Remote brake release mechanism for an elevator machine

A brake release mechanism for an elevator machine includes apparatus to reduce the braking force on the machine shaft. The apparatus may be actuated from a position located remotely from the machine.

TECHNICAL FIELD 
The present invention relates to elevator systems, and more particularly to 
brake mechanisms for elevator machines. 
BACKGROUND OF THE INVENTION 
A traditional elevator system for mid-rise and high-rise buildings includes 
a car and a counterweight interconnected by a rope and a traction machine 
engaged with the rope to drive the car and counterweight. The traction 
machine includes a sheave engaged with the rope, an electric motor for 
rotating the sheave, and a brake to hold the sheave when the car is 
stopped. The traction machine, along with an electronic controller for the 
elevator system and electronic drive for the machine, are housed in a 
machine-room located above the hoistway. 
Various configurations have been suggested to eliminate the machine-room in 
an effort to save on the associated construction costs. One suggested 
elevator system uses a linear induction motor driven elevator; another 
uses a traction machine having a disc type motor mounted in the hoistway; 
and still another uses a self-propelled cab having a pinch-roller type 
drive engaged with the guide rails of the car. 
While possibly saving construction costs of the building, an area of 
concern arises with such machine-roomless elevators in the event of an 
elevator shut-down. In a conventional elevator system having a 
machine-room, a mechanic may enter the machine-room and manually operate 
the traction machine to move the car to the nearest landing. Once there, 
the doors may be opened and the passengers evacuated. Due to the 
elimination of the machine-room in some of the suggested configurations, 
however, the traction machine may not be readily accessible. If a 
shut-down occurs, a mechanic may not be able to manually operate the 
traction machine. 
The above art notwithstanding, scientists and engineers under the direction 
of Applicants' Assignee are working to develop simple and effective 
methods and apparatus to permit manual operation of elevator machines that 
are difficult to access due to their location. 
DISCLOSURE OF THE INVENTION 
According to the present invention, a brake release mechanism for an 
elevator system includes means to reduce the braking force on the machine 
shaft from a position located remotely from the machine. 
The advantage of the invention is that in the event of a loss of power, 
which will cause the machine brake to engage the machine shaft, a mechanic 
may use the means to reduce the braking force to permit limited and 
controlled movement of the machine shaft, and thereby limited and 
controlled movement of the elevator car. The movement of the elevator car 
can be used to move the elevator car to a landing and permit evacuation of 
the elevator car. In addition, since the means is located remotely from 
the elevator machine, there is no need to get direct access to the machine 
and therefore the machine may be located in a difficult to access 
location, such as the overhead space in a hoistway. 
In a particular embodiment, the means to reduce braking force includes a 
release lever disposed proximate to the brake lever and a rope engaged 
with the release lever and extending to a remote location relative to the 
elevator machine. Tensile force on the rope urges the release lever to 
move the brake lever against the bias of the brake lever and thereby 
remove the braking force on the shaft. This particular embodiment provides 
the advantage of a simple design and one which takes advantage of the 
mechanical leverage of the lever mechanism. 
The foregoing and other objects, features and advantages of the present 
invention become more apparent in light of the following detailed 
description of the exemplary embodiments thereof, as illustrated in the 
accompanying drawings.

BEST MODE FOR CARRYING OUT THE INVENTION 
Illustrated in FIG. 1 is an elevator system 12 having a car 14, a 
counterweight 16, a plurality of ropes 18 interconnecting the car 14 and 
counterweight 16, and a traction machine 20 disposed in the overhead space 
22 of the elevator system 12. The overhead space 22 is defined as the 
space between the top of the car 14 and the top of the hoistway with the 
car 14 at its highest position. Placing the traction machine 20 in this 
location permits the elimination of a separate machine-room. 
The traction machine 20 includes a motor 24, traction sheave 26 and a brake 
assembly 28. The motor 24 drives the traction sheave 26, which is engaged 
with the ropes 18 to move the car 14 and counterweight 16 through the 
hoistway. The brake assembly 28 is engaged with an output shaft 30 of the 
motor 24 to hold the traction sheave 26 against movement when the car 14 
is stopped. 
The brake assembly 28 is illustrated in more detail in FIG. 2. The brake 
assembly 28 includes a brake drum 32 that is integrated with the output 
shaft 30 for concurrent rotation, a pair of brake levers 34, a pair of 
springs 36, an electromagnetic device 38, and a remote brake release 
mechanism 40. Each of the pair of brake levers 34 is mounted for pivoting 
motion about a pivot 42 and includes a brake shoe 44 disposed proximate to 
the brake drum 32. One end 46 of the brake lever 34 is engaged with the 
spring 36 to urge the brake lever 34 to pivot such that the brake shoes 44 
are urged toward the brake drum 32. This end 46 of the lever 34 is also 
engaged with the electromagnetic device 38. If the electromagnetic device 
38 is powered, the device 38 pivots the levers 34 opposite to and against 
the bias of the springs 36 such that the brake shoes 44 are urged away 
from the brake drum 32. 
The remote brake release mechanism 40 includes a frame 48, a pair of 
release levers 50, a pivoting lever 52, a rope 54, a spring 56 and a stop 
58. Each of the release levers 50 is mounted on the frame 48 for pivotal 
motion about a pin 60 and includes an adjustment screw 62 that extends 
inward from the release lever 50 and into engagement with the adjacent 
brake lever 34. The adjustment screw 62 is a threaded bolt that may be 
adjusted to permit proper engagement between the release lever 50 and the 
brake lever 34. The end 64 of each release lever 50 opposite to the pinned 
end 66 is attached to the pivoting lever 52. The pivoting lever 52 is 
mounted on the frame 48 for pivotal motion about a pin 68 that is disposed 
between the two ends 64,66 of the release levers 50. The rope 54 passes 
through an aperture 70 in the frame 48, through the spring 56, and through 
an aperture 72 in the pivoting lever 52. The end 74 of the rope 54 
adjacent to the pivoting lever 52 includes a catch 76 that is sized to 
prevent its passing through the aperture 72 in the pivoting lever 52. The 
opposite end 78 of the rope 54 is disposed in a location that is remote 
from the traction machine 20, such as a utility cabinet located at one of 
the landings for the elevator system 12. The spring 56 is disposed between 
the frame 48 and the pivoting lever 52 and urges the pivoting lever 52 
against the stop 58. 
The arrangement of the levers 50,52 is such that large movements of the end 
80 of the pivoting lever 52 engaged with the rope 54 will result in very 
small movement of the adjustment screw 62. This effect is achieved because 
the distance between the pin 68 and the ends 64 of the release levers 50 
is much less than the distance between the pin 68 and the end 80 of the 
pivoting lever 52 engaged with the rope 54. In addition, the distance 
between the release lever 50 pin 60 and the adjustment screw 62 is much 
less that the distance between the release lever 50 pin 60 and the end 64 
engaged with the pivoting lever 52. This arrangement multiplies the amount 
of movement required of the end 80 of the pivoting lever 52 for a given 
amount of movement of the adjustment screw 62. 
During normal operation, the electromagnetic device 38 is powered and the 
brake levers 34 are moved away from the brake drum 32 to permit rotation 
of the output shaft 30 and sheave 26. As a result, the car 14 and 
counterweight 16 may be driven through the hoistway by the traction 
machine 20. If the car 14 is brought to a stop, such as at a landing, the 
power is removed from the electromagnetic device 38 and the springs 36 
force the brake levers 34 to pivot and the brake shoes 44 to engage the 
brake drum 32, thus holding the output shaft 30 and the traction sheave 26 
against further movement. 
In the event of a shut-down of the elevator system 12 such that there is a 
loss of power to the electromagnetic device 38, the springs 36 force the 
brake shoes 44 against the brake drum 32 and the motion of the output 
shaft 30, traction sheave 26, counterweight 16 and car 14 is stopped. This 
is a fail safe operation to prevent unwanted movement of the car 14. If 
the car 14 is not at a landing when it stops, however, passengers may not 
be easily evacuated. In this event, a mechanic may get access to the 
cabinet having the end 78 of the rope 54. This rope 54 is pulled to create 
a tension in the rope 54 sufficient to move the pivoting lever 52 away 
from the stop 58 and to pivot the pivoting lever 52 about the pin 68. As 
the pivoting lever 52 moves, it also moves the ends of the release levers 
50 in the direction of the arrows A such that the release levers 50 pivot 
about their pinned connections 60. As the release levers 50 pivot, the 
adjustment screws 62 urge the brake levers 34 against the force of the 
springs 36 to pivot the brake levers 34 and reduce the braking force 
between the brake shoes 44 and the brake drum 32. The reduction in braking 
force permits the traction sheave 26 to rotate under the force of the 
unbalanced car 14 and counterweight 16. The car 14 will then either rise 
or descend, depending upon the weight imbalance. The rate of rise, or 
descent, will be slow since the brake force is not released completely. In 
addition, the motion caused by tension on the rope 54 is resisted by the 
springs 36,56 and by the release levers 50. As a result of being pinned, 
rigid links, the release levers 50 will resist motion other than in the 
direction of arrows B. The resistance to the tension in the rope 54 
assists in controlling the movement of the car 14. Once the car 14 is 
adjacent to a landing, the tension on the rope 54 is released, the spring 
56 forces the pivoting lever 52 against the stop 58 and the brake force 
between the brake shoes 44 and brake drum 32 is again sufficient to hold 
the car 14 against further movement. At this point the passengers may 
evacuate the car 14. 
Although shown and described with respect to a drum brake, it should be 
noted that the invention is equally applicable to other types of brakes 
such as sheave brakes, disc brakes or internal drum brakes. In addition, 
although the invention is shown and described as using a rope to actuate 
the release levers, it should be apparent to one skilled in the art that 
this actuation may also be done using other devices, such a solenoid 
powered by a back-up battery power system. 
Although the invention has been shown and described with respect to 
exemplary embodiments thereof, it should be understood by those skilled in 
the art that various changes, omissions, and additions may be made 
thereto, without departing from the spirit and scope of the invention.