GB2156109A

GB2156109A - A friction coupling for an electric clock with a decorative torsion pendulum

Info

Publication number: GB2156109A
Application number: GB08432207A
Authority: GB
Inventors: Helmut Hechinger; Carl Bank
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-02-25
Filing date: 1984-12-20
Publication date: 1985-10-02
Also published as: GB8432207D0; DE3406874C1; GB2156109B

Abstract

A friction coupling for the drive-connection of the seconds shaft (16) of an electrically driven clockwork to a star wheel (20) which is mounted rotatably on the seconds shaft (16) and which transmits the drive energy to the torsion spring of a decorative rotary pendulum, the friction coupling including a compressing spring (46) which is clamped frictionally between the star wheel (20) and a counterpressure member (40) which is fixed for rotation with the seconds shaft (16). To employ the maximum torque which can be transmitted by the friction coupling, the distance between the star wheel (20) and the counterpressure member (40), and therefore the tension of the compression spring, can be varied. <IMAGE>

Description

SPECIFICATION A friction coupling for an electric clock with a decorative torsion pendulum The invention relates to a friction coupling for making driving connection of the seconds shaft of an electrically driven clockwork to a star wheel which drives a decorative torsion pendulum.

German Utility Model 75 36 988 has disclosed a friction coupling of this type. The friction coupling is intended to transmit as uniform a torque as possible for a member fixed to the seconds shaft of the clock, to a star wheel which is rotatably mounted on the seconds shaft and which itself transmits the torque to the torsion spring of the purely decorative torsion pendulum, during each oscillation of the pendulum. It has been shown that, because of production tolerances and different material properties, the maximum torque transmitted by the friction coupling cannot be kept constant in the known design of the friction coupling, so that the amplitude of oscillation of the torsion pendulum can differ by up to + 30% from the desired value.Such high tolerances occur principally, because very light-weight plastic balls have often been used recently for torsion pendulums of this type, so that even very slight changes in the restoring force of the thin torsion spring have a considerable effect on the amplitude of oscillation.

A main object of the invention is to provide a friction coupling in which later correction of the maximum torque transmitted by it is possible.

According to the invention there is provided a friction coupling for making driving connection of the seconds shaft of an electrically driven clockwork to a star wheel which is mounted rotatably on the seconds shaft and which transmits drive energy to a torsion spring of a decorative rotary pendulum, the friction coupling containing a compression spring which is frictionally clamped between the star wheel and a counterpressure member which is fixed to the seconds shaft for rotation therewith, wherein the distance between the star wheel and the counterpressure member is adjustable.

As a result of a simple adjustment of the distance between the star wheel and the counterpressure member, the torsion of the compression spring and thus also the maximum torque determined by the friction of the compression spring on the two relatively-rotatable parts can be varied.

The counterpressure member may consist of a bearing plate for the compression spring, which plate is fixed on the seconds shaft.

The design of the counterpressure member as a bearing plate for the compression spring, is particularly advantageous. The bearing plate is preferably displaceable in the axial direction with such great difficulty that it maintains the entire friction coupling on the seconds shaft and is axially displaceable only when a relatively high axial load is exerted on the seconds shaft. In the simplest embodiment, this can be ensured simply by means of a push fit.

The bearing plate may be supported on the side opposite the compression spring, on a nut or on a supporting member fixed to the star wheel, the nut and the supporting member being connected to one another by an axial threaded connection.

The bearing plate is adjusted axially relative to the star wheel preferably by means of the nut which, when rotated, causes the distance between the star wheel and the bearing plate to be changed in either direction.

Preferab,r the compression spring is a helical spring, whose diameter is greater than the maximum radius of the start wheel. This is advantageous because of the greater radial lever arm achieved thereby for the frictional forces transmitted.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a rear view of an electrically driven clock with a star wheel and a friction coupling, the decorative torsion pendulum driven by the star wheel being omitted for the sake of greater clarity, Figure 2 is a top view of the clock of Fig. 1, with the star wheel and friction coupling shown in position for attachment to the seconds shaft of the clock, Figure 3 shows an enlarged view of the star wheel and friction coupling of Fig. 1, Figure 4 is a section of the line IV-IV in Fig. 3, and Figure 5 is a section corresponding to that of Fig. 4, with the mutually adjustable parts set in a different way.

The electric clock illustrated in Figs. 1 and 2 has a housing 10 with a battery compartment 1 2. The drive shafts, indicated generally at 14, of the clockwork which is not shown, project from the front of the housing 1 0. The seconds shaft 1 6 of the clockwork projects outwardly from the rear wall of the housing 10, which rear wall is illustrated in Fig. 1.

The assembly consisting of a star wheel 20 and a friction coupling connected to it and designed as a whole by the reference 22 is pushed with a push fit, in the direction of the arrow 18, on to its outward-projecting part of the seconds shaft 16, so that it is positioned as shown in Fig. 1 against the rear wall of the housing 1 0. The star wheel has spaced drive arms 24 projecting radially outwardly, and when the star wheel 20 is rotated, these come to rest, in known manner and therefore not shown in any more detail, against, a drive member which is fastened to the torsion spring, not shown, of the torsion pendulum and thereby transmit to the torsion pendulum a drive force determined by the maximum torque of the friction coupling.

The design of the friction coupling according to the invention is shown in detail in Figs.

4 and 5. The star wheel 20 with its drive arms 24 is mounted loosely and rotatably on the seconds shaft 1 6 of the clockwork. The star wheel 20 also has an axially projecting annular web 26, to which is connected firmly a generally channel-shaped supporting member 28, the profile of which is open towards the star wheel 20. The supporting member 28 has an axially extending inner annular web 30 which is at a distance from the seconds shaft 1 6 and which carries an internal thread 32 pointing towards the seconds shaft 1 6.

Connected to the internal thread 32 is an external thread 34 of a nut 36 which has, in its axial outer surface, radial adjusting slots 38 for the engagement of a screwing tool.

When the nut 36 is rotated, it can be adjusted axially relative to the supporting member 28.

Against the inner end face of the nut 36 rests a bearing plate 40 which is pressed onto the seconds shaft 1 6 by means of an axial sleeve 42, so that it retains the arrangement consisting of the star wheel 20 and friction coupling 22 on the seconds shaft 1 6. On a radial outer edge 44 of the bearing plate 40 is supported one end of a helical compression spring 46, the opposite end of which is supported in an annular groove 48 of the star wheel 20.

When the nut 36 is rotated, it moves axially relative to the supporting member 28, as a result of which the distance between the star wheel 20 and the bearing plate 40, and therefore the tension of the compression spring 46, changes. It is possible to adjust the distance between the fully tensioned position according to Fig. 4 and the fully relaxed position according to Fig. 5. In the fully relaxed position, the bearing plate 40 rests on bearing bosses 50 provided for it on the inner edge of the inner annular web 30. When the nut 36 is rotated inwardly, the compression spring 46 is tensioned, and the maximum torque transmitted by the friction coupling 22 is therefore increased, whereas, when the nut 36 is rotated outwardly, the compression spring 46 is relaxed and the maximum torque transmitted is consequently reduced.

Claims

1. A friction coupling for making driving connection of the seconds shaft of an electro cally drive clockwork to a star wheel which is mounted rotatably on the seconds shaft and which transmits driven energy to a torsion spring of a decorative rotary pendulum, the friction coupling containing a compression spring which is frictionally clamped between the star wheel and a counterpressure member which is fixed to the seconds shaft for rotation therewith, wherein the distance between the star wheel and the counterpressure member is adjustable.

2. A friction coupling according to Claim 1, wherein the counterpressure member consists of a bearing plate for the compression spring, which plate is fixed on the seconds shaft.

3. A friction coupling according to Claim 2, wherein the bearing plate is supported, on the side opposite the compression spring, on a nut or on a supporting member fixed to the star wheel, the nut and the supporting member being connected to one another by an axial threaded connection.

4. A friction coupling according to Claim 3, wherein the nut has an external thread and the supporting member has an internal thread which engage with each other, the adhesion torgue of the threaded connection being greater than the maximum torque transmitted by the friction coupling.

5. A friction coupling according to any one of Claims 2 to 4, wherein the end of the compression spring opposite the bearing plate is supported in an annular groove of the star wheel.

6. A friction coupling according to any one of the preceding claims, wherein the compression spring is a helical spring, whose diameter is greater than the maximum radius of the star wheel.

7. A friction coupling substantially as herein described with reference to the accompanying drawings.