AU648298B2 - Brake - Google Patents

Description

648 FORM 298 S F Ref: 123770 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int. Class Application Number: PJ9914 Lodged: 1 May 1990 Accepted.

Published: Priority: Related Art: Name and Address of Applicant: Actual Inventor: Address for Service: Walco Engineering Pty. Ltd.

Walco Drive Sawtell New South Hales 2452

AUSTRALIA

NOT KNOWN Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Market Street, Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: Brake The following statement is a full description of this invention, including the best method of performing it known to me/us 5815/2 ML-- 2 The present invention relates to brakes and more particularly, though not exclusively, to a high speed safety brake to arrest a plummeting lift car.

High speed safety brakes for lift cars are known. Such known brakes suffer from general complex design and unreliability.

It is the object of the present invention to overcome or substantially ameliorate the above disadvantages.

There is disclosed herein a braking device comprising: two rotationally fixed drums within each of which a plurality of brake shoes rotate about one of a pair of hubs, the shoes of each drum being pivotally attached to a respective hub, which hub is attached to or formed integrally with a pinion or the like, which pinion is adapted to engage a rack or the like which extends in a direction of motion of the drums, the shoes being so adapted that upon exceeding a predetermined rotational velocity about the hub, a centrifugal force draws the shoes outward so as to engage the inside face of the respective drum, and a pivoting copy bar adapted to communicate movement of any shoe of either drum to all other shoes of the first and second drums such that upon rotation of any one shoe about its hub, all shoes of both drums are activated by the copy bar.

Advantageously, the second drum is provided in fixed relation to the first drum, the second drum being substantially identical to the first drum and having a pinion or the like associated therewith adapted to act on said rack or the like.

Typically three shoes are provided in both the first and second drums.

Generally, each shoe is held in position by a governor spring, the spring force of which defines said predetermined rotational velocity at which the brake will engage.

Advantageously, the shoes are of such geometry so as to be self energising on the drum/s.

Beneficially, each shoe is provided with a main spring or springs between the shoe and the hub, which main spring(s) is(are) positioned to be compressed to a fixed length during brake operation thus providing a fixed braking torque.

Advantageously, an electrical switch is activated by the copy bar to disable electrics of a lift to which the braking device is attached.

1~1_ -3- Generally, the shoes are adapted to be released from the drum/s upon rotation about the hub in an opposite direction.

A preferred form of the present invention will now be described by way of example with reference to the accompanying drawing which is a schematic part cross-sectional elevational view of a braking device.

In Fig. 1 there is schematically depicted a braking device generally indicated as 1.

The braking device comprises two cylindrical drums and (3) attached to each other at area by means of welding. The drums are essentially identical and accordingly the internal detail as depicted in drum is shared with drum Within drum is located a hub connected to a shaft by means of a conventional key-in-slot arrangement for example. Extending from shaft is a pinion gear (not shown) which interacts with a rack which extends vertically the full distance of travel of the lift to which the braking device is attached. Accordingly, as the lift car moves up or down, the shaft and hub rotate as the pinion turns in mesh with the rack.

Each hub assembly has three shoe mechanisms at 1200 spacings around the hub assembly Each shoe mechanism comprises heavy steel shoe pivoted on two spring posts The shoes have lining (16) on their outer edges. Each shoe is held in a position close to the hub axis (11) by a governor spring (12) so as to pivot about the end of the two spring posts (10) toward the drum As each shoe (9) begins to move outward, the rate of increase of centrifugual force exceeds the rate of increase in spring force and thus each shoe will abruptly engage drum A curved portion of the shoes generally indicated as (16) allows each shoe to engage the drum surface gradually as the shoe rotates from its inactive position to its active position. This allows the shoes to freely engage the drum surface under zero force, and gradually be driven into the high torque fully self energising position by the shoes motion relative to the drum face.

It should be noted here that the direction of rotation of hub during descent of the lift is indicated by arrow (14).

Due to the geometry of the shoe and pivot points (13) and (14), the shoes are self energising on drum until the shoes are in the operating position, at which they are stable. In this operation position, RLF/26981 OL -4main springs (15) on spring post are compressed to a fixed length to provide a fixed braking torque.

A "copy bar" mechanism (17) links the two brake units such that any shoe in the engaged position passing the copy bar moves the copy bar (17) into the active pusition. In this position any shoe passing either end of the copy bar (17) will be guided out to engage with the drum and so within a single revolution, all shoes will be fully engaged with drums or An electric switch wired into the safety interlock circuit is force broken to disable hoist electrics, by the motion of the copy bar (17).

Upon resetting the copy bar and thereby the electrical system, and movement of the lift car upward after having come to a halt, the shaft (6) and hub rotate backwards allowing shoe to rotate away from drum in- the inactive position effectively resetting the brake.

It should be appreciated that changes or modifications obvious to those skilled in the art are considered to be within the scope of the present invention.

i jl RLF/26981 EL i r LC-

Claims (9)

1. A braking device comprising: two rotationally fixed drums within each of which a plurality of brake shoes rotate about one of a pair of hubs, the shoes of each drum being pivotally attached to a respective hub, which hub is attached to or formed integrally with a pinion or the like, which pinion is adapted to engage a rack or the like which extends in a direction of motion of the drums, the shoes being so adapted that upon exceeding a predetermined rotational velocity about the hub, a centrifugal force draws the shoes outward so as to engage the inside face of the respective drum, and a pivoting copy bar adapted to communicate movement of any shoe of either drum to all other shoes of the first and second drums such that upon rotation of any one shoe about its hub, all shoes of both drums are activated by the copy bar.

2. The braking device of claim 1 wherein the second drum is provided in fixed relation to the first drum, the second drum being substantially identical to the first drum and having a pinion or the like associated therewith adapted to act on said rack.

3. The braking device of claim 1 or claim 2 wherein three shoes are provided in both the first and second drums.

4. The braking device of any one of the preceding claims wherein each shoe is held in position by a governor spring, the spring force of which defines said predetermined rotational velocity at which the brake will engage.

The braking device of any one of the preceding claims wherein the shoes are of such geometry so as to be self energising on the drums.

6. The braking device of any one of the preceding claims wherein each shoe is provided with a main spring or springs between the shoe and the hub, which main spring(s) is(are) positioned to be compressed to a fixed length during brake operation thus providing a fixed braking torque.

7. The braking device of any one of the preceding claims wherein an electrical switch is activated by the copy bar to disable electrics of a lift to which the braking device is attached.

8. The braking device of any one of the preceding claims wherein the shoes are adapted to be released from the drum/s upon rotation about the hub in an opposite direction. .F/26981 EL -6-

9. A braking device substantially as hereinbefore described with reference to the accompanying drawing. DATED this EIGHTEENTH day of JANUARY 1994 Walco Engineering Pty Ltd Patent Attorneys for the Applicant SPRUSON FERGUSON RLF/26981 c I Li