'A Pattern' frames
Our 'A Pattern' lever frame closely resembles the McKenzie and Holland No. 6a pattern frame, with the levers appearing to stand vertical in the frame.
They are built in multiples of 5 levers, and employ what is known as "cam and tappet" locking, this is where the lever has a stud which traverses a slot in a cam which moves the tappet attached to it.
These frames can also be conditionally interlocked.
Where the interlocking controls a level crossing, a gate lever assembly can be provided at either or both ends of the frame.
The gate lever comprises of a 5 spoke gate wheel mounted on 'A' frame supports which houses a gear reduction assembly.
It takes 7 turns of the gate wheel to open or close the gates. This Extra mechanism is counted as an additional lever to a lever frame set.
These frames have either a cast or etched brass number disc on the levers