In elevators having a passenger cabin suspended from cables passed over a driving disk or sheave and counterbalanced by counterweights, problems may arise where the elevator is not sufficiently secured in an upward direction in the event of component failure. If the elevator attains some downward speed limit, a gripping or clamping device will engage. In the past, no such gripping device was provided for run-away upward movement (as may happen due to the counterweights.
For this reason, an additional brake was needed for retrofitting elevators to stop their upward movement and to so offer increased safety from accidents. Possible sources of malfunction include catastrophic failure of gearbox output shafts or of gears within the gearbox, and failure of the main system brake—although the brake is designed usually to operate as a dual-circuit system.
One object of the invention is an enhanced safety in upward and downward elevator travel by means of an additional brake placed in an optimum position.
This object is achieved by an additional brake which is directly attached to the driving sheave over which the passenger cabin and counterweight cables are passed and which directly acts on that driving sheave. This ensures additional safety at each stop where the brake is being engaged. Also, in an emergency, movement is stopped in both an upward and a downward direction whenever the brake receives a signal indicative of excessive speed.
As another object, it is desirable for the brake to be attached to existing elevator systems. Thus, the task was to find a design solution which enables a safety brake to be adapted to a variety of structural and design particularities where a driving sheave may be constrained to operate. There are sheave-driving gear-box output shafts which have a trunnion separately journalled at their far end, i.e. on the side opposite the drive (see shaft 16 in FIG. 4). Also known are conical output shafts with a pressure cap (shaft 16 in FIG. 5), and driving sheaves provided on the hub side (hub 27 in FIG. 6) with extra material where additional threaded bores (28 in FIG. 6) can be placed for torque transmission. If too little material is available on the hub side of the driving sheave, the sheave must be provided with screw thread(s) along the periphery (15 in FIG. 7). Another possibility is the use of the sheave spokes for torque transmission (FIG. 8).
The said objects are achieved by a brake designed to be externally mounted adjacent an existing driving sheave, said brake providing the possibility of additional support for the sheave or transmitting the torque from said brake to the sheave via an additional flange incorporating resilient elements.
These particular variants ensure that existing elevators can be retrofitted (without incurring major efforts) with an additional brake placed next to the existing driving sheave. What is needed for retrofitting is merely a structural element providing for height adjustment between the building-side brake support and the mounting bracket of the brake.
With this solution, the brake directly engages the driving sheave and is coupled to it in a torque-locked manner. Intermediate element between the drive and the driven sheave (which might cause malfunction) are eliminated or not present in the first place.
Various embodiments of the present invention will now be described under reference to the attached drawings.
FIG. 1 shows a section of the brake to be mounted externally;
FIG. 2 shows an elevation of the subject brake form the right hand side thereof;
FIG. 3 shows a perspective view of the brake to be mounted externally;
FIG. 4 shows a sectional view of the externally mounted brake and the driven shaft (trunnion 17) as well as the additional support thereof inside the brake;
FIG. 4
a shows a perspective view of the assembly in FIG. 4;
FIG. 5 shows a sectional view of the externally mounted brake in conjunction with a coupling flange 26 replacing a pressure cap for axially fixing the sheave;
FIG. 5
a shows a perspective view of FIG. 5;
FIG. 6 shows a sectional view of the externally mounted brake secured in place by threads 28 in hub 27 of the sheave;
FIG. 6
a shows a perspective view of FIG. 6;
FIG. 7 shows a sectional view of the externally mounted brake including a connecting flange, said brake secured to the outer ring 15 of the sheave;
FIG. 7
a shows a perspective view of FIG. 7;
FIG. 8 shows a sectional view of the externally mounted brake together with a connecting flange for entrainment by the spokes of the driving sheave; and
FIG. 8
a shows a perspective view of FIG. 8.
The brake to be externally mounted operates on the well-known principle of a normally energized spring-pressure brake, which acts as a safety brake as the compression springs therein cause the brake to engage as soon as the electrical current energizing the electromagnets fails.
FIG. 1 shows brake 1 comprising an electromagnetic coil 2. Compression springs 3 urge armature disk 4 against rotor 5, which has a friction liner 6 on both the right hand and the left hand sides. The torque (braking torque) is generated by said compression springs urging armature disk 4 against rotor 5 via both friction liners 6 and a flange plate 7. The torque is transmitted from rotor 5 to a peripherally toothed or splined transfer flange 8.
For releasing or disengaging the brake, electrical D.C. power is applied to electromagnetic coil 2, resulting in a magnetic field which (via air gap 30 and against the bias exerted by compression springs 3) attracts armature disk 4 against brake 1, thus releasing rotor 5 and transfer flange 8—through the peripheral teeth thereof—for rotation.
Brake 1 is threadingly connected with flange plate 7 via spacer sleeves 9 through fastener screws 10 which are parallel with the central longitudinal axis. In between, there is provided a mounting bracket 11 having in a perpendicularly bent base portion thereof slots 12 for fastening said bracket to a base plate or supporting base 23 (FIG. 4) of the respective building.
FIG. 2 shows a junction box 14 as well as a monitoring device 13 for monitoring, or signalling to the associated controller, the operating condition of the brake (engaged or disengaged).
FIG. 3 shows central transfer flange 8 and its peripheral teeth extending axially into rotor 5 (FIG. 1) for torque transfer. Bracket 11 is secured through its slots 12 to supporting base 23 (FIG. 4).
FIG. 4 shows sheave shaft 16 powered by a conventional drive assembly (not shown) and having driving sheave 15 keyed on it for torque-locked rotation. Conventionally, driving sheave shaft 16 has a trunnion 17 mounting the sheave by means of a conventional pedestal-type bearing. In accordance with the invention, such pedestal-type bearing is eliminated in that the externally mounted brake comprises an additional bearing 18 in the form of a self-aligning bearing which assumes the task of supporting trunnion 17. An attachment hub 19 having a supplementary hub section 20, which is keyed thereto, comprises resilient elements 21 for torque transfer to brake rotor 5. Attachment hub 19 is secured in place by trunnion 17 through a conical clampdown connection 31 so as to transfer the torque to driving sheave shaft 16, to which driving sheave 15 is keyed. Additional support is provided by a plain bearing (bush bearing) 22.
FIG. 5 shows attachment hub 19 connected with intermediate flange 25 by fasteners 29. In accordance with the invention, the pressure cap used in the past to secure driving sheave 15 axially to the tapered shaft section is replaced by a novel coupling flange 26 connected through resilient elements 21 for torque transfer. Attachment hub 19 is supported separately inside the brake by bearings 18 and 24.
FIG. 6 shows a variant similar to FIG. 5, but with coupling flange 26 connected by threaded bolts 28 with the interior hub 27 of driving sheave 15 only.
FIG. 7 shows a variant in which coupling flange 26 is connected to the outer ring of driving sheave 15.
FIG. 8 shows a variant in which resilient elements 21 extend from intermediate flange 25 in between the spokes of driving sheave 15, with each spoke engaged on the right- and lefthand sides by two such resilient elements 21 (FIG. 8a) so that torque transfer can be ensured to be optimally free from backlash.
LIST OF REFERENCE CHARACTERS
1 brake
2 electromagnetic coil
3 compression springs
4 armature disk
5 rotor
6 friction liners (right/left)
7 flange plate
8 transfer flange (peripherally toothed)
9 spacer sleeves
10 fastener screws
11 mounting bracket
12 slots
13 brake disengagement monitoring device (engagement/disengagement signalling)
14 junction/connection box
15 driving sheave
16 driving sheave shaft
17 trunnion
18 bearing in flange plate 7
19 attachment hub
20 supplementary hub portion
21 resilient elements
22 plain or bush bearing for supplementary support
23 supporting base
24 ball bearing in brake 1
25 intermediate flange
26 coupling flange (receiving resilient elements 21)
27 driving sheave inner hub
28 threaded bolts (securing part 26 to part 27)
29 threaded bolts (securing part 25 to part 19)
30 air gap between armature disk 4 and brake 1
31 clamp connection on hub 19 for coupling with trunnion 17