GB1566678A

GB1566678A - Pendulum clockwork mechanusm

Info

Publication number: GB1566678A
Application number: GB1887778A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-05-11
Filing date: 1978-05-11
Publication date: 1980-05-08

Description

(54) PENDULUM CLOCKWORK MECHANISM (71) 1, RONALD BLESSLEY HORST MANN, a British subject, of Merryfields, Colerne, Nr. Chippenham, Wiltshire SN14 8DG, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to pendulum clockwork mechanisms.

Traditional pendulum clocks have a pendulum which is maintained in constant amplitude oscillation by rocking movement of a crutch which receives periodic impulses from an escapement mechanism. The escapement mechanism is powered by an energy source which in a pendulum clock is usually gravitational in the form of a weight which descends progressively. Other energy sources may, however, be used.

The present invention affords a pendulum clockwork mechanism in which a mechanical escapement mechanism is avoided.

According to the present invention there is provided a clockwork mechanism having a pendulum the drive to which includes a rotary escape wheel of magnetic material formed with a circumferentially continuous wavy track and an oscillatory member carrying at least one permanent bar magnet having a single pole end cooperating with the escape wheel, the oscillatory member being connected through a rotatable layshaft to a crutch which is in driving engagement with the pendulum.

The rotary escape wheel and the oscillatory member cooperating with it through the permanent magnet together constitute a magnetic escapement, as distinct from the mechanical escapement traditionally employed in pendulum clocks. Magnetic escapements are known per se in the horological field and they have many advantages, notable among which are consistent accuracy and low energy loss.

In a preferred embodiment of the invention the permanent magnet cooperates with one face only of the escape wheel, so that the magnet may be free of slots or bifurcations. Preferably the escape wheel is visible through an aperture in a clock face, the visible face of the escape wheel being preferably opposite the face which cooperates with the magnet. By arranging for the escape wheel to be visible in the clock face a convenient indication is given of the operation of the clock, through the periodic stepwise rotations of the escape wheel. Such a visual running indication is desirable in this instance, especially where the pendulum itself is not visible, since the magnetic escapement is completely silent in operation unlike its mechanical counterpart.This silent operation makes the pendulum clock suitable for use in rooms where obtrusive noise would be undesirable such as, for example, bedrooms.

The layshaft preferably extends perpendicular to the clock face, so that the plane of oscillation of the pendulum is at the rear of the clock, while the escape wheel and its cooperating oscillatory member are near the front of the clock. The arrangement of the layshaft makes it possible to provide a suitable small clearance between the permanent magnet and the cooperating face of the escape wheel without imposing severe tolerances on the mounting of the pendulum itself. This is an important practical consideration affecting reliable running and the manufacturing cost of the clock.

Preferablv the escapement is provided with guard pins which project from the oscillatory member into the path of rotary movement of the escape wheel to prevent the latter running away, in a manner known per se.

An embodiment of the invention is illustrated, by way of example, in the accompanying purely diagrammatic drawings, in which: Figure 1 is a front elevation, on a reduced scale, of a clock using a pendulum clockwork mechanism embodying the invention Figure 2 is a plan view of the front of the clockwork mechanism, with the clock face removed to show the magnetic escapement, and Figure 3 is a side view of the clockwork mechanism, partly in section on line III-III of Figure 2.

The illustrated pendulum clockwork mechanism according to the invention is embodied as a grandfather clock and has a wooden pedestal case 1 in which a pendulum 2 oscillates. The pendulum 2 is connected by a connector piece 3 to a leaf spring 4 by which the pendulum is suspended from a boss fixed behind a rear plate 5 of the clockwork frame. The pendulum connector piece 3 is embraced by the two arms of a crutch 6 which is attached to one end of a horizontal layshaft 7 (Figures 2 and 3) extending between the rear plate S and a front plate 8 of the clockwork frame, the front plate 8 being parallel to and behind a dial plate 9 of the clock, omitted from Figure 2 for the safe of clarity.

The front end of the shaft 7 projects beyond the front housing plate 8 and is located between the plate 8 and the dial plate 9.

This front end of the shaft 7 carries an oscillatory member 10 which depends from the shaft 7 (Figure 2) and which is bifurcated at its lower end. The two lower ends of the bifurcated oscillatory member 10 are disposed substantially diametrically opposite each other with respect to a rotary escape wheel 11 mounted upon a shaft 12 parallel to the shaft 7.

The magnetic escape wheel 11 is made of a ferro-magnetic low loss material and has a number of radial outer spokes spaced apart at equal circumferential intervals, supported by an equal number of inner radial spokes spaced apart at the same cir cumferential intervals but staggered by a half of one such interval circumferentially with respect to the outer spokes. The portions of the escape wheel 11 interconnecting the inner and outer spokes constitute in effect a wavy circumferentially continuous track or path of magnetic material.

One of the lower ends of the oscillatory member 10 carries a short unslotted cylindrical permanent bar magnet 13 which projects towards the plane of the escape wheel 11 and which has a single flat pole end spaced a short distance, typically of the order of a few thousanths of an inch, from the rear face of the escape wheel 11.

The position of the permanent magnet 13 is such that upon rotation of the escape wheel 11 the magnet 13 is made to follow the wavy peripheral magnetic path defined between the radial spokes of the escape wheel, causing the oscillatory member 10 to oscillate about the axis of the shaft 7, and inducing corresponding oscillations of the crutch 6 which imparts periodic impulses to the pendulum 2 to maintain the latter in constant amplitude oscillation.

In order to drive the pendulum 2 from the escape wheel 11 as described above a constant torque must be applied to the escape wheel. This torque can be derived from any suitable drive source. In the illustrated embodiment the torque applied to the escape wheel 11 is derived from a weight (not shown) suspended from a wire 14 which is wound upon a drum 15 rotatably supported between the plates 5 and 8. The drum 15 carries a gear wheel 16 at its front end, the gear wheel 16 forming the head of a reduction gear train 17 of a known type. The reduction gear train 17 is connected to the escape wheel shaft 12 to apply a constant torque thereto. The oscillation of the pendulum 2 allows the escape wheel 11 to make periodic step-wise rotations by an amount equal to the "pitch" or wavelength of the wavy track of the escape wheel 11, allowing the weight on the wire 14 to descend.These rotations are transmitted through a further reduction gear train 18 to concentric shafts 19, 20 which project through the centre of the dial plate 9 and carry hour and minute hands l9a, 20a (Figure 1.) respectively, not shown in Figures 2 and 3.

The escape wheel 11 is mounted in the centre of a circular aperture 21 in the dial plate 9, above the concentric shafts 19, 20, so that the step-wise rotations of the escape wheel 11 are visible in the clock face, providing a silent running indication.

A winding shaft 22 is connected to the drum 15 through a ratchet mechanism (not shown), the winding shaft 22 being accessible through a hole in the dial plate 9, so that the clock can be wound up periodically by rotating the drum 15 to raise the weight. Because of the relatively low losses associated with the magnetic escape mechanism, in a clock constructed as shown in the drawings the full descent of the weight will be equivalent to one month of continuous running before the clock has to be rewound. Moreover, the magnetic escapement, the pendulum, and the gear reduction trains can be constructed with a sufficiently high degree of accuracy to achieve a time keeping precision of the order of five seconds per month.

In order to prevent the escape wheel 11 running away under the torque applied to it, in the event of loss of magnetic coupling, two guard pins (not shown) project forwardly from the two lower ends of the bifurcated oscillatory member 10 into the path of movement of the outer spokes of the escape wheel 11 in a manner known per se.

In a variant of the illustrated embodiment respective permanent bar magnets may be carried at the two lower ends of the bifurcated oscillatory member 10, having respective single poles of identical polarity cooperating with diametrically opposite portions of the escape wheel 11.

Although the invention is described with reference to a pendulum clock, it will be appreciated that the same clockwork mechanism could be utilized in other applications, for example in electrical time switches, scientific instruments or toys.

WHAT I CLAIM IS: - 1. A pendulum clockwork mechanism having a pendulum the drive to which includes a rotary escape wheel of magnetic material formed with a circumferentially continuous wavy track and an oscillatory member carrying at least one permanent bar magnet having a single pole end cocooperating with the escape wheel, the oscillatory member being connected through a rotatable layshaft to a crutch which is in driving engagement with the pendulum.

2. A mechanism according to Claim 1, in which the or each permanent magnet cooperates with one face only of the escape wheel.

3. A mechanism according to Claim 2, in which the escape wheel is visible through an aperture in a clock face, the visible face of the escape wheel being opposite the face which cooperates with the magnet.

4. A mechanism according to any one of Claims 1 to 3, in which guard pins project from the oscillatory member into the path of rotary movement of the escape wheel to prevent the latter running away.

5. A mechanism according to any one of the preceding claims, in which the escape wheel is mounted on a shaft to which a torque is applied by a weight which descends as the escape wheel rotates.

7. A pendulum clockwork mechanism substantially as herein described with reference to and as illustrated in Figures 2 and 3 of the accompanying drawings.

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

Claims

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

appreciated that the same clockwork mechanism could be utilized in other applications, for example in electrical time switches, scientific instruments or toys.

WHAT I CLAIM IS: -

1. A pendulum clockwork mechanism having a pendulum the drive to which includes a rotary escape wheel of magnetic material formed with a circumferentially continuous wavy track and an oscillatory member carrying at least one permanent bar magnet having a single pole end cocooperating with the escape wheel, the oscillatory member being connected through a rotatable layshaft to a crutch which is in driving engagement with the pendulum.

2. A mechanism according to Claim 1, in which the or each permanent magnet cooperates with one face only of the escape wheel.

3. A mechanism according to Claim 2, in which the escape wheel is visible through an aperture in a clock face, the visible face of the escape wheel being opposite the face which cooperates with the magnet.

4. A mechanism according to any one of Claims 1 to 3, in which guard pins project from the oscillatory member into the path of rotary movement of the escape wheel to prevent the latter running away.

5. A mechanism according to any one of the preceding claims, in which the escape wheel is mounted on a shaft to which a torque is applied by a weight which descends as the escape wheel rotates.

7. A pendulum clockwork mechanism substantially as herein described with reference to and as illustrated in Figures 2 and 3 of the accompanying drawings.