An Improved Safety Clutch for Mine Shaft Cages, Lifts, and the like.
Year: 1897

page_text: Date of Application, 13th Mar:, 1897-Accepted, 29th May, 1897
COMPLETE SPECIFICATION.
An Improved Safety Clutch for Mine Shaft Cages, Lifts, and
the like.
I CARL HERRMANN BLEY, of Oberhohndorf near Zwickau, Saxony, in the
Empire of Germany, Mine Manager, 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 and accompanying drawings :
:-
My said invention relates to improvements in safety clutches for application to
mine shaft cages, lifts and the like, for the purpose of preventing accidents in the
event of the chain or rope breaking. At present safety clutches of this nature are
in existence which consist of pivotted pawls turning upon what is usually a shaft in
loose bearings, the pawls being under the influence of springs which in the event
of the rope breaking throw the pawls into a position which enables them to grip
the guides and so prevent the fall of the cage or lift. Such appliances are however
not certain in their action and when they act their tendency is to arrest the cage or
lift so suddenly as to constitute a serious danger to the occupants and to put a
trying strain on the mechanism. According to my invention I so form the pawls
that the stoppage of the cage is brought about more gradually and without any of
the objectionable consequence of the old method. In certain constructive details.
my invention is also an improvement upon existing appliances of this type.
My invention will be most clearly understood by a reference to the annexed
sheet of illustrative drawings.
Fig. 1 is a side view of the upper part of a cage fitted with my improvements.
Fig. 2 is a view at right angles to Fig. 1.
Fig. 3 is a vertical section at the line a Fig. 1.
Fig. 4 is a plan.
Figs. 5 and 6 are side view and plan respectively to an enlarged scale of my
improved forked pawl with teeth set at different angles.
Fig. 7 shows the said pawls in their relative positions to the guide.
Figs. 8 and 9 are side and plan views of a modified form of my improved clutch
pawl.
In the upper part of the cage I mount cross shafts a a in fixed bearings in the
frame of the cage, and on the outer ends of the said shafts a I fix clutch pawls b,
having differentially angled knife edged teeth 61 62 as shown in the drawings. In
Figs. 1, 3 and 4 these pawls are shown out of contact with the guide battens c but
in Fig. 2 the pawls are shown engaged with the said battens as for instance when
the chain or rope has broken. The cage is suspended by a rope or chain attached
to the sliding central eye bolt g in the usual manner and the strain of the eye bolt g
by overcoming the force exerted by the springs f keeps the clutch pawls b away
from the guide battens c. Suppose however that the suspending rope or chain
were to break, the eye bolt g would drop and allow the springs f to turn the
shafts a a so as to bring round the pawls b with their forked differentially angled
teeth against the guide battens c whereupon the downwardly falling cage would
drive the said teeth into the guides c and so arrest the descent.
It is unnecessary
for me to describe minutely the connection between the eye bolt g and the shafts a.
The drawings will show that; and the said mode of connecting the eye bolt and
the pawl shafts is not new but is in use with all appliances of this type. The chief
novelty consists in the form of the clutch pawls b. It will be noted in Figs. 5, 6

page_text: and 7 for example that the outer end of each pawl is made forked, the example
showing two members or teeth 61 62 set at different angles to each other and knife
edged. The result of this construction is that when by the fall of the cage the
pawls are turned to engage with the guides c as indicated by the arrows in Fig. 7,
first one tooth and then another engages with the guide. For example the tooth b¹
would grip the guide first and sensibly retard the speed of the fall, then the tooth b*
would come into action and completely arrest the descent. To assist this gradual
retardation it will be seen that the first tooth is carried upward so as to have a
less retarding effect while the tooth 62 is turned downward so as to increase the
grip upon the guide c. Thus the retarding effect is cumulative from less to greater.
To prevent the pawls from turning too far round I form them with stops e which
come against stop plates d on the sides of the cage. In some cases to steady the
pawls and prevent side movement and twisting when in action, I bore the stop
plates d with recesses to receive the stops e the pawls thus having a secure hold
upon the plates d. Figs. 8 and 9 illustrate a modification of the foregoing
differentially toothed pawl. In this instance there are three progressive differentially
angled stopping teeth. No. I in the centre is the first to encounter the guide and
exercise a certain retarding influence. No. II on one side is the next to come into
operation and retards still more, while No. III on the other side follows on last of
all, and completes the arrest of the falling cage. It may also be noted that these
differentially angled teeth I, II, and III are also of different lengths, No. I being
the shortest and No. III the longest.
By these means the gradual retardation of the cage is obtained with still greater
certainty. I do not however limit myself to the number of knife edged teeth
which might be used on the said clutch pawls b nor to the angular variations at
which they stand.
The springs fare fixed to one side of the cage and at their free ends are connected
by levers (see Fig. 1) to the cross shafts a which carry the pawls.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is.
1) As means for retarding and arresting the fall of mine cages, lifts and the like
from the accidental breakage of the suspending rope or chain, the clutch pawls b
having differentially angled knife edged teeth or projections adapted to come
successively into engagement with the guide bars or battens and thus arrest the
falling cage or lift gradually and without too violent a shock, substantially as set
forth.
2) In combination, the differentially toothed clutch pawls b secured upon shafts a
mounted in fixed bearings and governed by springs so as to throw the pawls into
engagement with the guide bars and arrest or prevent the fall of the cage or lift,
upon the accidental breakage of the suspending rope or chain, substantially as
described and illustrated.
Dated this 10th day of March 1897.
For the Applicant,
E. K. DUTTON & Co.,
5 John Dalton Street, Manchester, Chartered Patent Agents.