Improvements in Safety Apparatus for Hoists or Lifts.
Year: 1891

page_text: Date of Application, 23rd Nov., 1891
Complete Specification Left, 23rd Aug., 1892-Accepted, 1st Oct., 1892
PROVISIONAL SPECIFICATION.
Improvements in Safety Apparatus for Hoists or Lifts.
I, EDWARD WILLIAM SANT, of South Church Lane, Bishop Auckland, County
of Durham, Engineer, do hereby declare the nature of this invention to be as
follows:-
The improvements relate to the safety gear in connection with lift or hoist cages,
applied to prevent the cage or platform from descending with undue speed. To
accomplish this I employ wedges acting upon the cage guide posts & the improve-
ment consists in the method of applying these wedges and bringing them into
action.
To each guide post (usually two in number) 1 apply a wedge, which is carried
by a grooved bracket fixed to the side of the cage, between the wedge and the
bracket is inserted an iron plate which does not bear direct on the bracket but on
intervening anti-friction rollers, or balls, to form a rolling surface for the wedge to
ride on.
The wedges rest on the end of levers which are connected by a spindle so that
any motion given to the levers causes the wedges to move simultaneously. To one
of the wedge levers an endless rope is attached which works vertically over grooved
pulleys & is also attached to a spiral or other form of spring with an adjustable
screw made fast to. any convenient part of the cage.
The spring pulls the rope in the direction of the wedges, but on the opposite side
of the rope a weight is suspended which counteracts the influence of the spring so
that in ordinary working the wedges remain at rest.
It will now be seen that if the cage is made to descend rapidly the weight on the
rope must ascend with corresponding speed, but the inertia of the weight is brought
to bear upon the spring which elongates & consequently the wedges move upwards
with the rope & levers, & wedge the brackets to the guide posts.
After the apparatus has been brought into action it is only necessary to reverse
the hoisting machinery & lift the cage to cause all the parts to resume their normal
condition.
As au additional safeguard the top wheel in connection with the endless rope
may have a V groove to be balanced on movable bearings to allow the wheel to be
pulled down on to the brake by the inertia of the weight.
Dated this 21st day of November 1891
EDWARD WM. SANT.
COMPLETE SPECIFICATION.
Improvements in Safety Apparatus for Hoists or Lifts.
I, EDWARD WILLIAM SANT, of The Globe Elwater Works, Stockton-on-Tees
in the County of Durham, Engineer 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:-
This invention relates to improvements in safety apparatus for hoists or lifts
and has for its object to prevent the cage or platform descending with undue
speed.
To accomplish this object I employ a wedge or locking device which acts upon
the cage or hoist guide posts and the improvement consists in the combination of
mechanism employed in bringing the parts to act as hereinafter described.
The locking mechanism is only intended to be brought into action in the event

page_text: of the cage descending with undue speed and I employ for this purpose a somewhat
delicately balanced apparatus wherein weights and spring power are caused to act
on one another.
Thus supposing a weight to be suspended from a rope passing over a pulley, the
opposite end of the rope being connected to a spring, then obviously the weight is
being carried or is balanced by the spring.
The tension of the spring is a regulated quantity in respect of the weight and if
the weight or what is equivalent to the weight is increased, then the spring will be
stretched and this stretching imparts a motion which I utilise to act on levers so as
to effect a locking between the cage guide bracket or its equivalent and the cage
guide posts.
I will fully describe my invention with reference to the accompanying drawings
in which
Figures 1 and 2 show two general elevations at right angles to one another of a
hoist or cage with guide posts and safety mechanism constructed in accordance with
my invention.
Figures 3 and 4 show a side and end view of a modified form of locking
mechanism.
Referring to the drawings, in which like letters of reference indicate like parts,.
a are the cage guide posts, a' the cage frame, and a² the cage guide brackets;
in Figs. 1 and 2, 4 is a socket for an adjustable screw 4: the socket may be
attached to any convenient part, e.g., the side planking or framing of the cage.
To the eye of the screw 4 is attached a spring 5 the upper end of which may be
attached to a thimble 5* secured to the rope 6.
One end of this rope is attached to one end of a slotted bar 7 whence it passes
upwards over pulley 8 and thence downwards to weight in to which it is attached
by an adjustable screw joint as shown in the figures. The
rope then
passes from
the weight downwards round pulley 9 and upwards to the lower end of slotted bar 7
to which it is attached.
A bent bar e connects bar 7 with lever mounted on axle a', and in Figs. 1 and 2
the end of lever n is shown carrying a wedge or locking device n².
The latter may have an iron plated backing a working in contact with roller
bearing surfaces n' as shown in Fig. 1.
The axle a traverses the width of the cage or hoist and a similar locking device
is arranged on each end thereof as shown in Fig. 2.
The cage hoisting gear is not shown in the figures but in ordinary working the
cage travels up and down without the mechanism constituting this invention coming
into action.
Thus the weight w and the spring 5 constantly travel up and down until from,
any cause the cage begins to descend with undue speed. Then the inertia of the
weight rapidly ascending with the descending cage somewhat stretches the spring 5
which through the medium of rope 6 slightly draws up bar 7 which in turn draws
up bar e and lever n whereby the wedge n' is drawn into the groove between the
bracket a and the guide post and there so locks itself that the further descent of
the cage is impeded.
Instead of the wedge device shown in Figs. 1 and 2, a simple modification such
as that shown in Figs. 3 and 4 may be substituted.
In this, the bar e connects the bar 7 to a serrated cam or lever 10, so that any
rapid descent of the cage causing the mechanism to act as above described, also
causes the serrated face of cam or lever 10 to be drawn towards and to grip the
guide post and so arrest the descent of the cage.
Various modifications might thus be introduced: I lay no claim to wedges or
serrated levers or cams or their equivalent by themselves as it is the locking device
in combination with the means for operating the same that constitutes the essential
feature of my invention.
The upper pulley 8 may be mounted on movable or resilient bearings of any
known suitable type so that when the inertia of the weight is acting through the

page_text: rope on the pulley groove as above described, it may somewhat depress the pulley
and so bring it in contact with any suitable frictional medium, such as a strap brake
or its equivalent: in this manner an additional safeguard may if desired be added
to further arrest the descent of the cage.
The weight w may be guided in its path by rings thereon running up and down a
light wire guide.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
1. The improved safety apparatus applicable to hoists or lifts consisting in the
combination with an endless rope situate alongside the cage pit and passing over
pulleys at its upper and lower extremities of a spring and weight the former of
which is attached at one end to an adjustable screw mounted on any convenient
part of the cage framing and at its other end to a point on the rope and the latter
of which is arranged to form as it were a part of the rope on the opposite side of
the pulley to the spring so that in the event of the cage descending with undue
speed the inertia of the weight shall operate on the spring so as to elongate it and
thus produce an automatic motion which is utilised to operate a simple locking
device between the cage brackets and the cage guide posts the several parts being
arranged and adapted to operate substantially as herein described and illustrated.
2. The combination with the endless rope having a spring attachment to the cage
or hoist and a weight, the rope and spring and weight being arranged to act on a
locking device as already described and claimed, of the means of further arresting
the unduly rapid descent of the cage by the intervention at the upper pulley over
which the rope travels of movable pulley bearings so that the inertia of the weight
may draw down the pulley and so bring it into contact with a frictional brake
device substantially as herein described.
3. The combination or general arrangement of parts constituting special inertia
safety gear for lifts or hoists substantially as herein set forth.
Dated this 20th day of August 1802
A. CRAWHALL CHAPMAN,
3, St. Nicholas Buildings, Newcastle-on-Tyne, Patent Agent.