Brakes – Operators – Speed-responsive
Reexamination Certificate
1999-01-19
2001-04-17
Oberleitner, Robert J. (Department: 3613)
Brakes
Operators
Speed-responsive
C187S375000
Reexamination Certificate
active
06216826
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in lifts, and more specifically in braking apparatus' used to stop BANK HOISTS and elevators smoothly in over speed situations.
Many home builders and home owners often find it desirable to build on large hills or cliffs overlooking lake fronts or scenic areas. An inherent problem with this type of terrain is that the user of the home often desires to get from the home up on a large hill or cliff, down to the lake or base. This often involves placing several flights of stairs or crossing walkways.
A common solution to this has been the use of BANK HOIST type lifts or baskets which run on a rail system and allow users to get up and down large embankments or cliffs easily and without effort. These lifts can be especially advantageous in transporting materials, as well as elderly and young users of the home, to and from different elevations. Often times these lifts may not be completely vertical as elevators commonly are and will run on a track system using wheels. The lifts are often pulled up and down via a cable system and some sort of pulley which winds or unwinds or turns the cable. It has been found that it is desirable to provide some type of braking system for these lifts that will be activated automatically in an over speed situation, such as when a cable spool or cable breaks. This type of brake would keep the BANK HOIST type lift or carriage from free falling. It has also been found that it would be advantageous to provide a system that would automatically brake or stop the carriage smoothly, with no sudden jerking motion to the occupants, in an over speed situation in either direction.
Finally, a large number of these types of lifts exist and are already installed but use out of date or aging braking apparatus'. It would therefore be advantageous to design a braking apparatus that could be used to retro fit older or existing lifts. This same type of braking system may also be used in other types of lifts and elevators.
SUMMARY OF THE INVENTION
It is the primary objective of the present invention to provide a method of effectively and safely stopping a lift in an over speed situation.
It is an additional objective of the present invention to provide such a method that uses a static cable that runs the length of the path of travel of the hoist which interacts with the braking system located on the bottom of the hoist.
It is a further objective of the present invention to provide such a braking mechanism that will engage without the intervention of the user of the lift.
It is still a further objective of the present invention to provide such a system that employs a speed sensitive clutch mechanism to trigger the brake.
These objectives are accomplished by the use of a braking mechanism that is attached to the bottom side of the frame of a lift. The BANK HOIST type lift is a lifting apparatus that is used to transport people and materials up and down inclines without having to resort to the use of stairs. This braking mechanism interacts with a fixed cable that runs the length of the path of travel of the lift. The interaction of the cable and braking mechanism is accomplished by first running the cable over and under a series of wheels in the wheel housing component of the brake and then through the cable cam housing component of the brake.
One of the wheels in the wheel housing transfers the rotational power created by the travel of the braking mechanism over the cable to a centrifugal clutch which is located on the outer side of the wheel housing. The centrifugal clutch is made up of an inner and outer hub in which only the inner hub rotates during the normal operation of the lift. The outer hub is connected to the drive sprocket which in turn is connected to a drive chain. The drive chain extends forward to a point where it engages an additional sprocket located on an axle which is connected to the hoist frame in the gap between the wheel housing and the cable cam housing. This axle also has an offset cam lobe protrusion that is located between the cam sprocket and the hoist frame and the offset portion of the lobe is oriented in a downward manner during the normal operation of the hoist.
The cable cam, which is the component of the invention which actually performs the braking operation, is located within the cable cam housing which is again attached to the hoist frame. The cable cam is pivotally mounted to the housing towards its lower end and is attached to a high tension spring at its upper end. During normal operation of the hoist, the upper end of the cable cam is forced forward and held in place by the use of the cam lock which extends rearward to end at a point just above the trip lobe located on the cam sprocket axle. The locking of the cable cam in this position loads the high tension spring and rotates the lower end of the cable cam just enough to allow the fixed cable to pass through the cam housing beneath the lower surface of the cable cam.
When an over speed situation is encountered by the lift, the centrifugal clutch located in the inner hub of the clutch assembly expands and catches a protruding tab located on the inner surface of the outer hub. This causes the rotational force of the inner hub to be transferred to the outer hub which rotates the cam sprocket through the drive sprocket and drive chain. The rotation of the cam sprocket forces the offset portion of the trip lobe upward until it engages and releases the cam lock. This releases the load on the spring which rotates the cable cam which in turn closes the distance between its lower surface and the floor of the cam housing. Therefore, the fixed cable is pinched between the cable cam and the cam housing which effectively stops the relative motion between the braking mechanism, which stops the motion of the lift.
For a better understanding of the present invention reference should be made to the drawings and the description in which there are illustrated and described preferred embodiments of the present invention.
REFERENCES:
patent: 1959528 (1934-05-01), Federici
patent: 2511697 (1950-06-01), Clift
patent: 2944635 (1960-07-01), Wittkuhns
patent: 4653612 (1987-03-01), Winkler
patent: 4662481 (1987-05-01), Morris et al.
patent: 4856623 (1989-08-01), Romig, Jr.
patent: 5052523 (1991-10-01), Ericson
patent: 5310022 (1994-05-01), Sheridan et al.
patent: 5492200 (1996-02-01), Korhonen
patent: 5630483 (1997-05-01), Karner
Harr Curtis V.
Oberleitner Robert J.
Talavera Melanie
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