GB2235793A - Clock - Google Patents

Abstract

A clock (10) comprises a circular track member (11) enclosing an area, with two externally-toothed endless belts (14) guided in respective tracks in the track member. Two pointers, of which one (15a) is thinner and longer than the other (15b), are connected one to each belt and extend radially inwardly of the track member. A respective electric drive motor is drivingly connected by a cog to each belt and the motors are operated to drive the belts in the same rotational direction but at different speeds so that one pointer (15a) executes a complete revolution in one hour and the other pointer (15b) a complete revolution in twelve hours. In a second embodiment solenoids which drive pawls to index the belts replace the motor drive. <IMAGE>

Description

CLOCK The present invention relates to a clock.

Clocks of a wide variety of forms are known but a feature common to substantially all clocks is drive of the hands from a single central axle, usually in the form of a coaxial shaft and sleeve. Such an arrangement obliges the drive mechanism to be centrally located, or at least disposed within the circumference of the clock dial, and to be concealed by a disc forming a face, unless the mechanism is intentionally a visual feature of the clock. In some clock designs the hands are represented by markings on rotating discs or rings, which thus supplant the more conventional pointers. All such clocks have the appearance of a solid object, or of a mechanical contrivance if the mechanism is exposed.

The present invention has as its principal object the provision of a clock which represents an alternative choice to conventional designs of the kind described above and which has a simple and aesthetic appearance, especially a skeletal format which avoids the appearance of a solid object yet is not marred by the presence of an exposed drive mechanism.

Other objects and advantages of the invention will be apparent from the following description.

According to the present invention there is provided a clock comprising an endless track member enclosing an area, two endless driven elements guided in respective endless tracks in the track member, two visually distinguishable pointers connected one to each driven element and extending inwardly of the track member in the general direction of the centre of the enclosed area, and drive means drivingly coupled to the driven elements for movement thereof in the same direction along the tracks at respectively different speeds to effect a full revolution of one driven element in one hour and of the other driven element in twelve hours.

At least one of the driven elements may be drivable to carry out continuous movement along its track. Alternatively, the movement may be stepped. The nature of the movement can be chosen in dependence on the desired manner of marking time change, i.e. by abrupt and discernible movement of a pointer or by a continuous and substantially indiscernible movement. Consideration can also be given to economy of operation of the driven means, as reduced energy consumption may be associated with a stepped movement provided by periodically operable drive means.

Conveniently, each of the driven elements is an externally toothed flexible belt, which may be a commercially available and therefore inexpensive item. Such belts can also accommodate departures of the tracks from purely circular, for example, polygonal or slightly oval tracks.

Various forms of drive means, including mechanical, can be used, but a particularly preferred form is electrical. Electrical drive means, whether operated by mains or battery current, has the merit of compactness, light weight and a low or negligible maintenance requirement. The drive means can take the form of atXTiast~one electrical motor, for example a step motor, drivingly coupled to the driven elements. The coupling can be by way of cogs, which may be associated with gear transmissions providing appropriate speed reductions. The drive means can also take the form of a respective solenoid drivingly coupled to each driven member, for example by way of pawls. The pawls can be resiliently biassed to restore the solenoids to a start setting.

Control of the electrical drive means, whether motors or solenoids, and thereby of the driving of the driven elements at the requisite speeds is preferably by way of electronic timing means.

In the track member, the tracks are preferably arranged side-by-side and may be defined by at least one partly closed channel. Two channels can be provided and separated by wall means within the track member.

To minimise friction, the driven elements and the tracks can contact each other by way of a low-friction coating material, such as polytetrafluoroethylene. Coatings of the material can be provided on the driven elements and/or on the track surfaces.

The pointers can be detachably connected to the driven elements and preferably in such a manner that if either pointer isstruck with a force sufficient to otherwise cause damage, the pointer will detach but can be reattached without difficulty. The connection -to the driven elements can be by way of transparent portions so that from a distance the pointers, if of solid colour, seem to float freely of the track member.

The clock can include mounting means to permit mounting on a vertical surface. If intended to be supported on a horizontal surface, the clock can include a base for that purpose.

Embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a partly broken-away front elevation of clock embody ing the invention, the clock having a support base; and Fig. 2 is a cross-section, to an enlarged scale and along the line II-II of Fig. 1, of the clock, with the base omitted and with schematic illustration of one form of drive means.

Referring now to the drawings, there is shown a clock 10 comprising an endless track member 11 which encloses an area and which in the illustrated embodiment is circular. The track member shape can, however, be a polygon with shallow angles, for example a dodecagon. The track member is preferably a circularly bent aluminium extrusion, but it can be made of plastics or other suitable material. Support of the clock on horizontal surfaces is provided by a cylindrical base 12 located at an intended lowermost portion of the track member. The track member can also be provided with mounting means, for example an opening to receive a hook or pin, to permit mounting on a wall surface, in which case the base is omitted.

Located within the track member are two endless guide tracks which are defined by two partly-closed channels 13 disposed side-by-side and separated by a T-section wall. Movably guided in each channel is a respective endless externally-toothed flexible belt 14 of rubber or plastics. The belts can be commercially available items and the dimensions of the track member can, for reasons of economy, by partly dictated by the dimensions of available suitable belts. Friction between the belts and the channel surfaces can be reduced by a coating of polytetrafluoroethylene or other low-friction material applied to the channel surfaces and/or the relevant belt surfaces. - Connected to the two belts 13 are respective pointers 15a and 15b of which the pointer 15a is, as shown in Fig. 1, thinner and longer than the pointer 15b.This difference in shape permits conventional recognition of the pointer 15a as a minute hand of the clock and the pointer 15b as an hour hand. The two pointers extend radially inwardly of the track member 10 towards the centre of the enclosed area, but end at spacings from that centre. Connection of each pointer to the respective one of the belts 13 is by way of a transparent foot portion 16, which is adhesively bonded or otherwise firmly secured to the internal belt face and which is slidably guided in a respective circular slot defined by the entrance to the associated channel. The transparent foot portion can be, for example, an acrylic plastics material.The pointers, which can be of solid colour plastics material, are detachably connected to the foot portions 16 by a simply produced but firm coupling, such as a pressurable plug-and-socket coupling in which the pointer is plugged into the foot portion or vice versa. The coupling is preferably such that if either pointer is accidentally knocked, that pointer can detach from its foot portion and be reattached with ease.

The use of a transparent portion 16 to connect each pointer to its belt is not necessary for technical reasons, but merely to provide the effect of the pointer apparently floating at a spacing from the track member. The aesthetics of the clock are further enhanced by omission of numbers or time markings. Numbers or other markings could be provided on the intended viewing side of the track member, but familiarity with the conventional disposition of numbers means that time should be able to be read simply from the angular position of the pointers and the difference in their appearance.

Drive of the belts 14 and thus of the pointers 15a and 15b is by way of respective cogs 17 and electric stepper motors 18, the cogs engaging the teeth of the belts by way of short slots in the lowermost portion of the track member 11. The couplings between the motors and the cogs include speed reduction gear trains (not shown). The motors, which may be powered by mains or battery current, are controlled to move the belts in the same rotational direction but at respectively different speeds by way of an electronic control unit 19, which provides timed drive pulses for the motors so that the belt with the pointer l5a completes one revolution in one hour and the belt with the pointer 15b one revolution in twelve hours. Intermittent drive of the motors and belts is particularly advantageous from the viewpoint of minimising current consumption.The drive arrangement should also include a freewheel to permit manual adjustment of the time indication by movement of the pointers at least in the advance direction.

The drive components are conveniently housed in the base 12 when provided, but in the absence of the base the components are sufficiently compact-to require only a small housing at the lowermost portion of the track member. If the track member is without time markings, the orientation of the clock is in fact a matter of free choice and the point of action of the drive cogs can be- in any angular postion.

It is also possible to locate part of the drive arrangement, in particular the control unit 19, separately from the rest of the clock. The control unit can be linked to the motors simply by electrical wires.

Such a separate location may be desirabie if, for example, current is provided by batteries which might add undue bulk to the outline of the clock.

In another embodiment, drive of the two belts 14 can be provided by respective solenoids, each having its plunger drivingly coupled to the teeth of the associated belt by way of a dog. The dog can be in the form of a doubled-over leaf spring which, on excitation of the solenoid and retraction of the plunger, displaces the belt by a predetermined amount and at the same time is stressed. When excitation of the solenoid is terminated, relief of the spring takes place to return the plunger to its start setting, with the spring idling in the manner of a pawl across the belt teeth without displacing the belt.

Drive of the belts by such a pawl and ratchet system would thus be unidirectional. Other forms of ratchet coupling are possible and drive can also be by other methods, including clockwork mechanisms, screw or worm drives,and remote drive units with cable or shaft coupling to drive cogs. Externally toothed belts are preferred, but solid rings, cables and other forms of endless element can be used in conjunction with appropriate drive arrangements.

The illustrated cross-section of the track member 10 is merely by way of example. If the pointers 15a and 15b are connected to the belts 14 adjacent to their edges rather than centrally, then the track member cross-section can be correspondingly shaped so that the exit slots for the foot portions 16 of the pointers are disposed at ends of the channel cross-sections. The provision of a separating wall between the channels can also be disposed with, so that the guide tracks for the belts are, in effect, simply respective portions of a single channel. The internal cross-sectional shape of the track member may be determined merely by the requirement to provide guide tracks for the two driven elements, in accordance with their cross-section and relative disposition, while retaining the elements in place and permitting the pointers to emerge from the track member. Thus, for example, the belts may be side-by side, concentric or staggered.

A clock embodying the invention has a simple but aesthetic appearance and when placed against a wall, for example, appears as lines rather than a solid object, any pattern or colour of the wall surface being visible through-the clock. The pointers can be made to appear as independently moving objects and this effect can be enhanced by, for example, applying coatings of a highly light reflective or luminescent material to the pointers.

Claims (21)

1. A clock comprising an endless track member enclosing an area, two endless driven elements guided in respective endless tracks in the track member, two visually distinguishable pointers connected one to each driven element and extending inwardly of the track member in the general direction of the centre of the enclosed area, and drive means drivingly coupled to the driven elements for movement thereof in the same direction along the tracks at respectively different speeds to effect a full revolution of one driven element in one hour and of the other driven element in twelve hours.

2. A clock as claimed in claim 1, wherein at least one of the driven elements is drivable by the drive means to carry out continuous movement along the respective track.

3. A clock as claimed in claim 1, wherein at least one of the driven elements is drivable by the drive means to carry out stepped movement along the respective track.

4. A clock as claimed in any one of the preceding claims, wherein each of the driven elements is an externally toothed flexible belt.

5. A clock as claimed in any one of the preceding claims, the drive means being electrical.

6. A clock as claimed in claim 5, the drive means comprising at least one electric motor drivingly coupled to the driven elements.

7. A clock as claimed in claim6 , wherein the motors are drivingly.

coupled to the driven elements by cogs.

8. A clock as claimed in claim 5, the driven means comprising a respective solenoid drivingly coupled to each driven element.

9. A clock as claimed in claim 8, wherein the solenoids are drivingly coupled to the driven elements by pawls.

10. A clock as claimed in claim 9, wherein the pawls are resiliently biassed to restore the solenoids to a start state.

11. A clock as claimed in any one of claims 6 to 10, the drive means comprising electronic timing means to control driving of the driven elements.

12. A clock as claimed in any one of the preceding claims, wherein the tracks are circular.

13. A clock as claimed in any one of claims 1 to 11, wherein the tracks are polygonal.

14. A clock as claimed in any one of the preceding claims, wherein the tracks are arranged side-by-side in the track member.

15. A clock as claimed in any one of the preceding claims, wherein the tracks are defined by at least one partly closed channel in the track member.

16. A clock as claimed in any one of the preceding claims, wherein the driven elements and the tracks contact each other by way of a low-friction coating material.

17. A clock as claimed in any one of the preceding claims, wherein the pointers are detachably connected to the driven elements.

18. A clock as claimed in any one of the preceding claims, wherein the pointers are connected to the driven elements by transparent portions.

19. A clock as claimed in any one of the preceding claims, comprising mounting means for mounting of the clock on a vertical surface.

20. A clock as claimed in any one of the preceding claims, comprising a base for supporting the clock on a horizontal surface.

21. A clock substantially as hereinbefore described with reference to the accompanying drawings.