PENDULUM CLOCK AND METHOD FOR THE MODIFICATION OF A PENDULUM CLOCK

Abstract: Method for modernizing a pendulum clock, by which the original character of the clock is maintained. For that purpose a control unit is added, together with a reference clock, a pneumatically driven cylinder and arresting means for arresting the pendulum. The pendulum clock is adjusted such that it runs slightly fast. Periodically, for example every hour, the pendulum is arrested up to the moment that the pendulum clock is in time with the reference clock. While the pendulum is arrested, the pendulum clock is wound up by the cylinder.

Description: Pendulum clock and method for the modification of a pendulum clock The invention relates to a pendulum clock, provided with a wind up drum, around which a cable or a chain is coiled, to a first end of which a weight is attached. Pendulum clocks of this type are well known. The invention more specifically relates to pendulum clocks of the above type with a historical or art-historical value, which are at risk and are eventually liable to disappear due to ever- continuing rationalization schemes that are carried through in modern society, or which are modernized in such a way that severe damage is done to the cultural heritage. The problem with the known pendulum clocks is that they require constant for attention. They must be wound up with a crank at the location of the clock and must be regularly set right. The setting of the summer time and the winter time twice a year entails a relatively complex operation, especially because for the hands of larger pendulum clocks often have to be turned with great difficulty forward or backward. In order to reduce costs it is therefore often decided to replace the entire pendulum clock by a modern clockwork and to maintain only the original hands. The object of the present invention is to offer a solution that is more justifiable. According to the invention, a modernized pendulum clock is characterized in that a second end of the cable or chain is connected to an actuator which is periodically activated by a control unit, for at least partially winding up the pendulum clock, and that arresting means are provided, which are periodically activated by the control unit, for arresting the pendulum in a predefined position before the actuator is activated and for releasing 2 the pendulum after the actuator has been deactivated. The advantage of this solution is that the pendulum clock as such is not modified. The only item added are in fact the arresting means to stop the pendulum. Preferably, this is done in an extreme position of the pendulum, when the velocity is zero, such that there is no additional load on the pendulum clock. Stopping the pendulum is advisable during winding up, because during winding up no driving forces act on the clockwork and its behaviour is undetermined at that moment. Especially when introducing an actuator, with a limited span, necessitating frequent winding up, this could lead to an unpredictable deviation in the timekeeping. Moreover the cable or chain, originally ending at a connecting point on the drum, must be extended or a piece of cable or chain must be added. Both modifications are evidently 100% reversible and no original parts of the clock, like the weight, will be lost. The invention also relates to a method for the modification of an existing pendulum clock provided with a wind up drum around which a cable or a chain is coiled, to a first end of which a weight is connected. The method aims at maintaining the pendulum clock in its original state to the greatest extent possible and is characterized in that an actuator is coupled to a second end of the cable or chain, that arresting means for the pendulum are added and that a control unit is connected to the actuator and the arresting means, for periodically activating the arresting means for arresting the pendulum in a predefined position, for then activating the actuator for at least partially winding up the pendulum clock, for subsequently deactivating the actuator, and for lastly deactivating the arresting means in order to release the pendulum. A favourable embodiment of the pendulum clock according to the invention is characterized in that a sensor is provided, connected to the control unit, for determining a position of the pendulum. It is then possible to ascertain that the pendulum approaches an extreme position and to activate the arresting means with the pendulum substantially in an extreme position. According to another aspect of the invention, the pendulum clock may be set much easier. For that purpose the control unit is provided with reference time measurement means and the pendulum clock is adjusted such that it is faster than the reference time measurement means. Setting the clock may then simply take place by activating the arresting means until the moment that the pendulum clock displays the same time as the reference time measurement means. According to another aspect of the invention, the clock may be set completely automatically. The pendulum clock is thereto characterized in that the control unit is arranged for counting the number of oscillations of the pendulum with the sensor and for periodically activating the arresting means for synchronizing the pendulum clock. According to another aspect of the invention, the pendulum clock is characterized in that the actuator comprises a pneumatically driven cylinder. An actuator of this type is robust and will continue to work even when the mains supply incidentally fails. Moreover, a pneumatically driven cylinder entails a reduced firerisk as compared to an electromotor and it will never overwind the pendulum clock, thanks to its well-defined length. A further advantage that may be brought up is the fact that a pneumatic cylinder has a very long service life and can easily be replaced by local workers in case of failure. The same argument holds 4 for the compressor, necessary for delivering compressed air for the pneumatic cylinder. The actuator is preferably located above the weight, or at least such that a point of application of the actuator to the second end is chosen such that a force on the second end caused by the actuator during winding up is aligned with a force caused by the weight. This unburdens the main axis of the wind up drum during winding up, which may significantly increase the service life of the bearing of the main axis. According to another aspect of the invention the arresting means may be located at some distance from the pendulum, preferably in a clean, dustfree room. In this embodiment the pendulum clock is characterized in that the arresting means comprise rotatably mounted and mutually coupled first and second rollers, that a first thread, connected to the pendulum, is coiled around the first roller, that a second thread, connected to a weight, is coiled around the second roller, and that the rollers are provided with a brake disk on which a brake may act by means of a second pneumatic actuator. The first thread may be glued to the pendulum, making this operation also reversible and substantially invisible. In a favourable realization of this embodiment the brake disk is realized as a ratchet wheel, shaped as a freewheeling bearing, on its periphery provided with sawtooth-shaped teeth, the pneumatic actuator being provided with a pawl that may be placed against the outer contour for arresting the disk. This enables the pendulum to completely finish a swing, after which it will be arrested automatically. An additional advantage is that, if for some reason the compressed air supply, feeding the pneumatic actuators, should cease, the clock will stay with the pendulum in its upper position, from which position it is possible to automatically restart. A favourable realization of the inventive method is characterized in that moreover a sensor is added, arranged for determining a predefined position of the pendulum. The sensor enables the arresting means to act onto the pendulum, such that substantially no additional acceleration or deceleration of the pendulum occurs. A further favourable realization of the inventive method is characterized in that moreover reference time measurement means are added, that the sensor is used for measuring a number of oscillations of the pendulum in a predefined time span, measured with the reference time measurement means, and that the arresting means are activated for temporarily arresting the pendulum for obtaining a synchronization between the pendulum clock and the reference time measurement means. A still further favourable realization of the inventive method is characterized in that a time switching function is added to the control means, for switching from summer time to winter time and from winter time to summer time, which switching is effected by activating the arresting means during one hour or during eleven hours. The invention will now be further explained with reference to the following figures, in which: Fig. 1 schematically shows a first embodiment of the pendulum clock according to the invention; Fig. 2 schematically shows a second embodiment of the pendulum clock according to the invention; Fig. 3 shows a possible embodiment of pneumatic controlled arresting means; Fig. 4 shows a possible embodiment of electromagnetic controlled arresting means; Fig. 5A shows a possible embodiment of arresting means, located at some distance; Fig. 5b shows arresting means based on a pneumatical controlled ratchet wheel. Fig. 1 schematically shows a first embodiment of the pendulum clock according to the invention. Around a wind up drum 1 a cable or chain 2 is coiled a few turns, which is on one side provided with a weight 3 that delivers a driving force for a clockwork, not shown here, that finally drives a pendulum 4 and the hands, not shown here, and possibly also periodically activates striking parts, not shown here. The second end 5 of cable or chain 2 must be periodically pulled, in order to wind up the pendulum clock. During winding up weight 3 is pulled upwards, while the clock mechanism is simultaneously decoupled with the aid of an existing slip coupling or a freewheel. In the embodiment shown with reference to Fig. 1 the second end is coupled to a pneumatic actuator 6 to which periodically compressed air is fed for winding up the pendulum clock. As during the winding up no driving force is exerted on the mechanism, its behaviour at that moment is undetermined. Therefore a sensor 7 is provided which is adapted to detect pendulum 4 for being almost in an extreme position and arresting means 8 are provided for arresting pendulum 4 in the extreme position. Control unit 9 regularly checks, for example every hour, if pendulum 4 is in an extreme position; if this is the case then arresting means 8 are activated, compressed air is then fed to actuator 6 for some time, thereby winding up the pendulum clock, and finally arresting means 8 are deactivated. 7 Control unit 9 is arranged for checking, with the aid of sensor 7, if the pendulum clock goes and consequently if it is functioning properly. If this is not the case, a signal may be generated for preventing actuator 6 from being activated again, in this way preventing further damage to the pendulum clock, and also for warning a person responsible for the pendulum clock. Moreover control unit 9 may activate arresting means 8 and generate a warning to the person responsible on the basis of other criteria, such as the pendulum clock being much too fast or too slow. In the above embodiment control unit 9 is a PLC, well known in the art, provided with reference time measurement means 10, for example based on a DCF wireless control, a crystal controlled clock or an atom clock. The advantage of using a PLC is that standard sensors and standard controls are available, suitable for directly connecting to the PLC. In this way sensor 7 and a control for actuator 6 and arresting means 9 are easily realized and can even after a long time be easily replaced by a local electrician. Fig. 2 schematically shows a second embodiment of the pendulum clock according to the invention. In this embodiment pneumatic actuator 6 has been arranged such that the winding up force acts against the force on weight 3 due to gravity. This substantially unburdens the bearing of the main axis of the wind up drum 1, further not shown, which will prolong the service life of the pendulum clock. In fact, actuator 6 may be located anywhere if one or more pulleys are applied for guiding the pulling force such that the point of application is located exactly above weight 3, as shown in this embodiment. In the embodiment as shown, the reference time measurement means 10 of control unit 9 are moreover used for realizing 8 good timekeeping of the pendulum clock. For that purpose the pendulum clock is adjusted in a known manner, for example by adjusting the length of pendulum 4, such that it runs fast. If pendulum 4 should swing for example 3600 periods per hour, this value is now adjusted to 3620 periods. This implies that, without corrective measures, the pendulum clock gains about twenty seconds an hour. With the aid of sensor 7 the number of periods made by the pendulum clock in on hour is exactly registered. Once every hour, if the pendulum has swung exactly 3600 times, control unit 9 activates arresting means 8, until, according to the reference time measurement means 10, the hour is full, after which arresting means 8 are deactivated. While arresting means 8 are activated the opportunity is used for winding up the pendulum clock with the aid of actuator 6. This does not necessarily have to take place every hour. Generally speaking it is better to wind up the pendulum clock a few times a day. Therefore, under the condition that space is available, actuator 6 should preferably be chosen long. If the reference time measurement means 10 are provided with a summer time and a winter time, a summer time and a winter time can easily be realized for the pendulum clock as well, by activating the arresting means 8 at the beginning of the winter time during one hour and at the beginning of the summer time during eleven hours. Fig. 3 shows a possible embodiment of arresting means 8, where pendulum 4 is arrested in its end position by a pawl 11. Pawl 11 is rotatably mounted on an axis 12 and has two possible positions 11a en lib, such that for position 11a pendulum 4 may pass unhindered and for position lib pendulum 4 is arrested. Pawl 11 is controlled in turn by a pneumatic cylinder 13, which in turn is controlled by control unit 9. For a proper timing, use can be made of a sensor 7, not shown here, connected to control unit 9. This can for example be a LED and photodiode combination, well known in the art, such that the photodiode receives light emitted by the LED and reflected by the passing pendulum, or such that the pendulum interrupts an existing light path. Fig. 4 shows a possible embodiment of arresting means 8 where pendulum 4 is arrested in its end position by means of an electromagnet 14. The poles of electromagnet 14 are preferably provided with a layer of a soft, elastic material 15, for example rubber, which layer provides for a soft landing of the pendulum 4 and also prevents pendulum 4 from getting stuck onto electromagnet 14 due to remanent magnetism after electromagnet 14 has been switched off. This embodiment is applicable only when pendulum 4 comprises a ferromagnetic material or if it is provided with a piece of this material, which is for example glued to it. Fig. 5A shows a possible embodiment of arresting means, located at some distance, where a thin synthetic or metal thread 16 is connected to pendulum 4 which, possibly via one or more pulleys 17, is guided to a system of two mutually coupled, rotatably mounted rollers 18,19. Thread 16 is coiled a few times around roller 18 and is finally connected to it on a point 20. A second thread 21 is connected on a point 22 to roller 19 and is coiled a few times around it. The second end of thread 21 is provided with a small weight 23. Due to the movement of pendulum 4, weight 23 will successively go up and down, which movements are easily monitored by a sensor, not shown here. The stroke of weight 23 may be selected by choosing the diameters of the rollers 18 en 19, thus reducing it to a 10 practical or even a standard value. The arresting as such may take place by means of a brake disk 24, by breaking the disk in a known matter, for example by pressing a piece of high friction material against it with the aid of a second pneumatic actuator. For reason of clarity, brake disk 24 is shown separated from roller 19 in Fig. 5A, but in practice it is connected to it. Fig. 5B shows arresting means in which disk brake 24 is in fact a ratchet wheel, realized as a backrun bearing. According to the invention pawl 25 is lifted up by a second pneumatic actuator 26 during normal use of the pendulum clock. If pendulum 4 is to be arrested, actuator 26 is deactivated, which causes pawl 25 to be placed onto ratchet wheel 24. Due to the sawtooth shape of the teeth, pendulum 4 can finish its pendular movement unhindered, but in the extreme position it will be arrested by pawl 25 dropping into ratchet wheel 24. The arresting can be easily ended by activating actuator 26 again.

Claims: 11 Claims 1. Pendulum clock, provided with a wind up drum, around which a cable or a chain is coiled, to a first end of which a weight is attached, characterized in that a second end of the cable or chain is connected to an actuator, which is periodically activated by a control unit, for at least partially winding up the pendulum clock, and that arresting means are provided, which are periodically activated by the control unit, for arresting the pendulum in a predefined position before the actuator is activated and for releasing the pendulum after the actuator has been deactivated. 2. Pendulum clock according to claim 1, characterized in that a sensor is provided, connected to the control unit, for determining a position of the pendulum. 3. Pendulum clock according to claim 2, characterized in that the control unit is provided with reference time measurement means and that the pendulum clock is adjusted such that it is faster than the reference time measurement means . 4. Pendulum clock according to claim 3, characterized in that the control unit is arranged for counting the number of oscillations of the pendulum with the sensor and for periodically activating the arresting means for synchronizing the pendulum clock. 5. Pendulum clock according to claim 4, characterized in that the control unit is arranged for activating the arresting means during one hour for switching from summer time to winter time and for activating the arresting means during eleven hours for switching from to winter time to summer time. 12 6. Pendulum clock according to one of the previous claims, characterized in that dat the control unit is a suitably programmed PLC. 7. Pendulum clock according to claim 1, characterized in that the actuator comprises a pneumatically driven cylinder. 8. Pendulum clock according to claim 1, characterized in that a point of application of the actuator to the second end is chosen such that a force on the second end caused by the actuator during winding up is in line with a force caused by the weight. 9. Pendulum clock according to claim 1, characterized in that the arresting means comprise rotatably mounted and mutually coupled first and second rollers, that a first thread, connected to the pendulum, is coiled around the first roller, that a second thread, connected to a weight, is coiled around the second roller, and that the rollers are provided with a brake disk on which a brake may act by means of a pneumatic actuator. 10. Pendulum clock according to claim 9, characterized in that the brake disk is realized as a ratchet wheel, shaped as a freewheeling bearing, on its periphery provided with sawtooth-shaped teeth, and that the pneumatic actuator is provided with a pawl that may be placed against the outer contour for arresting the disk. 11. Method for the modification of an existing pendulum clock provided with a wind up drum, around which a cable or a chain is coiled, to a first end of which a weight is connected, characterized in that an actuator is coupled to a second end of the cable or chain, that arresting means 13 for the pendulum are added and that a control unit is connected to the actuator and the arresting means, for periodically activating the arresting means for arresting the pendulum in a predefined position, for then activating the actuator for at least partially winding up the pendulum clock, for subsequently deactivating the actuator, and for lastly deactivating the arresting means in order to release the pendulum. 12. Method according to claim 11, characterized in that moreover a sensor is added, arranged for determining a predefined position of the pendulum. 13. Method according to claim 12, characterized in that moreover reference time measurement means are added, that the sensor is used for measuring a number of oscillations of the pendulum in a predefined time span measured with the reference time measurement means, and that the arresting means are activated for temporary arresting the pendulum for obtaining a synchronization between the pendulum clock and the reference time measurement means. 14. Method according to claim 12, characterized in that a time switching function is added to the control means, for switching from summer time to winter time and from winter time to summer time, which switching is effected by activating the arresting means during one hour or during eleven hours.

Inventors: HOENCAMP MENNO BART, SPAANDER MELGERT, HOENCAMP, MENNO, BART, SPAANDER, MELGERT
Applicants: HOENCAMP MENNO BART, SPAANDER MELGERT, HOENCAMP, MENNO, BART, SPAANDER, MELGERT
Application year: 1999
Main classification: G04C1
IPC codes: G04C1, G04C3, G04C11