The Quadding and Centering system on the Monotype composition caster is controlled by two actuators on the paper tower.

The one for Quadding is a simple piston inside the tower housing which causes the motion of the paper tower cam to rotate a notched counting wheel; only when the counting wheel has advanced 5 (or 10) positions (to the next notch) is the paper ribbon allowed to advance. As a result the character coded on the ribbon is repeated 5 (or 10) times. The choice of 5 or 10 is controlled by rotating part of the notched counter wheel, thus closing up half its notches.

The one for Centering is a rocker arm outside the tower housing which is tilted one way to initiate centering by preventing paper ribbon advance, and is tilted back to its normal position when a sensor on the galley detects that the line is full. It is also forced to its normal position when both Quadding and Centering are coded on the same ribbon line (which IMHO is a keyboarding error).

Both of these receive their pneumatic signals via a manifold in the mounting plate of the Unit Shift valve, and these control signals originate in another valve (to be detailed later) mounted on the rear apron of the caster table.

The Centering actuator contains quite a few parts with a bit of clever pneumatics involved:

The clever part is the reset piston (which returns the rocker arm to its normal position). Firstly, it is a double piston, so it can either be actuated by the line-full signal from the galley or by the redundant selection of both Quadding and Centering on the same ribbon position. Each of these signals has its own isolated cavity in the cylinder, and either one will raise the upper piston and push the rocker arm to its normal position. Secondly, by using a larger diameter piston for the reset piston, the air pressure that rocks the arm when starting centering is able to be overcome by the reset piston actuated by the same pressure.

It should be noted that the two mounting screws (the long ones above and below the pistons) are not the same length (and are shown in the wrong positions in the above photo). The longer screw penetrates into the inside of the paper tower housing and acts as a mounting screw for the Quadding actuator as well.

The centering actuator was reassembled and installed on the side of the paper tower facing the operator just below the notched Quadding counting wheel:

The second photo is taken looking obliquely downward between the paper tower and the centering pin arm from the left side of the machine.

The Quadding actuator is installed inside the paper tower and all the air lines connect to the manifold in the Unit Shift Valve mounting plate:

The Centering actuator is also visible in the first photo.

The next pneumatic parts to clean are the dummy valve and mounting plate for Unit Adding, and I might also correct the messy repair job on one of the related air lines.

The last task left for Unit Shift was to install (what I call) the buffer valve. I use this term because its purpose is to store the Unit Shift selection (on or off) from the end of the ribbon read (just after the pin jaws close) until the time when the matcase is positioned (just as the matrix jaws close).

The buffer valve is in the right foreground, connected to the Unit Shift valve by three copper tubes. If you want to remove any of this (for instance to adjust the stroke length on the jaws) by far the easiest way is to remove the Unit Shift valve, its buffer valve, bracket and tubing all at once. This is done by removing the two bolts and four screws marked by red arrows (one of the screws is hidden by one of the pipe fittings).  All the parts then come off as a unit, connected by the tubing.

The next task is to reinstall the Quadding and Centering actuators on the paper tower.

In my next task of getting the paper tower operational on my Monotype composition caster, I have started cleaning and lubricating the various pneumatic control valves. The first one I did is a combination of the Unit Shift control valve and a manifold for the Quadding and Centering unit, located on the left table apron below the paper tower. After removing the valve body and its mounting plate I was left with a mess of pipe connections:

Unfortunately the pipes have some spring to them and shifted out of position once the valve base was removed. Removing this base required a specially modified cabinet-tip screwdriver to remove the retaining nuts for the pipes.

I disassembled the valve and base and cleaned all the parts with solvent and a brush:

Those little rings near the upper left are the retaining nuts for the pipes. I reassembled the valve using a light oil, and got to work on reinstalling the base plate. This job was made difficult by the shifted positions of the pipes as there is not enough room to reach behind the plate and put them in their holes individually. Furthermore, the mould blade cam lever prevents the plate from dropping into place from more than about an inch away. I put short lengths of wire into each pipe, which allowed me to guide each into its own hole. Inn retrospect though I should have chosen wire that was a closer fit to the inside diameter of the pipe, and also stiffer than the soft iron stove wire I actually used. This would have made it easier to coax each pipe into its proper hole just by shifting the wire.

This shows the base plate in position with some of the pipes secured, and others with the positioning wires still in place. This photo and the next were lit by my work light which was below the valve area, hence the spooky upside-down shadowing. Once I had all the pipes secured I could re-mount the valve body; I cleaned the mating surfaces, applied a heavy oil, and screwed the valve onto the mounting plate.

The control knob now moves freely allowing Unit Shift to be turned on and off easily. The other buffer valve, which connects to the three flare fittings on the front, still remains to be installed.

The next valve and base plate I will clean is the one for Unit Adding, which is not installed on my caster, so instead of the valve there is a dummy plate mounted on the base plate which routes all the air lines as if Unit Adding were turned off.