating means; the provision of such digital timer and method which provide for automatically releasing the drive of the driving means for the digital timer upon the occurrence of a certain or preselected condition; the provision of such digital timer and method which not only maintains the digital time indicating means against slippage from the time indicating positions thereof at the selected location in the timer but also at least momentarily isolates the drive of the digital timer from the digital time indicating means thereof upon the occurrence of a preselected condition; and the provision of such digital timer which is simplistic in design, economically manufactured, and easily assembled. 
     In general, a digital timer in one form of the invention has means operable generally for indicating digital time, and means is provided for actuating the indicating means to effect the digital time indicating operation thereof. A drive train for connection with the actuating means includes means adapted to be intermittently rotatable, means for driving the rotatable means in a predetermined time sequence to effect the intermittent rotation thereof, and means for translating the intermittent rotation of the rotatable means to the actuating means. 
     Also in general and in one form of the invention, a digital timer has means operable generally for indicating digital time and means for actuating the indicating means to effect the time indicating operation thereof. Means is provided for driving the actuating means, and means is disposed between the actuating means and the driving means for transmitting the drive thereof to the actuating means and for automatically releasing the drive of the driving means upon the occurrence of a preselected condition. 
     Further in general and in one form of the invention, a digital timer has means operable generally at a selected location in the timer for indicating digital time, and the digital timer also has a drive train. Means is driven by the driven train for actuating the indicating means toward digital time indicating positions at the selected location. Means is associated with a part of the drive train and the actuating means for generally maintaining the indicating means against slippage from the respective digital time indicating positions thereof at the selected location and for automatically releasing the drive of the drive train upon the occurrence of a preselected condition. 
     Still in general, a method is provided in one form of the invention for operating a digital timer having a drive train and at least one means operable generally for indicating digital time at a selected location in the timer. This method comprises the steps of: actuating the drive train and effecting the digital time indicating operation of the at least one indicating means; and releasing automatically the drive of the drive train upon the occurrence of a mechanical condition with respect to the at least one indicating means inhibiting the digital time indicating operation thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevational view of time indicating drums for a digital timer in one form of the invention and such digital timer teaching principles of a method of operating such also in one form of the invention; 
     FIG. 2 is a front elevational view of a drive train and resetting train of the digital timer of FIG. 1; 
     FIG. 3 is a plan view of the drive train and the resetting train of FIG. 2; 
     FIGS. 4, 4a and 4b are respectively enlarged fragmentary views taken from FIG. 3 and illustrating co-action between gearing of the drive train for effecting intermittent rotation of the time indicating drums; 
     FIG. 5 is a partial perspective view illustrating a coupling for interconnecting the time indicating drums of FIG. 1; 
     FIG. 6 is a sectional view taken along line 6--6 of FIG. 2; and 
     FIG. 7 is a perspective view of a clutch device of FIG. 2. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     The exemplifications set out herein illustrate the preferred embodiments of the invention in one form thereof, and such exemplifications are not to be construed as limiting to in any manner to the scope of the invention. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings in general, there is illustrated in one form of the invention a digital timer 1 having means, such as a plurality of digital time indicating drums 3, 5, 7, for indicating digital time (FIG. 1). Means, such as at least a face or crown gear 9 or the like, for actuating or effecting the time indicating operation of drums 3, 5, 7 is connected therewith. A drive or gear train, indicated at 11, is actuated for intermittently driving the operation effecting means or gear 9 and for conjointly driving in idling relation a resetting or gear train, indicated generally at 13, which is manually operable for driving drums 3, 5, 7 through gear 9 to selected digital time indicating positions (FIGS. 2 and 3). Drive train 11 is released from gear 9 upon the manual operation of resetting train 13 for driving drums 3, 5, 7 through the gear to the selected digital time indicating positions thereof independently of the drive train. 
     More particularly and with specific reference to FIGS. 1-3, a synchronous or timing motor 15 of a type well known in the art is provided for actuating drive train 11 at a predetermined rate of speed. Typically this type of synchronous motor will operate at a speed of approximately one to three revolutions per minute. Drive train 11 includes at least a drive shaft 17 which carriers a reduction gear 19 and an impulse gear segment 21, and a motor pinion 23 is drivingly engaged with the reduction gear while the impulse segment intermittently drives a mutilated geneva pinion or gear 25 in a predetermined time relation or sequence, as discussed in detail hereinafter. Of course, mutilated gear 25 comprises means adapted to be intermittently rotatable, and impulse gear segment 21 comprises means for driving the rotatable means or mutilated gear in a predetermined time sequence to effect the intermittent rotation thereof. 
     Resetting train 13 is provided with a time set gear 27 which drives a pinion gear 29 through an idler gear 31. A time set shaft 33 is adapted to be manually moved into rotatable driving engagement with time set gear 27 for manually actuating or operating resetting train 13 to effect the resetting of drums 3, 5, 7 to the selected time indicating positions, as discussed in greater detail hereinafter. Resetting train 13 is connected with gear 9 through a drive shaft 35 which carries pinion gear 29 adjacent the lower end thereof and another pinion or driven gear 37 is carried adjacent the upper end of the drive shaft in driving or meshing engagement with gear 9. Geneva pinion 25 of drive train 11 is mounted for relative rotation on drive shaft 35. 
     A clutch mechanism or device, indicated generally at 39, is interposed between driven gear 37 and drive and resetting trains 11, 13 so that the drive and resetting trains are mechanically interconnected generally in parallel relation. Resetting train 13 normally is idly driven by drive train 11 through clutch device 39; however, when the resetting train is manually driven by the driving engagement of reset shaft 33 with time set gear 27, as previously mentioned, the clutch device momentarily releases the drive of the drive train. It may be noted that clutch device 39 is also operable automatically to at least momentarily release the drive of drive train 11 in the event of the occurrence of a certain mechanical or preselected condition, such as for instance any malfunction of the component parts of digital timer 1 generally between the clutch device and drums 3, 5, 7 which might lock them or otherwise inhibit the digital time indicating operation or rotation thereof. Of course, the manual operation of resetting train 13 drives driven gear 37 through shaft 35, and in turn, the driven gear drives gear 9 to effect the resetting movement or rotation of time indicating drums 3, 5, 7 to selected digital time indicating positions, as discussed in detail hereinafter. In view of the above, it is apparent that pinion gear 37, shaft 35, and clutch device 39 generally comprise means for controlling the operation of indicating means 3, 5, 7 in response to the drive of drive train 11, and the clutch device generally comprises means for or translating the drive of the driving means or drive train to the indicating means and means for releasing automatically the drive of the drive train upon the resetting operation of the resetting train 13 or upon a mechanical malfunction in digital timer 1 so as to inhibit the time indicating operation of the indicating means, as previously mentioned. 
     Digital timer 1, as shown in FIG. 1, is provided with a rotatable member, such as a rod or shaft 41, and drums 3, 5, 7 are rotatably mounted on the rod and adapted to be driven or actuated thereby for indicating digital time. A support or housing, indicated generally at 43, is provided in which opposite end portions of rod 41 are rotatably received or mounted. Drum 3 is a minute wheel or counter and is adapted to carry numerals from 0 to 9; drum 5 is a tens-of-minute wheel or counter and is adapted to carry a dual set of numerals from 0-5; and drum 7 is an hour wheel or counter and is adapted to carry numerals from 1 to 12. Of course, the numerals on drums 3, 5, 7 are adapted to align with windows 44 provided in housing 43 as shown in phantom in FIG. 1. Drums 3, 5, 7 are rotatably mounted on rod 41, and drum 3 is secured by suitable means (not shown) to the rod for conjoint rotation therewith. Drums 3, 5 are respectively provided with impulse gear segments 45, 45a which may be integrally formed therewith, and drums 5, 7 are respectively provided with ring gears 47, 47a disposed adjacent and generally opposite to impulse gear segments 45, 45a. Ring gears 47, 47a may also be integrally formed with drums 5, 7, respectively. A pair of like mutilated or geneva pinions or gears 49, 49a are rotatably mounted on shafts 51, 51a which are respectively secured to support 43 by suitable means (not shown) between drums 3, 5, and 5, 7. For the sake of brevity and clarity, only the mutilated pinion 49 for engagement with impulse gear segment 45 and ring gear 47 of drums 3, 5 is shown in greater detail in FIG. 5; however, the impulse gear segment, ring gear, and mutilated pinion disposed between drums 5, 7 are indicated by the subletter &#34;a&#34;. Impulse gear segments 45, 45a are provided with single recesses, 53, 53a  defined between adjacent half-tooth forms, and the recesses are adapted to mesh with or receive gear teeth 55, 55a of mutilated pinions 49, 49a. Gear teeth 57, 57a of mutilated pinions 49, 49a are adapted to mesh with or receive the teeth of ring gears 47, 47a. In this manner, conjoint rotation of drum 3 with rod 41 effects intermittent driving engagement of recess 53 in impulse gear segment 45 with a cooperating tooth 55 of mutilated pinion 49, and in turn, teeth 57 of the mutilated pinion mesh with teeth of ring gear 47 to intermittently drive or rotate drum 5 about rod 41. This intermittent rotation of drum 5 effects intermittent driving engagement of recess 53a in impulse gear segment 45a with a cooperating tooth 55a of mutilated pinion 49a, and in turn teeth 57a of the mutilated pinion intermittently mesh with teeth of ring gear 47a to intermittently drive or rotate drum 7 about rod 41 (as best seen in FIG. 1). It may be noted that the number of teeth on ring gears 47, 47a, mutilated pinions 49, 49a and the number of recesses 53, 53a on impulse gear segments 45, 45a may be selected to establish a predetermined time relation or sequence with respect to the relative driven rotation of drums 3, 5, 7. The coupling relation of mutilated pinions 49, 49a between drums 3, 5 and 5, 7 is described and shown in the Dec. 23, 1965 issue of Machine Design on page 125 thereof. Gear 9 is fixedly connected with rod 41 at the rightward end portion thereof, and if desired, other gearing or drives (not shown) may be taken off of the leftward end portion of the rod. Gear 9 on rod 41 is meshed with driven gear 37 thereby to translate the rotation of the driven gear into conjoint rotation of the rod. 
     Referring now to FIGS. 2, 6 and 7, clutch device 39 has a resilient member or spring 59, and a base or generally flat portion 61 of the spring is associated with or disposed in abutting engagement with the lower side of driven gear 37. An opening 63 is provided in base portion 61 through which drive shaft 35 is received in press-fit or other displacement preventing engagement so that spring 59 and driven gear 37 are conjointly rotatable. A depending spring or clutch arm 65 is integrally formed with base portion 61 and has a free end portion 67 which is resiliently urged into clutching or releasable engagement between at least one pair of adjacent teeth or opposite abutments 69 provided on geneva gear 25. It may be noted that the releasable engagement of clutch arm 65 with adjacent teeth or abutment means 69 on geneva gear 25 serves to positively maintain drums 3, 5, 7 in their respective digital time indicating positions by compensating for any backlash which may be created in the drive train 11 or resetting train 13. If desired, it is contemplated within the scope of the invention that another depending spring arm may be integrally formed on base portion 61 opposite spring arms 65 for releasable engagement with another pair of adjacent teeth or opposite abutments 69 of geneva gear 25 opposite to those with which spring arm 65 is engaged. 
     Referring now to the drawings in general and recapitulating at least in part, it may be noted from the foregoing discussion that digital timer 1 in one form of the invention has means, such as drums 3, 5, 7, operable generally at a selected location, such as windows 44, for indicating digital time (FIG. 1), and means, such as at least clutch 39 and geneva gear 25, is provided for intermittently driving the indicating means or drums toward digital time indicating positions at the selected location or windows (FIG. 2). The driving means includes means, such as resilient arm 65 of clutch 39, releasably engaged with another part, such as geneva gear 25, of the driving means for generally maintaining the drums against slippage from the respective digital time indicating positions thereof at the selected location (FIGS. 1 and 2). 
     More particularly, geneva gear 25, as best seen in FIGS. 2 and 6, is provided with a bore 71 therethrough, and the bore is rotatably received on drive shaft 35 so as to effect relative rotation between the geneva gear and the drive shaft. Opposite pairs of flats 73 are provided on the peripheral portion of geneva gear 25, and teeth 69, for indexing or abutting engagement with clutch arm 65, as previously mentioned, extend generally lengthwise of the geneva gear between adjacent pairs of flats 73. 
     Impulse gear segment 21 of drive train 11 is provided with a recess 75 in the peripheral portion 77 thereof between adjacent half-tooth forms for intermittent driving or meshing engagement with the teeth 69 of geneva gear 25, as illustrated in FIGS. 4, 4a and 4b. Adjacent pairs of teeth 69 on geneva gear 25 are adapted to engage peripheral portion 77 of impulse segment 21 so as to prevent rotation of the geneva gear with the impulse segment throughout a predetermined part of its rotation, as shown in FIG. 4. As the rotation of impulse gear segment 21 advances its recess 75, the recess engages a geneva gear tooth 69 to conjointly drive or rotate geneva gear 25 with the impulse segment through another predetermined part of its rotation, as shown in FIGS. 4a and 4b. Upon further rotation of impulse gear segment 21, recess 75 thereof is released from its driving engagement with geneva gear tooth 69 so that successive adjacent teeth 69 of geneva gear 25 are once again engaged with peripheral portion 77 of the impulse segment, as shown in FIG. 4b. Of course, upon successive revolutions of impulse gear segment 21, recess 75 thereof again drivingly engages tooth 69 of geneva gear 25 to effect further intermittent drive or rotation thereof, as previously described. It may be noted that the engagement of spring arm 65 of clutch device 39 with adjacent teeth 69 on geneva gear 25, as shown in FIGS. 2 and 6, effects conjoint intermittent rotation or driving of driven gear 37 with geneva gear 25. Of course, such intermittent rotation of driven gear 37 is translated by gear 9 meshed therewith into conjoint intermittent rotation of rod 41 for indexing or effecting intermittent rotation of drums 3, 5, 7 to advance the digital time indication thereof, as described hereinabove. The releasable engagement or connection of spring arm 65 of clutch device 39 with geneva gear 25 also transmits the intermittent movement thereof through drive shaft 35 to resetting train 13 so that it is normally idly driven by drive train 11. From the foregoing, it may be seen that timing motor 15 drives motor pinion 23 at a predetermined speed which is reduced by reduction gear 19 meshed therewith so that impulse gear 21 intermittently drives geneva gear 25 in a predetermined time relation or sequence which is transmitted through clutch device 35, gears 37 and 9, and rod 41 to drums 3, 5, 7, as previously mentioned. 
     Resetting train 13 is normally idly driven by drive train 11, as previously mentioned, wherein the intermittent drive of driven gear 37 is transmitted through shaft 35 to pinion gear 29 and therefrom through idler gear 31 to time setting gear 27, FIG. 2. In the event it is desirable to reset or move drums 3, 5, 7 to selected digital time indicating positions, time set shaft 33 is manually moved to a position in driving engagement with time set gear 27 and thereafter rotated with a force at least great enough to overcome the clutching engagement of clutch device 39 with geneva gear 25 of driven train 11. When this manual force is applied for time setting gear 27 to actuate or operate resetting train 13, rotation of the time setting gear 27 drives or rotates pinion gear 29 through idler gear 31 meshed therebetween. Driven gear 37 is conjointly rotated or driven with pinion gear 37 through drive shaft 35 connected therebetween, and since clutch device 39 is conjointly rotated with the driven gear, the spring arm 65 of the clutch device is indexed or moved over one of the teeth 69 of geneva gear 25 into releasable engagement with successive teeth 69 thereof. During the indexing rotation of clutch 39 on geneva gear 25, the engagement of successive teeth 69 of the geneva gear with peripheral portion 77 of impulse segment 21, as shown in FIGS. 4 and 4b for instance, obviates rotation of the geneva gear during the manual operation of resetting train 13. Of course, rotation of driven gear 37 is translated by gear 9 meshed therewith into conjoint rotation of rod 41 for rotatably driving drums 3, 5, 7 to the selected digital time indicating position. The releasable engagement of clutch device 39 with geneva gear 25 permits operation of resetting train 13 in both the forward and backward or opposite directions for resetting the digitally indicated time. 
     From the foregoing, it is now apparent that a novel digital timer 1 and a method of operating such have been provided meeting the objects and advantages set out hereinbefore, as well as others, and that changes may be made by those having ordinary skill in the art not only as to the precise arrangements, shapes, connections and details of the construction set forth herein but also with respect to the precise arrangements or order of the steps of the method without departing from the spirit of the invention or the scope thereof which is defined by the claims which follow.