AN IMPROVED SAFETY DETACHING APPARATUS FOR PREVENTING ACCIDENTS FROM OVERWINDING IN MINES, OR LIFTS, OR HOISTS
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by John Snowdon at the Office of the
Commissioners of Patents on the 8th May 1877.
JOHN SNOWDON, of Stanghow Mines, Margrove Park, near Guisborough, in the
County of York. "AN IMPROVED SAFETY DETACHING APPARATUS FOR PREVENTING
ACCIDENTS FROM OVERWINDING IN MINES, OR LIFTS, OR HOISTS."
This Invention consists in certain improvements in the construction of safety
apparatus for the purpose of preventing accidents from overwinding in mines, and in
connection with lifts or hoists, and whereby the winding rope or chain by which
the load is suspended is disconnected therefrom, whilst at the same time the load
is suspended in safety after the rope or chain has been disconnected.
The apparatus is constructed with four links or levers, the same being respec-
tively hinged together at or about the centre of their lengths to a centre block
having four projecting wings, and so formed that the four links or levers above the
centre block are mitred together at their edges, leaving an aperture which extends
from the top of links or levers down to the top of the centre block. The upper part
of such last-mentioned aperture receives a ball or swivel bolt which is connected to
the rope or chain.
The four links or levers are held or "tired" together by means of a cylindrical
hoop, which encircles the four levers, and is kept up by soft metal pins, one of
which is passed through each link or cover. The cylindrical hoop has projecting
sides on the exterior thereof, which come in contact with a fixed ring, and shear the
soft metal pins by which the cylindrical hoop is kept up. The hoop is provided
with " suugs " cast on the interior thereof for shearing the soft metal pins, whilst at
the same time the lower ends of the links or levers project at an angle from each
other. The upper ends of the links or levers are constructed with projecting jaws,
so that when the lower ends close nearly together the upper ends open, and are
securely held in a ring, which is fixed at the desired point beyond which the load
is not to be raised.
The before-mentioned centre block is provided with a hole or aperture in the
centre thereof, through which passes a rod with a large tapered end at the top
thereof, and which acts as a pawl or lock. The pawl or lock is enclosed in a proper
aperture to receive it, and drops down into the aperture, and securely locks the
apparatus in safety when detached.

page_text: In order to ensure the certain action of the pawl or lock a cross bar with wings
is provided on the bottom of the rod, the wings being in such a position that when
the cylindrical hoop is dropped sufficiently far to liberate the links or levers, and to
allow the same to open so as to release the rope or chain, it drives the pawl or lock
into the bottom of the aperture, and securely locks the apparatus.
In order to ensure the proper action of the pawl or lock a spiral spring is fixed
on the rod, and acts between the under side of the four-winged centre block and the
before-mentioned cross bar, with wings to force it down into the aperture imme-
diately the jaws begin to open. A hanger is also provided with six eyes, connected
to the lower ends of the main links or levers, and also four double eyes or similar
connections, and to which the cage or lead-hangs.
The four double eyes or similar connections are at an angle projecting outwards,
whilst the apparatus is in its usual or working position, but when the operation of
detaching takes place the action of the weight or load draws the said last-mentioned
eyes or connections into a vertical position, and thereby prevents any backward
action taking place which would tend to disarrange the apparatus with regard to
safety when once detached.
In the event of overwinding taking place the apparatus is partly drawn up
through the fixed ring, and at the same time the projecting ends of the cylindrical
hoop come in contact with the fixed ring, thereby shearing off the soft metal pins,
and liberating the links or levers, so as to open and allow the jaws to lay hold of
the top of the fixed ring, the pawl or lock being driven down into the aperture
provided for it, and thus securely fastening the whole apparatus and load and weight
in safety.