A Gents Bell Striker. Part1: Switching Lever:

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A fellow enthusiast, who wishes to remain anonymous, has very kindly forwarded some really excellent images of his Gents' Pulsynetic bell striker. This device allowed master clock controlled, impulse clock systems to strike the number of hours on a large bell.  As can be seen in these fine images there is a very large wormwheel and hammer lifting cam. These lift the hammer away from the bell and drop it a suitable number of times to match the hour.

Due to the complexity and the number of images available I shall split discussion of the mechanism into several parts. The first will discuss and illustrate the switching involved in starting and ending the striking sequence:

Rather than repeat the sequence of actions, word for word, here is an earlier post describing an earlier bell striker.

http://waitingtrain.blogspot.dk/2012/12/gents-pulsynetic-bell-striker-c54.html

A general view is seen here of the bell striker from the front. The drive motor is on the far left. The main worm, its wormwheel and snail-shaped, hammer lifting cam are raised high on a sturdy bracket in the centre rear of the mechanism. The round, count plate, with slots in its periphery, limits the number of strikes each hour and is seen in the centre foreground. I will discuss its drive and how it functions in a later part.

The linkage on the extreme right would be connected to a bell hammer pull wire or rope. Note that the long, black, hammer lifting lever is quite separate from the white switching lever in the foreground. The black, bell striking lever is pushed down and released by the large, snail-shaped cam in the centre when the motor runs. The black striking lever is hinged just in front of the drive motor.

The long white arm in the foreground [which I shall call the switching lever] is counterbalanced by the lump of metal cast onto it on the left. This lever is hinged like a see-saw. The lever is made of aluminium and is the switching actuator for initiating and stopping the strike. It does so by means of several switches, or electrical contacts. Which are either open or closed depending on the lever's precise condition. [Either up or down]

The actual switches or contacts used varied over the history of Gents' bell striker mechanisms. Their purpose remains the same. A microswitch was used in some bell strikers to turn the drive motor on and off. There appears to be a box above the switching arm's pivot. Which may contain the switch for the drive motor.

Note the two large electromagnets hiding under the switching arm just to the right of its pivot. The switching lever normally rests with the counterweight down and the far end lifted upwards against the brass, height stop. An electrical contact can be seen supported by an L-shaped bracket fixed just above the counterweight. This contact would be closed only when the arm is lowered [at the far end] during striking.

This image shows the far end of the switching lever furthest away from the counterweight. Note the brass height adjusting screw and its large lock nut. This screw fixes the maximum height to which the switching arm may rise when free to do so. This is its normal or rest position.

Note also the shiny, steel, stepped latch on the right and the strangely twisted arm just to the left of the height adjusting screw. At rest, between striking sequences, the switching lever is normally raised and unlatched. The latch is connected [in a continuous U-shape] to the twisted metal arm. A brass leaf spring presses upwards against the base of the U-shaped lever/latch. Ensuring that the lever will latch itself via its long pin when it falls far enough.

When the contacts just above the counterweight close they pass electricity to the motor shaft brake release electromagnet. The shaft brake is released for as long as the arm is latched down.

Rotation of the main wormwheel and cam shaft also rotates a trip vane clamped to the same shaft. When this long metal arm strikes the top of the U-shaped arm the switching lever is unlatched. Due to the counterweight the switching lever can now rise again. The contacts above the counterweight open and the motor shaft brake is instantly re-applied.

Usually a separate timing device [known as a bell ringer] is driven by the controlling master clock of the entire clock system. The bell ringer sends out an electrical signal every hour on the hour.


The terminals for the low voltage, timing signal and brake solenoid are fixed on two insulated blocks at the front of the massive, cast iron, bed plate.

N.B. There is no connection between the low voltage wiring and the 250V mains electricity which drives the electric motor.

WARNING: Connecting these low voltage terminals to the mains electricity would immediately destroy the electromagnets. Very probably causing a dangerous fire! Exposed, bare metal parts would be very likely to carry a lethal mains voltage! Even if you survived, the bell striking mechanism and its entire clock system would probably be completely destroyed! Fires might even occur throughout the building! You have been warned! Low voltages only to be connected to these bare terminals.

Click on any image for an enlargement.

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