John King (1814 -1886) was my Great, Great, Great Uncle. He is buried in Pinxton Churchyard. There is /or was a small museum dedicated to him and his invention of the cage detachment hook.
On learning of my ancestor I made a plywood model of the Detachment Hook, mainly to see how it worked. Here are a few details.
Colin Pounder.

Wooden models completed October 17th 2006 .

Fixed horizontally in the Headstocks of a mine is a heavy steel plate, the King Plate, having a central hole. This hole in the King Plate is slightly greater in diameter than the width of the upper section of the detachment hook.

The wire shaft cable from the winding drum passes over the headstock wheel and through the King Plate.

Cleated End

D Shackle

The cleated end of the cable is attached to a D shackle. The horizontal part of the shackle passes through the endplate slots of the Detachment Hook. It is held in by the two opposing jaws of the swivel plates.

At the bottom of the Detachment Hook (in the model occupied by a simple small diameter bolt) the horizontal bar of a second D shackle is attached.

From this hang four chains one to each corner of the mine cage.

Two Models

Left swivel plate – Parallel outer plates – Right swivel plate - Pin which holds all in location – Bolt which acts as pivot for swivel plates and which takes weight of suspended cage.

Side view of hook (ignore lower pin)

How it works.

Under normal conditions the cage hangs from the Detachment hook.

If the cage is over wound the King Hook rises up through the King Plate. The projecting ends of the two swivel plates are rammed inwards by the edges of the hole in the King Plate.

The pin beneath the main throughbolt is sheared into three pieces. The swivel plates can now move right inside the endplates of the hook.

The two triangular projections on the swivel plates project clear of the Hook’s endplates.

At the same time the swivel plate jaws open releasing the upper D shackle with the attached winding cable. The loaded cage still rises but the lower section of the endplates prevent the hook from passing completely through the King Plate.   The whole falls but is held by the triangular projections on the swivel plates as they now come to rest on the King Plate. The cage now hangs on the swivel plate projections. The hook plus cage are supported by the through bolt. In due course the Detachment hook is put back into commission by first driving a drift or second lower pin through the aligned four plates of the hook.

The broken pieces of the sheared pin are knocked out and a new pin inserted.