IMPROVEMENTS IN SELF-ACTING TRAP-DOORS FOR MINES
Year: 1857

page_text: LIVO
PROVISIONAL SPECIFICATION left by Robert Rennie at the Office of
the Commissioners of Patents, with his Petition, on the 21st December
1857.
I, ROBERT RENNIE, of Netherwood, in the County of Dumbarton, North
Britain, Contractor, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN SELF-ACTING TRAP-DOORS FOR MINES," to be as follows:-
This Invention relates to the so arranging the trap-doors used in mines.
for ventilating purposes, and the actuating mechanism of such doors that the
passage through of the waggons shall open and close the doors without any
manual or secondary interference.
According to one modification of this arrangement the hinge side of the
door has attached to it a back lever piece in which is an eye by which it is
jointed to one end of a connecting rod, which passes along the side of the
railway or working to some distance beyond the door, where its opposite end is
jointed to the back end of a short horizontal lever piece. There is one of
these levers at the same distance on each side of the trap-door, each being set
on a vertical stud centre in the ground. These two levers are connected
together by opposed or reversed diagonal rods working through the partition.
These rods are jointed and attached in such manner that the rod jointed at
one end to the end of the horizontal lever nearest the rails of the working is
jointed at its other end to the opposite end of the other horizontal lever, or

page_text: that end of this lever which is furthest from the line of rails. The other rod
is jointed to the levers in a precisely similar way, so that in all cases when
one horizontal lever is moved the corresponding end of the opposite one moves
in the reverse direction, the corresponding ends of the levers always approach-
ing to or receeding from the trap-door in concert. The ends of tho horizontal
levers nearest the rails are each fitted with pendant catches or stop pieces.
There are two of these pendant catches in each end, and they are hung on
stud centres with reverse stops, that is to say, one catch holds in one direction
and gives in the other, and vice versa. The waggons each carry a projecting
pin, or are so provided in other respects that as they approach the door they
act upon the pendant catches of the lever on that side in such manner as to
press forward the front end of the lever, and this movement through the
agency of the connections herein-before described opens the door just as tho
horse's head reaches it.
The same action brings forward the corresponding end of the other lever so
that when the waggon has passed through the door it operates upon this other
lever just as in the previous instance, closing the door and putting the lever
first operated upon into a proper position for again opening the door on the
approach of a succeeding waggon. This arrangement answers well for the
passage of a single waggon or a short train, but when it is required to work
trap-doors for long trains it becomes necessary to provide such an arrange-
ment as will secure the opening of the door only just as the horse or waggon
approaches it, and yet allow a sufficient length of time to elapso after the first
waggon has passed through the door for the last of the train to clear beforo
the shutting action comes into play. This may be effected in various ways,
but it is satisfactorily accomplished according to one modification by an
arrangement of rocking shafts or bell crank actions and reverse action levers
or catches. One of such rocking shafts is placed near the door on each side,
and each of them is connected by a back cord or light rod with two other
rocking shafts or bell crank movements which are placed one on each side of
the door at the proper distance from it to allow of the passage of the train.
The movements are also connected with the actual door closing mechanisın
any convenient manner. "
in
The result of this arrangement is that when a waggon comes up to tho
closed door it operates upon the catch of the movement near the door, and
this action opens the door. The latter remains open until the first waggon
has reached the further off rocking shaft or movement on the other side of the
door, when the proper catch of that movement having been set to the requisite
position by the same action which opened the door, is now acted upon by the

page_text: waggon to close the door. In this way the waggons as they approach the
door always miss the far out action on that side of the door, and operate upon
that near the door, and on passing through the door the waggons always
miss the rocking shaft action nearest the door on that side, and operate upon
the one furthest away.
Various arrangements of operating catches may be used for this purpose,
for instance, the waggons may be caused to act upon incline plane pieces or
levers disposed at proper distances from the doors so as to act in the general
manner herein-before described.
To prevent the doors being left open by foot passengers, a spring or weight
is attached to each so as to close the doors in the absence of the closing action
of the waggons.