Elevator – industrial lift truck – or stationary lift for vehicle – Having specific means contacting or on load support for... – Includes movable contact component on support for engaging...
Reexamination Certificate
1998-08-21
2001-01-23
Olszewski, Robert P. (Department: 3652)
Elevator, industrial lift truck, or stationary lift for vehicle
Having specific means contacting or on load support for...
Includes movable contact component on support for engaging...
C187S359000, C187S370000, C187S375000, C188S041000
Reexamination Certificate
active
06176350
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a progressive safety gear for elevators consisting of a carrier, which is positioned in a transverse direction to the guide rail and which encompasses one guide rail for an elevator car, on which two brake shoes which are positioned one on each side of the guide rail are supported. One of the brake shoes functions as a passive brake shoe and the other as an active brake shoe. The active brake shoe is supported on an eccentric which is fastened to a cam in such a way that it rotates with it. The cam and the eccentric are able to rotate about a common center.
2. Discussion of the Prior Art
A progressive safety gear of the type mentioned above is already known from German reference DE 21 39 056. In this safety gear the blocked governor rope actuates a tripping lever on the safety gear which causes the tensioning eccentric fastened to the positioning eccentric to rotate. As a result, the tensioning eccentric comes into contact with the guide rail. As a result of this, and because the elevator car is still moving, the tensioning eccentric continues to rotate of its own accord due to the friction contact with the guide rail, and the active brake shoe is moved into the braking position via the positioning eccentric. In the braking position, the positioning eccentric has reached the end position before the greatest distance from the guide rail, because in this position the tensioning eccentric, due to the shape of its external contour, has reduced or lost its friction contact with the guide rail and is therefore no longer caused to rotate.
However, this progressive safety gear functions only in one direction, either up or down, and it is not possible in all necessary cases to release it by moving the car in the direction opposite to the direction in which it fell. This means that the safety gear cannot always be simply released after it has engaged.
A progressive safety gear which also works with an eccentric is the safety gear BFx3 of the East German elevator industry (Liftreport, Issue 5, 1991). When this progressive safety gear is tripped, two cams with rolling and sliding surfaces are rotated either counter-clockwise or clockwise depending on the direction of travel of the elevator, which causes in the downward travel direction a strong, and in the upward direction a weaker, braking deceleration of the elevator car. Tripping takes place by means of a governor rope passing over a separate pulley which, by transmitting its rotational movement, causes the eccentric to rotate in one direction or the other depending on the direction of travel. If braking takes place in the upward direction the angle of rolling and the radius to the sliding surface in the braking position is smaller than when braking takes place in the downward direction. This results in a different degree of compression of the braking springs and correspondingly the desired different braking forces for the two directions of travel.
A disadvantage of this device is that the controlling surfaces and the braking surface are on the same component, because of which the braking surface has a relatively small contact surface, which after several trippings as a result of wear can lead under certain circumstances to a reduced braking effect or even to faulty functioning. The complete eccentric must then be replaced. Furthermore, because of the additional rotational transmission device, an elaborate and relatively expensive triggering device is necessary.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to provide a safety gear which can produce in the two directions of travel the different braking effect required, and which does not have the disadvantages described above.
Pursuant to this object, and others which will become apparent hereafter, one aspect of the present invention resides in a progressive safety gear having a console arranged so as to encompass the guide rail and be in a transverse direction to the guide rail, an active brake shoe and a passive brake shoe supported on the console so as to be positioned on one each side of the guide rail, a cam rotatably mounted on the housing, and an eccentric fastened to the cam so that they rotate together between a ready position and braking positions. The cam and the eccentric are rotatable about a common center. The cam is rotatable in both a clockwise and a counter clockwise direction so that the safety gear can be tripped in both travelling directions. The cam is configured so as to remain in contact with the guide rail after a braking operation has taken place so as to permit the cam to be turned backwards, thereby making it possible to release the engaged safety gear by pulling the elevator car out of a position in which it is blocked.
The progressive safety gear according to the invention is simply constructed, inexpensive to manufacture, and easily to install. One aspect of the invention, among other things, is that the friction contact between the cam and the guide rail which is still present after the safety gear engages makes it easy to release the safety gear.
The passive brake shoe is able to move freely for a certain distance in a vertical direction during braking and when pulling the safety gear out of its engaged position. By initially reducing the frictional force, this makes it easier to pull the safety gear out of its engaged position.
The angles alpha and beta between the zero point of the point nearest to the guide rail of a cam in the ready position and the upper dead point of the eccentric, or the smaller working angle which is dependent on these two angles up to the point of braking, determine, in combination with the shape of the rolling contour of the cam, the ratio between the braking force in the downward direction and in the upward direction.
By means of the shape of the rolling contour of the cam, and particularly a flat point which in the ready position is turned towards the guide rail, individual characteristics for the start of deceleration, which means rapid initiation of the braking effect after the safety gear is triggered, can be achieved.
For certain applications the cam can also have an external contour in the shape of a circle, with or without a flat point, which makes it simpler and cheaper to manufacture.
The circular contour of the cam rolling on the guide rail results in an identical pattern of movement of the cam for both directions of travel, which means that only the rolling angle up to the point of braking (working angle), and to a partial extent the angular position between the cam and the eccentric, determine the ratio between the braking force in the two directions of travel.
The cam and the eccentric can be produced as a single piece, which is advantageous for manufacturing.
The cam and the eccentric can also be produced as separate parts whose angle in relation to each other can be adjusted, which makes it possible to influence certain parameters such as, for example, the onset of the braking effect.
The final position of the safety gear and of the cam when braking takes place is determined without a stopper by a naturally occurring equilibrium between the pressure forces of the active brake shoe and the cam.
The frictional engagement present between the guide rail and the cam, together with the vertical play of the passive brake shoe, makes it particularly easy to pull the safety gear out of its engaged position by rotating the cam in the reverse direction on the guide rail.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the ingestion, its operation advantages, and specific objects attained by its use, reference should be had to the drawing sand descriptive matter in which there are illustrated and described preferred embodiments of the invention.
REFERENCES:
patent: 5487450 (1996-01-01), Gerber
patent: 805 782 (1951-03-01), None
patent: 1081635 (1960-05-01), None
pa
Autzugstechnologie Schlosser GmbH
Cohen & Pontani, Lieberman & Pavane
Olszewski Robert P.
Tran Thuy V.
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