Field of Search:
BACKGROUND OF THE INVENTION
This invention relates to a pendulum clock powered by direct current, and more particularly, to a unique separate electromagnetic mechanism for driving a pendulum of a clock.
Most contemporary battery-operated clocks include a low power electronic timekeeping movement which is adequate for driving the hands of a clock, and while such a clock movement is entirely satisfactory for the functional purpose of timekeeping, the timekeeping motor or movement is not capable of driving a relatively large ornamental pendulum.
Old-fashioned swinging pendulum clocks wherein a pendulum is structurally integrated into the clock mechanism to perform a timekeeping function are still considered by the clock industry to be asthetically appealing to a significant number of people. Accordingly, some contemporary prior art pendulum clocks have the appearance and apparent external operation of an old-fashioned swinging pendulum clock, and yet the pendulum does not serve a timekeeping function. Most of these contemporary pendulum clocks have included a synchronous electric motor which utilizes the ordinary house wiring as a source of electric power, and all of these prior art simulated pendulum clocks have used the same motor that is used for timekeeping to provide the power to drive the pendulum. For example, in a prior U.S. Pat. No. 2,995,005 to Boyles, dated Aug. 8, 1961 and assigned to the same assignee as the present invention, there is disclosed a simulated swinging pendulum clock in which an electric motor 14 is provided for driving the hands of the clock and also the pendulum of the clock. Such a prior art simulated pendulum clock mechanism requires a relatively high torque motor to drive both the hands of the clock and the pendulum.
This invention is concerned with a battery-powered simulated pendulum clock wherein the pendulum does not serve a timekeeping function, and has as its general object the provision of a unique driving movement for the pendulum which may be operated with low battery power.
Some of the prior art electronic battery-operated clocks have utilized relatively small pendulums which are intimately connected with the timekeeping movement of the clock for providing a mechanical oscillator to accurately synchronize the frequency of an electronic oscillator. However, such pendulums commonly have the drive force applied to the pendulum some distance from the fulcrum of the pendulum so that such a clock cannot take on the appearance of an old-fashioned pendulum clock. Accordingly, it is also an object of this invention to provide a unique driving mechanism for a pendulum which may be located very close to the fulcrum of the pendulum. With this arrangement, the fulcrum of the pendulum and the electromagnetic drive for the pendulum may be covered by a clock casing so that a person viewing the pendulum clock may readily observe the hands of the clock and the pendulum without seeing the electromagnetic drive mechanism.
SUMMARY OF THE INVENTION
In accordance with one of the aspects of this invention, an electronic movement powered by direct current is provided for driving the hands or other time display elements of a clock, and a pendulum including an elongated arm and a bob is mounted below the electronic timekeeping movement. A unique electromagnetic drive mechanism is positioned close to the fulcrum of the pendulum for driving the pendulum. The electromagnetic drive includes a highly permeable field and coil for driving a permanent magnet which is attached to an arm of the pendulum.
BRIEF DESCRIPTION OF THE DRAWING
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 elevational view of my improved pendulum clock partly broken away to show details of construction;
FIG. 2 is a front elevational view of the pendulum movement and the pendulum of the clock shown in FIG. 1;
FIG. 3 is a perspective view of a portion of the pendulum and the elecromagnetic movement for driving the pendulum of the pendulum clock shown in FIG. 1;
FIG. 4 shows an electronic circuit for delivering driving pulses to the pendulum for moving the pendulum;
FIG. 5 is an enlarged fragmentary front elevational view of the upper and lower arms of the pendulum; and
FIG. 6 is an enlarged fragmentary side elevational view of the upper and lower arms of the pendulum similar to FIG. 5 showing the lower arm of the pendulum being connected to the upper arm of the pendulum.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawing and first particularly to FIG. 1, there is shown a pendulum clock which includes my unique pendulum movement construction. In the embodiment illustrated, the clock includes an ornamental casing 10 of a type which is capable of being hung from a wall. A conventional hour hand 12, a minute hand 14, and Roman numerals are provided for indicating the hours and minutes.
The hands of the clock may be driven by any conventional timing mechanism 16, and as shown in FIG. 2 an electronic battery-powered movement is utilized for this purpose. The battery-powered movement includes a casing 18 which may be conveniently formed from plastic or other suitable material. A battery 20 is positioned in an upper portion of the casing and an electric motor 22, a mechanical oscillator 24, and an electronic oscillator circuit 26 is positioned in the lower portion of the casing along with drive gearing 28 for the hands of the clock. It can be appreciated that the gearing from the motor 22 is connected to a center stack of concentric shafts 30 and 32 which extend through a front wall of the timing mechanism casing and the front casing 10 of the clock for driving the hour and minute hands 12 and 14, respectively.
The specific electronic battery-operated clock movement illustrated does not form a part of my invention and is described and shown in greater detail in a prior patent of C. M. Jones U.S. Pat. No. 3,454,856, issued July 8, 1969, and assigned to the same assignee as the instant invention. In accordance with my invention, a unique separate movement is provided for driving the pendulum.
With particular reference to FIG. 1, it can be appreciated that the usual electronic battery-operated timekeeping movement 16 for driving the hands of a clock is not too large, and yet as shown by the dotted lines it occupies a considerable amount of space behind the front face of the clock. As shown, it extends roughly from the lower portion of Roman numeral I to the upper portion of numeral VII. My electronic pendulum movement 34 is so small that it may be positioned within a casing 36 which does not extend below the outer circumference of the clock casing 10. In this manner, all of the driving mechanism for the pendulum 38 may be position so that it is not seen. Thus, a person viewing the pendulum clock may readily observe the hands of the clock and what appears to be a swinging pendulum with a relatively long pendulum arm 40 and a large decorative pendulum bob 42.
Since the pendulum movement 34 which is powered by direct current is separate and distinct from the time-keeping mechanism 22, 24 and 26 for driving the hands of the clock, it can be conveniently housed in the separate plastic casing 36. As shown, the electrical connections from the battery 20 to the separate pendulum movement 34 may be conveniently made by a pair of electrical wires 48 and 50 which may extend through an aperture 82 which is formed in a top wall of the casing 36.
The pendulum movement casing 36 may be readily attached to the conventional battery-operated clock timing mechanism casing 16 by means of a sheet metal plate 50 which may be conveniently secured to the mechanism casing by a nut 52 and a threaded collar 53 which are also required for assembling the timekeeping movement casing 16 to the clock casing 10. As illustrated, the sheet metal plate 50 extends downwardly from the collar 53, and the pendulum movement casing 36 may be readily attached to the plate 50 by any suitable connection means.
The pendulum 40 is constructed so that a variety of different ornamental pendulums may be operated and driven by my unique pendulum movement 34. The construction details of the pendulum 40 and the general arrangement of the pendulum 40, the pendulum movement 34, and the time-keeping movement 16 in a clock do not form a part of this invention and are described and illustrated in greater detail in a co-pending application of Chester B. Marble (6D-4319), Ser. No. 211,343, assigned to the same assignee as the instant invention.
As described in more detail in the aforementioned application, the pendulum 40 is constructed in two parts, a very short upper portion 58 and a removable lower portion 56. The short upper portion includes a flexible spring fulcrum 60, a drive arm 66, and a bracket portion 74 which is provided for supporting a removable lower pendulum arm 56. The flexible leaf spring fulcrum 60 has its upper end clamped between two L-shaped brackets 62 and 63 which may be riveted or otherwise secured to the sheet metal plate 50. The upper drive arm 66 functions as a mounting bracket for supporting a permanent magnet 64 for driving the pendulum.
In accordance with my invention, the permanent magnet 64 for driving the pendulum 40 is arranged to be driven by a highly permeable core structure 101 and coils 102 and 104 so that the relatively large pendulum may be readily driven by the magnetic forces produced by the core and coils although the excursions of the pendulum arm 58 and the magnet 64 in the area where they are being driven may be as small as 0.1 to 0.2 inch, and as with most pendulums the swinging frequency could be approximately one cycle per second.
In accordance with my invention, the magnet 64 is constructed so that it provides a very high flux density, and it is magnetically coupled to the highly permeable magnet core structure 101 and its push-pull coils 102 and 104. The coil 102 is formed with many turns of wire, and in the embodiment illustrated approximately 5,000 turns are utilized for providing an adequate field for moving the magnet 64 and the pendulum 40. With particular reference to FIG. 3, it can be seen that the gap between the two pole pieces of my highly permeable iron core structure 101 can be small so that the rate of flux change is large.
With particular reference to FIG. 4, the coils 102 and 104 are provided for triggering operation of the two transistors 106 and 108. In order to obtain the greatest amount of rate of flux change (voltage) as the magnet 64 on the pendulum swings to and fro the iron utilized in the field laminations 101 is highly permeable. As illustrated in FIGS. 3 and 4, the coil 104 is wound on the same highly permeable magnet core structure 101 as the 102, and in the embodiment illustrated, the 10,000 turn coil 104 operating with my highly permeable magnetic core laminations 101 may obtain an induced voltage of the order of 0.3 volts as the magnet moves through its excursion of from 0.1 to 0.2 inch. Thus, in the preferred embodiment illustrated in FIG. 4, the coils 102 and 104 alternately feed strong control signals to the input of a two silicon transistor circuit.
My improved circuit illustrated in FIG. 4 is essentially a push-pull switching oscillator circuit which causes the transistors to alternately conduct by signals generated by the swinging magnet 64 on the upper pendulum arm. The circuit contains relatively few components for achieving its unique switching function of alternately providing substantial flow to the coils 102 and 104 at just the right times to keep the pendulum oscillating. The principal components of the circuit are transistors 106 and 108 which are used with intercoupling and feedback from the coils 102 and 104 resulting in a well performing oscillator. This circuit is quite efficient because of the push-pull arrangement of the coils 102 and 104, respectively. The coil 104 is connected to the collector of transistor 106 while the coil 102 is connected to the collector of transistor 108. The coils are essentially in parallel and are connected to a battery 110 of approximately 1.5 volts or other suitable source of direct current. A 68K resistor 112 is positioned between the collector of transistor 106 and the base of transistor 108 while the collector of transistor 108 is directly coupled to the base of transistor 106 to suitably provide intercoupling between the transistors 106 and 108.
A .1 microfarad capacitor 114 is positioned between the bases of transistors 106 and 108 and the collector of transistor 108 for the suppression of high frequency oscillations.
A 3.3K resistor 116 is connected to the emitters of the transistors 106 and 108 and the negative terminal of battery 110 for increasing the input impedance of the transistor input circuits.
With this circuit the transistors 106 and 108 are readily turned on and off by signals generated by the swinging magnet 64 on the pendulum 40. When the transistor 108 is off transistor 106 is on and the magnet swings under the force provided by coil 104. Alternately, when transistor 106 is off transistor 108 is on and the magnet swings under the force provided by coil 102 thereby keeping the pendulum in motion.
From the foregoing description, it will be appreciated that my unique separate electromagnetic motor may be readily operated as a true pendulum with its pleasing swinging motion although the frequency of oscillation of the electronic transistor oscillator is much higher than the pendulum frequency. Moreover, in contrast to the usual pendulum my electrically driven pendulum is less sensitive to the operating position of the clock, and it does not require a length adjustment. Moreover, with my highly permeable field and coil assembly the electromagnetic drive for the upper arm of the pendulum is applied so close to the fulcrum portion of the pendulum that the portion of the lower pendulum arm and the pendulum bob may be visible substantially in their entirety and may be made quite long while the relatively small drive mechanism may be conveniently shielded from an observer by the clock casing.