Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-06-30
2002-10-01
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S093000, C310S071000, C188S171000, C188S161000
Reexamination Certificate
active
06459182
ABSTRACT:
The invention relates to an electric motor with an electromagnetically actuated brake.
BACKGROUND OF THE INVENTION
From the German patent DE 41 26 672 C2 an electric motor with an electromagnetically actuated brake is known. The brake comprises between a body of an electromagnet and a brake disk an axially movable armature plate that is guided nonrotatably along a shaft of the electric motor. The shaft is supported by a brake-mounting end shield of the motor, which closes off the end of a housing of the motor. The shaft extends through the brake-mounting end shield to the exterior thereof. When the brake is applied, i.e. after the current through the electromagnet has been turned off, the armature plate is pressed by spring force against brake linings of a lining carrier that is connected to the shaft on the outside of the brake-mounting end shield. The armature plate thus stops the rotational movement of the lining carrier by friction against the brake lining, as soon as the magnetic field of the electromagnet has sufficiently decayed.
When the brake is being raised, i.e. in particular when the current through the electromagnet is turned on, a force is exerted on the armature plate, in particular an attractive magnetic force, which is stronger than the opposing mechanical force exerted by the springs, so that the armature plate is released from the lining carrier and returns to rest against the magnet body.
The armature plate is guided in such a way that it cannot rotate about the axis of rotation of the shaft, which in the known electric motor is achieved by axial bores or axially directed recesses in the armature plate, through which extend in the axial direction bolts or screws that simultaneously attach the magnet body of the brake to the brake-mounting end shield of the electric motor.
These bolts or screws also determine the distance in the axial direction between the brake-mounting end shield of the motor and the magnet body of the brake, so that an axial travel distance for the operation of the brake, or the axial movement of the armature plate, is specified. By adjusting the bolts or screws, the axial travel can be reduced, in order to compensate for frictional wear of the brake lining on the carrier disk.
An electric motor with brake of the kind described in DE 41 26 672 C2 is also known to comprise a terminal box for electrically connecting the motor and the brake. From the terminal box, cables to supply the brake or its electronics pass to the brake through the end of the housing on the brake side of the electric motor.
The brake described in DE 41 26 672 C2 is a pre-fitted brake, which is mounted directly as part of the electric motor. Therefore the brake can be made compact. The overall length, the weight and the work of manufacturing it are thus less than in brakes constructed separately which need to be installed subsequently on the housing of the motor.
One such subsequently installed brake, for example, is screwed to a flange on the outer surface of an end face of the electric motor. In order to bear the weight of the brake, the flange is of relatively thick and stable construction. The outer side of the flange serves as brake surface, against which the lining carrier rotating with the shaft is pressed when the brake is applied. The lining carrier, as in the case of the pre-fitted brake described above, comprises on its side facing away from this frictional flange surface a brake lining which, when the brake is applied, performs frictional work on the armature plate. The armature plate of the subsequently installed brake likewise is secured against rotating with the motor shaft by bolts or screws, which simultaneously serve to attach the electromagnet to the flange.
During installation or maintenance of known electric motors with electromagnetically actuated brakes, in many cases the brake can be installed or removed only together with the brake-mounting end shield of the motor. In other cases, although the brake can be taken away from the end shield while leaving the latter attached to the motor, there are other parts besides the lining carrier between the shield of the brake and the brake-mounting end shield of the motor, which must be installed individually or which when the brake is being removed can unintentionally become detached and fall down. Examples of such additional parts include compression springs, which press a brake inductor core by way of pressure rings aginst the stop provided by long fixation screws, and spacer sleeves to determine the axial distance between brake shield and motor end shield.
Furthermore, when the braking process is initiated, i.e. when the brake is applied, in the electric motors with brakes described above the armature plate and/or the fixation bolts or screws or the spacer sleeves are exposed to wear and tear because owing to its braking torque the armature plate strikes against the bolts or screws. The parts thus striking against one another are customarily all made of metal, which causes a high degree of wear. The noise produced by these impacts is also frequently disturbing. In some conditions, it is impossible to maintain the prescribed noise limits in the workplace. In addition, the effort of installing and removing many individual parts and the costs of manufacturing them are considerable.
When brakes are being removed from an electric motor into which one or more cables pass, if the work is not carried out with the greatest care and precaution, the cables may be damaged or even torn out.
It is the object of the present invention to disclose an electric motor with an electromagnetically actuated brake of the kind cited above that is reliable in operation and in which the effort of installing and removing the brake is minimized.
SUMMARY OF THE INVENTION
In accordance with the invention the brake is constructed as a completely prefabricated unit which can be screwed to the housing of the electric motor.
The brake rotor, however, is already provided within the completely prefabricated brake, so that the entire component represented by the prefabricated brake can be installed on the electric motor by inserting the shaft of the motor into the brake rotor, after which all that must be done is to create the mechanical connection (fixation bolts) between brake and motor.
Therefore when the brake is being installed, all that is required is to connect the brake rotor in a rotationally stable manner to the shaft of the electric motor and fix the brake to the housing, in particular by means of screws. The installation of other individual parts such as spacer sleeves, compression springs and the like is eliminated. Therefore operations, in particular exchanging the brake for a replacement, can be carried out in an extremely short time. This is especially important for use in mass-production equipment, because the stoppage time for maintenance can be kept short. Furthermore, the brake-mounting end shield of the electric motor need not be removed, so that during the maintenance work the interior of the motor remains largely protected from dirt. Complete prefabrication also offers the advantage that the brake can be more rapidly and hence economically assembled at the site of manufacture than at the place where it is to be used.
When such a prefabricated brake in accordance with the present invention is compared with a conventional, completely assembled brake for subsequent installation, the main difference is that once the assembly of a brake according to the state of the art has been completed, the brake is functional in itself, whereas the prefabricated brake disclosed here initially does not function. The reason is that it lacks the brake-mounting end shield of the electric motor, without which neither the large moment of torque produced here nor the heat generated during braking can be dissipated.
Preferably a plug-and-socket device is provided through which current can be supplied to the coil of the brake's electromagnet, which can be connected together when the brake is being installed, in particular is being screwed
Flörchinger Gerhard
Pfann Jochen
Dinh Le Dang
Marshall Gerstein & Borun
Ramirez Nestor
Sew-Eurodrive GmbH
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