Year: 1898

page_text: Date of Application, 1st June, 1898
Complete Specification Left, 1st Mar., 1899-Accepted, 29th Apr., 1899
We, JAMES PITCAIRN HALKET, of 135, East India Road, Poplar, in the County
of Middlesex, and JOHN KENNEDY, of 11, Fellows Road, South Hampstead, in the
County of Middlesex, Engineers, do hereby declare the nature of this invention
to be as follows:-
Our invention relates to improvements in safety gear for lifts or hoists, and has
for its object the prevention of a dangerously rapid descent of the cage, whether
due to bursting of the lift pipes or the breaking of the supporting rope, or to any
other cause.
Our invention consists in applying, to an apparatus for gripping the lift guides
by cams brought into operation by the sudden increase in the downward velocity
of the cage, a means for bringing the cage to rest gradually, and not suddenly,
as takes place with such appliances previously used.
In our improved appliance we do not depend on the sliding friction of the
gripping cams on the guides to bring the cage to rest gradually, and we prefer,
indeed that practically no such sliding should take place.
We may also provide a governor of any known kind to bring the cams into
engagement with the guides in case of a dangerously high downward velocity
being acquired by the cage gradually.
In carrying our invention into effect according to one modification we provide
a cross shaft suitably supported preferably on the bottom of the cage. This shaft
carries two cams one at each end. Suitably strong wooden, or metal guides are
used for the cage. The cam shaft is so supported that it can, move backwards in
guides from the lift guide as the cams turn into position, in gripping the guide.
Springs are suitably placed to resist this backward motion, and are of sufficient
strength to absorb the energy of motion in the cage and load when the apparatus
comes into action. The cams grip the guides against suitable brackets fixed on
the cage bottom. The cams are made of such a shape that their centre of mass
is well on the lift guide side of the centre of the shaft, and they are held up in
this position by means of a suitable spring acting on a lever placed on the cam
shaft or a weight may be placed on a lever fixed to the cam shaft and this weight
will then be held up by the spring. In this case the cams need not be loaded as
described. When a sudden downward acceleration is given to the cage as by the
breaking of its supporting ropes, or ram, in any way, the inertia of the cams or
the weight on the weight lever prevents their at once taking up this suddenly
increased speed, and the cam supporting spring, acting through the lever on the
cam shaft, brings the cams into engagement with the guides. The cams then roll
on the guide surfaces, compressing the buffer springs, which gradually absorb the
energy of motion, just as in a gun the energy of recoil is sometimes absorbed by
springs.
A stop is provided against which the spring cross-head bears solidly when the
limit of travel of the spring has been reached. The strength of springs and the

page_text: travel of the cage after engagement with the guides should be so proportioned
that no severe shock is caused by the stoppage of the lift in this manner.
The cam surfaces may be toothed so that no slipping can take place between
them and the guides. If a plain metal guide be used, short but sharp and strong
teeth are preferable, and should be so made that if the guide be lubricated the
teeth can penetrate the lubricant, and so bite on the guides. Teeth might be
provided on the guides also.
We, JAMES PITCAIRN HALKET, of 135, East India Dock Road, Poplar, in the
County of Middlesex, and Jonx KENNEDY, of 11, Fellows Road, South Hampstead.
in the County of Middlesex, Engineers, 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 improvements in safety gear for lifts or hoists, and has
for its object the prevention of a dangerously rapid descent of the cage, whether
due to bursting of the lift pipes or to the breaking of the supporting rope or to any
other cause.
Our invention consists in applying to an apparatus for gripping the lift guides
by cams brought into operation by the sudden increase in the downward velocity
of the cage, means for bringing the cage to rest gradually, and not suddenly
as takes place with such appliances previously used. The cams may be brought
into operation in other ways such as by spring or gravity devices released by the
breaking of the supporting rope or by means of a governor driven from the cage.
In our improved appliance we do not depend on the sliding friction of the
gripping cams on the guides to bring the cage to rest gradually, and we prefer,
indeed that practically no such sliding should take place.
We may also provide a governor of any known kind to bring the cams into
engagement with the guides in case of a dangerously high downward velocity
being acquired by the cage gradually.
In carrying our invention into effect according to one modification we provide
a cross shaft suitably supported preferably at the bottom of the cage. This shaft
carries two cams, one at each end. Suitably strong wooden or metal guides are
used for the cage. The cam shaft is so supported that it can move backwards in
guides from the lift guide as the cams turn into nosition, in gripping the guide.
Springs are suitably placed to resist this backward motion, and are of sufficient
strength to absorb the energy of motion in the cage and load when the apparatus
comes into action. The cams grip the guides against suitable brackets fixed on
the cage bottom. The cams are made of such a shape. that their centre of mass
is well on the lift guide side of the centre of the shaft. and they are held up in
this position by means of a suitable spring acting on a lever placed on the cam
shaft or a weight may be placed on a lever fixed to the cam shaft and this weight
will then be held up by the spring. In this case the cams need not be loaded as
described. When a sudden downward acceleration is given to the cage, as by the
breaking of its supporting ropes, or ram in any way. the inertia of the cams or
the weight lever prevents their at once taking up this suddenly increased speed.
and the cam supporting spring, acting through the lever on the cam shaft, brings

page_text: the cams into engagement with the guides. The cams then roll on the guide
surfaces, compressing the buffer springs, which gradually absorb the energy of
motion, just as in a gun the energy of recoil is cometimes absorbed by springs.
A stop is provided against which the spring cross-head bears solidly when the
limit of travel of the spring has been reached. The strength of springs and the
travel of the cage after engagement with the guides should be so proportioned
that no severe shock is caused by the stoppage of the lift in this manner.
The cam surfaces may be toothed so that no slipping can take place between
them and the guides. If a plain metal guide be used, short but sharp and strong
teeth are preferable, and should be so made that if the guide be lubricated the
teeth can penetrate the lubricant and so bite on the guides. Teeth may be
provided on the guides also.
Referring to the accompanying sheets of drawings:-
Figure 1 is an elevation showing the first modification of our invention with the
cams C in the normal position before coming into action.
Figure 2 is another elevation of the same, but with the cams C in gear with the
guides 1), and showing the bolster E pushed solidly home against the end F
of the spring box F.
Figure 3 shows a front elevation partly in section, of a modified form of our
invention.
Figure 4 shows a side elevation of the same, but with the double spring box
in section.
Figure 5 shows a plan of the same, partly in section.
In carrying our invention into effect according to one modification, as illustrated
in Figures 1 and 2, where the cams are operated by the inertia of a mass on
a lever fixed to the cam shaft, we provide a cross shaft B suitably supported pre-
ferably on the bottom of the cage A. This shaft carries two cams C, one at
each end. Suitably strong wooden or metal guides 1) are used to guide the cage.
The cam shaft B is so supported by the bolsters E and the spring box F that it may
move backwards in guides F attached to the spring box, away from the lift
guides) as the cams C turn in position, in gripping the guide D. Springs H
are suitably placed to resist this motion, and are of sufficient strength to absorb
the energy of motion in the cage and load when the apparatus comes into action,
and to arrest the fall of the cage without dangerous shock. Instead of the
springs H a hydraulic buffer of any of the well known types may be used. The
cams C grip the guides D against suitable brackets I fixed on the cage bottom. A
weight is placed on a lever J fixed to the cam shaft B, (see Figures 3, 4, and 5),
and this weight J¹ is held up as shown by the spring J2. When a sudden down-
ward acceleration is given to the cage, as by the breaking of its supporting ropes,
or ram in any way, the inertia of the weight J on the weight lever J prevents
its at once taking up this suddenly increased speed, and the cam supporting
spring acting through the lever J, brings the cams C into engagement with
the guides D. The cams C then roll on the guide surfaces, compressing the buffer
springs H, which gradually absorb the energy of motion, just as in a gun the
energy of recoil is sometimes absorbed by springs.
A stop F is provided against which the spring crosshead or bolster E bears
solidly when the limit of travel of the spring has been reached. The strength
of springs and the travel of the cage after engagement with the guides should be
so proportioned that no severe shock is caused by the stoppage of the lift in
this manner.
The cam surfaces may be toothed so that no slipping can take place between
them and the guides. If a plain metal guide be used, short but sharp and strong
teeth are preferable and should he so made that if the guide be lubricated the
teeth can penetrate the lubricant, and so bite on the guides. Teeth may be
provided on the guides also.
We may bring the cams C into operation by means of springs which are under
tension or compression by the tension of the cage carrying ropes, and when this

page_text: breaks these springs would be set free, and would move the cams into engagement
with the guides D.
In another modification of our invention, where we use a governor to actuate
the cams C, as shown in Figures 3, 4, and 5 we provide a second spring J held
in compression by a tubular sleeve J5 which has an annular recess J6 at its top,
adapted to receive the edges of the plates J7 of an iris diaphragm of the usual
construction as used in a photographic lens. The plates J' of this diaphragm are
withdrawn by the turning of the plate J8 which has angle slots into which pins
on the plates J project. The plate 18 is turned by means of a chain L, attached
to the weight M, which falls when released by the governor. The ball governor K
is driven from a pulley K' engaging by friction or otherwise with the guide D.
The weight M is suspended normally by a lever M¹ pivoted at M², and engaging
at M³ with the moving part of the governor sleeve.
When the governor sleeve is withdrawn on account of the cage speed having
become excessive, the lever M is set free, and the weight M falls until checked
by the chain L, and therefore turns the plate J8, and sets free the spring J. This
spring J then rises and brings the cams into engagement with the guides D, thus
stopping the fall of the cage.
This governor arrangement acts as a check on the inertia gear.
The arrangement last described of actuating the cams by the governor might
be advantageously used alone, without the inertia gear, in which case the weight J¹
and spring J2 would be omitted; or both may be used together as shown. The
second spring J may be operated in other ways from the governor without depart-
ing from our invention.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is:-
1. In safety gear for lifts, cams on the cage adapted to engage with the elevator
guides, and provided with buffers substantially as described.
2. In safety gear for lifts the combination of buffer supported cams with an
inertia device bringing the cams into action, substantially as described.
3. In safety gear for lifts the combination of buffer supporting cams with
governor operated releasing gear, substantially as described.
4. The improved lift safety gear hereinbefore described and illustrated in the
accompanying drawings.
Dated this 28th day of Fab
February 1900
MARKS & CLERK,
18, Southampton Buildings, London, W.C., 13, Temple Street, Bimingham,
and 25, Cross Street, Manchester, Agents.