Gear range selector:
The head has 2 speed ranges - direct drive from the driven belt pulley to the spindle - and a 2-stage gear reduction stage, rather like a conventional back gear. Unlike the classical Bridgeport head that uses a toothed belt and a gear reduction, this doesn't cause a reversal of direction when the reduction gear train is engaged. This is a section view of the AN-S but apart from the mechanical speed variator, it's 90% identical as far as I have discovered.
On the manual machines and the more commonplace AN-S models, there is a rotary knob on the side of the head that is turned either manually or by an external electric drive. For direct drive, the splined driven shaft connects to the spindle by means of a sliding dog clutch. For low ratio, the dog clutch / gear assembly is slid the other way and the gears are engaged.
On this machine there is a rotary pneumatic actuator to make the range selection. It clearly has a direct action (no internal reduction gears), although I haven't taken it apart to look closer. The actual position is reported back by means of 2 microswitches. There are two 24V pneumatic solenoids to drive the actuator in the correct direction. Simple enough, although currently I have no compressor...
Impact driver:
This machine was specified with the optional power drawbar / toolchanger. This is not the full "ATC" carousel automatic toolchanger option unfortunately but otherwise allows semi-automated tool changes.
The impact driver is literally a modified pistol-style Bosch hand tool with the handle removed. The 4 wire for the brushes and field winding are brought out - that's necessary in order to be able to control the direction of rotation. There is a pneumatic piston that pulls the driver down against a return spring, to engage it with the drawbar. There's no microswitch to tell the controller it has done so, so I assume there is a time delay to give it a chance before the impact driver starts up. I also assume the controller checks the spindle is stopped and the spindle brake has been applied.
I dismantled the impact driver, cleaned the patina off the commutator, lightly greased the bearings, rearranged the gear box grease and reassembled it. It seems to work fine and the brushes have lots of life left.
Drawbar controller:
The power drawbar / tool changer was automatically controlled. The system controller clearly told the drawbar system how and when to operate. The low voltage (24V) push buttons on the front of the head went back to the controller and came back up via 240V relays to a box on the side of the head containing a lot of discrete components including 2 relays, an SCR and a handful of transistors, pots and caps. It's all 240V stuff, so clearly the relays in the old cabinet were to interface between the low voltage system and this high voltage box.
There are 4 wires to the impact driver on the top of the drawbar, 2 going to the 240V pneumatic solenoid that forces the impact driver down to engage with the drawbar and 3 red wires that come from the main cabinet. These 3 red wires are 240V but appear to be signal rather than power connections, judging by the circuit on the PCBA. The actual power comes in as a L-N-E cable elsewhere, via a switch on the outside of the steel box. So it seems this PCB is told to engage the impact driver, then energise it in the correct direction, depending on whether it needs to tighten or loosen the toolholder. Question is - can I reuse this module? If not, I may have to come up with a cunning plan to control the sequence of operations require to bring about a tool change - I'd rather not.
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