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The Ingraham electric strike mechanism

This clock belongs to my daughter. I worked on it two or three years ago and had Satan's own time figuring out the dang strike thingy. Failed to write down any notes. She brought it to me last week for something else, and I had to figure it out all over again. This time I got smart and wrote up a description. I'm posting it here for the benefit of anyone who might encounter one of these weird creatures.



The strike assembly has four main parts:
•An inner shaft, synchronized to the hour hand. It rotates once in twelve hours.
•An outer shaft, synchronized to the minute hand. It rotates once an hour.
•A trip wheel or pin wheel for tripping the hammer tail
•A thing I call the Hour Disk, driven by the inner shaft and so, synchronized to the hour hand.

•A fifth item, not part of the assembly, is the spring-loaded trigger lever. It triggers the trip wheel to move into operating position.

The minute wheel (motion work) also has a pinion on its bottom side. The pinion drives the inner shaft; the wheel drives the outer shaft.

The trip wheel rotates freely on the inner shaft, and is driven by a pinion splined directly to the motor gear driving the going train.

The trip wheel is spring-loaded, and can move up and down on its shaft. It rotates constantly while the clock is running, but is only able to trip the hammer when it is in the "up" position. The way it is moved up is described next.

The outer shaft carries a spiral ramp that rotates once per hour. A boss sticking out from the trigger lever rides on top of the ramp, and is raised as the ramp turns.

The trip wheel has a smooth lower rim, with a small gap in it. As the trigger lever rises, its upper extension eventually becomes even with that rim. When the ramp ends, the lever falls off it and the lever's spring forces its upper extension against the rim of the rotating trip wheel.

When the gap in the rim gets to the lever extension, the lever springs through the gap. The bottom of the trip wheel is convex, like a bowl. The force of the lever sliding across the bowl forces the trip wheel into the "up" position. It can now trip the hammer. The lever falls to the bottom, where it will again be lifted by the spiral ramp, to generate the next strike.

The trip wheel has a spring-loaded hook on its top side. When it springs into the "up" position, the hook grabs the rim of the Hour Disk and prevents the trip wheel from falling back.

The Hour Disk (which rotates at the same speed as the hour hand) has a small slit in it, for the hook to escape through. The pins on the trip wheel will continue to trip the hammer until the slit arrives at the hook, when the hook falls through the slit and the trip wheel falls into the "down" position. The strike ends.

The duration of the strike is determined by the distance of the slit in the disk (corresponding to the position of the hour hand) from the point on the disk where the hook grabs it. At 3:00 the grab is close; at 12:00 it's far.

Whoever invented this contraption deserves a prize of some kind. :Party:

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