Brakes – Operators – Speed-responsive
Reexamination Certificate
1999-06-08
2001-07-17
Oberleitner, Robert J. (Department: 3613)
Brakes
Operators
Speed-responsive
C188S029000, C187S288000, C187S358000
Reexamination Certificate
active
06260673
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a holding brake for a traction sheave elevator.
DESCRIPTION OF THE BACKGROUND ART
The function of a holding brake is to hold an elevator stationary at a floor and also to stop the elevator car or prevent its motion during a power failure. Therefore, the braking action of the holding brake is based on a mechanical pressure element, such as a spring, which keeps the brake engaged when there are no external forces acting on it. As the holding brake is activated each time when the car arrives at a floor and releases each time the car leaves a floor, its operation must be as fast, accurate and noiseless as possible so that it will not be noticed by elevator users. For this reason, the air gap between the brake shoe of the holding brake and the traction sheave or a possible separate brake wheel must be as narrow as possible to allow the braking to occur as quickly as possible and to keep the impact energy of the brake shoe as low as possible and the locking of the brake as noiseless as possible. On the other hand, it is to be noted that there must be a definite air gap between the brake shoe and the braking surface and that the brake shoe must not chafe the braking surface as this would result in undesirable noise during elevator travel.
In holding brakes used at present in traction sheave elevators, i.e. in normal slide brakes, bearing tolerances in the brake lever systems and structural deflections impair the accuracy of the braking action, which is why it is necessary to use relatively large air gaps in holding brakes. Therefore, the required movements in the brake shoe and in the parts actuating it are large, implementing the movements requires relatively large and expensive components, and the braking action produces a relatively noisy impact due to the large air gap. Especially the electromagnet used to release the brake is relatively large and expensive due to the long brake shoe travel upon release of the brake.
SUMMARY OF THE INVENTION
The object of the present invention is to eliminate the drawbacks described above. A specific object of the invention is to disclose a new type of holding brake for a traction sheave elevator, a brake which is accurate in operation as well as fast and noiseless, which is easy to adjust and which can be implemented using smaller, lighter and less expensive components.
The brake shoe of the invention for a traction sheave elevator comprises a brake body and a brake shoe attached to the brake body. Moreover, the holding brake comprises a mechanical pressure element, which may be a spring or equivalent, arranged to press the brake shoe against a brake wheel to prevent rotation of the brake wheel. The holding brake also comprises a retractor arranged to apply a pull to the brake shoe to keep it clear of the brake wheel when the brake is not active, i.e. when the car is moving. The element used as a retractor is generally an electromagnet, but other mechanical, electrical, hydraulic or corresponding arrangements may be used as well.
According to the invention, the holding brake comprises an intermediate frame disposed between the brake body and the brake shoe, with a pressure element applying a pressure on the intermediate frame. In addition, the holding brake comprises adjusting elements between the intermediate frame and the brake shoe to allow the position of the brake shoe to be adjusted in relation to the intermediate frame so as to maintain an air gap of exactly the desired width between the brake shoe and the brake wheel. Thus, in the holding brake of the invention, the brake shoe and the intermediate frame are connected together by the adjusting elements so that, due to the action of the electromagnet or mechanical pressure element, they move together as a rigid assembly during the braking action. The intermediate frame and the brake shoe are only moved or adjusted relative to each other when the air gap between the brake shoe and the brake wheel is to be adjusted. Thus, the holding brake of the invention has a fixed and stationary brake body while adjustment of the air gap is accomplished as an internal adjustment between brake components within the brake.
The braking surface of the brake shoe is preferably an elongated part with a curved shape in the direction of motion of the brake wheel so that it has a relatively long contact area with the braking surface of the brake wheel along the rim of the wheel. In this case, the holding brake preferably comprises two adjusting elements between the intermediate frame and the brake shoe, disposed on both sides of the middle portion of the brake shoe, preferably relatively close to its ends.
In the adjusting element between the brake shoe and the intermediate frame, preferably an adjusting spring and a clamping element are used, the clamping element being arranged to pull the brake shoe toward the intermediate frame against the pressure of the adjusting spring. As a result, there is no clearance in the joint between the intermediate frame and the brake shoe and a precise motion between them is achieved.
In another embodiment, the adjusting element is implemented using a pack of adjusting shims and a tightening means so that a pack of suitable total thickness consisting of one or more adjusting shims is formed in the adjusting element, whereupon the intermediate frame and the brake shoe are tightened to each other by means of the adjusting element, thus setting them to a position determined by the pack of adjusting shims relative to each other.
The holding brake preferably comprises suitable guides, rails, pins, holes or equivalent disposed between the brake body and the brake shoe to keep the brake shoe accurately in the correct direction and position relative to the brake wheel, these guide elements only permitting perpendicular compressive motion of the braking surfaces against each other.
As compared with prior art, the holding brake of the invention has significant advantages. Thanks to the structure of the invention, a well-functioning brake with a very narrow air gap is achieved. The brake wheel may consist of the traction sheave, which has a relatively large diameter. As a consequence of the small air gap and advantageous diameter ratio, a smaller brake magnet and smaller brake components can be used, resulting in a lower price. The long and narrow brake shoe and the two adjusting screws at its ends allow accurate control of the brake shoe so as to achieve a precise engagement with the surface of the brake wheel, resulting in effective braking. As the adjusting elements act directly on the brake shoe, the bearing clearances and structural deflections in the brake lever mechanisms have no effect on the operation of the brake, unlike normal sliding brakes. Moreover, the small air gap means a low impact energy of the brake shoe, so the closing action of the brake is quieter than in traditional brakes. In addition, as the long brake shoe needs only two adjusting elements, the brake is very easy to adjust.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 2702101 (1955-02-01), Dewhurst
patent: 3795290 (1974-03-01), Hori et al.
patent: 4049089 (1977-09-01), Rundle
patent: 4805741 (1989-02-01), de Jong et al.
patent: 5007505 (1991-04-01), Lindegger
patent: 5153389 (1992-10-01), Nomura
patent: 5373919 (1994-12-01), Siegrist
patent: 2343918 (1975-03-01), None
Birch & Stewart Kolasch & Birch, LLP
Kone Corporation
Oberleitner Robert J.
Siconolfi Robert A.
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