Expansible chamber devices – Abutment connection between working member and power...
Patent
1980-05-06
1982-07-06
Maslousky, Paul E.
Expansible chamber devices
Abutment connection between working member and power...
74110, 188343, F16J 110
Patent
active
043376908
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a fluid pressure actuated brake unit, comprising a housing with a piston axially movable in a cylinder, a push rod axially movable substantially perpendicular to the piston and a wedge element, which is attached to the piston for transmitting a force from the piston to the push rod and further to a vehicle brake and has a wedge surface inclined relative to the axis of the piston and intended for coaction during the brake operation stroke with a working roller on the push rod.
BACKGROUND ART
A brake unit of the kind defined above is shown in German Patent Office Publication No. 25 13 870. In this case the wedge surface of the wedge element has a constant wedge angle not only for the brake operation stroke but also for the brake application stroke. The leverage is in other words constant over the whole working range of the wedge element. The brake application stroke will thus not be faster than the brake operation stroke.
One solution to the problem of attaining a faster brake application stroke is disclosed in German Patent Office Publication No. 26 53 320. In this case there are two wedge surfaces on the wedge element: a first wedge surface with a comparatively great wedge angle for a fast application stroke and a second wedge surface with a comparatively small wedge angle for a slower and more powerful brake operation stroke.
This solution, however, has certain drawbacks, of which one is the comparatively great width required for the wedge element due to the two wedge surfaces and another one is the abrupt transition from one wedge angle to another. This latter disadvantage means that it may happen, for example if a built in slack adjuster does not work quite properly, that the application stroke is consumed, before the transition point is reached.
DISCLOSURE OF INVENTION
A more advantageous solution may according to the invention be attained in that the wedge surface at its end remote from the piston has an edge intended for coaction with the working roller during the brake application stroke. This edge thus corresponds to the wedge surface with the great angle in the device according to DE No. 26 53 320.
In this way the width of the wedge element may be kept at a minimum resulting in a minimum volume of the brake unit, which is essential. Further, the internal play in the unit will be taken up during the very fast initial application movement. There will also be a gradual transition from the low leverage in the beginning of the stroke to the high and constant leverage when the working roller has entered the wedge surface.
Forces acting non-axially on the push rod will occur in this design. They may be taken up in that according to the invention a support part coacting with a reaction plane in the housing along the push rod is arranged coacially with the working roller.
BRIEF DESCRIPTION OF DRAWING
The invention will be described in further detail below, reference being made to the accompanying drawing, in which
FIG. 1 is a side view, partly in section, of a brake unit with an arrangement according to the invention, and
FIGS. 2 and 3 illustrate the coaction between three parts in this brake unit in two working positions.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In a housing 1, forming a cylinder at its upper part, a piston 2 is axially movable. The piston 2 is sealed in a conventional way relative to the cylinder. The housing 1 is provided with an inlet 1 for fluid under pressure, preferably compressed air.
A push rod 3 is axially movable in the housing 1 substantially perpendicular to the piston 2. The push rod 3 preferably contains a suitable slack adjuster of any kind and is provided with a yoke 4 for connection to further parts (not shown) of a vehicle brake rigging.
A push rod return spring 5 is arranged between the housing 1 and the push rod 3, whereas a piston return spring 6 is arranged between the piston 2 and the push rod 3.
A fork-shaped wedge element 7 (of which only one leg is visible in the drawing) is attached to the piston 2. This wedg
REFERENCES:
patent: 1771907 (1930-07-01), Abramson
patent: 1799229 (1931-04-01), Hanna
patent: 1848775 (1932-03-01), Girling
patent: 3663115 (1972-05-01), Vindez et al.
patent: 3831720 (1974-08-01), Williams
patent: 3995537 (1976-12-01), Severinsson
Brown Laurence R.
Maslousky Paul E.
SAB Industri AB
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