Year: 1898

page_text: I, EDGAR LISTER POWELL, of Winterfield, Harrogate, in the County of York,
Engineer, do hereby declare the nature of this invention to be as follows:-
The object of this invention is to prevent the undue straining of the wire or
chain for operating the signal from the cabin and yet to allow the signal lever
always to be moved through the complete stroke.
As has before been proposed the chain is not attached to the lever but when
the signal is raised it is disconnected from it and is kept stretched by a weight
at its end so that it can expand and contract freely and yet is always under a
constant tension. When it is desired to lower the signal the chain is taken hold
of by the lever but in place of this temporary attachment being as heretofore a
rigid one I make it in such a manner that it can yield under any undue strain
so that the lever can always be moved without damage through its complete stroke
even although the signal has been fully lowered before it reaches the end of
its course.
For this purpose I carry the chain round a stationary pulley and then round
two pulleys on a rocking frame. One of these pulleys is loose on the shaft of a
brake drum to which it is connected by a pawl and ratchet so that it can revolve
independently of the drum in one direction but in the other the two move together.
One end of the brake strap is fixed to a radial arm connected by levers or other-
wise to the signal lever whilst the other end is fixed to a weighted lever which
normally rests on the rocking frame, the brake strap being preferably normally
loose.
In lowering the signal the first part of the movement of the signal lever
turns the radial arm tightening the brake strap and then turning the brake and
chain wheels. The radial arm then comes against a stop and the further move-
ment of the signal lever rocks the frame and since the chain pulley is prevented
from turning by the brake strap this movement draws in chain from the signal
and so lowers it. When however the signal is fully lowered and no more chain
can therefore be drawn in the brake drum and with it the chain pulley can turn
against the resistance of the brake strap so that the stroke of the signal lever
can be completed without unduly straining the chain.
Dated this 22nd day of August 1808

page_text: same is to be performed to be particularly described and ascertained in and by
the following statement:.
The object of this invention is to prevent the undue straining of the wire or
chain for operating the signal from the cabin and yet to allow the signal lever
always to be moved through the complete stroke.
As has before been proposed the chain is not attached to the lever but when
the signal is raised it is disconnected from it and is kept stretched by a weight
at its end so that it can expand and contract freely and yet is always under a
constant tension. When it is desired to lower the signal the chain is taken hold
of by the lever but in place of this temporary attachment being as heretofore a
rigid one I make it in such a manner that it can yield under any undue strain
so that the lever can always be moved without damage through its complete stroke
even although the signal has been fully lowered before it reaches the end of
its course.
Figures 1, 2 and 3, are side elevations of the apparatus respectively showing
the positions of the parts before the beginning of the stroke of the signal lever,
during its stroke, and at the end of its stroke. Figure is a plan of Figure 1.
is
a is the signal pivotted at a¹ and connected by the rod a to the weighted
lever which is pivotted at 6 and normally keeps the signal in its raised or
danger position. c is the chain fixed at one end to the lever b and carrying the
weight at its other end. The chain c passes under pulleys dd, over inter-
mediate pulleys which are not shown and over the pulleys ele on the rocking
frame e which is pivotted at e³. When in the position shown at Figure 1 the
frame e rests on a stop or support e¹. The chain passes once or more round the
pulley or is otherwise prevented from slipping on it. The pulley
mounted loose on the shaft f of the brake drum f and has fixed to it the ratchet
wheel gearing with the pawl f2 on the drum. One end of the brake strap f³
is fixed to the weighted lever pivotted at gl whilst the other end is fixed to
the cross bar connecting the bell crank levers pivotted on the shaft f. The
bell crank levers h¹ are connected by the link j to the bell crank levers k which
are pivotted at k to the frame e and are connected by the link to the arm m¹
fixed to the signal lever m which is pivotted at m². One arm of the bell crank
levers is prolonged and carries the weight 2.
Normally the weighted lever rests on the frame e as shown in Figure 1 the
brake strap being slack and when the parts are in this position the pulley
can turn in either direction and the chain can expand or contract freely being
always kept at a constant tension by the weight c¹.
The action of the apparatus is as follows:-During the first part of the motion
of the lever m from the position shown in Figure 1 the frame e remains stationary
but the bell crank levers are turned (by the movement of the link j levers k
and link ) tightening the brake strap and raising the weighted lever turning
the brake drum and chain wheel as shown in Figure 2. The cross bar h now comes
against the frame e so that the levers are arrested and the further movement
of the lever m turns the frame e as a whole raising the pulley el so drawing in
the chain and pulling down the signal a. When the signal is fully down and
no more chain can therefore be drawn in the brake drum f and with it the
pulley rotate against the resistance of the brake strap 3 and the stroke of the
lever m can be completed without putting any undue strain on the chain, the
parts finally assuming the position shown in Figure 3.
Figure 5 is a side elevation and Figure 6 a plan of a modification which differs
principally from that shown in Figures 1 to 4 by the frame e being pivotted on
the shaft by the weight being omitted and by the bell crank lever h¹ being
connected by the link to the lever o pivotted at o' to frame e and carrying the
weight o. In most other respects the foregoing description applies. The result
of this arrangement is that the brake strap is always kept tight by the
weights and o².
It will be observed that in both of these arrangements the first action of the

page_text: lever m is to draw in the chain c without tilting the frame e and if the chain is
too slack so that its tension is not sufficient to raise the weight o' the amount
so pulled in is not given back again when the movement of the lever is reversed
and in this way the chain is tightened.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:-
1. The combination of a chain wheel round which the signal chain passes, a
brake drum, a pawl and ratchet connecting the wheel and drum and means for
pulling on the chain between the signal and the wheel.
2. The combination of a chain wheel round which the signal chain passes a
brake drum, a pawl and ratchet connecting the wheel and drum and means
whereby the signal lever first rotates the wheel and drum and then pulls on the
chain between the signal and the wheel.
3. The combination of a signal, a chain operating it, a weight at the end of
the chain and tending to keep it tight, a signal lever, a rocking frame, a pulley
carried by the frame around which the chain passes, a brake drum, a pawl and
ratchet connecting the pulley and the drum, a brake operating on the drum and
means whereby the movement of the lever first rotates the chain wheel and drum
and then tilts the frame.
4. Apparatus substantially as described and illustrated in the drawings.