Am-pm indicator for 24 hour clock
United States Patent Boyles [54] AM-PM INDICATOR FOR 24 HOUR CLOCK {75] Inventor: Robert L. Boyles, Wayland. Mass.  
 [73] Assignee: General Electric Company,  
 Bridgeport, Conn.  
 [22] Filed: May 28. I974 {2 [1 App]. No.: 473,769  
 (52) U.S. Cl. 58/125 C; 58/127 R [5H Int. Cl G04b 19/02; G041) l9/O6 [58] Field of Search 58/4 R. 6 R, I25 C, I26 E, 58/l27 R [56] References Cited UNITED STATES PATENTS 2.459.107 1/1949 Johnson 58119 Apr. 8, 1975 1601073 9/l97l Terada 58/6 3.823.552 7/l974 Boyles Sit/I25 C Primary E.\&#39;aml&#39;nerEdith Simmons .lackmon Attorney, Agent, or Firm-Leonard J. Platt; George R. Powers; John F. Cullen [57] ABSTRACT An AM-PM indicator for a digital clock wherein the indicator is positioned to the left of an hours drum and a gcneva driver is integrally formed with the hours drum for moving a shutter to indicate AM or PM. A geneva gear having a cam integrally formed therewith is positioned between the geneva driver and the shutter for moving the shutter to an AM or PM position.  
 6 Claims, 5 Drawing Figures PATENTEBAPR ms 3,875,740  
 SHEEIEQEZ AM-PM INDICATOR FOR 24 HOUR CLOCK BACKGROUND OF THE INVENTION This invention relates to an AM-PM indicator for a digital clock, and more particularly. to a unique shutter mechanism which is actuated by an hours drum for indicating AM or PM.  
  In my co-pending application (GD-4474) Ser. No. 339,213 which is now U.S. Pat. No. 3,823,552, filed Mar. 8, 1973. and assigned to the same assignee as the present invention, there is disclosed a digital clock wherein hours, tens of minutes, and minutes numerals are positioned on drums or wheels which are rotated by an electric motor in order to bring successive numerals into position behind a viewing window. The drums or wheels are positioned between two support plates which are arranged generally parallel to each other, and a geneva mechanism is positioned at the left of the numerals for driving an hours drum. The present invention is concerned with such a digital clock, and more particularly, to an AM-PM indicator for such a clock.  
  Accordingly it is a primary object of my invention to provide an improved AM-PM indicator mechanism for a digital clock having relatively few parts which may be readily manufactured, and it is also an object of my invention to provide an AM-PM indicator mechanism which may be readily and uniquely combined with a digital clock of the type disclosed in the above mentioned co-pending application without increasing the overall size of the clock.  
 SUMMARY OF THE INVENTION In accordance with one of the aspects of this invention, a digital clock includes a support plate and a rotatable hours drum positioned adjacent to the support plate. The hours drum is rotated as a function of time and includes suitable indicia for visually displaying numerals from one to twelve. My improved AM-PM indicator is uniquely constructed to be actuated by the hours drum and is positioned generally within the space between the hours drum and the support plate. In order to achieve this, a geneva driver lug is integrally formed on the hours drum and extends outwardly from the drum for driving a geneva gear. The geneva gear includes an integrally formed cam for moving a shutter to indicate AM or PM. The integrally formed geneva gear and cam are rotatably mounted on the support plate between the support plate and the hours drum, and the shutter is pivotally mounted on the support plate adjacent to the cam for actuation by the cam. The cam is shaped so that the position of the shutter is changed each time the numerals of the hours drum change from the l 1 o&#39;clock to the l2 o&#39;clock position. In this manner, at noon when the numerals change from the l 1 oclock to the 12 oclock position. the cam moves the shutter to its PM position and the cam holds the shutter in its PM position through all of the consecutive number changes of the hours drum until midnight is approached. At that time, when the numbers of the hours drum change from the 11 oclock to the 12 oclock position, the cam moves the shutter to indicate AM.  
  With this unique simplified construction, the shutter and the integrally formed geneva gear and cam are readily located within existing space between the hours drum and a support plate without increasing the space requirements of the clock.  
  It can also be appreciated that relatively few parts are required for achieving my unique AM-PM indicator. All that is required is the addition of an integrally formed geneva gear and cam and an elongated shutter member. The geneva driver lug may be integrally formed with the hours drum at the same time that the hours drum is being molded. Thus, a very compact, exceedingly simple, and readily manufactured AM-PM indicator for a digital clock has been achieved.  
 BRIEF DESCRIPTION OF THE DRAWINGS Other objects and attendant advantages of the invention will be apparent from the following description taken in connection with the accompanying drawing in which:  
  FIG. 1 is a front perspective view of a digital clock which includes my improved AM-PM indicator mechanism;  
  FIG. 2 is a cross-sectional view of the clock illustrated in FIG. 1; taken substantially on the plane of 2:2 of FIG. 1;  
  FIG. 3 is a fragmentary cross-sectional view of the clock of FIG. 1 including my improved AM-PM indicator mechanism taken substantially on the plane of 3:3 of FIG. 2&#39;,  
  FIG. 4 is an enlarged perspective view of the integrally formed geneva gear and cam for actuating the shutter of my improved AM-PM indicator mechanism; and  
  FIG. 5 is a fragmentary exploded perspective view of the clock illustrated in FIG. I, showing the components of my improved AM-PM indicator mechanism.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing and first particularly to FIGS. 1 and 2, there is shown a digital clock which includes my improved AM-PM indicator mechanism. As shown, the digital clock includes three sets of pages 2, 4, and 6, for minutes. tens of minutes, and hours. respectively.  
  The digital clock may be driven by a conventional self-starting synchronous motor 8. and as shown more particularly in FIGS. 1 and 5, the minutes and hours numerals may be printed or otherwise formed on both sides of pages so that the relatively large numerals may be presented in a clock which is relatively small. With particular regard to the hours display indicator 6, l2 numerals are required for the hours display, and as shown in FIG. 5, this is accomplished by using six panels 8, 10, l2, l4, l6, and 18, which are pivotally mounted on flanges 20 and 22 of an hours drum 24.  
  Two support plates 26 and 28 are arranged generally parallel to each other for supporting the hours drum 24, a tens of minutes drum 30, and a minutes drum 32. A geneva gear mechanism 34 is located at the left of the numerals, as shown more particularly in FIG. 2, for driving the tens ofminutes drum 30 and the hours drum 24. As shown, a geneva driver cam 36 is arranged in engagement with a geneva gear 38 that is integrally formed with the flange 20 of the hours drum for driving the hours drum one increment each hour. Since numerals are formed on both sides of the pages 8, l0, 12, 14, I6, and 18, it can be appreciated that the geneva driver mechanism for the hours drum rotates the hours drum at the rate of two complete revolutions every l2 hours. and naturally, four revolutions every 24 hours.  
  The mechanism for flipping the pages 8, 10, 12, 14, I6, and 18 to display numerals which are formed on both sides of the hours pages, is uniquely incorporated with support plate 26. As shown more particularly in FIG. 5, a generally circular skirt member 40 is integrally formed with the plate 26 and extends outwardly to the right in order to flip the pages. As illustrated, the skirt 40 does not extend 360 but is formed with a gap or cut-out portion 42 of approximately 30 for tipping and flipping the display pages 8, 10, 12, 14, 16, and 18.  
  With this construction, as the drum 24 is rotated and one of the pages reaches the cut-out portion 42 of the skirt, it is not confined by the skirt and the leading portion of the page moves outwardly beyond the skirt. Thus. as the page moves through the gap or cut-out portion of the skirt, it abuts a lower edge cam portion 44 of the skirt which flips the page to display a new numeral. It can be appreciated that after the page has been flipped to display a numeral which had been posi tioned on the back side of the page, the skirt 40 will hold the page in its desired position until it again reaches the gap 42 in the skirt.  
  As shown more particularly in FIG. 1, a suitable plastic lens plate 46 may be positioned in front of the numbers drums for providing a cover for the drums, for suitably spacing the plates 26 and 28, and for holding a lamp 48 to illuminate the numerals.  
  The details of the mechanism for supporting and driving the hours drum 24 do not form a part of this invention and are described and illustrated in greater detail in my co-pending application (6D-4474) Ser. No. 339,213, filed Mar. 8, I973, and assigned to the same assignee as the present invention. However, in accordance with the instant invention, the hours drum 24 is utilized for driving my improved AM-PM indicator and the support plate 26 is utilized for uniquely supporting and guiding my improved AM-PM indicator.  
 AM-PM IN DICATOR According to this invention, there is combined with the aforedescribed digital clock elements, an AM-PM indicator mechanism which is uniquely positioned within the space between the left side of the hours drum 24 and the support plate 26. As shown more particularly in FIGS. 2, 3, and 5, the principal component of the AM-PM indicator is a shutter 60. As illustrated, the shutter 60 includes a lever 62 which may be formed of an elongated piece of sheet metal which is pivotally mounted on the inside ofthe support plate by means of a pivot 64. The shutter lever 62 extends generally forwardly and upwardly above an enlarged central aperture 66 which is provided in the support plate, and as illustrated in FIGS. 3 and 5, the side and front wall portion of the support plate 26 is formed to include an aperture 66 for receiving a forward portion 68 of the shutter lever 62.  
  The shutter 60 also includes a flag-like element 70 which is located at its forward portion. In the preferred embodiment illustrated. the flag 70 is constructed as a separate element so that it may be readily connected to the shutter lever 62 by means ofa pin and slot connection 72, and 74. However, it can be appreciated that the shutter 60 including its flag 70 could be formed as a single member.  
  As illustrated more particularly in FIG. 5 and FIG. 3, it can be seen that the skirt portion 40 of the support plate which is utilized for flipping the pages of the hours drum 24, may be provided with a generally flat, inclined front surface 78 for forming a suitable shelf guiding surface for the movable flag member 70.  
  With the construction thus far described, it can be appreciated that the shutter 60, 62, 70, should be retained in one position during the AM hours and in another position during the PM hours in order to appropriately display AM and PM. In order to achieve this, a unique geneva gear and cam mechanism 80 is provided for holding the shutter 60 in an upper position during the PM hours and for holding the shutter 60 in a lower position during the AM hours. A geneva driver lug 82 is integrally formed with the flange 20 of the hours drum 24 for driving a geneva gear 81 one increment during each complete rotation of the hours drum or one increment every 6 hours. Thus, as shown more particularly in FIG. 4, geneva gear 81 is shaped to include four lobes 84, 86, 88, and 90, so that it may be rotated four increments during a 24 hour period. Since it is only necessary to move the shutter to two different positions during a 24 hour period, a cam 94 which is integrally formed with the geneva gear 80, is provided with an appropriate cam surface 104 for holding the shutter in only two positions. As illustrated in FIG. 3, the integrally formed cam and geneva gear 81-94 is rotatably mounted on the inside of the support plate 26 by means ofa bearing 100, and the relatively thin shutter lever 62 is sandwiched between the support plate 26 and the lobes of the geneva gear so that a cam surface 102 of the shutter may readily ride on the surface 104 of cam 94.  
  In operation, as the hours drum 24 is moved from an 11 AM position to a 12 noon position, the geneva driver lug 82 of the hours drum rotates the four lobe geneva gear 81 one increment. During this incremental movement of the geneva gear 81, the cam 94 which is integrally formed with the gear will move one increment to lift the shutter 60 and its flag to indicate PM. The next movement of the geneva gear 81 will occur when the hours drum is moved from 5 to a 6 oclock position, however, during this movement the cam surface 104 will continue to hold the shutter 60 in its raised position. When the numerals of the hours drum are next moved from an 11 position to a 12 midnight position, the geneva gear 81 will be rotated its next increment and the cam 94 which is integrally formed with the geneva gear will lower the shutter 60 to indicate AM. The next movement of the geneva gear will occur when the hours drum is moved to its next 6 position, and naturally during this movement, the shutter will be retained in the lower AM position.  
  In accordance with a further aspect of my invention, the shutter 60 is uniquely incorporated with AM-PM indicia so that a relatively small shutter may be utilized for providing a relatively large AM-PM display. In order to achieve this, the left portion of the lens 46 is made opaque or is provided with a black background member in the vicinity of the shutter 70 and the letters PM are printed in white on the black background. The letter P includes a generally vertical elongated bar 101 at its left, two generally horizontal bars 103 and 105 extending to the right from the vertical bar 101 and a relatively short vertical bar 107 connecting the right end portions of the horizontal bars 103 and 105. In order to form the letter A, a generally vertical transparent bar 106 is positioned below and in line with the generally vertical short bar 107 which is utilized for forming the letter P and extends downwardly from the short bar. The flag 70 of the shutter is positioned behind the bar 106, and as shown more particularly in FIG. 5, it includes a colored portion 108 which is the same color as the background of the lens and another colored portion 110 which is the same color as the bars of the letters to be displayed. With this arrangement, it can be appreciated that when the darkened portion 108 of the shutter is positioned in front of the bar 106, the letter P will be displayed and when the shutter is lowered to position the lighter colored portion 110 in front of the bar, the letter A will be displayed.  
  In the embodiment illustrated. the shutter lever 62 is positioned above the cam surface 104 and the force of gravity may be utilized for holding the shutter lever on the cam 94 for allowing the shutter lever to move downwardly under the force of gravity when the hours drum is moved from the 11 oclock position to the 12 oclock position at midnight to display the letters AM. In order to insure more positive movement of the lever 60 when it is moved toward the axis of the hours drum, a spring may be provided for urging the lever toward the cam 94. As shown more particularly in FIGS. 3 and 5, this may be achieved with the use of a relatively thin wire spring member 112 which may be shaped as illustrated. In order to suitably hold the ends of the spring, an aperture 120 may be formed in an end portion of the shutter lever 62 and a lug 122 may be integrally formed with the support plate 26 for suitably holding the upper end of the spring. With this arrangement, the lever 60 is resiliently urged in a counterclockwise direction about pivot 64, as shown in FIG. 3.  
  In view of the foregoing, it can be appreciated that my improved AM-PM indicator mechanism may be formed of relatively few parts which may be readily connected to each other and incorporated in a digital clock of the type disclosed in my above mentioned copending application without increasing the overall space requirements of the clock. Many of the components may be simply integrally formed with other parts ofthe digital clock while the overall clock is being manufactured. For example. the geneva driver lug 82 may be integrally formed on the hours drum 24 at the same time that the flange and the geneva gear 38 of the hours drum are being formed. In regard to the support plate 26, the lug 122 for holding the spring 112, apertures 130 and 132 for receiving the geneva gear and shutter bearings. aperture 66 for receiving the forward end of the shutter lever 62, and the inclined shelf 78, may all be formed at the same time that the support plate 26 is being molded. Thus. an exceedingly simple and reliable AM-PM indicator mechanism is achieved with the use of relatively few parts which may be readily connected to each other.  
 What I claim is;  
  I. An AM-PM indicator mechanism for a 24 hour digital clock comprising:  
 a. a support plate:  
 b. a rotatable hours drum positioned adjacent to said support plate. said hours drum having hours indicia 6 for visually displaying numerals from one to twelve; c. a geneva driver means integrally formed on said hours drum extending outwardly from said hours drum and rotatable with said hours drum as a function of time;  
 d. a geneva gear mounted for rotation on said support plate adjacent to said hours drum. said geneva gear being positioned for cooperation with the driver means so that the geneva gear is rotated each time the hours drum and the geneva driver means on the hours drum advances from an ll oclock position to a l2 oclock position;  
 e. a cam integrally formed with said geneva gear;  
 f. an AM-PM indicator shutter positioned for actuation by the cam that is integrally formed with the geneva gear, said cam being shaped so that the position of the shutter is changed each time the numerals of the hours drum change from 11 to 12.  
  2. An AM-PM indicator mechanism as defined in claim 1 wherein the AM-PM indicator shutter is sandwiched between the geneva gear and the support plate in order to suitably confine the shutter for movement on the cam which is integrally formed with the geneva gear.  
  3. An AM-PM indicator mechanism as defined in claim 1 wherein a spring is positioned between the support plate and the shutter for urging the shutter downwardly toward the cam which is integrally formed with the geneva gear.  
  4. An AM-PM indicator mechanism as defined in claim 1 wherein said shutter comprises:  
 a. an elongated shutter lever formed of a relatively thin piece of sheet metal, said shutter lever extending forwardly above the cam which is formed with the geneva gear and through a slot which is formed in the support plate and being pivotally mounted to a rear portion of said support plate; and,  
 b. a generally flat indicator member connected to said lever for movement therewith, said indicator member being arranged generally perpendicular to the lever so that it may be viewed at the front of the clock.  
  5. An AM-PM indicator mechanism as defined in claim 4 wherein a skirt is formed on said support plate for partially surrounding the hours drum, and the skirt includes an inclined, generally flat surface for suitably guiding and holding the generally flat indicator member.  
  6. An AM-PM indicator mechanism for a 24 hour digital clock comprising:  
 a. a support plate;  
 b. a rotatable hours drum positioned adjacent to said support plate. said hours drum having hours indicia for visually displaying numerals from one to twelve;  
 c. a geneva driver lug integrally formed on said hours drum extending outwardly from said hours drum and rotatable with said hours drum at two revolutions every 12 hours;  
 d. a four lobe geneva gear mounted for rotation on said support plate adjacent to said hours drum, said geneva gear being positioned generally above the geneva driver lug for cooperation with the driver lug so that the geneva gear is rotated each time the hours drum and the geneva driver lug on the hours drum advances from an 1 1 oclock position to a 12 o&#39;clock position and from a 5 oclock position to a 6 o&#39;clock position;  
 e. a cam integrally formed with said geneva gear and positioned between the geneva gear and the support plate;  
 earn from a 5 to a 6 oclock position, is lowered during the next movement of the cam to a l2 midnight position, and is retained in the lowered AM position during the next cam movement from a 5 to a 6 position.