Turbine clocks
United States Patent 3871167
A pendulum clock powered by a slow turning water turbine is disclosed, the clock comprising of a source of liquid (or any other agent, such as sand, air, or a subminiature electric motor that can turn the turbine) for supplying motive power, a pivotally mounted pendulum that oscillates at its own natural frequency. The oscillation being sustained by the cooperation of the said turbine. The pendulum thus affected causes a multifunction pawl to advance a "second" a "minute" and an "hour" spur gears synchronously and directly. The damping of the oscillations so as to prevent the pendulum from swinging too far is inherent in the system. The use of specially shaped Cams, Levers and Gear trains usually found in all clocks is thus eliminated.
US Patent References:
PENDULUM CLOCK
Kuhn - July 1970 - 3520125
TIMED MATERIAL-DISPENSING MECHANISM UTILIZING ACCUMULATION OF A LIQUID
Ruth - November 1971 - 3620415
PENDULUM CLOCK
Kuhn - July 1970 - 3520125
TIMED MATERIAL-DISPENSING MECHANISM UTILIZING ACCUMULATION OF A LIQUID
Ruth - November 1971 - 3620415
Application Number:
05/363174
Publication Date:
03/18/1975
Filing Date:
05/22/1973
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
368/134, 368/139, 368/203, 968/22
International Classes:
G04B1/26; G04B1/00; G04B45/00; G04B21/08
Field of Search:
58/2,33,129,130,144,14
Primary Examiner:
Jackmon, Edith Simmons
Claims:
What is claimed is
1. The turbine powered pendulum clock comprising, a turbine wheel, a source of liquid turning said turbine wheel, a hairspring means, a shaft fixedly attached to one end of said hairspring, a drum means rigidly attached to said wheel and housing said hairspring; the other end of said hairspring being in frictional contact with the inside of said drum but free to slip therein; a rod means having two ends and a member having at least two parallel members thereon; said parallel members engaging said shaft means to be driven thereby; clock hands, gear means for moving the said clock hands; a pawl means pivotally attached at a suitable point on the said rod means for transmitting motion from said rod means to the gear means for moving said hands, whereby said shaft is driven in circular motion by said liquid and said circular motion of said shaft means is transformed into oscillatory motion of said rod means via engagement of said shaft means with said two parallel members.
2. The clock of claim 1 further comprising of a frame plate, wherein said pawl means is a multifunction knife pawl having four blades rigidly connected thereto, said hands comprising a "second" hand, a "minute" hand and an "hour" hand, said gear means comprising at least three ratchet gears, one for each of said "second" hand, said "minute" hand, said "hour" hand whereby each of said ratchet gears is driven by a different one of said blades and at least one blade is in continuous frictional contact with and sliding upon the upper edge of said frame plate.
3. The clock of claim 2 wherein all of said gears are coaxially mounted.
4. The clock of claim 2 wherein all three of said gears are free to rotate independently of one another, the two of said gears each has all except at least one tooth root depth being equal, the other of said tooth root depth being deeper than all the rest, for synchronizing all three gears.
5. The clock of claim 1 further comprising a single frame plate wherein said shaft is rotatable in a single bearing in said plate.
6. The clock of claim 1 further comprising a micro switch for actuating a time announcing system, said switch being closed by each movement of said gear means.
1. The turbine powered pendulum clock comprising, a turbine wheel, a source of liquid turning said turbine wheel, a hairspring means, a shaft fixedly attached to one end of said hairspring, a drum means rigidly attached to said wheel and housing said hairspring; the other end of said hairspring being in frictional contact with the inside of said drum but free to slip therein; a rod means having two ends and a member having at least two parallel members thereon; said parallel members engaging said shaft means to be driven thereby; clock hands, gear means for moving the said clock hands; a pawl means pivotally attached at a suitable point on the said rod means for transmitting motion from said rod means to the gear means for moving said hands, whereby said shaft is driven in circular motion by said liquid and said circular motion of said shaft means is transformed into oscillatory motion of said rod means via engagement of said shaft means with said two parallel members.
2. The clock of claim 1 further comprising of a frame plate, wherein said pawl means is a multifunction knife pawl having four blades rigidly connected thereto, said hands comprising a "second" hand, a "minute" hand and an "hour" hand, said gear means comprising at least three ratchet gears, one for each of said "second" hand, said "minute" hand, said "hour" hand whereby each of said ratchet gears is driven by a different one of said blades and at least one blade is in continuous frictional contact with and sliding upon the upper edge of said frame plate.
3. The clock of claim 2 wherein all of said gears are coaxially mounted.
4. The clock of claim 2 wherein all three of said gears are free to rotate independently of one another, the two of said gears each has all except at least one tooth root depth being equal, the other of said tooth root depth being deeper than all the rest, for synchronizing all three gears.
5. The clock of claim 1 further comprising a single frame plate wherein said shaft is rotatable in a single bearing in said plate.
6. The clock of claim 1 further comprising a micro switch for actuating a time announcing system, said switch being closed by each movement of said gear means.
Description:
SUMMARY OF THE INVENTION
The purpose of the invention is to produce a clock described in the abstract, which is very simple in design and construction and can run on almost any agent which is capable to turn the turbine. Wide and sudden variations in the rotational speed of the turbine wheel shall have no effect whatsoever on the natural frequency of the oscillating body, so that a time piece with sufficient accuracy is attained.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in detail, with reference to the figures of the accompanying drawings, wherein:
FIG. 1 is a schematic rear view of the turbine wheel, with the cover 9a removed to show the spiral hairspring.
FIG. 2 is a side view of the turbine wheel, with the cups removed for clarity, the method of coupling a subminiature electric motor into turbine is shown, if and when used.
FIG. 3 is the front view of the "second" spur gear showing the deeper tooth root A.
FIG. 4 is the front view of the "minute" spur gear showing the deeper teeth roots B, C, D and E.
FIG. 5 is the front view of the frame plate.
FIG. 6 is the front and side views of the multifunction pawl.
FIG. 7 is the side view of one of the three similar detents.
FIG. 8 is the side view of the clock (only four cups on the turbine wheel are shown to avoid crowding).
FIG. 9 is the front view of the clock showing basic operations.
FIG. 10 is the front view of the complete clock.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The pendulum 3, comprising the bob 1 and the rod 2, is mounted free to swing by means of the pivot 4. Above the said pivot the pendulum rod 2 is rigidly attached to the U-shaped fork 5 with its fingers 5a and 5b, FIGS. 9 and 10. The said fingers cooperate with the link 7, which is rigidly attached to the shaft 6. On the said shaft is pivoted the disc 8, which is free to rotate, the said disc has several cups 10 rigidly attached to its rear surface, spaced equally around a circle whose diameter is somewhat smaller than the diameter of the disc 8, FIG. 1. The purpose of placing these cups at a smaller circle is to free the rim of the disc 8 for coupling to it a subminiature electric motor "M" of any kind, which draws no more than 50 to 100 microamps., if and when it is so desired, FIG. 2 (cups 10 on disc 8 not shown for clarity). Rigidly attached to the disc 8 is the drum 9, which contains the spiral hairspring 9b (the kind used with the balance wheel of the ordinary table clocks). The inside end of 9b is rigidly attached to the shaft 6, and the outside end presses against the circular inside wall of the drum 9, and is free to slip under tension. The member 9a is the cover of the said drum.
An outlet 11 for liquid is located directly above the center of a cup 10, the droplets of liquid flow down into the cups. The amount of torque to rotate the turbine wheel 8 is so small that the mere weight of a couple of drops of water in each cup 10 will create the necessary torque to turn the said wheel in the direction shown. This in itself saves liquid and results in a smaller reservoir. When the said drum starts to turn, the end 9c of the hairspring also turns together with the said drum due to purely frictional catch between the inside wall and the end 9c. This action tends to wind the said hairspring, until the amount of the stored energy in it exceeds the frictional force that holds the end 9c, when 9c will slip to a new random point balancing the stored energy. As the turbine wheel speeds up, then the end 9c will simply keep slipping continuously, but certain amount of energy stored in the said hairspring will always be present until used. It is clear that wide variations in the speed of the turbine can have very little or no affect on the average amount of the energy stored in the said hairspring. This stored energy creates a torque on shaft 6, the link 7 rigidly attached to the said shaft transmits this energy into the oscillating body. The link 7 is confined between the two fingers 5a and 5b of the fork 5, and when permitted, it can rotate in a circle whose diameter is somewhat larger than the distance between the two fingers 5a and 5b, FIG. 9. When link 7 cooperates with 5a it causes the pendulum to swing to the right. Contrary to other pendulums, this pendulum is self starting. When the pendulum swings to its maximum point to the right the link 7 escapes its contact with the finger 5a, and slams itself into the finger 5b. First, this action imparts damping to the said pendulum and then imparts enough pulse to swing the said pendulum in the opposite direction, thus sustaining the natural oscillations of the said pendulum. The link 7 repeats the same action with the finger 5b to complete the cycle. The damping of the pendulum prevents unnecessary high amplitudes.
Rigidly attached to the pendulum rod 2 is the bracket 12, with the shaft 12a rigidly attached to it. The multifinger advancing pawl 13 is pivoted on the shaft 12a and is free to turn.
The time keeping members comprise of three coaxially mounted spur gears. All the teeth in these three gears are evenly spaced around their pitch circles. The diameters of all three gears are equal, and the teeth are preferably saw-tooth in shape.
The gear 14, FIG. 3, is the "second" gear mounted rigidly on the arbor 22, which is free to turn in a single bearing 22b in frame plate 16. The number of teeth on the gear 14 depends on the natural frequency of the oscillating body, in this case the said pendulum, and is chosen so that the said gear will make exactly one turn per 60 seconds or 1 minute. In my working model I choose a pendulum with a natural frequency of 60 cycles per minute, which gave me a gear of 60 teeth. On the said gear, one tooth root depth marked A is three times as deep as the remaining 59 teeth root depths (in FIG. 3, teeth are shown in free hand and the count is not correct). The frame plate 16 has a V-shape cut on its upper edge with a depth S equal to the tooth root depth A on gear 14. The inclined surface S cooperates with pawl 13. The seat 21 carries all three detents 15, 18 and 20 which index the gears 14, 17 and 19 repectively to line up the teeth of said gears precisely at 12 o'clock point each time. All detents have a round catch f, which is designed to permit the said saw-tooth gears to be indexed CW or CCW when setting them manually, FIG. 7.
The "minute" gear 17, FIG. 4, has also 60 teeth and a cannon shaft coaxially mounted on the arbor 22 and is free to rotate. The said gear has four teeth root depths B, C, D and E located 90° apart and are twice as deep as the remaining 56 teeth root depths (teeth count in FIG. 4 is free hand and not correct). The "hour" gear 19 (side view shown in FIG. 8 only) has 48 teeth, with no special tooth root depths. It has a cannon shaft coaxially mounted on the cannon shaft of gear 17 and is free to rotate.
The multifunction advancing pawl 13, FIG. 6, has four blades a, b, c, and d. a is the sensing and advancing blade for the "second" gear 14, b is the master sensing and control blade which rides and slides upon the upper edge of the frame plate 16, FIG. 9. c is the sensing and advancing blade for the "minute" gear 17, and d is the advancing blade for the "hour" gear 19.
OPERATION OF THE GEARS
There are two ways to advance the gears 17 and 19 synchronously with the "second" gear 14.
1. By step construction of the diameters of gears 17 and 19 with respect to gear 14 and each other (not shown). This is the expensive way to do the job.
2. By bending the blades c and d up as shown in FIG. 6. This is easy, needs no special adjustment screws and is by far less expensive method. This is the method shown in FIGS. 8 and 9.
Assume the pendulum is swinging from left to right. The master sensing and control blade b on pawl 13 is held down by gravity (or a spring) and is sliding on the upper edge of the frame plate 16. When the tip of the blade b arrives at the V-cut it simply drops into the V-cut causing all remaining three blades to drop down. If tooth root depth A on gear 14 is not at 12 o'clock position, blade a will drop until its tip hits the root of a tooth on gear 14, which will determine how far down the pawl can drop. At this moment the blade c will be passing about 1 millimeter above the teeth of the gear 17 and can not advance said gear. The blade d will also pass a tooth high above the teeth of gear 19, also not able to advance gear 19. Then the only gear to be advanced one tooth at this time will be gear 14. The inclined surface S' in the frame plate 16 is machined at a correct angle to lift up the master control blade b to disengage the blade a from the tooth of the gear 14 immediately after one tooth is advanced. This insures that only one tooth will be advanced in each active stroke. When the pendulum swings from right to left no action takes place, it is the idle half cycle. Assume again that the pendulum swings from left to right, and this time the tooth root depth A on gear 14 is adjacent to the left of the tooth which is exactly at 12 o'clock position. The blades a and b both will drop one tooth deeper into the said A and said V cut, which will drop blade c further down just enough to engage the tooth on gear 17. This time the root of the tooth on gear 17 will determine how far down the pawl can drop. At this moment the blade d is passing just about 1 millimeter above the tooth of the "hour" gear 19 and can not advance the said gear. Therefore, only the "second" gear 14 and the "minute" gear 17 will both be advanced simultaneously one tooth each by the pawl 13.
When either one of the tooth root depths B, C, D or E on gear 17 line up with A adjacent to the left of the teeth positioned at 12 o'clock, then, the master control blade b will drop to the root of V-cut S and so will blades a, c and d, as a result of which all blades will engage a tooth on each gear and advance one tooth each simultaneously. The action of the inclined surface S' is common to all three gears. To sum up the result; once every 60 seconds one tooth equal to 1 minute is advanced on gear 17, and once every 15 minutes one tooth is advanced on gear 19.
The "second" hand 25 FIG. 8 and 10, is lined up with A on gear 14 and fastened rigidly into shaft 22. The "minute" hand 24 is lined up with either one of the four tooth root depths B, C, D, or E on gear 17 and fastened rigidily into the cannon shaft of the said gear. The 90° positions of said tooth root depths keep the hand 23 (which the "hour" hand and is fastened rigidly into the cannon shaft of the gear 19) to register commonly accepted positions of one-fourth, one-half, three-fourths and full hour.
The clock is synchronized manually at the start, after which the pawl 13 will maintain this synchronization for ever. It is also very simple to set this clock. Assume that the clock shows 5 minutes after 9 and we want to set it to 10 minutes past 3 o'clock. In ordinary clocks this requires that the minute hand be turned 360° six times, and 5 minutes more to set it at 10 minutes past 3. In my clock it is only necessary to turn the hour hand independently half way or 180° and set it on the 3 o'clock position just once, and turn the minute hand only 5 minutes more to show 10 after 3. It saves time.
In FIG. 10, the hour hand is set at 23/4 hour, the minute hand is set at 59 minutes and the second hand should be at 59 second position too, but I have intentionally put it at 55 second position so that to show the line up of the tooth root depths A and B clearly, just before the full 3 o'clock will be registered. The numerals of the clock are shown as circles 26, and the 12 o'clock numeral is not shown for sake of clarity.
In FIG. 10, the micro switch M.S. means actuated by the "hour" gear detent every 15 minutes, serves to initiate operation of a tape recorder or other announcing devices to announce the time. A control signal located upon the track of the tape serves to terminate operation of the tape movement.
The purpose of the invention is to produce a clock described in the abstract, which is very simple in design and construction and can run on almost any agent which is capable to turn the turbine. Wide and sudden variations in the rotational speed of the turbine wheel shall have no effect whatsoever on the natural frequency of the oscillating body, so that a time piece with sufficient accuracy is attained.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in detail, with reference to the figures of the accompanying drawings, wherein:
FIG. 1 is a schematic rear view of the turbine wheel, with the cover 9a removed to show the spiral hairspring.
FIG. 2 is a side view of the turbine wheel, with the cups removed for clarity, the method of coupling a subminiature electric motor into turbine is shown, if and when used.
FIG. 3 is the front view of the "second" spur gear showing the deeper tooth root A.
FIG. 4 is the front view of the "minute" spur gear showing the deeper teeth roots B, C, D and E.
FIG. 5 is the front view of the frame plate.
FIG. 6 is the front and side views of the multifunction pawl.
FIG. 7 is the side view of one of the three similar detents.
FIG. 8 is the side view of the clock (only four cups on the turbine wheel are shown to avoid crowding).
FIG. 9 is the front view of the clock showing basic operations.
FIG. 10 is the front view of the complete clock.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The pendulum 3, comprising the bob 1 and the rod 2, is mounted free to swing by means of the pivot 4. Above the said pivot the pendulum rod 2 is rigidly attached to the U-shaped fork 5 with its fingers 5a and 5b, FIGS. 9 and 10. The said fingers cooperate with the link 7, which is rigidly attached to the shaft 6. On the said shaft is pivoted the disc 8, which is free to rotate, the said disc has several cups 10 rigidly attached to its rear surface, spaced equally around a circle whose diameter is somewhat smaller than the diameter of the disc 8, FIG. 1. The purpose of placing these cups at a smaller circle is to free the rim of the disc 8 for coupling to it a subminiature electric motor "M" of any kind, which draws no more than 50 to 100 microamps., if and when it is so desired, FIG. 2 (cups 10 on disc 8 not shown for clarity). Rigidly attached to the disc 8 is the drum 9, which contains the spiral hairspring 9b (the kind used with the balance wheel of the ordinary table clocks). The inside end of 9b is rigidly attached to the shaft 6, and the outside end presses against the circular inside wall of the drum 9, and is free to slip under tension. The member 9a is the cover of the said drum.
An outlet 11 for liquid is located directly above the center of a cup 10, the droplets of liquid flow down into the cups. The amount of torque to rotate the turbine wheel 8 is so small that the mere weight of a couple of drops of water in each cup 10 will create the necessary torque to turn the said wheel in the direction shown. This in itself saves liquid and results in a smaller reservoir. When the said drum starts to turn, the end 9c of the hairspring also turns together with the said drum due to purely frictional catch between the inside wall and the end 9c. This action tends to wind the said hairspring, until the amount of the stored energy in it exceeds the frictional force that holds the end 9c, when 9c will slip to a new random point balancing the stored energy. As the turbine wheel speeds up, then the end 9c will simply keep slipping continuously, but certain amount of energy stored in the said hairspring will always be present until used. It is clear that wide variations in the speed of the turbine can have very little or no affect on the average amount of the energy stored in the said hairspring. This stored energy creates a torque on shaft 6, the link 7 rigidly attached to the said shaft transmits this energy into the oscillating body. The link 7 is confined between the two fingers 5a and 5b of the fork 5, and when permitted, it can rotate in a circle whose diameter is somewhat larger than the distance between the two fingers 5a and 5b, FIG. 9. When link 7 cooperates with 5a it causes the pendulum to swing to the right. Contrary to other pendulums, this pendulum is self starting. When the pendulum swings to its maximum point to the right the link 7 escapes its contact with the finger 5a, and slams itself into the finger 5b. First, this action imparts damping to the said pendulum and then imparts enough pulse to swing the said pendulum in the opposite direction, thus sustaining the natural oscillations of the said pendulum. The link 7 repeats the same action with the finger 5b to complete the cycle. The damping of the pendulum prevents unnecessary high amplitudes.
Rigidly attached to the pendulum rod 2 is the bracket 12, with the shaft 12a rigidly attached to it. The multifinger advancing pawl 13 is pivoted on the shaft 12a and is free to turn.
The time keeping members comprise of three coaxially mounted spur gears. All the teeth in these three gears are evenly spaced around their pitch circles. The diameters of all three gears are equal, and the teeth are preferably saw-tooth in shape.
The gear 14, FIG. 3, is the "second" gear mounted rigidly on the arbor 22, which is free to turn in a single bearing 22b in frame plate 16. The number of teeth on the gear 14 depends on the natural frequency of the oscillating body, in this case the said pendulum, and is chosen so that the said gear will make exactly one turn per 60 seconds or 1 minute. In my working model I choose a pendulum with a natural frequency of 60 cycles per minute, which gave me a gear of 60 teeth. On the said gear, one tooth root depth marked A is three times as deep as the remaining 59 teeth root depths (in FIG. 3, teeth are shown in free hand and the count is not correct). The frame plate 16 has a V-shape cut on its upper edge with a depth S equal to the tooth root depth A on gear 14. The inclined surface S cooperates with pawl 13. The seat 21 carries all three detents 15, 18 and 20 which index the gears 14, 17 and 19 repectively to line up the teeth of said gears precisely at 12 o'clock point each time. All detents have a round catch f, which is designed to permit the said saw-tooth gears to be indexed CW or CCW when setting them manually, FIG. 7.
The "minute" gear 17, FIG. 4, has also 60 teeth and a cannon shaft coaxially mounted on the arbor 22 and is free to rotate. The said gear has four teeth root depths B, C, D and E located 90° apart and are twice as deep as the remaining 56 teeth root depths (teeth count in FIG. 4 is free hand and not correct). The "hour" gear 19 (side view shown in FIG. 8 only) has 48 teeth, with no special tooth root depths. It has a cannon shaft coaxially mounted on the cannon shaft of gear 17 and is free to rotate.
The multifunction advancing pawl 13, FIG. 6, has four blades a, b, c, and d. a is the sensing and advancing blade for the "second" gear 14, b is the master sensing and control blade which rides and slides upon the upper edge of the frame plate 16, FIG. 9. c is the sensing and advancing blade for the "minute" gear 17, and d is the advancing blade for the "hour" gear 19.
OPERATION OF THE GEARS
There are two ways to advance the gears 17 and 19 synchronously with the "second" gear 14.
1. By step construction of the diameters of gears 17 and 19 with respect to gear 14 and each other (not shown). This is the expensive way to do the job.
2. By bending the blades c and d up as shown in FIG. 6. This is easy, needs no special adjustment screws and is by far less expensive method. This is the method shown in FIGS. 8 and 9.
Assume the pendulum is swinging from left to right. The master sensing and control blade b on pawl 13 is held down by gravity (or a spring) and is sliding on the upper edge of the frame plate 16. When the tip of the blade b arrives at the V-cut it simply drops into the V-cut causing all remaining three blades to drop down. If tooth root depth A on gear 14 is not at 12 o'clock position, blade a will drop until its tip hits the root of a tooth on gear 14, which will determine how far down the pawl can drop. At this moment the blade c will be passing about 1 millimeter above the teeth of the gear 17 and can not advance said gear. The blade d will also pass a tooth high above the teeth of gear 19, also not able to advance gear 19. Then the only gear to be advanced one tooth at this time will be gear 14. The inclined surface S' in the frame plate 16 is machined at a correct angle to lift up the master control blade b to disengage the blade a from the tooth of the gear 14 immediately after one tooth is advanced. This insures that only one tooth will be advanced in each active stroke. When the pendulum swings from right to left no action takes place, it is the idle half cycle. Assume again that the pendulum swings from left to right, and this time the tooth root depth A on gear 14 is adjacent to the left of the tooth which is exactly at 12 o'clock position. The blades a and b both will drop one tooth deeper into the said A and said V cut, which will drop blade c further down just enough to engage the tooth on gear 17. This time the root of the tooth on gear 17 will determine how far down the pawl can drop. At this moment the blade d is passing just about 1 millimeter above the tooth of the "hour" gear 19 and can not advance the said gear. Therefore, only the "second" gear 14 and the "minute" gear 17 will both be advanced simultaneously one tooth each by the pawl 13.
When either one of the tooth root depths B, C, D or E on gear 17 line up with A adjacent to the left of the teeth positioned at 12 o'clock, then, the master control blade b will drop to the root of V-cut S and so will blades a, c and d, as a result of which all blades will engage a tooth on each gear and advance one tooth each simultaneously. The action of the inclined surface S' is common to all three gears. To sum up the result; once every 60 seconds one tooth equal to 1 minute is advanced on gear 17, and once every 15 minutes one tooth is advanced on gear 19.
The "second" hand 25 FIG. 8 and 10, is lined up with A on gear 14 and fastened rigidly into shaft 22. The "minute" hand 24 is lined up with either one of the four tooth root depths B, C, D, or E on gear 17 and fastened rigidily into the cannon shaft of the said gear. The 90° positions of said tooth root depths keep the hand 23 (which the "hour" hand and is fastened rigidly into the cannon shaft of the gear 19) to register commonly accepted positions of one-fourth, one-half, three-fourths and full hour.
The clock is synchronized manually at the start, after which the pawl 13 will maintain this synchronization for ever. It is also very simple to set this clock. Assume that the clock shows 5 minutes after 9 and we want to set it to 10 minutes past 3 o'clock. In ordinary clocks this requires that the minute hand be turned 360° six times, and 5 minutes more to set it at 10 minutes past 3. In my clock it is only necessary to turn the hour hand independently half way or 180° and set it on the 3 o'clock position just once, and turn the minute hand only 5 minutes more to show 10 after 3. It saves time.
In FIG. 10, the hour hand is set at 23/4 hour, the minute hand is set at 59 minutes and the second hand should be at 59 second position too, but I have intentionally put it at 55 second position so that to show the line up of the tooth root depths A and B clearly, just before the full 3 o'clock will be registered. The numerals of the clock are shown as circles 26, and the 12 o'clock numeral is not shown for sake of clarity.
In FIG. 10, the micro switch M.S. means actuated by the "hour" gear detent every 15 minutes, serves to initiate operation of a tape recorder or other announcing devices to announce the time. A control signal located upon the track of the tape serves to terminate operation of the tape movement.