Patent Description:
<CIT> discloses a spring brake actuator. The spring brake actuator has a push rod assembly with a base located in a service brake chamber and a push rod extending from a service brake chamber. Pneumatic activation of the spring brake actuator causes the push rod to further extend out of the service brake chamber to thereby engage a wheel brake with a wheel of the vehicle. Pneumatic deactivation of the spring brake actuator causes the push rod to retract back into the service brake chamber to thereby disengage the wheel brake from the wheel of the vehicle.

The following U. Patents further describe the state of the art: <CIT>; <CIT>; <CIT>; <CIT>;<CIT>; <CIT>; <CIT>; <CIT>; and <CIT>.

Prior art document <CIT> discloses an actuating arrangement with an electric motor with a coupling element connected to a brake clamping mechanism and movable from a braking position to a released position by the stimulated electric motor, an electrically actuated blocking arrangement for blocking the coupling element, at least in the released position, and a spring storage device. The spring storage device is coupled to the coupling element so that it adopts an energy storage position with the coupling element in the released position and moves the coupling element to the braking position when the block is released. The blocking arrangement is mechanically held in the blocking position and is electrically and optionally mechanically actuated to remove the blocking action in the coupling element's release position. A parking brake system with an actuating arrangement is also described.

In certain examples, a spring brake actuator for applying a brake of a vehicle includes a housing containing a diaphragm that separates the housing into first and second chambers. A push rod assembly has a push rod that extends out of the second chamber. The diaphragm is flexible in a first direction to retract the push rod inwardly relative to the second chamber and in an opposite second direction to extend the push rod outwardly from the second chamber. A compression spring is in the first chamber, and a return spring in the second chamber. A port is for conveying pressurized air to the first chamber. A clutch actuator device is for selectively compressing the compression spring. The spring brake actuator is operable in a plurality of states including a parking state, a driving state, and a braking state. In the parking state the clutch actuator device permits extension of the compression spring, which flexes the diaphragm in the second direction, compresses the return spring, and extends the push rod further outwardly from the second chamber for applying the brake of the vehicle. In the driving state the clutch actuator device compresses the compression spring, which permits the return spring to extend, which flexes the diaphragm in the first direction and retracts the push rod further inwardly relative to the second chamber for disengaging the brake of the vehicle. In the braking state the clutch actuator device compresses the compression spring, and pressurized air is conveyed to the first chamber via the port, which flexes the diaphragm in the second direction, which compresses the return spring and extends the push rod further outwardly from the second chamber for applying the brake of the vehicle.

The clutch actuator device is specially configured to selectively retain the compression spring of the spring brake actuator in a compressed position. The clutch actuator device includes a drive rod that extends into the spring brake actuator and operably engages the compression spring. An inner and outer cylinders are concentrically aligned on the drive rod. Relative rotation between the inner and outer cylinders causes the drive rod to move further out of the inner cylinder for decompressing the compression spring and alternately to move further into the inner cylinder for compressing the compression spring. A motor causes the relative rotation, and a pneumatically actuated clutch mechanism is movable into an engaged position preventing said relative rotation and a disengaged position permitting said relative rotation.

Various other features, objects, and advantages will be made apparent from the following description taken together with the drawings.

The present disclosure includes reference to the following Figures. The same numbers are used throughout the Figures to reference like features and like components.

Trucks, trailers and other vehicles often have pneumatically-operated spring brake actuators, which provide the braking force necessary to stop the vehicle. A brake pedal is positioned on the floor of the vehicle's cab and, upon activation, causes pressurized air from a reservoir to enter the spring brake actuator, which in turn causes a push rod to extend out of the spring brake actuator and activate a wheel brake. The wheel brake typically has brake shoes with a brake lining material that is pressed against a brake drum at the vehicle wheel-end to thereby brake the vehicle. The wheel brake often includes a slack adjuster which turns a cam roller via a camshaft to force the brake shoes to engage the brake drum and brake the vehicle. Releasing the brake pedal causes the pressurized air to be released from the air chamber such that a return spring within the air chamber retracts the push rod back to its original position. The spring brake actuator of the present disclosure can be used in conjunction with a variety of known brake assemblies, including both brake drum assemblies and brake disc assemblies.

Whereas the prior art predominately consists of fully pneumatically-actuated spring brake actuators, during research and development, the present inventor has determined that it would be advantageous to provide improved spring brake actuators that are both pneumatically and electro-mechanically actuated. The present disclosure is a result of the inventor's efforts in this regard.

<FIG> depict a spring brake actuator <NUM> of the present disclosure for applying a wheel brake of a vehicle. The spring brake actuator <NUM> extends along a center axis <NUM> and has an axially elongated housing <NUM>. The housing <NUM> includes opposing cup-shaped end portions, namely a first end portion <NUM> and a second end portion <NUM>. The first and second end portions <NUM>, <NUM> have perimeter flanges <NUM>, <NUM> respectively, that engage each other in a sealing relationship. The housing <NUM> defines a first chamber <NUM> and a second chamber <NUM>. The first chamber <NUM> is separated from the second chamber <NUM> by a diaphragm <NUM>. The perimeter of the diaphragm <NUM> is held and compressed by the perimeter flanges <NUM>, <NUM>. A port <NUM> formed through the first end portion <NUM> is configured to admit and release compressed air to and from the first chamber <NUM>. The pressurized air can be provided by a conventional source of pressurized air located on the vehicle. A novel clutch actuator device <NUM> is located on the end of the housing <NUM> adjacent the first chamber <NUM>. The clutch actuator device <NUM> will be further described herein below.

A bracket <NUM> is coupled to the first end portion <NUM>. The bracket <NUM> has a stub portion <NUM> that axially extends through a hole <NUM> defined in the first end portion <NUM>. The stub portion <NUM> has a bore <NUM> extending there through, and a pair of annular grooves <NUM> is defined in the stub portion <NUM> and encircles the bore <NUM>. A flange <NUM> radially extends from the stub portion <NUM> along the outer end wall <NUM> of the first end portion <NUM>.

A compression spring <NUM> is in the first chamber <NUM> and has a first end compressed against the inner end wall <NUM> of the first end portion <NUM> and an opposite second end compressed against a pressure plate <NUM>. The pressure plate <NUM> is located axially between the compression spring <NUM> and the diaphragm <NUM>. The pressure plate <NUM> has a stub portion <NUM> with a bore <NUM> extending there through and a flange <NUM> that radially extends from the stub portion <NUM>. The second end of the compression spring <NUM> encircles the stub portion <NUM> and engages the flange <NUM>.

A push rod assembly <NUM> has a first end portion <NUM> abutting the diaphragm <NUM> and an opposite, second end portion <NUM> extending out of second chamber <NUM>. The second end portion <NUM> is pivotably coupled to a lever arm of a conventional slack adjuster or cam roller (not shown). The slack adjuster and/or cam roller is configured to translate reciprocal movement of the push rod assembly <NUM> to a wheel brake for the vehicle (refer to the above-incorporated references for further description of the slack adjuster and cam roller). The push rod assembly <NUM> has a push rod <NUM> located in the second chamber <NUM> and extending through a hole in the end wall <NUM> of the second end portion <NUM>. The push rod assembly <NUM> also includes an end flange <NUM> that abuts the diaphragm <NUM> such that as the diaphragm <NUM> flexes back and forth in the housing <NUM>, the push rod <NUM> reciprocates out of and back into the second chamber <NUM>.

A flexible bellows <NUM> is coupled to the end wall <NUM> of the second end portion <NUM> and the push rod <NUM> and is configured to prevent debris and moisture from entering the second chamber <NUM>. In certain examples, a return spring <NUM> is located in the second chamber <NUM> and is compressed between the end wall <NUM> of the second end portion <NUM> and the end flange <NUM> to thereby bias the push rod <NUM> into the second chamber <NUM> and oppose movement of the push rod <NUM> out of the second chamber <NUM> via the hole in the end wall <NUM>.

The clutch actuator device <NUM> is coupled to the first end portion <NUM> and is for selectively compressing the compression spring <NUM>. The clutch actuator device <NUM> has a shroud <NUM> having a shroud cap <NUM>. The shroud <NUM> is coupled to the outer end wall <NUM> of the first end portion <NUM>. The shroud <NUM> has a slot <NUM> (see <FIG>) and defines a cavity <NUM> (see <FIG>) in which a hollow inner cylinder <NUM> and a hollow outer cylinder <NUM> are positioned. The inner cylinder <NUM> is fixed to the flange <NUM> of the bracket <NUM> and has a sidewall <NUM> (<FIG>) with a diametrically opposed curved slots <NUM> defined therein (<FIG>). In the illustrated embodiment, the curved slots <NUM> are helical. The inner cylinder <NUM> has a surface <NUM> (<FIG>) along which pins <NUM> (described herein below) slide. Note that in some instances the surface <NUM> acts as ramps (described further herein below). The outer cylinder <NUM> is concentric with the inner cylinder <NUM> and is rotatable relative to the inner cylinder <NUM>. The outer cylinder <NUM> has a sidewall <NUM> (<FIG>) with a diametrically opposed axial slots <NUM> defined therein (see <FIG>), a first end <NUM> located near the bracket <NUM>, and an opposite second end <NUM> with a plurality of saw teeth <NUM> (<FIG>) that axially extend in a first direction (see arrow A on <FIG>). Note that the saw teeth <NUM> are depicted as part of a collar <NUM> of the outer cylinder <NUM>. In other examples, the collar <NUM> is excluded and the teeth <NUM> axially extend from the sidewall <NUM>. Note that <FIG> exclude the shroud <NUM> and the shroud cap <NUM> which are depicted in <FIG>.

A drive rod <NUM> is in the hollow interior of the inner cylinder <NUM> and axially extends between a first end <NUM> and an opposite second end <NUM>. The first end <NUM> has one or more radially extending pins <NUM>. Note that in the example depicted in <FIG>, the pins <NUM> are at the ends of a bolt that extends through the first end <NUM> of the drive rod <NUM>. In another example, the pins <NUM> are welded or otherwise fastened onto the outer surface of the drive rod <NUM>. Each pin <NUM> is received in one of the curved slots <NUM> of the inner cylinder <NUM> and one of the axial slots <NUM> of the outer cylinder <NUM> (see <FIG>). The number of pins <NUM> and curved and axial slots <NUM>, <NUM> can vary. In the example depicted in <FIG>, there are two pins <NUM>, two curved slots <NUM>, and two axial slots <NUM>. Note that in other examples, a unitary rod extends through the inner and outer cylinders <NUM>, <NUM> and thus the ends of the rod are located in the curved and axial slots <NUM>, <NUM> and are the pins <NUM> noted above.

The second end <NUM> of the drive rod <NUM> is received in the bore <NUM> in the bracket <NUM> and the bore <NUM> of the pressure plate <NUM>. The second end <NUM> has an enlarged head <NUM> that engages a contact surface or lip of the pressure plate <NUM>. Accordingly, as the drive rod <NUM> is axially moved in a first direction (see arrow A) the pressure plate <NUM> is also axially moved in the first direction such that the compression spring <NUM> is compressed between the inner end wall <NUM> of the first end portion <NUM> and the pressure plate <NUM> (described herein). The annular grooves <NUM> in the bracket <NUM> contain O-rings (not shown) providing a fluid-tight seal between the drive rod <NUM> and the bracket <NUM> which prevents debris and/or moisture from entering the first chamber <NUM>.

Referring to <FIG>, the clutch actuator device <NUM> has a clutch mechanism <NUM>, which is located at the second end <NUM> of the outer cylinder <NUM>. The clutch mechanism <NUM> has a clutch cap <NUM> having a plurality of saw teeth <NUM> that extend in a second direction (see arrow B) for engagement with the saw teeth <NUM> on the top of the outer cylinder <NUM>. Engagement between the teeth <NUM>, <NUM> prevents rotation of the outer cylinder <NUM> relative to the clutch cap <NUM>. The clutch cap <NUM> is normally biased upwardly out of engagement with the top of the outer cylinder <NUM> via a biasing element, such as a clutch spring <NUM> (<FIG>), such that the clutch mechanism <NUM> is normally in a disengaged position (<FIG>). The clutch mechanism <NUM> further includes a clutch diaphragm <NUM> coupled to the clutch cap <NUM> and the shroud cap <NUM>. The clutch diaphragm <NUM> is flexible so as to move the saw teeth <NUM> of the clutch cap <NUM> into engagement the saw teeth <NUM> of the outer cylinder <NUM>, thus preventing rotation of the outer cylinder <NUM> relative to the clutch cap <NUM>. The clutch mechanism <NUM> is in an engaged position (<FIG>) when the saw teeth <NUM>, <NUM> are engaged with each other. The clutch diaphragm <NUM> is fixed between the shroud cap <NUM> and the upper perimeter of the shroud <NUM>. A clutch chamber <NUM> is defined between the shroud cap <NUM> and the clutch diaphragm <NUM>. A port <NUM> located on the shroud cap <NUM> is configured to admit and release compressed air to and from the clutch chamber <NUM>.

Referring to <FIG>, an electric motor <NUM> (see <FIG>) is operably connected to the outer cylinder <NUM> via the slot <NUM> and is for rotating the outer cylinder <NUM> relative to the inner cylinder <NUM> when the clutch mechanism <NUM> is in the engaged position (<FIG>). The motor <NUM> (<FIG>) is preferably a bidirectional motor capable of rotating the outer cylinder <NUM> in either a first rotational direction or an opposite second rotational direction (see arrows R1 and R2 on <FIG>). As will be described herein below, as the motor <NUM> rotates the outer cylinder <NUM>, the drive rod <NUM> is axially moved to thereby move the pressure plate <NUM> and compress the compression spring <NUM> and alternately decompress the compression spring <NUM>. The motor <NUM> can be any suitable motor, such as a worm gear and a helical drive, and/or comprise mating gears, such as gear <NUM> (<FIG>), coupled to the outer cylinder <NUM>. Note that the drive rod <NUM> moves into and out of the first chamber <NUM> depending on the rotational direction of the outer cylinder <NUM> (e.g., rotation of the outer cylinder <NUM> relative to the inner cylinder <NUM> in a first rotation direction moves the drive rod <NUM> out of the first chamber <NUM> and rotation of the outer cylinder <NUM> relative to the inner cylinder <NUM> in an opposite, second rotation direction moves the drive rod <NUM> further into the first chamber <NUM>).

<FIG> depict the spring brake actuator <NUM> during various operational states. <FIG> depicts the spring brake actuator <NUM> in a parking state when the vehicle is off and/or a parking or emergency brake is activated. In the parking state, the compression spring <NUM> pushes against the pressure plate <NUM> in the second direction (arrow B) thereby pushing the diaphragm <NUM> and the push rod assembly <NUM> in the second direction (arrow B) such that the wheel brakes are applied. In the parking state, the motor <NUM> is off and the clutch mechanism <NUM> is in the disengaged position (see <FIG> and <FIG>). When moving into the parking state, the drive rod <NUM> is pulled in the second direction (arrow B) by the pressure plate <NUM> as the compression spring <NUM> decompresses and extends in the second direction (arrow B).

The operator can change the operational state of the spring brake actuator <NUM> from the parking state (noted above) to a driving state (<FIG>), in which the vehicle may be driven, by releasing the parking brake (e.g., manually release a lever). Releasing the parking brake causes pressurized air to flow from the noted source of pressurized air on the vehicle to the spring brake actuator <NUM>, into the clutch chamber <NUM> via the port <NUM> such that the clutch chamber <NUM> is pressurized, causing the clutch diaphragm <NUM> to flex in the second direction (arrow B). This moves the clutch mechanism <NUM> into the engaged position (<FIG> and <FIG>). Subsequent activation of the motor <NUM> rotates the outer cylinder <NUM> such that the sidewall <NUM> of the outer cylinder <NUM> engages and applies camming force on the pins <NUM>. Accordingly, the pins <NUM> are caused to slide along the curved slots <NUM> of the inner cylinder <NUM> and move generally axially in the first direction (arrow A). The pins <NUM> slide along the surfaces <NUM> (<FIG>) of the inner cylinder <NUM>. The pins <NUM> also axially slide in the axial slots <NUM> of the outer cylinder <NUM>, and the drive rod <NUM> rotates as it is axially moved in the first direction (arrow A). In certain examples, a thrust bearing (not shown) is utilized between the pressure plate <NUM> and the drive rod <NUM>. As the drive rod <NUM> is axially moved in the first direction (arrow A), the compression spring <NUM> is compressed between the inner end wall <NUM> of the first end portion <NUM> and the pressure plate <NUM> (e.g., the drive rod <NUM> and the pressure plate <NUM> move towards the inner end wall <NUM> in the direction of arrow A). The return spring <NUM> moves the diaphragm <NUM> and the end flange <NUM> of the push rod assembly <NUM> in the first direction (arrow A) such that the push rod <NUM> of the push rod assembly <NUM> retracts into the second chamber <NUM>. Thus, no braking forces are applied to the wheels of the vehicle (e.g., the wheel brakes are not applied). Note that the return spring <NUM> biases the diaphragm <NUM> and the push rod assembly <NUM> into the positions depicted in <FIG>. Note that the pressure in the clutch chamber <NUM> causes the clutch diaphragm <NUM> to exert an axial force on the clutch cap <NUM> such that the teeth <NUM> engage with the teeth <NUM> on top of the outer cylinder <NUM>. So long as the pressure in the clutch chamber <NUM> remains, the teeth <NUM> of the clutch cap <NUM> engage the teeth <NUM> on top of the outer cylinder <NUM> and prevent rotation of the outer cylinder <NUM> when the motor <NUM> is deactivated. As such, the outer cylinder <NUM> does not rotate due to the potential energy or force in the compressed compression spring <NUM> that acts on the outer cylinder <NUM> via the drive rod <NUM> and the pins <NUM>. This potential energy or force would axially pull the drive rod <NUM> in the second direction (arrow B). Thus, the clutch mechanism <NUM> and the clutch cap <NUM> prevent rotation of the outer cylinder <NUM> when the motor <NUM> is deactivated and thereby hold the drive rod <NUM> in place and prevent the compression spring <NUM> from decompressing. In certain examples, the clutch cap <NUM> is coupled (e.g., mechanical fasteners such as nuts and bolts, adhesives such as glue) to the clutch diaphragm <NUM>.

Referring now to <FIG>, the spring brake actuator <NUM> is depicted in a braking state in which the operator is depressing a brake pedal <NUM> (<FIG>) to thereby apply the wheel brake to slow or stop the vehicle. When depressing the brake pedal <NUM>, pressurized air is provided via the port <NUM> to the first chamber <NUM> such that the diaphragm <NUM> is moved in the second direction (arrow B). The push rod <NUM> moves in the second direction (arrow B) further out of the second chamber <NUM>, causing the wheel brakes to be applied. When the operator releases the brake pedal <NUM>, the pressurized air in the second chamber <NUM> is released or exhausted and the spring brake actuator <NUM> returns to the driving state (<FIG>) due to the forces exerted by the return spring <NUM> on the diaphragm <NUM> and the push rod assembly <NUM>.

Note that during the driving state (<FIG>) and the braking state (<FIG>), the clutch mechanism <NUM> remains in the engaged position (<FIG> and <FIG>) and the compression spring <NUM> remains compressed because the pressurized clutch chamber <NUM> causes the clutch diaphragm <NUM> to act on the clutch mechanism <NUM>, as noted above. In the event that the parking brake is engaged by the operator and/or pressurized air in the clutch chamber <NUM> is lost (e.g., due to failure of the air system of the vehicle), the pressurized air in the clutch chamber <NUM> is released or exhausted and the clutch mechanism <NUM> moves into the disengaged position (<FIG> and <FIG>) due to the clutch spring <NUM>. As the clutch mechanism <NUM> moves from the engaged position (<FIG> and <FIG>) to the disengaged position (<FIG> and <FIG>), the outer cylinder <NUM> begins to rotate and the teeth <NUM>, <NUM> slide past each due to the compression spring <NUM> decompressing and extending in the second direction (arrow B). That is, as the compression spring <NUM> extends in the second direction (arrow B), the second end of the compression spring <NUM> applies force on the pressure plate <NUM> which causes the pressure plate <NUM> to move in the second direction (arrow B). Accordingly, the pressure plate <NUM> acts on and moves the diaphragm <NUM> and the push rod assembly <NUM> in the second direction (arrow B) such that the wheel brakes are applied. The movement of the pressure plate <NUM> in the second direction (arrow B) also causes the drive rod <NUM> to be pulled in the second direction (arrow B) and the pins <NUM> to slide along the curved and axial slots <NUM>, <NUM>. Generally, the drive rod <NUM> and the pins <NUM> are axially moved in the second direction (arrow B), and the curved slots <NUM> of the inner cylinder <NUM> (and the surface <NUM> along which the pins <NUM> slide) cause the pins <NUM> to act on the sidewall <NUM> of the outer cylinder <NUM> such that the outer cylinder <NUM> rotates.

Referring to <FIG>, a controller <NUM> is schematically depicted. The controller <NUM> includes a memory <NUM> and a processor <NUM>. The controller <NUM> is operably coupled to the motor <NUM>, the brake pedal <NUM>, an user input device <NUM>, the vehicle air pressure system (not shown), and/or other vehicle systems (not shown). The motor <NUM> may be controlled by the controller <NUM> based on inputs received via the brake pedal <NUM>, the user input device <NUM>, and/or operational programs stored on the memory <NUM>. The user input device <NUM> can include an indicator (not shown) for indicating the operational state of the spring brake actuator <NUM> and/or other information to the operator.

The motor <NUM> can have a defined start and stop position that correlates to the position of the drive rod <NUM> when the spring brake actuator <NUM> is in the driving state (<FIG>) or the braking state (<FIG>) and the parking state (<FIG>). The position of the motor <NUM> can be controlled by the controller <NUM> and/or with inputs from limit switches, encoders, and other suitable devices. Furthermore, the controller <NUM> can be configured to determine the position of the motor <NUM> and/or the drive rod <NUM> at or between two position extents to thereby determine operational details of the spring brake actuator <NUM>. For example, if the controller <NUM> determines that the motor <NUM> moved the drive rod <NUM> into a position past the position that corresponds to the parking state (<FIG>), the controller <NUM> can further determine the compression spring <NUM> has failed or is broken and thereby alert the operator via the user input device <NUM>.

Note that in other examples, the outer cylinder <NUM> is fixed relative to the flange <NUM> and the inner cylinder <NUM> is rotatable (see <FIG>). In these examples, the motor <NUM> rotates the inner cylinder <NUM>, or the inner cylinder <NUM> is an integral part of the motor <NUM>, such that the pins <NUM> are caused to slide along the slots <NUM> of the inner cylinder <NUM> and generally axially move in the first direction (arrow A). The pins <NUM> also slide in the axial slots <NUM> of the outer cylinder <NUM>, and the drive rod <NUM> rotates as it is axially moved in the first direction (arrow A).

In certain examples, a spring brake actuator <NUM> for applying a brake of a vehicle includes a housing <NUM> containing a diaphragm <NUM> that separates the housing <NUM> into first and second chambers <NUM>, <NUM>. A push rod assembly <NUM> having a push rod <NUM> extends out of the second chamber <NUM>. The diaphragm <NUM> is flexible in a first direction to retract the push rod <NUM> inwardly relative to the second chamber <NUM> and in an opposite second direction to extend the push rod <NUM> outwardly from the second chamber <NUM>. A compression spring <NUM> is in the first chamber <NUM>, and a return spring <NUM> in the second chamber <NUM>. A port <NUM> is for conveying pressurized air to the first chamber <NUM>. A clutch actuator device <NUM> is for selectively compressing the compression spring <NUM>. The spring brake actuator <NUM> is operable in a plurality of states including a parking state in which the clutch actuator device <NUM> permits extension of the compression spring <NUM>, which flexes the diaphragm <NUM> in the second direction, compresses the return spring <NUM>, and extends the push rod <NUM> further outwardly from the second chamber <NUM> for applying the brake of the vehicle. A driving state in which the clutch actuator device <NUM> compresses the compression spring <NUM>, which permits the return spring <NUM> to extend, which flexes the diaphragm <NUM> in the first direction and retracts the push rod <NUM> further inwardly relative to the second chamber <NUM> for disengaging the brake of the vehicle. A braking state in which the clutch actuator device <NUM> compresses the compression spring <NUM>, and further in which pressurized air is conveyed to the first chamber <NUM> via the port <NUM>, which flexes the diaphragm <NUM> in the second direction, which compresses the return spring <NUM> and extends the push rod <NUM> further outwardly from the second chamber <NUM> for applying the brake of the vehicle.

In certain examples, the clutch actuator device <NUM> comprises a drive rod <NUM> extending into the first chamber <NUM>, wherein movement of the drive rod <NUM> further into the first chamber <NUM> permits extension of the compression spring <NUM> and wherein movement of the drive rod <NUM> out of the first chamber <NUM> compresses the compression spring <NUM>.

In certain examples, the clutch actuator device <NUM> includes inner and outer cylinders <NUM>, <NUM> that are concentrically aligned on the drive rod <NUM>, and wherein relative rotation between the inner and outer cylinders <NUM>, <NUM> moves the drive rod <NUM> out of the first chamber <NUM> and wherein opposite relative rotation between the inner and outer cylinders <NUM>, <NUM> moves the drive rod <NUM> into the first chamber <NUM>.

In certain examples, the clutch actuator device <NUM> further comprises a motor <NUM> for causing said relative rotation. In certain examples, the outer cylinder <NUM> is rotatable relative to the inner cylinder <NUM>, and wherein rotation of the outer cylinder <NUM> relative to the inner cylinder <NUM> in a first rotation direction moves the drive rod <NUM> out of first chamber <NUM> and wherein rotation of the outer cylinder <NUM> relative to the inner cylinder <NUM> in an opposite, second rotation direction moves the drive rod <NUM> into the first chamber <NUM>.

In certain examples, the clutch actuator device <NUM> further comprises a motor <NUM> for causing rotation of the outer cylinder <NUM> relative to the inner cylinder <NUM>.

In certain examples, a pin <NUM> is on the drive rod <NUM>. The pin <NUM> being engaged in curved slots <NUM> on the inner cylinder <NUM> and in axial slots <NUM> on the outer cylinder <NUM>, and wherein rotation of the outer cylinder <NUM> relative to the inner cylinder <NUM> causes the outer cylinder <NUM> to apply camming forces on the pin <NUM>, which causes the pin <NUM> to translate along the curved slot <NUM>.

In certain examples, translation of the pin <NUM> along the curved slot <NUM> moves the drive rod <NUM> into and alternately out of the first chamber <NUM>.

In certain examples, the clutch actuator device <NUM> includes a clutch mechanism <NUM> that is movable into a disengaged position preventing extension and retraction of the push rod <NUM> and into an engaged position permitting extension and retraction of the push rod <NUM>.

In certain examples, the clutch mechanism <NUM> is pneumatically actuated into the engaged position.

In certain examples, the clutch mechanism <NUM> comprises a clutch cap <NUM> on the outer cylinder <NUM>, a clutch spring <NUM> that normally biases the clutch cap <NUM> away from the outer cylinder <NUM>, and a clutch diaphragm <NUM> coupled to the clutch cap <NUM>. The clutch diaphragm <NUM> is flexible towards the outer cylinder <NUM> to engage the clutch cap <NUM> with the outer cylinder <NUM> in the engaged position and wherein the clutch diaphragm <NUM> is flexible away from the outer cylinder <NUM> to disengage the clutch cap <NUM> from the outer cylinder <NUM> in the disengaged position.

In certain examples, the clutch actuator device <NUM> includes a shroud cap <NUM> and a port <NUM> through the shroud cap <NUM> for supplying pressurized air to a clutch chamber <NUM> defined between the shroud cap <NUM> and the clutch diaphragm <NUM>, and wherein supplying pressurized air to the clutch chamber <NUM> flexes the clutch diaphragm <NUM> towards the outer cylinder <NUM>, and wherein removing pressurized air from the clutch chamber <NUM> permits the clutch spring <NUM> to bias the clutch cap <NUM> away from the outer cylinder <NUM>.

In certain examples, a source of pressurized air supplies pressurized air to both the clutch chamber <NUM> and to the first chamber <NUM>.

In certain examples, the clutch actuator device <NUM> comprises a clutch mechanism <NUM> that is positionable in a disengaged position preventing extension and retraction of the push rod <NUM> and an engaged position permitting extension and retraction of the push rod <NUM>.

In certain examples, a clutch actuator device <NUM> is for selectively retaining a compression spring <NUM> of a spring brake actuator <NUM> in a compressed position. The clutch actuator device <NUM> includes a drive rod <NUM> for extending into the spring brake actuator <NUM> and operably engaging the compression spring <NUM>. Inner and outer cylinders <NUM>, <NUM> are concentrically aligned on the drive rod <NUM>, wherein relative rotation between the inner and outer cylinders <NUM>, <NUM> causes the drive rod <NUM> to move further out of the inner cylinder <NUM> for decompressing the compression spring <NUM> and alternately to move further into the inner cylinder <NUM> for compressing the compression spring <NUM>. A motor <NUM> causes the relative rotation, and a pneumatically actuated clutch mechanism <NUM> is movable into an engaged position preventing said relative rotation and a disengaged position permitting said relative rotation.

In certain examples, the outer cylinder <NUM> is rotatable relative to the inner cylinder <NUM>, and wherein rotation of the outer cylinder <NUM> relative to the inner cylinder <NUM> in a first rotation direction moves the drive rod <NUM> out of the first chamber <NUM> and wherein rotation of the outer cylinder <NUM> relative to the inner cylinder <NUM> in an opposite, second rotation direction moves the drive rod <NUM> into the first chamber <NUM>.

In certain examples, a pin <NUM> is on the drive rod <NUM>, and the pin <NUM> is engaged in curved slots <NUM> on the inner cylinder <NUM> and in axial slots <NUM> on the outer cylinder <NUM>, wherein rotation of the outer cylinder <NUM> relative to the inner cylinder <NUM> causes the outer cylinder <NUM> to apply camming forces on the pin <NUM>, which causes the pin <NUM> to translate along the curved slot <NUM>, and wherein translation of the pin <NUM> along the curved slots <NUM> moves the drive rod <NUM> into and alternately out of the first chamber <NUM>.

In certain examples, the clutch mechanism <NUM> includes a clutch cap <NUM> on the outer cylinder <NUM>, a clutch spring <NUM> that normally biases the clutch cap <NUM> away from the outer cylinder <NUM>, and a clutch diaphragm <NUM> coupled to the clutch cap <NUM>. The clutch diaphragm <NUM> is flexible towards the outer cylinder <NUM> to engage the clutch cap <NUM> with the outer cylinder <NUM> and the clutch diaphragm <NUM> is flexible away from the outer cylinder <NUM> to disengage the clutch cap <NUM> from the outer cylinder <NUM>.

In certain examples, the clutch actuator device <NUM> includes a shroud cap <NUM> and a port <NUM> through the shroud cap <NUM> for supplying pressurized air to a clutch chamber <NUM> defined between the shroud cap <NUM> and the clutch diaphragm <NUM>. Supplying the pressurized air to the clutch chamber <NUM> flexes the clutch diaphragm <NUM> towards the outer cylinder <NUM>, and wherein removing pressurized air from the clutch chamber <NUM> permits the clutch spring <NUM> to bias the clutch cap <NUM> away from the outer cylinder <NUM>.

In certain examples, the clutch mechanism <NUM> comprises a clutch cap <NUM> on the outer cylinder <NUM>, a clutch spring <NUM> that normally biases the clutch cap <NUM> away from the outer cylinder <NUM>, and a clutch diaphragm <NUM> coupled to the clutch cap <NUM>. The clutch diaphragm <NUM> is flexible towards the outer cylinder <NUM> to engage the clutch cap <NUM> with the outer cylinder <NUM> and the clutch diaphragm <NUM> is flexible away from the outer cylinder <NUM> to disengage the clutch cap <NUM> from the outer cylinder <NUM>.

Claim 1:
A spring brake actuator (<NUM>) for applying a brake of a vehicle, the spring brake actuator (<NUM>) comprising:
a housing (<NUM>) containing a diaphragm (<NUM>) that separates the housing (<NUM>) into first and second chambers (<NUM>, <NUM>);
a push rod assembly (<NUM>) having a push rod (<NUM>) extending out of the second chamber (<NUM>);
wherein the diaphragm (<NUM>) is flexible in a first direction (A) to retract the push rod (<NUM>) inwardly relative to the second chamber (<NUM>) and in an opposite second direction (B) to extend the push rod (<NUM>) outwardly from the second chamber (<NUM>);
a compression spring (<NUM>) in the first chamber (<NUM>);
a return spring (<NUM>) in the second chamber (<NUM>);
a port (<NUM>) for conveying pressurized air to the first chamber (<NUM>); and
a clutch actuator device (<NUM>) for selectively compressing the compression spring (<NUM>),
wherein the spring brake actuator (<NUM>) is operable in a plurality of states comprising:
a parking state in which the clutch actuator device (<NUM>) permits extension of the compression spring (<NUM>), which flexes the diaphragm (<NUM>) in the second direction (B), compresses the return spring (<NUM>), and extends the push rod (<NUM>) further outwardly from the second chamber (<NUM>) for applying the brake of the vehicle;
a driving state in which the clutch actuator device (<NUM>) compresses the compression spring (<NUM>), which permits the return spring (<NUM>) to extend, which flexes the diaphragm (<NUM>) in the first direction (A) and retracts the push rod (<NUM>) further inwardly relative to the second chamber (<NUM>) for disengaging the brake of the vehicle; and
a braking state in which the clutch actuator device (<NUM>) compresses the compression spring (<NUM>), and further in which pressurized air is conveyed to the first chamber (<NUM>) via the port (<NUM>), which flexes the diaphragm (<NUM>) in the second direction (B), which compresses the return spring (<NUM>) and extends the push rod (<NUM>) further outwardly from the second chamber (<NUM>) for applying the brake of the vehicle.