Hi Tony,
>The Development of RAF Guns and Ammunition from WW1 to the Present Day
Thanks, quite interesting!
Here a translation of the patent for an interrupter gear, granted to Franz Schneider on July 15, 1913 (according to a reproduction on display on the Deutsches Museum in Munich):
"Imperial Patent Bureau
Patent Document
No. 276396
Class 77 h Group 5
Franz Schneider in Johannesthal near Berlin
Trigger device for firearms aboard aircraft
Patented in Imperial Germany from July 15, 1913 on.
Object of the invention is a device for facilitating firing between the propeller blades without doing them any harm. For this purpose, the firearm is mounted directly in front of the pilot and behind the propeller, and it can be mounted flexibly within certain limits.
To avoid damage to the propeller, it is intended to use an interrupter mechanism for the trigger. This interrupter device is kept in continuous rotation by the propeller shaft and blocks the trigger each time when a propeller blade is in front of the weapon muzzle. Accordingly, the firing of the gun can only take place through the gap between the propeller blades.
On the drawing, an execution example of the invention is shown.
Figure 1 depicts the front part of the aircraft in side view, while
Figure 2 shows a illustrative view of the cam disk.
The weapon, in the execution example shown as a rifle, is in some suitable manner fixed to a mounting connected advantageously to the engine and can be trained within certain limits laterally and up and down. A lever e mounted on a fixed bearing f moves behind the trigger of the gun, while the lower end of the lever contacts the cam disk A (see figure 2). This cam disk is driven by the propeller shaft a by conical gear wheels b and the vertical shaft c and is designed so that it pushes the lever e against the trigger of the gun while a blade of the propeller is in front of the rifle muzzle. In the instant the propeller blades have cleared the muzzle, the firearm can be triggered.
Naturally, the blocking of the trigger can be achieved in many other ways, and the invention is not limited to the described layout.
Patent Claims:
1. Trigger mechanism for firearms on aircraft, characterized by an interrupter mechanism for the trigger of the firearm which is placed behind the motion plane of the propeller blades, which engages the trigger through a device driven by the propeller shaft as long as a propeller blade is in front of the muzzle of the firearm.
2. Device according to claim 1, characterized by the device consisting of a cam disk d, driven by the propeller shaft, that prevents triggering the firearm by means of a blocking lever e when a propeller blade is in front of the firearm's muzzle.
Attached 1 sheet of drawings."
Note that it does not describe how the firing is commenced after shooting, a problem solved by Lübke, who designed the synchronizer gear for Fokker. In my opinion, this might explain why the name "interrupter gear"/"Unterbrechergetriebe" stuck - the idea and the name had been around before the more sophisticated synchronizer gear was designed to fulfill the job.
Karlheinz Kens in his "Flugzeuge des Ersten Weltkrieges" ('WW1 aircraft') mentions that Fokker was cleared of obligations to pay license fees to Schneider in a lawsuit. I'd guess the solution of the practical problem of commecing firing after an interruption might have something to do with it.
Kens also mentions that Fokker had to pay license fees anyway - to August Euler, who had patented the idea of using a fixed forward-firing weapon from an aircraft, using the flight controls to aim the weapon by aiming the entire aircraft.
One of your books is titled "Flying Guns" ... well, August Euler was the man who invented the concept
Regards,
Henning (HoHun)