Safety Apparatus for Lifts.
Year: 1895

page_text: Date of Application, 29th June. 1895
Complete Specification Left, 12th Oct., 1895-Accepted, 16th Nov., 1895
PROVISIONAL SPECIFICATION.
Safety Apparatus for Lifts.
We, JAMES PITCAIRN HALKET, of 135 East India Road, Poplar in the County
of Middlesex, Engineer and JOHN KENNEDY, of 11 Fellows Road, South
Hampstead in the County of Middlesex, Engineer, do hereby declare the nature of
this invention to be as follows:-
Our invention relates to safety apparatus for lifts so arranged that when there is
any sudden or undue acceleration of the speed of the cage in its descent, brakes
are automatically brought into action so as to retard or stop the cage.
For this purpose near one of the upright guides of the cage we mount a pair of
levers each having a heavy arm inclined downwards and supported by a spring, in
such a position that usually when the cage descends at a moderate speed these arms
are out of contact with the guide but when the speed of the cage is suddenly
accelerated, the inertia of the heavy arms causes them to lag behind bringing them
into such a position that they grip the guides forcibly between them thus forming
a powerful brake. The apparatus may be applied to more than one of the
vertical guides.
In order to provide for cases of gradual acceleration in which inertia might not
act as described, we may connect to the heavy arms the sliding part of a centrifugal
governor driven by a roller running under spring pressure against one of the guides.
When the speed of the cage becomes too great, the arms are moved by the governor
into position to grip the guide and act as a brake.
Dated this 29th day of June 1895.
ABEL & IMRAY,
Agents for the Applicants.
Safety Apparatus for Lifts.
We, JAMES PITCAIRN HALKET, of 135 East India Road, Poplar, in the County
of Middlesex, Engineer, and JOHN KENNEDY, of 11 Fellows Road, South
Hampstead, in the County of Middlesex, 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 :-
Our invention relates to safety apparatus for lifts so arranged that, when there
is any sudden or undue acceleration of the speed of the cage in its descent, brakes
are automatically brought into action so as to retard or stop the cage.
We shall
describe apparatus for this purpose referring to the accompanying drawings.
Fig. 1 is an elevation with part of one of the fixed guides shewn in section, and
Fig. 2 is a plan of the brake apparatus with the guide shewn in horizontal section.
Fig. 3 shews a modification.
Referring first to Figs. 1 and 2; on the cage C we mount in a suitable frame F
attached to the cage near one of the guides G a pair of heavy armed cam levers LL
supported by springs S S which are adjusted by screws and nuts N so as to support
the cam levers L L in such a position that usually, when the cage descends at
n

page_text: moderate speed, the cam surfaces are close to but not in contact with the sides of
the guide G, but, when the speed of the cage is suddenly accelerated, the inertia
of the cam levers causes them to lag behind the cage or relatively raises them to
such a position that they come in contact with the sides of the guide and are then
moved farther by friction until they grip the guide forcibly between them thus
forming a powerful brake which retards or stops the cage.
As shewn in Fig. 3 the two cam levers L L may be connected by links A A to a
weight W which is suspended by a single adjustable spring S, the inertia of the
weight W acting as well as that of the cam levers themselves to cause the cam
levers to grip the guide, both cams moving together. Not only may the guide at
one side of the cage be gripped, but also, the guide on the opposite side as is shewn
in Fig. 3. And in this case the weight W may extend across the lift shaft, each
end of it being connected by links A to a pair of cam levers. When the weight is
thus arranged it may consist, as shown, of two parallel bars with clear space between
them for the ram or plunger which raises the cage.
The springs S Fig. 1, instead of being attached at N to brackets fixed on the
cage, may be attached to a crosshead adjustably connected to the sliding sleeve of
a centrifugal governor driven in the known manner by a roller pressed by a spring
against the side or face of one of the guides G, and the single spring S Fig. 2 may
be connected directly to the sleeve.
If then the descent of the cage became accelerated, not suddenly, but so gradually
that the inertia of the cam lever L failed to make them grip the guide, the governor,
on a predetermined speed of descent being attained, would raise the cam levers
causing them to grip the guide.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
--
1. In combination with the cage and guide of a lift, a pair of heavy or loaded
cam levers mounted on the cage and supported by adjustable springs so that in case
of too rapid descent of the cage they are caused by inertia to grip the guide,
substantially as described.
2. In combination with the cam levers and springs above referred to, a centrifugal
governor arranged and operating substantially as and for the purpose set forth.
Dated this 12th day of October 1895.
ABEL & IMKA1,
Agents for the Applicants.