Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
1996-11-21
2001-02-13
Butler, Douglas C. (Department: 3613)
Brakes
Wheel
Axially movable brake element or housing therefor
C188S25000B
Reexamination Certificate
active
06186287
ABSTRACT:
TECHNICAL FIELD
The invention herein resides in the art of power transmission devices such as clutches and brakes. More particularly, the invention relates to a brake for employment with steel mill cranes. Specifically, the invention relates to a caliper disk brake for steel mill cranes which is readily adapted for replacing drum brakes previously employed for the same purpose.
BACKGROUND ART
In the United States steel industry, direct current (DC) motors having drum-shoe brakes are predominantly used for crane hoist drives. Such drum-shoe brakes pose a significant maintenance problem for the steel mills due to the necessity of frequent adjustments, the existence of thermal limitations, and the extreme difficulties encountered during servicing. Until presently, caliper disk brakes have not been employed in these applications for a number of reasons, among which is the American Iron and Steel Engineers (AISE) specification that the brake coil must be wired in series and must accommodate all of the electric current to the motor of the crane hoist drive. As a consequence, extremely large coils and armatures for releasing the brake are necessitated—significantly increasing the difficulty of adapting a caliper type of brake design. Additionally, the DC motor shaft has a significant amount of axial movement, on the order of {fraction (3/16)} inch, which the brake must accommodate. Such axial movement poses a significant problem for caliper disk brakes of the necessary size, particularly with respect to drag and wear.
Additionally, drum-shoe brakes are given to high wear rates, requiring frequent servicing and shoe replacement. Typically, these brakes are in areas which are difficult to access, being associated with cranes in elevated locations. The brake shoes are both heavy and cumbersome. Indeed, in the prior art the process of shoe replacement was not only frequently undertaken, but was a lengthy one.
The position and area allotted for crane drive brakes is rather fixed, requiring that the brake fit into a defined and somewhat limited envelope. Accordingly, any improvement or modification to the brake system must necessarily be confined to that same envelope.
As shown in
FIG. 1
, a prior art electromagnetic drum brake is designated generally by the numeral
10
. The drum brake
10
includes a base
12
maintaining at one end thereof, a pair of armatures
16
,
18
having an electromagnetic coil
14
interposed therebetween, the armatures
16
,
18
and the electromagnetic coil
14
defining a magnet assembly. A torque spring
20
is also interposed between the inner armature
16
and the outer armature
18
, the spring
20
urging the two armatures apart. As is well known and understood by those skilled in the art, the armatures
16
,
18
are pivotally or flexibly maintained at the bottoms thereof at the base
12
by angle
15
plates to operate in a clam shell fashion. However, such angle plates were given to fatigue and routinely failed.
An inner shoe lever
22
and outer shoe lever
24
respectively receive inner and outer shoe linings
26
,
28
. The inner shoe lever
22
is connected to the inner armature
16
by means of an appropriate connector
30
, while a pull rod
32
interconnects the outer shoe lever
24
and the outer armature
18
, as shown. The shoe linings
26
,
28
are maintained in diametric opposition with respect to the drum
34
. The drum
34
is rotatable by means of a hub
36
having an aperture and key way
38
adapted for securely receiving the shaft of a crane hoist drive.
In operation of the prior art, with the electromagnetic coil
14
energized, the armatures
16
,
18
are drawn together, pulling the brake shoes
26
,
28
away from the rotating drum
34
, allowing the crane hoist drive to operate freely. However, when the coil
14
is de-energized, the torque spring
20
forces the armatures
16
,
18
apart, urging the brake shoes
26
,
28
into frictional contacting engagement with the drum
34
to inhibit rotation of the drum
34
and the attached shaft.
In the prior art brake
10
, the shoes
26
,
28
are heavy, cumbersome, and given to rapid wear. Additionally, the structure of the brake assembly
10
is such that removal and replacement of the brake shoes
26
,
28
require substantial dismantling and disassembly of the brake assembly
10
. Accordingly, it is desirable to devise a disk brake assembly in substantially the same general envelope as that employed by the brake
10
, and employing the same armature and coil assembly and various other structural features of the prior art.
The drum-shoe brakes of the prior art are generally characterized by a limited thermal capacity, restricting the operability of the brakes, since every brake operates on the basis of converting mechanical energy to thermal energy. Accordingly, it is desirable to devise a disk brake assembly having increased disk diameter over the drum-shoe brakes of the prior art, thus accommodating higher duty cycles of operation than with the prior art. The increased productivity demands of the steel industry can only be met by the provision of a brake that accommodates such high duty cycles and which can be placed in the same space as the prior art brakes.
DISCLOSURE OF INVENTION
In light of the foregoing, it is a first aspect of the invention to provide a caliper disk brake for steel mill cranes which may readily replace prior art drum-shoe brakes by utilizing the same armature, coil, torque spring, and similar structures.
Another aspect of the invention is to provide a caliper disk brake for steel mill cranes which provides for ease of friction wear part replacement.
A further aspect of the invention is to provide a caliper disk brake for steel mill cranes which reduces the weight and bulk of the replacement wear parts.
Still a further aspect of the invention is to provide a caliper disk brake for steel mill cranes which maximizes the disk size while staying within the prior art envelope for the brake.
Still another aspect of the invention is to provide a caliper disk brake for steel mill cranes in which the armatures act directly on caliper arms without intermediate linkage.
An additional aspect of the invention is to provide a caliper disk brake for steel mill cranes which provides for ease of brake adjustment.
Yet a further aspect of the invention is to provide a caliper disk brake for steel mill cranes which has minimal friction pad drag.
Still a further aspect of the invention is to provide a caliper disk brake for steel mill cranes which employs self aligning pressure plates with respect to the friction pads.
Another aspect of the invention is to provide a caliper disk brake for steel mill cranes which accommodates manual adjustment of the holding torque.
A further aspect of the invention is to provide a caliper disk brake for steel mill cranes in which there is no torque reaction into the caliper arms, thereby minimizing weight and drag.
A further aspect of the invention is to provide a caliper disk brake for steel mill cranes which employs uniquely shaped wear pads to accommodate disk misalignment and pad misalignment as it wears.
Yet another aspect of the invention is to provide a caliper disk brake for steel mill cranes in which the wear pads are formed in two halves to provide for economy and ease of replacement.
A further aspect of the invention is to provide a caliper disk brake for steel mill cranes in which a self adjuster automatically adjusts for wear.
Another aspect of the invention is to provide a caliper disk brake for steel mill cranes in which free moving caliper arms adjust for axial movement of the shaft and disk.
Still a further aspect of the invention is to provide a caliper disk brake for steel mill cranes which employs sealed and lubricated caliper arm bushings for free movement of the arms and for low maintenance.
Yet an additional aspect of the invention is to provide a caliper disk brake for steel mill cranes in which armature hinge plates are move flexible than in the prior art, significantly reducing fatigue and failure.
The foregoing and
Heidenreich David C.
Richards Thomas L.
Butler Douglas C.
Power Transmission Technology, Inc.
Renner Kenner Greive Bobak Taylor & Weber
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