Patent Description:
Hydraulic brakes are normally used for braking any kinds of vehicle.

Some heavy vehicles, specifically work vehicles such as tractors, combine, excavators, wheel loaders, and the like are provided with a hydraulic circuit and a parking brake being actuated by the hydraulic circuit and suitable for automatically engaging when no hydraulic power is supplied thereto.

The hydraulic circuit includes a pump, which is driven by a power source.

Typically, this kind of parking brake operates based on a friction member being spring biased against a fixed abutment element. The hydraulic circuit opposes the biasing of the friction member during the normal vehicle advancing to disengage the parking brake.

With the pump being inactive, the hydraulic pressure in the circuit should be relieved to obtain the biasing of the friction member and so the engagement of the parking brake.

The type of parking brake described above is known in the art as a spring activated hydraulic release or SAHR brake.

Vehicles that mount SAHR type brakes are usually equipped with an actuating assembly including at least two independent control mechanism that are placed in different locations and both manually operable by a driver.

Examples are shown in <CIT>, <CIT>, <CIT>, <CIT>.

One of the control mechanisms is operable to control the brake proportionally and in an indirect manner through an electronic control unit. The other control mechanism is purely mechanic and serves to engage fully the brake by carrying out a pressure relief in the hydraulic circuit.

The latter control mechanism is useful when the availability of electric power is suddenly interrupted and the residual pressure in the circuit is sufficient for maintaining the brake disengaged.

In general, the need is felt to improve the control of SAHR type brakes, in particular by facilitating the operations of the driver.

Furthermore, the need is also felt to increase the compactness of the actuating assemblies for SAHR type brakes.

An aim of the invention is to satisfy at least one of the needs, preferably in a simple and cost saving fashion.

The aim above is reached by an actuating assembly for a hydraulic brake as claimed in the appended set of claims.

Dependent claims disclose particular embodiments of the invention.

For a better understanding of the invention, a preferred embodiment is described in the following, by way of a nonlimiting example, with reference to the attached drawings wherein:.

In <FIG>, reference number <NUM> indicates, as a whole, a vehicle, in particular a work vehicle such as a tractor.

Vehicle <NUM> comprises an apparatus for braking comprising a hydraulic brake <NUM>, in particular a spring applied hydraulically released or SAHR brake. Specifically, the brake <NUM> comprises a first brake element <NUM>, in particular in the form of a brake disk, attached to an axle of vehicle <NUM>, and a second brake element <NUM>, in particular in the form of a brake pad, adapted to cooperate with the first brake element <NUM> to generate a braking force on the axle.

The apparatus further comprises an actuating assembly for actuating the hydraulic brake <NUM>.

More in detail, the actuating assembly comprises a hydraulic actuator <NUM> configured to be supplied with pressurized liquid and to actuate the hydraulic brake <NUM> by means of the pressurized liquid.

In particular, the actuator <NUM> comprises a cylinder <NUM> to receive the pressurized liquid and a piston <NUM> carrying the second brake element <NUM> in a fixed position. Piston <NUM> is coupled to the cylinder <NUM> in an axially sliding manner inside the cylinder between a fully engaged brake position, in which the first and second brake element <NUM>, <NUM> cooperate to generate the maximum braking force, and a fully disengaged brake position, in which the first and second brake element <NUM>, <NUM> are separated. Piston <NUM> can take a plurality of intermediate engaged brake positions between the fully engaged and disengaged brake position, in which cooperation between the first and second brake element <NUM>, <NUM> occurs with the generation of a reduced braking force than the maximum one. More precisely, the braking force decrease as the piston <NUM> moves toward the fully disengaged brake position.

The pressurized liquid is received in the cylinder <NUM> such that the pressure of the liquid drives the piston <NUM> toward the fully disengaged brake position.

The actuator <NUM> further comprises a spring <NUM> acting inside the cylinder <NUM> on the piston <NUM>. The spring <NUM> opposes to the pressure, such that the piston <NUM> reaches the fully engaged brake position when the pressure is absent or when the force exerted by the pressure is less than that exerted by the spring <NUM>.

Furthermore, the actuating assembly comprises a hydraulic circuit <NUM>, for supplying the actuator <NUM> with pressurized liquid.

The circuit <NUM> comprises a source of the pressurized liquid for supplying the actuator <NUM>, for example a powered pump <NUM>. Moreover, the circuit <NUM> specifically comprises two control valves <NUM>, <NUM> arranged in series and through which the pressurized liquid is supplied. The valve <NUM> is a proportional valve. The valve <NUM> has two positions: in a first position, the valve <NUM> behaves as a check valve, thereby allowing the actuator <NUM> to be supplied with the pressurized liquid processed by the source; in a second position, the valve <NUM> behaves as a venting or pressure relief valve, thereby allowing a relief of the pressure or a venting of the pressurized liquid supplied to the actuator <NUM>, i.e. of the pressure in the cylinder <NUM>.

This relief corresponds to the engagement of the brake <NUM>, i.e. more precisely to the movement of the piston <NUM> toward the fully engaged brake position. On the other hand, supplying the pressurized liquid to the actuator <NUM> corresponds to the disengagement of the brake <NUM>, i.e. more precisely to the movement of the piston <NUM> toward the fully engaged brake position. Therefore, the actuating assembly and the brake <NUM> make part of a SAHR brake arrangement.

Valves <NUM>, <NUM> are electrically actuated. Hence, if no electric power is available, the supplying of the pressurized liquid and/or the pressure relief is not possible.

For this reason, the actuating assembly comprises an override element <NUM> that is manually operable by a driver of vehicle <NUM> to cause the pressure relief, in particular by overriding the position of the valve <NUM>. Hence, the override element <NUM> makes part of a pressure relief device to relieve the pressure of the pressurized liquid supplied to the actuator <NUM>.

Moreover, the actuating assembly comprises a pump device <NUM> that is manually operable by the driver for supplying the pressurized liquid to the actuator <NUM>, namely a further source of pressurized liquid. For example, both the sources are coupled to a tank <NUM> or to respective tanks <NUM>, to take the liquid therefrom. Each tank <NUM> can make part of the actuating assembly.

The actuating assembly further comprises a control mechanism <NUM>, shown in <FIG>, which is manually operable by the driver for controlling the brake <NUM>.

The mechanism <NUM> comprises a frame <NUM>, specifically fixed to the vehicle <NUM>. Moreover, the mechanism <NUM> comprises two levers <NUM>, <NUM> being hinged to the frame about a same hinge axis H. The mechanism <NUM> also comprises a movable element or member <NUM> (<FIG>) carried by the lever <NUM> in a movable manner with respect to the lever <NUM> itself.

To couple the lever <NUM> to the element <NUM>, the mechanism <NUM> comprises a transmission <NUM> configured to transmit power from the lever <NUM> to the element <NUM>. More in detail, the transmission <NUM> is configured to confer a movement to the element <NUM> in response to a corresponding movement of the lever <NUM>, more precisely in response to a relative rotation thereof with respect to the lever <NUM>. The transmission <NUM> transmits power from the lever <NUM> to the element <NUM> only if the lever <NUM> moves relatively to the lever <NUM>; otherwise, namely when lever <NUM> integrally rotates with lever <NUM>, no power is transmitted and the element <NUM> remains stationary accordingly.

To constraint the lever <NUM> to rotate integrally with lever <NUM>, the mechanism <NUM> comprises an interlocking device <NUM> (<FIG>) configured to lock the lever <NUM> to the lever <NUM>. In other words, the interlocking device <NUM> is operable, in particular by the driver in a manual manner, more in particular to set the levers <NUM>, <NUM> in a interlocked configuration, in which the levers <NUM>, <NUM> are reciprocally constrained to rigidly move together, such that in particular the element <NUM> does not move with a rotation of the lever <NUM>, and to release the levers <NUM>, <NUM> in an unlocked configuration, in which the lever <NUM> can rotate relatively to the lever <NUM>, thereby moving in particular the element <NUM> via the transmission <NUM>.

For the control of the brake <NUM>, in addition to the mechanism <NUM>, the actuating assembly comprises a control unit <NUM>, a transducer <NUM>, and an actuating device <NUM>.

The actuating device <NUM> is coupled to the lever <NUM> and configured to operate the brake <NUM> in response to a rotation of the lever <NUM>; this rotation can be for example achieved by locking the lever <NUM> to the lever <NUM> through the interlocking device <NUM> and by rotating the lever <NUM>. Thus, the actuating device <NUM> can be manually operated by the driver in the described manner. More in detail, the actuating device <NUM> comprises the actuator <NUM> and the aforementioned pressure relief device. The pressure relief device is configured to relieve the pressure of the pressurized liquid supplied to the actuator <NUM> in response to the rotation of the lever <NUM>. Specifically, the actuating device <NUM> further comprises a mechanical member <NUM>, such as a Bowden cable, which is coupled to the lever <NUM> so as to react to the rotation of the lever <NUM>. The mechanical member <NUM> is coupled to the override element <NUM> and is configured to drive the override element <NUM> in response to the rotation of the lever <NUM>. The override element <NUM> driven in this manner causes the pressure relief.

The transducer <NUM> is associated to the element <NUM> to detect the movement thereof, which is caused by the transmission <NUM>. Transducer <NUM> is configured to generate a signal associated to the detected movement. The signal is indicative of the rotation of the lever <NUM> relatively to the lever <NUM>. This relative rotation corresponds, indeed, to the actual movement of the element <NUM>, which is specifically a rotation, but it may also be alternatively a translation according to not shown embodiments. For example, transducer <NUM> may be a potentiometer.

Preferably, the element <NUM> is carried by the lever <NUM> in a rotatable manner about an axis A, which is parallel to axis H. More in detail, the transducer <NUM> comprises an external casing <NUM> fastened to the lever <NUM>, e.g. by means of fastening means such as bolts. The element <NUM> has at least a portion housed within the external casing <NUM>, in particular where the means for detecting the movement are housed. In particular, the portion is a pin.

The element <NUM> may be supported about axis A by the lever <NUM> even indirectly via the casing <NUM>; in other words, the element <NUM> may be supported by the casing <NUM> or the lever <NUM> directly by means of one or more bearings.

The control unit <NUM> is coupled to the transducer <NUM>. Control unit <NUM> is configured to extract from the signal generated by the transducer <NUM> an item of information related to the relative rotation of the lever <NUM> or to the movement of the element <NUM>. Control unit <NUM> is further configured to control the brake <NUM> as a function of the extracted item of information. More precisely, control unit <NUM> controls the brake <NUM> in a proportional manner based on the item of information. In other words, the engagement and disengagement of the brake <NUM> is controlled gradually according to the extent of the relative rotation of the lever <NUM> and the direction thereof. According to one direction, the brake <NUM> is engaged; according to the opposite direction, the brake <NUM> is disengaged. The higher is the relative rotation angle of the lever <NUM> about the axis H with respect to the lever <NUM>, the greater is the extent to which the brake <NUM> is engaged or disengaged, depending on the direction of the relative rotation. Hence, the relative rotation of the lever <NUM> direction corresponds to a movement of the piston <NUM> toward the fully engaged brake position or the fully disengaged brake position, depending on the direction of the relative rotation.

In particular, control unit <NUM> is configured to control the valve <NUM> proportionally to the relative rotation of the lever <NUM>. When control unit <NUM> controls the supplying of the pressurized liquid by means of the valve <NUM>, it also controls the position of the valve <NUM>. Specifically, the valve <NUM> is set by control unit <NUM> in the position corresponding to the check valve. When no pressurized liquid is to be supplied, the valve <NUM> is set by control unit <NUM> in the position corresponding to the venting valve.

In the embodiment shown, the lever <NUM> comprises a handle <NUM> extending along an axis L perpendicular to the axis H. The handle <NUM> extends between two opposite ends <NUM>, <NUM>.

The lever <NUM> further comprises a hinged portion <NUM>, which is hinged to the frame <NUM>, in particular directly.

Specifically, the hinged portion <NUM> is attached to the end <NUM>. More in detail, the hinged portion <NUM> comprises a wall <NUM> attached to the end <NUM> and having a free surface <NUM> facing the axis H according to the axis L. Preferably, the wall <NUM> is planar and perpendicular to the axis L. In addition, the hinged portion <NUM> comprises two lateral walls <NUM>, <NUM>. The lateral walls <NUM>, <NUM> extend from opposite sides of the wall <NUM> toward the axis H. In other words, the lateral walls <NUM>, <NUM> have respective free surfaces <NUM>, <NUM> facing to each other. Conveniently, both lateral walls <NUM>, <NUM> are hinged to the frame <NUM>, specifically in a direct manner.

The lever <NUM> has a portion, specifically defined by the hinged portion <NUM>, which defines a recess, in particular defined by walls <NUM>, <NUM>, <NUM>, more in particular between the surfaces <NUM>, <NUM>. In other words, according to a direction parallel to axis H, the recess is arranged intermediately between two walls, in particular hinged to the frame <NUM>, more in particular in a direct manner.

Preferably, the lever <NUM> has a portion <NUM> that is arranged within the recess. In particular, the portion <NUM> is hinged to the frame <NUM> about axis H.

When the interlocking device <NUM> unlocks the levers <NUM>, <NUM> (unlocked configuration), the latter lever <NUM> stands in a position, which is specifically a rest position, in which the pressure relief device is not operated to relieve the pressure. Preferably, the lever <NUM> is maintained in the rest position through an elastic device, e.g. a spring <NUM>, coupling the lever <NUM> to the frame <NUM>. Precisely, the spring <NUM> has two ends respectively attached to the lever <NUM> and the frame <NUM>.

The elastic device opposes to a rotation of the lever <NUM> according to one direction, specifically anticlockwise or the direction for the activation of the pressure relief device. In particular, the lever <NUM> abuts against the frame <NUM> in the rest position, such that a rotation according to the other direction (i.e. clockwise, specifically) is prevented.

The lever <NUM> can rotate from the rest position (<FIG>) to a further position (<FIG>), specifically an activation position, in particular against the action of the elastic device, in which the pressure relief device is operated to relieve the pressure, i.e. in particular to engage the brake <NUM> (more in particular, the piston <NUM> is in the fully engaged brake position.

The lever <NUM> can rotate between a first position and a second position, specifically between a rest position (<FIG>), in which the brake <NUM> is controlled by the control unit <NUM> to be disengaged (i.e. piston <NUM> in the fully disengaged position, in particular), and a fully braking position (<FIG>), in which the brake <NUM> is controlled by the control unit <NUM> to be fully engaged (i.e. piston <NUM> in the fully engaged position, in particular). In particular, the rotation of the lever <NUM> from the rest position to the fully braking position occurs according to an anticlockwise direction.

The above operation of the brake <NUM> holds specifically when the lever <NUM> can freely rotate relative to the lever <NUM> (unlocked configuration), but also in particular when the lever <NUM> is locked to the lever <NUM> (locked configuration), precisely because the rotation of the lever <NUM> from the rest position to an intermediate position before the fully braking position implies or corresponds to an equal rotation of the lever <NUM> from the rest position to the activation position. Since the activation position of the lever <NUM> causes the pressure relief, the brake <NUM> engages anyway.

Otherwise, in the unlocked configuration, the rotation of the lever <NUM> is independent from that of the lever <NUM> and transmitted to the element <NUM> through the transmission <NUM>. In other words, the relative rotation of the lever <NUM> with respect to the lever <NUM> coincides with the absolute rotation of the lever <NUM>, while the lever <NUM> stands in the rest position. In the locked configuration, the transmission <NUM> entirely rotates integrally with the levers <NUM>, <NUM>, specifically because the element <NUM> is carried by the lever <NUM>, which integrally rotates with the lever <NUM> when the latter rotates. Hence, the element <NUM> is stationary, specifically because the rotation of the lever <NUM> is not transmitted thereto.

Preferably, the lever <NUM> is maintained in the rest position through an elastic device, e.g. a spring <NUM>, coupling the lever <NUM> to the frame <NUM>. Precisely, the spring <NUM> has two ends respectively attached to the lever <NUM> and the frame <NUM>.

The elastic device opposes to a rotation of the lever <NUM> according to one direction, specifically anticlockwise or the direction for the engagement of the brake <NUM>.

As shown in <FIG>, the interlocking device <NUM> comprises a slot <NUM> obtained in the lever <NUM>, specifically in the portion <NUM>. In particular, the slot <NUM> is a groove extending perpendicularly to the axis H. More in particular, the slot <NUM> is placed within the recess defined by the hinged portion <NUM>. The slot <NUM> faces the free surface <NUM>.

The interlocking device <NUM> further comprises an insertion member <NUM> having a shape or configured to engage the slot <NUM>, thereby interlocking the levers <NUM>, <NUM>. The insertion member <NUM> is carried by the lever <NUM> in a movable manner between two positions, at least when the lever <NUM> is in the rest position. Actually, the insertion member <NUM> is movable between the two positions for any position of the lever <NUM>.

When the lever <NUM> is in the rest position (<FIG>, <FIG>), the two positions correspond to an interlocking position (<FIG>), in particular corresponding to the interlocked configuration, in which the insertion member <NUM> engages the slot <NUM> to interlock the levers <NUM>, <NUM>, and an unlocked position (<FIG>), in particular corresponding to the unlocked configuration, in which the lever <NUM> is relatively rotatable with respect to the lever <NUM>.

The insertion member <NUM> is carried by the lever <NUM> in a movable manner parallel to the axis L.

Preferably, the handle <NUM> is tubular. Hence, the handle <NUM> has a through hole <NUM> (<FIG>) extending along the axis L, more precisely between ends <NUM>, <NUM>. The insertion member <NUM> comprises a rod at least partially introduced in the hole <NUM>. The insertion member <NUM> is carried in a movable manner along the axis L within the hole <NUM>.

In particular, the insertion member <NUM> is axially guided through the hole <NUM> (i.e. by walls defining the hole <NUM>) in a sliding manner.

The hole <NUM> has two opposite ends <NUM>, <NUM>, defining respective openings, of which one faces the slot <NUM>, at least when the lever <NUM> is in the rest position. In particular, the end <NUM> communicates with the recess defined by the hinged portion <NUM>.

At least a portion of the insertion member <NUM>, specifically the rod, extends along the axis L and has two opposite ends <NUM>, <NUM> (<FIG>). Preferably, the end <NUM> axially protrudes with respect to the handle <NUM>, at least in the interlocking position, where it engages the slot <NUM>. Actually, as shown in <FIG>, the end <NUM> protrudes also in the unlocked position, with respect to the handle <NUM>. Therefore, in particular, the end <NUM> is arranged within the recess defined by the hinged portion <NUM>.

The end <NUM> of the hole <NUM> has a greater radial extent than the end <NUM>, namely the end <NUM> is larger than the end <NUM>. Therefore, a surface <NUM> is defined within the hole <NUM>; the surface <NUM> is transversal, more precisely orthogonal to the axis L and arranged in an intermediate axial position between the ends <NUM>, <NUM>.

The end <NUM> of the insertion member <NUM> is placed at least partially within the end <NUM> of the hole. Moreover, the end <NUM> has a greater radial extent than the end <NUM>, namely the end <NUM> is larger than the end <NUM>.

The end <NUM> is axially guided through the end <NUM> (i.e. by walls defining the end <NUM>) in a sliding manner.

Preferably, the insertion member <NUM> is maintained in the unlocked position by means of an elastic device, e.g. a spring <NUM>, arranged to oppose to the movement of the insertion member <NUM> toward the locked position. In particular, the elastic device acts on the end <NUM> of the insertion member <NUM>.

Specifically, the elastic device is arranged between the surface <NUM> and the end <NUM>. Precisely, the elastic device has two ends respectively in contact with the surface <NUM> and the end <NUM>.

The elastic device biases the end <NUM> away from the surface <NUM>, in particular at least for a distance along the axis L that is equal or greater than the minimum distance along the axis L between the end <NUM> and the slot <NUM>.

The insertion member <NUM> can be thrusted toward the interlocked position manually by the driver, for example with the aid of an appropriate instrument, such as a screwdriver.

In the embodiment shown, the transmission <NUM> is a bar mechanism. As shown in <FIG>, the transmission <NUM> comprises two levers <NUM>, <NUM> hinged to one another about an axis B, parallel to axis H, and respectively hinged to the lever <NUM> and the element <NUM> about respective axes C, D, parallel to axis H. In particular, axis D coincides with axis A.

More precisely, the lever <NUM> has two ends respectively hinged to the levers <NUM>, <NUM>. The lever <NUM> has two ends respectively hinged to the lever <NUM> and the element <NUM>.

The operation of the described actuating assembly is the following.

During normal operation, i.e. when electric power is available, the driver can selectively engage the brake <NUM> with the interlocking device <NUM> in the unlocked configuration by rotating the lever <NUM> from the rest position (<FIG>) toward the fully braking position (<FIG>). The transmission <NUM> transmits the rotation of the lever <NUM> to the element <NUM>, whose movement is detected by the transducer <NUM>. The transducer <NUM> generates the signal, from which the control unit <NUM> extracts information regarding the amount of rotation, which coincides with a relative rotation of the lever <NUM> with respect to the lever <NUM>. The control unit <NUM> controls the opening of the valve <NUM> proportionally to the amount of rotation. In this manner, the pump <NUM> supplies the cylinder <NUM> while the control unit <NUM> controls the valve <NUM> to operate as a check valve. The pressure of the liquid supplied to the cylinder <NUM> moves the piston <NUM> proportionally to engage the brake <NUM>.

If the electric power becomes suddenly not available, the control unit <NUM> stops its operation. If the pressure in the cylinder <NUM> is high and the driver wants to engage the brake <NUM>, the driver can operate the interlocking device <NUM> to interlock the levers <NUM>, <NUM>. In particular, the driver pushes the insertion element <NUM> from its unlocked position until the latter reaches the interlocking position. Now, the driver rotates the lever <NUM> to reach the fully braking position, while levers <NUM>, <NUM> are interlocked. The lever <NUM> rotates integrally with the lever <NUM> and reaches the actuating position, in which the pressure relief device is operated. The pressurized liquid in the cylinder <NUM> is vented and the break <NUM> becomes fully engaged.

In view of the foregoing, the advantages of the actuating assembly according to the invention are apparent.

In particular, the proportional control of the brake <NUM> and the pressure relief can be carried out through the operation of a single control, i.e. the lever <NUM>, which carries the interlocking device <NUM>.

The arrangement of the levers <NUM>, <NUM> is extremely simple and compact. Furthermore, the coordination of the components of the mechanism <NUM> is optimal.

It is clear that modifications can be made to the described actuating assembly without extending beyond the scope of protection defined by the claims.

For example, the insertion element <NUM> and the hole <NUM> may be internally and externally screwed to form a screwed coupling; this renders the elastic device unnecessary.

The transmission <NUM> may be different; for example, the element <NUM> may have a linear motion, instead of a rotational motion.

Moreover, the lever <NUM> may be used to operate the pump device <NUM>, instead of the pressure relief device.

Claim 1:
An actuating assembly for a hydraulic brake (<NUM>), the assembly comprising:
- a frame (<NUM>),
- a second lever (<NUM>) hinged to the frame (<NUM>) about a hinge axis (H),
- a movable member (<NUM>) carried by the second lever (<NUM>) in a movable manner with respect to the second lever (<NUM>),
- a control unit (<NUM>)
- actuating means (<NUM>, <NUM>) coupled to the second lever (<NUM>) for operating the hydraulic brake (<NUM>) in response to a rotation of the second lever about said hinge axis (H);
said actuating assembly is characterized in that it further comprises: a first lever (<NUM>) hinged to the frame (<NUM>) about the hinge axis (H),
- transmission means (<NUM>) for coupling the first lever (<NUM>) to the movable member (<NUM>) in a manner that a relative rotation of the first lever (<NUM>) with respect to the second lever (<NUM>) corresponds to a movement of the movable member (<NUM>) with respect to the second lever (<NUM>),
- a transducer (<NUM>) associated to the movable member (<NUM>) and configured to detect the movement of the movable member (<NUM>) transmitted by the transmission means (<NUM>), and to generate an associated signal indicative of the relative rotation corresponding to the movement of the movable member, wherein the control unit is configured to extract from the signal an item of information related to the relative rotation of the first lever (<NUM>) and to control the hydraulic brake (<NUM>) as a function of the extracted item of information,- interlocking means (<NUM>) for selectively locking the first lever (<NUM>) to the second lever (<NUM>), such that the second lever (<NUM>) is constrained to rotate integrally with the first lever (<NUM>).