Improvements in Safety Mechanism for Elevators.
Year: 1897

page_text: Date of Application, 28th Dec., 1897-Accepted, 23rd Apr., 1898
COMPLETE SPECIFICATION.
Improvements in Safety Mechanism for Elevators.
I, DAVID IRVING PRUDDEN, residing at Morristown, in the County of Morris,
and State of New Jersey, United States of America, Carpenter, 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 that class of safety elevator catches which embody a
pivoted lever or dog adapted to engage a vertical ratchet bar. The object of my
invention is to provide a simple and improved safety device of this character which
will serve to effectively and automatically arrest the descent of the car whenever
the latter attains abnormal speed either by reason of accident or other causes.
The invention is fully disclosed in the following specification, of which the
accompanying drawing forms a part, in which the separate parts of my improve-
ment are designated by the same letters of reference in each of the views, and in
which:-
Fig. 1, is a front elevation, partly in section, showing an elevator mechanism
provided with my improvements:
Fig. 2, is a side elevation of the elevator showing part of the safety mechanism;
Fig. 3, is a detail horizontal sectional view, of the elevator guides and ratchet;
Fig. 4 is a detail side view of the dog or catch device; and,
Fig. 5, a detail edge of the dog or catch device. Referring to the drawings A A
designates the vertical side beams, comprised in the elevator shaft, which carry
vertical guides or plates b b, between which are housed vertical racks or ratchet
bars, C. The rack bars C normally maintain a fixed position, but are adapted to slide
vertically, when engaged by the safety catch mechanism, against the tension of
springs or cushions D), arranged at their bottom ends, which mechanism operates
to relieve the jar or shock in the operation of the safety mechanism. The rack
bars C are thus virtually supported upon the bottom springs or cushions.
E designates the elevator car, which may be in the main or any suitable or adapted
construction, it being preferably provided at its bottom with a transverse cross piece
or beam, f, upon which the catch mechanism is mounted. The beam f carries at
its ends brackets, G, which may embody laterally projecting parallel flanges, as
at g, embracing the vertical guides b b.
h designates the gravity dogs or catches, which are mounted so as to swing
transversely with respect to the elevator car, one at each side, and beneath the
bottom of the same, said dogs or catches being pivoted or fulcrumed, as at h, im
the brackets G and adapted to be thrown into engagement with the rack bar C.
The catches or dogs h¹ can be retained in engagement with the vertical rack
bars by means of lever arms h³ h², fulcrumed at h in connection with the gravity
dogs and extending inwardly therefrom.
The relative arrangement of the levers 2 and the gravity dogs h¹ is such that
the dogs can swing independently of said levers and into engagement with the racks
bars C, when operated by the automatic mechanisms hereinafter described. But
when said levers he swing downwardly they operate as weighted arms which force
Price 8dl

page_text: the dogs into engagement with the rack bars and retain them in this position as
long as said levers h³ remain down, this operation being effected by means of
shoulders, h which bear against the dogs below the fulcrum h of the latter and
swing them outwardly when the levers h² drop. Whenever the levers h³ are
retained in raised position so that their shoulders h do not operate upon the gravity
dogs, the latter will hang downwardly in normal position and free from engage-
ment with the rack bars. To provide for this retention of the levers h³ in raised
position, cords or cables I I, are respectively connected to the inner ends of said
levers and extend upwardly therefrom and over guide rollers, i, upon the beam f
to their suitable mounted guide rollers, ¹¹, over which they pass and are turned
downwardly, their ends being connected with a vertically moving foot piece, J,
mounted in the bottom of the elevator car.
When this foot piece is depressed the levers h³ will be held in raised position.
and the dogs or ratchets h' will depend in normal position free from engagement
with the racks C, but when the pressure upon the foot piece is released, the levers h³
will drop downwardly and force the dogs or catches houtwardly into engagement
with the racks.
Upon the bottom of the car and in transverse relation to the dogs or catches, are
mounted, in a pivoted or hinged manner, as at k, relatively diverging fan plates, K,
provided upon their outer faces with a bracket, k, adapted when the fans are
thrown upwardly and outwardly to engage the respective dogs h¹ and force the
same into engagement with the rack bars. These fans K are suspended in normal
position by means of chains, L, depending from the bottom of the elevator car.
It will be understood that the weight or gravity function of the fans is so regu-
lated that the descent of the car at normal speed will not operate the fans, but when
an unusual rate of speed is attained in the descent by accident or from any other
cause the fans will be forced upwardly by air pressure and operate against the dogs
to force the same into engagement with the ratchet bars. During the descending
movement of the car, the dogs will slip over the ratchet edge of the bars C (should
the levers h² be dropped down) or they will swing free from engagement with the
latter if the foot piece is operated to raise the lever h². Said foot piece mechanism
will also serve to retain the lever h² in raised position and permit the dogs h¹ to
swing free from engagement with the rack bars during the descent of the car.
M designates arms, which are pivotally suspended, as at m, at the bottom of the
elevator car, and are adapted to bear at their free ends with relation to the dogs or
catches h¹, to force the latter outwardly and into engagement with the rack bars,
when said arms are swung upwardly. These arms are adapted to be operated by a
parachute mechanism, O, which is mounted at the top of the car and is connected
with said arms by means of cords or cables, N, passing upwardly at the sides of
the car, through suitable guide openings n, and over guide rollers, n¹, at the top of
the car, from whence said cords or cables pass inwardly and under guide rollers, n²,
and from thence upwardly to the parachute mechanism. The parachute mechanism
preferably comprises an upright or standard, P, mounted at the top of the oar and
carrying a 'folding and expanding body, o, having a sliding collar connection, p,
to which the ends of the cords or cables N are connected, said collar being arranged
to slide upon the standard P..
In operation, the parachute mechanism is adapted to automatically open, when
the descending speed of the car becomes abnormal, so that the collar ย slides up-
wardly on the upright P and draws upon the cords or cables N, which latter pull
the pivoted arms M upwardly and thereby effect the engagement of the dogs or
catches with the rack bars.
Whenever an abnormal rate of speed is attained by the car in its descent, the
pivoted dogs will be instantly and automatically thrown into engagement with the
rack bars, by operation of the fan or parachute mechanism, and the movement of
the car will thus be checked, any consequent jar or shock being taken up or relieved
by the springs or cushions upon which the rack bars are mounted.

page_text: This engagement of the dogs with the rack bar, to stop or check the car in its
descent may also at any time be effected by the simple release of the foot piece
mechanism and the consequent dropping of the levers h³ which serve to operate
the dogs.
It will be noted that whenever the operator leaves the car, and the foot piece
mechanism is in released condition, the levers h² will retain the dog h¹ in engage-
ment with the rack bars and thus automatically serve to lock the car against a
descending movement.
If desired, the outer face of the dogs h¹ may be cushioned with rubber or other
elastic material, as shown at h³ to provide a friction piece which will slide noise-
lessly over the ratchet face of the rack bar during the ascending movement of the
car.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. In a safety mechanism for elevators, vertical ratchet or rack bars slidably
mounted in the elevator shaft, in combination with the elevator car operating longi-
tudinally with relation to the slidable rack bars and carrying catch devices for
engaging the same, substantially as and for the purpose set forth.
2. In a safety mechanism for elevators, vertical ratchet or rack bars slidably.
mounted in the elevator shaft, and springs or cushions supporting and sustaining
said rack bars, in combination with the elevator car travelling longitudinally with
respect to said slidable spring mounted rack bars and carrying catch devices adapted
to engage the latter on the descending movement of the elevator car, substantially
as and for the purpose set forth.
3. In an elevator mechanism comprising vertical ratchet or rack bars longi-
tudinally arranged with respect to the travel of the elevator car and adapted to be
engaged by the car, a slidable ratchet or rack bar longitudinally mounted with
relation to the travel of the elevator car and sustained by a spring or cushion, sub-
stantially as and for the purpose set forth.
4. A safety mechanism for elevators, comprising vertical ratchet or rack bars,
gravity catches or dogs fulcrumed upon the elevator car, levers forming a weighted
arm adapted to bear upon and operate said dogs, ropes or cables extending from said
weighted arms, and a foot piece or operating device connected with said ropes
or cables, whereby the gravity dogs may be forced into engagement with the rack
bars by simple release of the foot piece mechanism, substantially as and for the
purpose set forth.
5. A safety mechanism for elevators, comprising vertical ratchet or rack bars,
dogs or catches mounted upon the elevator car and adapted to engage said rack bars,
and a pivotally arranged fan mechanism adapted to be forced open by air pressure
during the descent of the car at abnormal speed, said fan mechanism operating with
relation to the dogs or catches to throw the same into engagement with the rack
bars, substantially as and for the purpose set forth.
6. A safety mechanism far elevators, comprising vertical ratchet or rack bars,
dogs or catches pivotally suspended from the elevator car and adapted to engage
said rack bars, and fan plates pivotally suspended from the car and adapted
to be swung by air pressure into operative relation to said dogs or catches, whereby
the latter are forced into engagement with the rack bars, substantially as and for
the purpose set forth.
7. A safety mechanism for elevators, comprising vertical ratchet or rack bars,
catches or dogs pivotally suspended from the elevator car and adapted to engage
said rack bars, fan plates suspended in pivoted or hinged position from the elevator
car and arranged transversely with respect to said dogs or catches and adapted to
bear against the latter when they are swung by air pressure, and means for sustain-
ing said fan plates in normal operative position, substantially as and for the purpose
set forth.

page_text: 8. A safety mechanism for elevators, comprising vertical rack or ratchet bars,
dogs or catches mounted upon the elevator car and adapted to engage said rack
bars, a parachute mechanism carried by the elevator car, and devices connecting
said parachute mechanism with the dogs or catches, whereby the latter are thrown
into engagement with the rack bar when the parachute opens, substantially as and
for the purpose set forth.
9. A safety mechanism for elevators, comprising vertical rack or ratchet bars,
dogs or catches pivotally suspended from the elevator car, a parachute mechanism
carried by the elevator car and connecting cords or devices extending between the
parachute mechanism and the pivoted dogs or catches, whereby when the parachute
opens and draws upon the cords the dogs or catches are carried outwardly into
engagement with said rack bars substantially as and for the purpose set forth.
10. The combination, with an elevator car, of a parachute mechanism, safety
catch mechanism for governing the speed of operation of the car, and mechanism.
connecting the parachute mechanism with the safety catch mechanism, substantially
as and for the purpose set forth.
11. A safety mechanism for elevators, comprising vertical ratchet or rack bars
slidably mounted and sustained by springs or oushions, pivoted dogs or catches
suspended upon the elevator car and adapted to project into engagement with said
rack bars and automatic mechanism carried by the elevator car and governing the
operation of the pivoted catches with relation to said spring sustained rack bars,
substantially as and for the purpose set forth.
12. A safety mechanism for elevators, comprising levers forming weighted arms,
catch mechanism adapted to be operated by the dropping movement of said arms,.
a depressible foot piece mechanism arranged within the car, and mechanism con-
necting said foot piece mechanism with the lever arms and operating to retain the
latter up in elevated position when the foot piece is depressed whereby when the
operator leaves the car and the foot piece mechanism is released the lever arms will
automatically operate the catch mechanism to lock the car in position, substantially
as and for the purpose set forth.
Dated this 28th day of December 1897
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W.C., Agents.