GB1584913A - Electric clocks - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO ELECTRIC CLOCKS (71) We; KIENINGER & OBERGFELL, a German kommanditgesellschaft, of Postfach 81t, St. Georgen im Sohwarzwald; West Germany; do- hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to an electric clock comprising a time keeping element for the time-defining regulation of the clock mechanism and a torsion pendulum which is not provided for regulating the clock but is arranged to be driven by a drive member arranged to be drivingly and operatively coupled in the course of its rotating motion with a driven element which is coupled to the torsion pendulum by being attached to a torsion spring of the pendulum, there being provided means for compensating for discrepancies between the motion of the drive member and the motion of the torsion pendulum, the drive member being constructed as a rotating disc cam arranged to be intermittently drivingly coupled by means of one or more cams thereon to the driven element which is attached to the torsion spring so as to be movable therewith in a horizontal plane and which is constructed as an elongate element.

An electric clock of the kind described hereinbefore is known. In this clock the torsion pendulum is driven by a balance whose guiding motions are electrodynamically maintained and which serves to keep time as well as to drive the hand mechanism and the torsion pendulum.

However, it has been found that in the interests of current consumption and running accuracy of the clock mechanism the magnitude of the drive impulses supplied to the hand mechanism is limited. The double load imposed on the mechanism by the hand mechanism and by the co-driven but nonfunctional torsion pendulum calls for a certain compromise in the design of the clock mechanism with the result that satisfactory operation of the clock, also taking into account the necessity of small current consumption, is possible only within a limited voltage range of the source - of feed current -(dry battery).

It is therefore an object of an embodiment of the invention to improve the running accuracy and to increase the load- bearing capacity of the hands mechanism.

This is important, more particularly for large dial diameters, for example, on wall clocks, and in the case of special loads applied to the clock mechanism, for example loads represented by a chiming mechanism or similar devices.

It is also an object of an embodiment of the invention to improve the operational reliability of the electrical clock and more particularly to reduce its sensitivity to installation According to the invention, there is provided an electric clock comprising a time keeping element for the time-defining regulation of the clock mechanism and a torsion pendulum which is not provided for- regulating the clock but is arranged to be driven by a drive member arranged to be drivingly and operatively coupled in the course of its rotating motion with a driven element which is coupled to the torsion pendulum by being attached to a torsion spring of the pendulum, there being provided means for compensating for discrepancies between the motion of the drive member and the torsion pendulum and the drive member being constructed as a rotating disc cam arranged to be intermittently drivingly coupled by means of one or more cams thereon to the driven element which is attached to the torsion spring so as to be movable therewith in a horizontal plane and which is constructed as an elongate element, the time keeping element comprising an electronic crystal in an oscillating circuit arranged to control at least one electric motor via a frequency divider circuit and via an output stage, the electric motor being arranged to index the hands mechanism and the electric motor or another of the electric motors being arranged to index the disc cam which drives the torsion pendulum.

Surprisingly it has been found that the oscillating motions of the torsion pendulm can be more readily maintained and started in a preferred embodiment of the invention. This unpredictable circumstance is due to the fact that the disc cam drive, which is applied only approximately every second or half second, is performed over a longer angular path and with a more distinct intermittent action on the driven member and therefore the restoring spring of the tension pendulum can move more correctly in synchronism with a seconds hand of the clock.

The stepping mechanism applies the drive in greater steps whereas, in the arrangement disclosed in British Patent No.

1 462 230, the disc cam traverses its path of movement with a plurality of smaller steps. The longer path of motion at longer intervals of the disc cam in a preferred embodiment of the invention maintains the oscillating motion very effectively with a comparable expenditure of electrical energy so that an adequate oscillation amplitude of the pendulum and reliable starting, even with a supply battery whose voltage has already diminished, can be achieved even for clocks exposed to a certain ingress of dirt due to a prolonged operating time or in clocks which are loaded by larger pendulums or by long hands.

The invention will be further described, by way of example, with reference.to the accompanying drawings, in which: Fig. 1 is a diagrammatic view of the construction of a preferred electric clock; Fig. 2 is a view of part of the mechanical construction of a preferred electric clock, with inset Fig. 2a illustrating a detail thereof; Fig. 3 is another view of the construction according to Fig. 2; Fig. 4 shows a detail of a preferred electric clock; and Fig. 5 is another view of the detail of Fig. 4.

In Fig. 1 the numeral 150 represents an oscillator circuit with an electronic crystal, followed by a frequency divider 151 which in turn controls a driver circuit 152.

The output of the drive circuit 152 is connected to an electromagnetic stepping motor 120, more particularly a polarized motor, which can be indexed by the driver circuit 152, more particularly at a halfsecond rhythm or a one-second rhythm.

The spindle 1441 of the electromagnetic stepping motor 120 is provided with a pinion 144 which meshes with a second wheel 105 mounted on a seconds spindle 1051 and drives the said wheel. Through intermediate wheels 10611, 106l and 107 the seconds wheel 105 drives a disc cam 101 which cooperates with a driving member 41 (Figs. 2 to 5) of the torsion pendulum.

The crystal controlled circuit, comprising the elements 150, 151, 152 and 120, is fed from a common current source 153.

The stepping motor is conveniently constructed as a stepping mechanism which is polarized by at least one permanent magnet.

A stepping mechanism of this kind can be constructed to operate in monopolar or in bipolar manner (i.e. in push-pull operation).

The advantage of such stepping motors is that they can be reliably controlled with relatively low pulse energises. The lastmentioned bipolar method of operation with push-pull control provides particularly reliable operation for the stepping motor. To this end pole changing current pulses flow through the energizing coil of the stepping motor to perform the stepping motion.

Stepping mechanisms of this kind can be constructed with very advantageous dimensions. Conveniently a stepping motor of this kind is provided with a cylindrical rotor made of permanent magnet material which is magnetized around its periphery and which can be electromagnetically biased on its circumference by means of a stator formed of laminated magnetizable parts forming air gaps that vary along the rotor circumference and being disposed in the magnetic circuit of the electric coil.

Conveniently the stepping motor 120 is disposed between the side plates 114 of the clock mechanism. To this end the stator of the stepping motor can be constructed in cup shape, the interior of which contains the coil and the permanent magnet of the rotor is disposed on the end face thereof where it can be biased by the magnetic laminations of the core as well as by those of the magnetic cup.

In another embodiment of the stator system, laminated U-shaped magnet sheets are retained in the coil by being assembled together and the rotor is disposed between the free ends of the thus-formed members.

The last-mentioned arrangement is generally the spatially better embodiment of the stepping motor. The end faces of the members form the air gaps which vary along the circumference of the permanent magnet rotor.

A support member 1, disposed on the clock mechanism either directly in the form of a retaining bracket or on a retaining part of the clock which supports the clock mechanism is indicated at the top of the torsion pendulum in Fig. 2. The support member 1 is constructed of plastics, for instance by injection moulding, so that a fork formed at the end of the support member 1 by a slot 3 and an aperture 4 (see Fig. 2a) has a resilient action. The cylindrical part 5 of a screwthreaded bolt 2 can be sprung through the slot 3 into the bore 4 of the support member 1. The contact pressure acting on the cylindrical part 5 of the screwthreaded bolt 2 is adjusted so that the latter can be adjusted by friction through its nut 7.

An extension 8 with screwthreading 9 is provided on the screwthreaded bolt 2 beneath the nut 7.

The extension 8 is provided with a bore having a bush 10, preferably of plastics, which provides radial support for a bearing pin 12.

The torsion pendulum comprises a pendulum rod 11 restrained at the top by the bearing pin 12 which is radially guided by the bush 10 and the bottom of the pendulum rod projects into an extension which is formed by a hexagon 14 of a bush part 20.

A helical spring 17, comprising numerous turns, is disposed between the extension 8 of the screwthreaded bolt 2 and the hexagon 14 and is screwmounted at the top by means of its end turns 18 on the fine screwthreading 9 of the screwthreaded bolt 2 and its lower end turns 19 are secured on the hexagon 14 of the top bush member 21 by means of a fixing ring 16.

The diameter of the helical spring 17 is selected so that its internal radius concentrically and loosely surrounds the external diameter of the pendulum rod 11 so that be tween the said pendulum rod and the helical spring 17 there remains clearance which will just ensure the reliably free twisting and untwisting of the helical spring 17 during the pendulum oscillations.

The pendulum crown or bottom part is formed by the bush 20 comprising a cylindrical top bush member 21, a middle bush member 22 and a conical bottom bush member 23. The middle bush member 22 is constructed in the form of a container which is hollow and open at the bottom and from which the bottom bush member 23 projects. Webs 25 which extend from the pendulum centre are integrally formed on the bush members 22, 23 and support hemispherical cups 26 on their free bottom ends 24. The bush 20, the webs 25, and the cups 26 may be integrally formed by plastics injection moulding.

Corresponding cover parts 27 are placed on the hemispherical cups 26 so Xhat the parts are combined into a complete sphere.

At the bottom the torsion pendulum is radially supported on the casing base 31 by means of a bearing pin 34 and a bush 36, axial support being provided against a cylinder member 39. Tthe thrust force of an axially stressed helical spring 38 when mounted in a bore 37 as shown is greater than the effective deadweight of the torsion pendulum so as to support and suspend the torsion pendulum. - If the torsion pendulum is subjected to external impact stresses, for example due to incorrect handling such as incorrect and hard lowering of the clock onto a suport surface, the impact pulse imparted to the torsion pendulum is partially absorbed by the cylinder part 39 which is deflected against the thrust of the helical spring 38 into the axial bore 37 in the lower part of the pendulum, downward movement of the pendulum being limited by the lower end of the tapering portion 33 striking against the bush 32 on the casing bottom 31. Accordingly, the shock pulse is completely absorbed and breakage of the bearing pin 34 or of the hard cylinder part 39 is avoided.

The transmission element 40, conveniently constructed of plastics and supporting on its side the driving element 41 which takes the form of a pin, is disposed on the helical spring 17.

Fig. 5 shows the transmission element 40 in a plan view to an enlarged scale. An internal bore 42, surrounding the helical spring 17, adjoins an opening 43 which is situated opposite to recesses 44 which provide one-sided weakening of the cross-section of the transmission element 40. Bores 45 serve to permit holding of the transmission element 40 by a tool, for example by expanding pliers so that the transmission element 40 can be expanded by means of its opening 43 to enable the component 40 to be placed from the outside on the helical spring 17 where it is clamped by the profile stress of its own cross-section.

The driving member 41 of the transmission element 40 projects through a slot 1141 in a side plate 114.

The disc cam 101 is coupled via a disc cam bush 101' to the wheel 107 and to the spindle 110. The rocker 112 is supported on the spindle 110 so as to be freely pivotable; said rocker supports a weight 1121. The intermediate wheels 106l and 1061l are supported on a spindle 117 which is mounted on the rocker 112. Both intermediate wheels are interconnected and are arranged on the spindle 117 so as to be freely rotatably thereon. They form the wheel 106.

Due to the weight of the rocker 112 the intermediate wheel 10611 meshes with the seconds wheel 105. The intermediate wheel 106l is in constant mesh with the wheel 107. Pivoting the rocker 112 against the action of the weight 1121 releases engagement between the wheel 105 and the intermediate wheel 10611.

The seconds wheel 105 is driven by the polarized electromagnetic stepping motor 120 which is pulsed by the crystal control circuit.

The stepping motions of the stepping motor 120 are transmitted to the minute spindle and the hour tube via the pinion 144, the seconds wheel 105 and the other transmission elements, not shown, on the downstream side. At the same time the wheel 106,.which is rotatably supported by means of the spindle 117 on the rocker 112, is cm driven via- the second wheel 105 and the intermediate wheel 10611 and by means of the intermediate wheel 1061; the said wheel 106 transfers the rotating motion transmitted to it to the wheel 107 which is fixedly connected to the disc cam 101 and is supported on the spindle 110.

Accordingly, engagement between the interrnediate wheel 10611 on the rocker 112and the seconds wheels 105 is maintained by virtue of the torque applied by the mass 112l to the rocker 112 about the bearing point 1101. This menas that the spindle 117 maintains its position against an edge 1131r of d cut-out 118 in the plate 114 although the seconds wheel 105 tends to release its engagement with the intermediate wheel 10611 by lifting- of the rocker 112.

The driving member 41 which is associ ated with the torsion spring 17 oscillates with its front end 411 in the recess 114 of the rear plate 114 and thus reaches- a stop abutment at the right-hand edge of the recess 114l in one oscillàting direction.

One of the cams 102 situated on the circumference of the disc cam 101 wi-ll thus bear upon the driving member 41 and impart a driving motion thereto under the action of the drive applied to the disc cam 101 by the seconds wheel 105 via the wheel 106.

The stop abutment position within the recess - ll4l, corresponding approximately to a position centrally over the disc cam 101, is maintained during a portion of the oscillating motion of the torsion pendulum' at one angular extremity thereof.

The rotating motion of the disc cam 101 is therefore blocked by the cam 102 bearing upon the driving member 41. However, this causes the intermediate wheel 1061 of the wheel 106, which continues to be driven by the seconds wheel 105, to roll against the action of the force produced by the mass 1121 and along the tooth system of the gearwheel 107 so that its intermediate wheel 106ill is disengaged from the seconds wheel 105. The outward pivoting motion is assisted by the driving motion of the wheel 105.

For the period of time that the disc cam 101 is blocked by the driving element 41 the engagement between the seconds wheel 105 and the intermediate wheel 10611 of the wheel 106 on the rocker 112 is released as the teeth of these two wheels step over each other, so that discrepancies between the motion of the hands mechanism drive, controlled with respect to time by the stepping motor 120, and the motion of the torsion pendulum is compensated. The application of drive to the torsion pendulum 100 via the driving member 41 is however maintained during the ratchet "stepping over" motion between the seconds wheel 105 and the intermediate wheel 10611 of the gearwheel 106.As the torsion pendulum pivots- ih the opposite direction after reaching the changeover point and as the end 411 of the driving member leaves the stop abutment position within the recess 1141, the cam 102 of the disc cam 101 will roll on the driving member 41 under the action of the rotating motion trlnsr mitted to the said disc cam to apply drive to the driving' member 41 ahd therefore via' the torsion spring 17 to the torsion pendulum.The cam 102 of the disc cam 101 is advantageously profiled so-that a theoretically rolling motion can take place while motion is transmitted to the driving mem- ber 41. Immediately at the commencement of the rolling procedure and when the driving member 41 travels out of the recess1141, the intermediate wheel 1061l of the wheel 106 on the rocker 12 resumes the engaged position with the seconds wheel 105.The coupling between the seconds wheel 105 and the intermediate wheel 106 of the wheel 106 can be released in dependence on the load torque which occurs on the disc cam 101 and thus permits autb- matic equization of the rotation motion to take place between the seconds wheel 105 and the disc cam 101. Engagement of the coupling between the wheel 106 and the seconds wheel 105 takes place only when rotation of the disc cam 101 becomes pos sible.When the disc cam 101 is blocked or stopped due to an operative connection having occurred between said disc cam and the driving member 41 of the torsion pendulum this will result merely in the tooth systems of the wheels 105 and 106 slipping i.e. step ping over each other, under the action of the force produced by the weight of the rocker 112. One of the cams 102 rolls upon the driving member 41 and therefore imparts thereto the drive required for the torsion pendulum 100 when this pivots back and the driving member 41 begins to travel out of the recess 1141.

The rocker 112 may be provided with a spring 112ill which engages by means- of a nose 112111 with the gearwheel 107 in a lightly resiliently manner, while reaching over the wheel 1061. This provides additional stabilization of the movement of the seconds wheel 105 on the spindle 1051 and the disc cam 101 so as to compensate for backlash.

This arrangement is disclosed in detail in Figs. 4 and 5.

An additional improvement in operation can be achieved by providing a resilient coupling between the disc cam bush 1011 and the wheel 107. The disc cam 101, the disc cam bush 1011 and the wheel 107 initially form a structural unit which is supported on the' spindle 110 so as to be loosely rotatable thereon. The resilient coupling is conveniently formed by constructing the body of the wheel 107 in the manner of a spring casing of which the disc cam bush 1011 forms the core. Both parts, namely the wheel member 107 and the disc cam bush 1011 will then be coupled to each other by means of a spiral spring disposed in the wheel 107.

When clockwork mechanisms are installed into clock cases of the most diverse kind structural difficulties often arise because it is sometimes not possible to combine the arrangement of the dial and the arrangement of the non-functional pendulum in a suitable manner.

It is possible to provide two stepping motors, one for indexing the hands mechanism which indicates second, minutes and hours and the other for driving the nonfunctional pendulum. Both systems are mechanically separated from each other so that the hands mechanisms and the pendulum drive device can be mounted completely independently of each other in the clock case. Both subassemblies are then connected to each other merely by means of cables or wires. The dry battery supplying the feed and the crystal control circuit can be associated with one or the other subassemblies as required. This further embodiment is of substantial advantage for clocks with casings of large dimensions.

The hands mechanism and more particularly the minute spindle may be associated with a disc cam by which at least one hammer can be raised, for example during the hourly rotating motion, and can be released at the full hour. Due to its own deadweight or by means of spring pull, the hammer will then drop upon a gong or bell and thus provide a single gong tone.

In this way and particularly if the slightly increased current consumption of the stepping mechanism can be tolerated, it is possible with few means to develbp the preferred clock into a chiming clock which performs simple chimes.

The preferred clock offers the advantage that it operates reliably with only slight wear, it permits the time to be indicated with great accuracy and is insensitive with regard to impacts or shock and with regard to the location of the clock.

WHAT WE CLAIM IS:- 1. An electric clock comprising a time keeping element for the time-defining regulation of the clock mechanism and a torsion pendulum which is not provided for regulating the clock but is arranged to be driven by a drive member arranged to be drivingly and operatively coupled in the course of its rotating motion with a driven element which is coupled to the torsion pendulum by being attached to a torsion spring of the pendulum, there being provided means for compensating for discrepancies between the motion of the drive member and the motion of the torsion pendulum, the drive member being constructed as a rotating disc cam arranged to be intermittently driving coupled by means of one or more cams thereon to the driven element which is attached to the torsion spring so as to be movable therewith in a horizontal plane and which is constructed as an elongate element, the time keeping element comprising an electronic crystal in an oscillating circuit arranged to control at least one electric motor via a frequency divider circuit and via an output stage, the electric motor being arranged to index the hands mechanism and the electric motor or another of the electric motors being arranged to index the disc cam which drives the torsion pendulum.

2. An electric clock as claimed in claim 1, in which the or each electric motor comprises an electric stepping motor which is polarized by at least one permanent magnet.

3. An electric clock as claimed in claim 2, in which the polarized electromagnetic stepping motor is provided with a cylindrical, permanent magnetic rotor which is peripherally magnetized and whose circumference cooperates with magnetic laminations which form the stator and provide varying air gaps along the rotor circumference and which are disposed in the magnetic circuit of an electric coil.

4. An electric clock as claimed in claim 1, in which a coupling arranged to be temporarily disengaged when movement of the disc cam is restrained via the driven element by the torsion pendulum is disposed in the drive connection between the electric motor and the disc cam.

5. An electric clock as claimed in claim 4, in which the coupling is formed by a displaceable gearwheed which is disposed in a gear transmission between the electric motor and the disc cam and which is disengageably engaged with the tooth system of a fixedly supported wheel on the electric motor side and is in constant engagement with the tooth system of a further gearwheel which is constantly coupled to the disc cam, so that, under the action of the driving force provided by the fixedly supported wheel, the displaceable gearwheel can pivot outwardly against the action of a force which tends to maintain tooth engagement between the said gearwheel and the fixedly supported gearwheel.

6. An electric clock as claimed in claim 5, in which the displaceable gearwheel is disposed on a rocker arranged to be pivoted about the bearing point of the further gearwheed, displacement of the displaceable gearwheel being limited by stop abut

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (16)

**WARNING** start of CLMS field may overlap end of DESC **. coupling is conveniently formed by constructing the body of the wheel 107 in the manner of a spring casing of which the disc cam bush 1011 forms the core. Both parts, namely the wheel member 107 and the disc cam bush 1011 will then be coupled to each other by means of a spiral spring disposed in the wheel 107. When clockwork mechanisms are installed into clock cases of the most diverse kind structural difficulties often arise because it is sometimes not possible to combine the arrangement of the dial and the arrangement of the non-functional pendulum in a suitable manner. It is possible to provide two stepping motors, one for indexing the hands mechanism which indicates second, minutes and hours and the other for driving the nonfunctional pendulum. Both systems are mechanically separated from each other so that the hands mechanisms and the pendulum drive device can be mounted completely independently of each other in the clock case. Both subassemblies are then connected to each other merely by means of cables or wires. The dry battery supplying the feed and the crystal control circuit can be associated with one or the other subassemblies as required. This further embodiment is of substantial advantage for clocks with casings of large dimensions. The hands mechanism and more particularly the minute spindle may be associated with a disc cam by which at least one hammer can be raised, for example during the hourly rotating motion, and can be released at the full hour. Due to its own deadweight or by means of spring pull, the hammer will then drop upon a gong or bell and thus provide a single gong tone. In this way and particularly if the slightly increased current consumption of the stepping mechanism can be tolerated, it is possible with few means to develbp the preferred clock into a chiming clock which performs simple chimes. The preferred clock offers the advantage that it operates reliably with only slight wear, it permits the time to be indicated with great accuracy and is insensitive with regard to impacts or shock and with regard to the location of the clock. WHAT WE CLAIM IS:-

1. An electric clock comprising a time keeping element for the time-defining regulation of the clock mechanism and a torsion pendulum which is not provided for regulating the clock but is arranged to be driven by a drive member arranged to be drivingly and operatively coupled in the course of its rotating motion with a driven element which is coupled to the torsion pendulum by being attached to a torsion spring of the pendulum, there being provided means for compensating for discrepancies between the motion of the drive member and the motion of the torsion pendulum, the drive member being constructed as a rotating disc cam arranged to be intermittently driving coupled by means of one or more cams thereon to the driven element which is attached to the torsion spring so as to be movable therewith in a horizontal plane and which is constructed as an elongate element, the time keeping element comprising an electronic crystal in an oscillating circuit arranged to control at least one electric motor via a frequency divider circuit and via an output stage, the electric motor being arranged to index the hands mechanism and the electric motor or another of the electric motors being arranged to index the disc cam which drives the torsion pendulum.

2. An electric clock as claimed in claim 1, in which the or each electric motor comprises an electric stepping motor which is polarized by at least one permanent magnet.

3. An electric clock as claimed in claim 2, in which the polarized electromagnetic stepping motor is provided with a cylindrical, permanent magnetic rotor which is peripherally magnetized and whose circumference cooperates with magnetic laminations which form the stator and provide varying air gaps along the rotor circumference and which are disposed in the magnetic circuit of an electric coil.

4. An electric clock as claimed in claim 1, in which a coupling arranged to be temporarily disengaged when movement of the disc cam is restrained via the driven element by the torsion pendulum is disposed in the drive connection between the electric motor and the disc cam.

5. An electric clock as claimed in claim 4, in which the coupling is formed by a displaceable gearwheed which is disposed in a gear transmission between the electric motor and the disc cam and which is disengageably engaged with the tooth system of a fixedly supported wheel on the electric motor side and is in constant engagement with the tooth system of a further gearwheel which is constantly coupled to the disc cam, so that, under the action of the driving force provided by the fixedly supported wheel, the displaceable gearwheel can pivot outwardly against the action of a force which tends to maintain tooth engagement between the said gearwheel and the fixedly supported gearwheel.

6. An electric clock as claimed in claim 5, in which the displaceable gearwheel is disposed on a rocker arranged to be pivoted about the bearing point of the further gearwheed, displacement of the displaceable gearwheel being limited by stop abut

ments, the disc cam being coaxially connected to the further gearwheel.

7. An electric clock as claimed in claim 6, in which the further gearwheel is biased by a spring connected to the rocker so as to compensate for backlash.

8. An electric clock as claimed in claim 5, in which the disc cam is resiliently connected to the further gearwheel.

9. An electric clock as claimed in claim 8, in which the further gearwheel is constructed as a spring casing and is connected to the disc cam by means of a spiral spring which is inserted into said spring casing.

10. An electric clock as claimed in claim 1, in which the torsion pendulum is rigid and is guided in a bottom radial and thrust bearing and in a top radial bearing, the torsion spring being helical and coaxially surrounding a pendulum rod, the bottom end of the torsion spring being fixed to the pendulum rod and the top end of the torsion spring being fixed to the top radial bearing, a sleeve-like transmission element being disposed on the helical spring in the top region thereof and being connected through the driven element to the clock mechanism so as to transmit torque to the helical spring.

11. An electric clock as claimed - in claim 10, in which the torsion pendulum is provided with an elongate concentric bush into the top of which the pendulum rod is inserted, radial webs being integrally formed on the elongate concentric bush to the exterior of which webs are attached open, half spherical shells with corresponding cover parts placed upon the open shells to form spheres, the elongate concentric bush together with the webs and open half spherical shells being integrally formed by plastics injection moulding.

12. An electric clock as claimed in claim 11, in which the elongate concentric bush is provided at the top with an extension which surrounds the pendulum rod and is surrounded by turns of the helical spring which is secured at its lower end on an extension of the pendulum rod by means of a fixing ring.

13. An electric clock as claimed in claim 10, in which there is provided an externally screwthreaded sleeve which retains the top of the helical spring and guides the top of the pendulum rod and whose cylindrical part is expanded into a stationary retaining member, which is injection moulded from plastics.

14. An electric clock as claimed in claim 11, in which the elongate concentric bush is provided at its bottom end with a bore into which there is inserted a cylindrical part which forms the thrust bearing and a bush which forms the radial bearing.

15. An electric clock as claimed in claim 14, in which, in order to absorb loads applied axially of the torsion pendulum, the cylindrical part forming the thrust bearing is suspended in the axial direction by a helical spring and axial movement of the bush is limited by a stop abutment.

16. An electric clock substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.