Patent Description:
Spring brake actuators are widely used in compressed air brake systems of large vehicles, for example of commercial vehicles like heavy trucks, buses, and trailers. A spring brake actuator is operated using compressed air provided by a compressed-air supply container, which is filled by a compressor. The spring brake actuator comprises a service chamber, a parking chamber, and at least one diaphragm, which moves a push rod to operate a disc brake or a drum brake of the vehicle when the service chamber is filled with compressed air during a braking action initiated by a respective driver of the vehicle.

A commonly used spring brake actuator <NUM> comprises a service brake part <NUM> and a parking brake part <NUM>, as depicted in <FIG> in a cross section. The service brake part <NUM> comprises a service chamber cover <NUM> and the parking brake part <NUM> comprises a parking chamber cover <NUM>, wherein both parts <NUM> and <NUM> are conjoined by a housing base <NUM>. The housing base <NUM> and the service chamber cover <NUM> each comprise a flange lip <NUM>, respectively <NUM>, wherein a diaphragm <NUM> is clamped between the two flange lips <NUM> and <NUM> using a removable clamp ring <NUM>. The diaphragm <NUM> may in particular be a rubber diaphragm comprising an edge <NUM>, which is deformed when the clamp ring <NUM> is fixed at the spring brake actuator <NUM>. The clamp ring <NUM> can be removed and, therefore, allows an easy replacement of the diaphragm <NUM> by a service person in case of wear of the diaphragm <NUM>.

The clamp ring <NUM> is a metal ring and is mounted at the spring brake actuator <NUM> using a screw <NUM> and a nut <NUM>, <FIG>. The clamp ring <NUM> with the screw <NUM> and the nut <NUM> provide a secure mechanical connection. A tightness for the service brake part <NUM> is ensured by the mechanical deformation of the edge <NUM> of the diaphragm <NUM>, caused by forces generated when the screw <NUM> and the nut <NUM> are screwed together. <FIG> shows in detail in a cross section how the edge <NUM> of the diaphragm <NUM> is clamped by the clamp ring <NUM> between the flange lips <NUM> and <NUM>.

Known are also mechanical connections, which provide a permanent connection between a housing base <NUM> and a service chamber cover <NUM> of a spring brake actuator <NUM>, as shown in <FIG> in a cross section. The housing base <NUM> comprises a flange lip <NUM> and the service chamber cover <NUM> comprises an end <NUM> with an extension <NUM>. To connect the housing base <NUM> with the service chamber cover <NUM>, the extension <NUM> is bent over the flange lip <NUM> and an edge <NUM> of a diaphragm <NUM>, as shown in more detail in <FIG>. This connection is known as rolling and also provides a secure mechanical connection but does not allow an easy replacement of the diaphragm <NUM>.

Another permanent connection, in an embodiment for the housing base <NUM> and the service chamber cover <NUM> of <FIG>, is illustrated in <FIG> in a cross section. For connecting the service chamber cover <NUM> with the housing base <NUM>, an additional ring <NUM> is used, which is crimped for pressing the flange lip <NUM> of the housing base <NUM>, the flange lip <NUM> of the service chamber cover <NUM>, and the edge <NUM> of the diaphragm <NUM> together. The crimp connection also provides a secure mechanical connection between the housing base <NUM> and the service chamber cover <NUM>, but is a more complicated assembly compared with the embodiment shown in <FIG>, and the ring <NUM> cannot be reused when removed from the spring brake actuator <NUM>.

It is an object of the present invention to provide a spring brake actuator having an improved assembly.

The invention is as set out in the independent claims <NUM> and <NUM>.

The spring brake actuator comprises a service brake part and a parking brake part conjoined by a housing base of the spring brake actuator, wherein the service brake part comprises a service chamber cover, a diaphragm, a service chamber, and a push rod for providing a service brake function. The service chamber cover comprises an outside wall with a rim for connecting the service chamber cover with a flange lip of the housing base, wherein the rim comprises cuts for providing a snap-fit connection with the flange lip.

In a preferred embodiment, the cuts divide the rim into several flexible segments.

In another preferred embodiment, the segments are movable in a diametral direction.

In another preferred embodiment, the segments each comprise a bent end designed to snap over the flange lip of the housing base when the service brake part is mounted with the service chamber cover at the housing base.

In another preferred embodiment, the bent ends are movable in a direction perpendicular to a center symmetry axis of the spring brake actuator.

In another preferred embodiment, the bent ends have a form of a "U" having an open side directed in a direction away from the center symmetry axis.

In another preferred embodiment, the cuts are co-parallel with regard to the center symmetry axis.

In another preferred embodiment, the flange lip of the housing base and the rim of the service chamber cover both have a rotational symmetry with regard to the center symmetry axis.

In another preferred embodiment, the flange lip of the housing base comprises a pin directing in a direction to the segments, which pin has a diameter that is smaller than a width of the cuts.

The pin is positioned particularly at the flange lip such that the pin slips into one of the cuts when the service chamber cover is mounted at the housing base at a correct angular position of components of the housing base with regard to the service chamber cover.

In another preferred embodiment, the parking brake part comprises a parking chamber cover, a ram assembly, a parking chamber, and a compression spring for providing a parking brake function and an emergency brake function.

The spring brake actuator is in particular a component of a compressed air brake system of a commercial vehicle.

The snap-fit connection leads to a simplified assembly when mounting the service brake part at the housing base. Any additional components, like clamp ring, bolt and nut, or complicated processes like rolling or crimp ring are reduced and replaced with the snap-fit connection.

The invention defines further a commercial vehicle comprising a respective spring brake actuator.

Preferred embodiments of the invention are explained in more detail below by way of example with reference to schematic drawings, which show:.

The present description illustrates the principles of the present invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope.

All examples and conditional language recited herein are intended for instructional purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof.

<FIG> depicts a spring brake actuator <NUM> in a cross section comprising a service brake part <NUM> and a parking brake part <NUM>. The service brake part <NUM> comprises a service chamber cover <NUM>, a diaphragm <NUM>, a service chamber <NUM>, and a push rod <NUM> for providing a service brake function. The parking brake part <NUM> comprises a parking chamber cover <NUM>, a ram assembly <NUM>, a parking chamber <NUM>, and a compression spring <NUM> for providing a parking brake function and an emergency brake function. The service brake part <NUM> and the parking brake part <NUM> are conjoined by a housing base <NUM> of the spring brake actuator <NUM>. The spring brake actuator <NUM> comprises a center symmetry axis Z.

The spring brake actuator <NUM> is in particular applicable for a commercial vehicle and further comprises two threaded bolts <NUM>, via which the spring brake actuator <NUM> can be fixed at the commercial vehicle.

The service chamber cover <NUM> has a cylindrical form like a pot and includes an outside wall <NUM> with a rim <NUM> for connecting the service chamber cover <NUM> with the housing base <NUM>. The rim <NUM> provides a function of a snap-fit connection for the service chamber cover <NUM> and the housing base <NUM>, which allows a fast assembly and disassembly of the service chamber cover <NUM> at the spring brake actuator <NUM>.

The rim <NUM> includes cuts <NUM> dividing the rim <NUM> into several or a multitude of segments <NUM>, as depicted in <FIG> shows the spring brake actuator <NUM> in a side view with the service chamber cover <NUM>, the parking chamber cover <NUM>, and the housing base <NUM>. The housing base <NUM> comprises two ports <NUM> for compressed air for providing an operation of the spring brake actuator <NUM>. The segments <NUM> surround a flange lip <NUM> of the housing base <NUM>, <FIG>, to provide a tight but reversible connection between the service chamber cover <NUM> and the housing base <NUM>. Because of the cuts <NUM>, the segments <NUM> are flexible and allow a diametral deformation.

The snap-fit connection, as provided by the segments <NUM> of the service chamber cover <NUM>, is shown in more detail in <FIG> in a cross section. The segments <NUM> are flexible in a diametral direction X, perpendicular to the center symmetry axis Z and perpendicular to the outside wall <NUM> of the service chamber cover <NUM>, so that the segments <NUM> snap over the flange lip <NUM> when the service brake part <NUM> is pressed with the service chamber cover <NUM> on the housing base <NUM>.

The diaphragm <NUM> is particularly a rubber diaphragm comprising an edge <NUM>, which is clamped between the outside wall <NUM> and deformed when the service brake part <NUM> is fixed at the spring brake actuator <NUM>.

The flange lip <NUM> of the housing base <NUM> and the rim <NUM> of the service chamber cover <NUM> are in particular both rotational symmetric with regard to the center symmetry axis Z, <FIG>, and the segments <NUM> each include a bent end <NUM>, which ends <NUM> are movable in a direction X perpendicular to the symmetry axis Z. The flange lip <NUM> is directed essentially in the X direction, away from the center symmetry axis Z, and the ends <NUM> have a form of a "U", where an open side is directed essentially in the X direction, in a direction away from the centre symmetry axis Z, to provide a reversible, annular snap-fit connection. The cuts <NUM> are in particular co-parallel with regard to the center symmetry axis Z.

The flange lip <NUM> of the housing base <NUM> comprises a pin <NUM>, <FIG>, directing in a direction of the segments <NUM>, which pin <NUM> has a diameter that is smaller than a width of the cuts <NUM>. The pin <NUM> is positioned particularly in such way at the flange lip <NUM> that the pin <NUM> slips into one of the cuts <NUM> when the service brake part <NUM> is mounted with the service chamber cover <NUM> at the housing base <NUM>. The pin <NUM> therefore allows only certain angular positions of the service chamber cover <NUM> with regard to the housing base <NUM>. With the pin <NUM>, a correct angular position of components of the spring brake actuator <NUM> can be provided, in particular a positioning of the ports <NUM> with regard to the bolts <NUM>, when the spring brake actuator <NUM> is mounted at the commercial vehicle.

The snap-fit connection leads to a simplification of the assembly of the service brake part <NUM> at the housing base <NUM>. Any additional components, like clamp ring, bolt and nut, or complicated processes like rolling or crimping with a crimp ring are reduced and replaced with the snap-fit connection. Because the segments <NUM> are flexible, an easy assembly is possible by positioning the service brake part <NUM> with the service chamber cover <NUM> at the flange lip <NUM> of the housing base <NUM> and pushing the ends <NUM> of the segments <NUM> at the flange lip <NUM>. The bent ends <NUM> of the segments <NUM> are then briefly deflected in the X direction and snap over the flange lip <NUM>. The bent ends <NUM> of the segments <NUM> and the flange lip <NUM> have a form such that a tight and secure mechanical connection is provided between the service brake part <NUM> and the housing base <NUM>, in particular during the operation of the spring brake actuator <NUM>.

The spring brake actuator is usable advantageously for a large vehicle, for example for a commercial vehicle, and is included particularly within a compressed air brake system, as described in the introduction of the specification.

Claim 1:
A spring brake actuator (<NUM>) comprising a service brake part (<NUM>) and a parking brake part (<NUM>) conjoined by a housing base (<NUM>) of the spring brake actuator (<NUM>), wherein
the service brake part (<NUM>) comprises a service chamber cover (<NUM>), a diaphragm (<NUM>), a service chamber (<NUM>), and a push rod (<NUM>) for providing a service brake function; and
the service chamber cover (<NUM>) comprises an outside wall (<NUM>) with a rim (<NUM>) for connecting the service chamber cover (<NUM>) with a flange lip (<NUM>) of the housing base (<NUM>); characterized in that
the rim (<NUM>) comprises cuts (<NUM>) for providing a snap-fit connection with the flange lip (<NUM>).