Improvements in Safety Brakes for Cages of Lifts or Mine Shafts.
Year: 1889

page_text: Date of Application, 13th Feb., 1889
Complete Specification Left, 8th Nov., 1889-Accepted, 14th Dec., 1889
PROVISIONAL SPECIFICATION.
[Communicated from abroad by ABEL PIFRE, of No. 23, Boulevarde de Strasbourg,
Paris, in the Republic of France, Engineer.
Improvements in Safety Brakes for Cages of Lifts or Mine Shafts.
I, OLIVER IMRAY, of No. 28 Southampton Buildings, Chancery Lane, in the County
of Middlesex, Fellow of the Institute of Patent Agents, do hereby declare the nature
of this invention to be as follows:-
The safety brakes employed for the cages of lifts or mine shafts are usually so
arranged that when the suspending rope or chain gives way, they act at once gripping
the guides or pressing against them with their full force. When this accident occurs
during the descent of the cage, which may be more or less rapid, the strain resulting
from stopping it suddenly often deranges or fractures the brake mechanism.
This invention has for its object to moderate the suddenness with which the brakes
are applied and to confine the strain resulting from their application within safe limits.
For this purpose, while the suspending rope or chain remains entire the brakes are
held off in the usual way by attaching the rope or chain to the brake levers, but
when the rope or chain breaks, a spring or set of springs of predetermined force acts
on the brakes and puts them on with a force limited by the strength of the spring or
springs applied to the brake levers. Some of the springs may be applied to the
levers while others of them are applied to the bearings of the pivots on which the
levers work, so that, however great may be the power of the former springs,
the pressure of the brakes is limited by the power of the springs that support their
bearings. In order to prevent the sudden movement of the brake levers when the
suspending rope or chain gives way, they are connected to a piston working in
an air cylinder from which there is a limited outlet; the air cushion in this cylinder
retards the movement of the piston and of the brake levers connected to it.
The guides for the cage may be of various forms, such for instance as that of a
railway rail, or of a metal rod or rope or of a wooden bar placed upright on each side
of the shaft.
In all cases the break levers are made with jaws arranged to embrace the guides
and clamp them when the brakes are put on. When rails are used as guides they are
sometimes subject to frost giving them a slippery coating which interferes with the
proper action of the brakes.
In order to prevent this the rail may be of hollow form and steam may be sent
along the hollow in frosty weather.
Dated this 12th dov of Fahru 1880
ABEL & IMRAY,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Safety Brakes for Cages of Lifts or Mine Shafts.
I, OLIVER IMRAY of No. 28 Southampton Buildings, Chancery Lane in the
County of Middlesex, Fellow of the Institute of Patent Agents do hereby
declare the nature of this Invention and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:
The safety brakes employed for the cages of lifts or mine shafts are usually so
arranged that when the suspending rope or chain gives way, they act at once, gripping
the guides or pressing against them with their full force. When this accident occurs

page_text: F
during the descent of the cage which may be more or less rapid, the strain resulting
from stopping it suddenly often deranges or fractures the brake mechanism.
This Invention has for its object to moderate the suddenness with which the brake
apparatus is applied, by limiting the gripping force of the brake jaws to a determined
constant amount, such force being independent of the speed of the cage or lift platform,
as is the case with railway brakes.
It results from this that the distance travelled through, before the cage is arrested
will be greater or less in proportion as the speed of the cage at the moment of
breaking of the cable is greater or less, while at no time will the strains to which the
brake apparatus is subjected exceed the predetermined amount, so that no damage to
the apparatus can occur.
I will proceed to describe my Invention with reference to the accompanying
drawings in which Figure 1 shews a vertical and Figure 2 a horizontal section of
the apparatus. A. A¹ are the guide rails of the cage or lift platform, which rails in
the case of the rupture of the cable, are firmly grasped by the jaws BC, BC of the
levers BDCE. B C D E. These levers are tied together by strong collars F FL
and are actuated at their ends by a series of "Belleville" disc springs X, or by
springs of other suitable construction.
These springs alone constitute the force for applying the brakes. Two small
springs are introduced at mand m³ between the levers for keeping the jaws away
from the guide rails.
It will be seen from Figure 1 that the springs X are kept in a state of compression
by the strain upon the suspension cable G, the latter being attached by links to bell
crank levers a a¹ that press inwards the sleeves bearing against the ends of the
levers DE D' E¹.
:
When the cable breaks, the levers, losing their outer abutment, are pressed outward
by the springs X, causing the jaws BC to grip the guide rails with a force corre-
sponding to their pressure, there being no wedging action of any kind. In order
'to prevent too rapid a gripping action of the jaws, the levers a a¹ are connected by
their links to the rod of the piston B of a dash pot or air buffer cylinder H, the piston
being provided with a leak, so that when it is subject to a downward pressure on the
release of the levers a'a¹ it will descend with moderate speed in the cylinder, and thus
prevent the springs X from acting too suddenly, but not in any way diminish their
maximum gripping power when fully applied.
:
The levers a a¹ are connected by chains 6 b¹ to the framing, so as to reliève them of
the strain due to the pull of the suspension cable G.
Figure shews a sectional plan of another arrangement. The only difference
between this and the above described arrangement is that the levers E D instead of
having their fulcra on fixed abutments, bear against strong springs K K' which serve
to lessen the shock produced by the momentum of the levers when made to grip
the guide rails. With this arrangement the dash pot or air buffer can be dispensed
with.
Figure 4 shews the construction of the jaws when the guides consist of stretched
cables; stretched bars of circular or rectangular section can also be employed as the
guides.
Figure 5 shews the use of a "Barlow" rail as guide..
Figures 6 and 7 shew respectively a vertical section and a sectional plan of another
construction of the apparatus suitable more particularly for guides of wood, which
require a considerable amount of play, between them and the jaws of 'the brake
apparatus.
It may however also be applied to other forms of guides.
In this arrangement there are two brake blocks SS¹ which are kept away from the
guides A by the tension of the cable G, but which are pressed against the guides by
springs when the cable breaks.
For this purpose the brake blocks are mounted on the ends of arms on shafts 'o'o'
which are connected by other arms to rode passing through the springs-I-I¹ and

page_text: connected by links and levers to the cable G so that the tension of the latter keeps the
shaft and brake blocks in the position shewn, with the springs I I¹ compressed.
When the cable breaks, the springs 11' effect the turning of the shafts o o¹ so as to
bring the blocks SS firmly against the guides; at the same time the backward
pressure exerted upon the shafts is taken by other springs LL, so that the pressure
of the brake blocks against the guides will be limited exactly to the pressure due to
these springs. The shafts o o¹ require to be very strong and may with advantage be
made of large diameter and hollow.
Figure 8 shows a modification of the above construction in which only the block S
is mounted on the arm of the shaft o having a rigid abutment, the block S¹ being acted
upon by the spring r.
In the modification at Figure 9 the block S is acted upon by the shaft o which has
a spring abutment, while the block S' is rigidly fixed.
Figure 10 shews an advantageous construction of the guides for shafts or pits where
the guides are liable to become coated with ice or rime in winter.
The guides A are constructed of the form of a Barlow rail, the hollow of the base
being closed by an iron plate t, thus forming a channel at the back of the guide into
which a jet of steam or hot air can be injected so as to melt or prevent the formation
of ice. The guides are fixed to transverse beams T arranged at suitable distances
apart in the shaft.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is :-
1. In safety brakes, the use of gripping jaws or blocks that are acted upon by
springs on the breaking of the suspension cable in such manner as to exert a pressure
upon the guides which shall be constant and independent of the speed of the cage, the
said springs being maintained in a compressed condition by the tension on the
suspension cable and liberated by the rupture of the latter, substantially as herein
described.
2. The construction of safety brake wherein levers E D with gripping jaws BC are
acted upon by springs X held in compression. by levers a a¹ connected to the suspen-
sion cable G, a dash pot or air brake cylinder HP being provided for retarding the
action of the springs on the breaking of the cable, substantially as described with
reference to Figures 1 and 2 of the drawings.
3. The modified arrangement of the safety brake apparatus referred to in the
preceding claim, wherein the dash pot is dispensed with and the fulcra of the
levers DE are provided with spring abutments, substantially as described with
reference to Figures 3 and 4 of the drawings.
4. The modified arrangement of the safety brake apparatus herein described with
reference to Figure to 9 of the drawings, wherein brake blocks or jaws S are
carried by arms on shafts o that are partially rotated by the action of springs I on the
breaking of the suspension cable, the pressure of the blocks or jaws being limited by
springs L or substantially as set forth.
5. The use in combination with safety brakes for lifts or mine cages or platforms
of guides having longitudinal passages for the admission of steam or hot air for
preventing the formation of ice or rime, substantially as described.
Dated this 8th day of November 1889.
ABEL & IMRAY,
Agents for the Applicant.