Brakes – Operators – Spring
Patent
1993-09-24
1995-02-14
Oberleitner, Robert J.
Brakes
Operators
Spring
188162, B60T 1304, B60L 700
Patent
active
053886747
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a brake unit--preferably but not exclusively for a rail vehicle--including a housing, a drive sleeve subjected to a torque of a prestressed coil spring, a locking spring between the drive sleeve, to which it is attached, and the housing for permitting rotation of the former in a first direction, and a control sleeve, which is rotatable by a control motor in the first direction to open the locking spring, connected to the control sleeve with one end, and allow the drive sleeve concentric therewith to rotate the same angular distance as the control sleeve.
BACKGROUND OF THE INVENTION
A brake unit of this kind, where the, coil spring is "loaded" by an electric motor and there is a further locking spring and a ball screw arrangement to transform the rotary motion into an axial movement, is shown and described in our EP-A-0 334 434. This electro-mechanical brake unit, in which both the brake energy and the control signal are supplied in electric form, has great advantages over both more conventional brake units, which are pneumatically supplied and controlled, and earlier attempts with electro-mechanical brake units.
However, the electro-mechanical brake unit as shown and described in EP-A-0 334 434 has the characteristic that a current supply to the control motor therein is required to obtain brake application under the action of the prestressed coil spring. This means that the brake unit does not have the safety feature with automatic brake application at the loss of the control current supply, which in this case thus is electric.
In certain instances it is a prerequisite with this feature, which in pneumatic installations often is obtained by means of a so called spring brake actuator. The feature does not only provide the necessary safety at the loss of the control current supply, but it may also give a simple and effective way of obtaining a parking brake.
THE INVENTION
In an electro-mechanical brake unit of the kind described above the desired safety and parking brake feature may according to the invention be attained in that the locking spring has a slightly smaller external rest diameter than the bore in the housing, with which it is to cooperate, but normally is held in engagement with the bore by the torque from the drive sleeve, and in that the control motor is provided with means to hold it against rotation in its rest position, unless the current supply is broken.
The preferred way of obtaining the feature with the holding of the control motor against rotation in its rest position is that the motor is provided with an electrically controlled brake, preferably an electro-magnetic brake.
Alternatively, the control motor can be held against rotation by means of a certain current supply to its windings.
BRIEF DESCRIPTION OF THE DRAWING
The invention will be described in further detail below reference being made to the accompanying drawing, which in a side view, partly in section, shows an actuator, namely an electro-mechanical brake unit, according to the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
An actuator or electro-mechanical brake unit according to the invention is basically the same as is described in EP-A-0 334 434.
A relatively brief description of the overall design is therefore given here, and reference is made to the earlier publication. Emphasis is put on the improvement afforded by the present invention.
The electro-mechanical brake unit has a housing 1 with lids 2 and 3. The unit is also provided with a force transmitting member 4, axially movable in relation to the housing 1. The housing 1 and the member 4 are provided with attachments 5 for the mounting of the unit, for example in a conventional disc brake caliper of a rail vehicle.
A powerful coil spring or clock spring 6 is arranged in the housing 1. The outer end of the spring 6 is anchored to a rotatable motor sleeve 7 and its inner end to a rotatable drive sleeve 8, which is journalled in the housing 1.
An electric motor 10, attached to the housing 1, is driving
REFERENCES:
patent: 2529490 (1950-11-01), Field
patent: 3698520 (1972-10-01), McClure
patent: 4546297 (1985-10-01), Washbourn et al.
patent: 4953668 (1990-09-01), Severinsson
patent: 4953669 (1990-09-01), Severinsson
Brown Laurence R.
Oberleitner Robert J.
Rutherford Kevin D.
SAB Wabco Holdings B.V.
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