GB2078425A - Improvements in or relating to bells - Google Patents

Abstract

A volume control for a bell, e.g. of a subscriber's telephone, consists of a pad 34 of friction material which is urged against a clapper rod 18 by a movable cam 40 to vary the amplitude of vibration of a clapper 19. The volume of the bell can thus be adjusted whilst both bell gongs remain operative if there two such bell gongs. The clapper rod may be relatively stiff, in which case the amplitude of vibration is controlled by the friction pad only, or the clapper rod may be flexible so that the clapper is lifted relative to conical bell gongs. In the latter case the distance between the bell gongs increases upwardly due to their shape and so little friction is required between the friction pad and the clapper rod. <IMAGE>

Description

SPECIFICATION Improvements in or relating to bell assemblies This invention relates to bell assemblies and more particularly to means for varying the volume of sound emanating from a bell.

Various methods of achieving this have been attempted, the more usual methods involving physically restricting the movement of the clapper rod of the bell with a moveable stop which is adapted to be contacted by the clapper rod. One problem normally encountered with these methods is that if the movable stop is directly connected to the clapper rod mountings, such as by a lever the vibrations of the clapper rod can be transferred via the stop to the clapper rod mountings causing additional noises and rattles in the bell mechanism.

It is an object of the present invention therefore to provide a bell assembly in which the volume of the sound emanating from the bell can readily be varied without transferring extra noises to the bell mechanism.

In some bell assemblies, such as in a subscribers telephone unit, the clapper is moved between the two bell gongs and to vary the volume of sound emanating from the two gongs the usual method is to reduce the amplitude of vibration of the clapper until it only strikes one of the gongs. It is a further object of the present invention therefore to provide a bell assembly having a clapper which is adapted to move between and strike two bell gongs in which the volume of sound can be varied whilst the clapper continues to strike both of the gongs.

According to the present invention a bell assembly comprises a bell and a clapper mounted on a pivoted clapper rod and friction means mounted in a plane parallel to the plane of movement of the clapper rod and adapted to be forced into contact with the clapper rod, the force being variable such that an increasing force reduced the amplitude of the clapper rod and hence reduces the momentum of the clapper at its maximum amplitude thus reducing the volume of sound emonating from the bell.

The clapper rod may be relatively stiff such that there is minimum amount of deflection of the clapper in the direction of the applied frictional force, or the frictional force may be applied substantially equally to opposite sides of the clapper rod.

Alternatively the clapper rod is preferably relatively flexible and the clapper is deflected in the direction of the applied frictional force.

In this case the side of the bell struck by the clapper may be equidistant from the position of maximum amplitude of the clapper whatever its deflection i.e. the bell may be cylindrical in shape, or the distance of the side of the bell from the position of maximum amplitude of the clapper may vary with its deflection i.e.

the bell may be substantially conical in shape.

In the latter situation the effect of the frictional force deflecting the clapper will cause a reduction in sound with a smaller movement of the clapper if the distance of the side of the bell from the position of maximum amplitude increases in the direction of deflection of the clapper by the frictional force. Also in this situation the amount of frictional force on the clapper rod may be relatively low.

Preferably there are two bells, one arranged on each side of the clapper in the plane of movement of the clapper.

The friction means may comprise a pad of relatively high friction or of relatively low friction.

Preferably the pad is forced against the clapper rod by cam means.

The cam is preferably mounted on a lever which is moveably mounted adjacent to the clapper rod whereby movement of the lever in one direction forces the friction pad against the clapper rod.

The friction pad may be mounted on a resilient member mounted adjacent to the clapper rod, movement of the lever deflecting the resilient member and forcing the friction pad against the clapper rod.

The cam may be provided with a plurality of grooves which are contacted by a portion of the resilient member which acts as stops for the lever over the surface of the cam, each groove setting the bell assembly at a different volume of sound.

An embodiment of the invention will now be described by way of example only in which: Figure 1 is a cross-section view of a complete bell assembly according to the invention for a subscribers telephone unit, Figure 2 is a perspective view of a portion of the assembly, Figure 3 is a perspective view of the bell assembly as shown in Fig. 1 without the base, the bell gongs and the clapper operating mechanism, Figure 4 is a view of a portion of the bell assembly as seen from line 4-4 on Fig. 1 and Figure 5 is a schematic view of the relative positions of the clapper and two conical bell gongs during operation of the bell assembly.

The bell assembly comprises a base 10 on which are mounted two domed or substantially conical bell gongs 1 2 and 1 4. A clapper 1 9 is adapted to vibrate between the bell gongs 1 2 and 14, the clapper 1 9 being mounted on the end of a flexible clapper rod 18, the other end of which is secured to a plate assembly 24. A coil 1 6 which is secured to the base 10 by a bracket 26 is intended to cause an oscillatory movement of the clapper rod 1 8 in substantially the same plane as the base 10 in well known manner by alternately energising two pole pieces, only one of which is shown at 22 to cause a rapid pivoting movement of the plate assembly 24, and hence vibrate the clapper 1 9 between the bell gongs 12 and 14.

Also mounted on the base 10 is a flexible metal plate 20 which is adapted to be secured by bolts passing through holes 28 and 30 formed in the plate. The plate 20 has an elongate extended portion 32 which extends in a plane parallel to the plane of the base 10 but is deformable away from the base 10 towards the clapper rod 1 8. At the end of the extended portion 32 is a pad 34 of low friction material which, when the extended portion is deflected sufficiently from the base, contacts the clapper rod 1 8. Pivoted under the plate 20 on a pivot pin 38 mounted in the base 10 is an operating lever 36. This lever can move in a plane parallel to the plane of the base 10 and carries approximately midway along its length a cam member 40.The cam member 40 could be a simpie wedge shape but is provided with three grooves 42, 44 and 46 each having a different height above the lever 36 the groove 42 being the lowest and the groove 46 being the highest.

Formed in the extended portion 32 is a downwardly extending contact member 48 which is in line with and adapted to be contacted by the cam member 40. Thus as the lever 36 is moved the contact member moves from one groove 42, 44 and 46 to another groove, best seen in Fig. 2 raising or lowering the portion 32 of the plate 20 and hence varying the pressure of the pad 34 on the clapper rod 1 8. If the lever 36 is moved to the right as seen in Fig. 2 so that the contact member 48 moves out of the groove 42 the contact member no longer contacts the cam member 40 and the pad 34 is not in engagement with the clapper rod 1 8. The bell assembly with the lever 36 in this position is thus not effected by the volume control mechanism and therefore emits its maximum volume of sound. The operation of the bell assembly is illustrated in Fig. 4 and 5.

The three grooves 42, 44 and 46 formed in the cam 40 represent medium volume, low volume and bell off positions respectively and a high volume is obtainable by moving the lever 36 to the left in Fig. 4 so that the contact 48 does not contact the cam 40 as mentioned below. When the contact is in the medium position as shown, the pad 34 lightly contacts the flexible clapper rod 1 8 applying a small amount of friction, and also lifting the clapper 1 9 to a position as shown in Fig. 5 between the two conical gongs 1 2 and 14.

The distance X in Fig. 4 represents the maximum motion of the clapper rod 18, the distance Yindicates the static limit of the clapper 1 9 swing, and the distances Z represent the overthrow clearance of the clapper 1 9.

Moving the lever further to the right provides the bell assembly with two more increments of lift to the clapper 19' and 19", the first increment 19' also being illustrated in Fig. 1 as well as the positions 18' of the clapper rod, the pad 34' and the elongate portion 32' of the flexible plate 20. These increments in lift increase the overthrow clearance Zand together with the effect of frictional resistance between the clapper rod 1 8 and the pad 34 and the conical bell gongs 1 2 and 1 4 reduce the impact of the clapper 1 9 on the gongs.

The amount of lift provided by the groove 46 to raise the clapper to the position 19" prevents the clapper from hitting the gongs altogether, and is thus a bell-off position. This position is usually provided or not by the installer of the telephone.

The bell assembly thus provides four distinct settings, loud, medium, soft and off and the clapper 1 9 acts equally on both bell gongs. The arrangement is substantially independent of production variations in the angle of swing of the plate assembly 24 and there are no additional collision surfaces, thus rattle and knock sound components are avoided.

Several variations can be made to the bell assembly as described. Thus for example the above described embodiment uses a comparitively low friction pad 34, relying more on the effect of the conical bell gongs to reduce the sound but the bell gongs could be cylindrical and a higher friction rod used to reduce the amplitude of swing of the clapper 1 9 as it is raised and more force is applied to the clapper rod 18.

Alternatively the clapper rod 1 8 may be relatively stiff, the reduction in amplitude being achieved solely by the friction between the pad 34 and the clapper rod 1 8 with negligible movement of the clapper caused by the application of the pad 34. To ensure that the clapper rod does not bend in this case a second friction rod could be arranged on the other side of the clapper rod, the clapper rod 18 being gripped between two pads 34 using a second similar cam system to the cam system 40 and 48.

The grooves 42, 44 and 46 are not essential, the cam and/or the projection 48 could consist of a tapered wedge arrangement and suitable means provided for locking the lever 36 in predetermined position.

Claims (14)

1. A bell assembly comprising a bell and a clapper mounted on a pivoted clapper rod and friction means mounted in a plane parallel to the plane of movement of the clapper rod and adapted to be forced into contact with the clapper rod, the force being variable such that an increasing force reduces the amplitude of movement of the clapper rod and hence reduces the momentum of the clapper at its maximum amplitude thus reducing the vol ume of sound emanating from the bell.

2. A bell assembly as claimed in claim 1 in which the clapper rod is relatively stiff such that there is minimum amount of deflection of the clapper in the direction of the applied frictional force.

3. A bell assembly as claimed in claim 2 in which the frictional force is applied substantially equally to opposite sides of the clapper rod.

4. A bell assembly as claimed in claim 1 in which the clapper rod is relatively flexible and the clapper is deflected in the direction of the applied frictional force.

5. A bell assembly as claimed in claim 4 in which the side of the bell struck by the clapper is equidistant from the position of maximum amplitude of the clapper whatever its deflection.

6. A bell assembly as claimed in claim 5 in which the bell is cylindrical in shape.

7. A bell assembly as claimed in claim 4 in which the distance of the side of the bell from the position of maximum amplitude of the clapper varies with its deflection.

8. A bell assembly as claimed in claim 7 in which the bell is substantially conical in shape whereby the effect of the frictional force deflecting the clapper will cause a reduction in sound with a smaller movement of the clapper if the distance of the side of the bell from the position of maximum amplitude increases in the direction of deflection of the clapper by the frictional force.

9. A bell assembly as claimed in claims 7 or 8 in which the amount of frictional force on the clapper rod is relatively low.

10. A bell assembly as claimed in any previous claim in which there are two bells, one arranged on each sida of the clapper in the plane of movement of tĕ clapper.

11. A bell assembly as claimed in any previous claim in which the friction means comprises a pad of relatively high friction or of relatively low friction.

1 2. A bell assembly as claimed in claim 11 in which the pad is forced against the clapper rod by cam means.

1 3. A bell assembly as claimed in claims 11 or 1 2 in which the cam is mounted on a lever which is moveably mounted adjacent to the clapper rod whereby movement of the lever in one direction forces the friction pad against the clapper rod.

14. A bell assembly as claimed in claim 1 3 in which the friction pad is mounted on a resilient member mounted adjacent to the clapper rod, movement of the lever deflecting the resilient member and forcing the friction pad against the clapper rod.

1 5. A bell assembly as claimed in claims 1 3 or 14 in which the cam is provided with a plurality of grooves which are contacted by a portion of the resilient member which acts as stops for the lever over the surface of the cam, each groove setting the bell assembly at a different volume of sound.

1 6. A bell assembly constructed and adapted to operate substantially as hereinbefore decribed with reference to accompanying drawings.