Disc brake for a lifting machine with one positive brake and one negative brake

Description

DOMAINE TECHNIQUE

[0001] This application concerns a disc brake particularly suitable for braking heavy loads (for example, more than several tons and up to 50t), such as a brake intended to equip an elevator, a cable car or a lifting device such as a crane, overhead crane, etc. ETAT DE LA TECHNIQUE

[0002] An elevator or lifting device comprises, on the one hand, a high-speed line including a motor (generally with a variable speed drive) and a high-speed shaft driven in rotation by the motor via a coupling system, and on the other hand, a low-speed line including a low-speed shaft and a drum around which the load suspension cables (elevator cabin or load to be lifted) are wound, the low-speed shaft being driven in rotation by the shaft of the high-speed line to which it is connected via a gearbox.

[0003] An elevator or lifting device needs to be equipped with brakes for several functions, including: slowing down and then stopping the elevator or lifting device as it approaches a stopping position (service brake), locking the elevator each time the doors open, or locking the lifting device when it is in its stopping position, i.e., when the load is at the desired height (parking brake). Standards also require that the elevator or lifting device be equipped with a safety brake, also called an emergency brake. « failsafe brake » In English, to slow down, stop and block the elevator or lifting equipment in case of power failure or, more generally, in case of any kind of emergency.

[0004] Service brakes (high speed and low torque) are generally associated with the high speed line, while safety brakes (low speed and high torque) are mounted on the low speed line.

[0005] A safety brake is specifically configured to trigger when it is no longer supplied with electricity (in case of power failure): this is called a fail-safe brake or negative brake.

[0006] Disc brakes have become the standard for this application since the 1960s, primarily because they pose few or no problems with overheating. Indeed, under the effect of heat, the discs expand radially rather than along their thickness, thus ensuring that braking torque remains controlled.

[0007] A disc safety brake typically includes: a disc attached to the line to be braked, on either side of which extend the two plates of a clamp suitable for clamping the disc, which plates are fitted with friction pads, for each plate or for one of the two plates only, a washer spring configured to impose a compressive force on said plate so as to push and maintain under pressure the plates against the disc and thus close and clamp the clamp, a hydraulic or electromagnetic or electromechanical actuator configured to, when under tension, compress the washer spring so as to move said plate away from the disc to open the clamp and release the rotating disc.

[0008] For elevators, service and parking brakes must be rated for 10 million operations, while the safety brake must be rated for 200,000 uses. Similarly, manufacturers of lifting equipment often require that the parking and safety brakes they integrate into their machines be guaranteed for 4 million and 200,000 uses, respectively, although no standard currently mandates this.

[0009] Some manufacturers of elevators and other lifting equipment use a single brake for both service and parking functions. Because this brake is used more frequently and / or for longer periods, its friction pads wear out faster, increasing maintenance costs. For the same reasons, the brake's lifespan decreases, requiring more frequent replacement. All of this results in periods of elevator or lifting equipment downtime that are inconvenient for users (in the case of residential elevators) or costly for the company (in the case of lifting equipment or non-standard elevators used in industry).

[0010] Other manufacturers of elevators and other lifting equipment use the safety brake as a parking brake, which necessitates oversizing the safety brake to ensure it is rated for 4 or 10 million uses instead of 200,000. This means multiplying the number of washers in the safety brake to compensate for potential washer breakage that may occur during repeated use. This results in an increased size and manufacturing cost for the brake.

[0011] Disc brakes are also used in the automotive field. US 3,647,030 discloses a motor vehicle brake that combines a negative washer actuator as previously described with a positive actuator. US 3,647,030 therefore discloses the preamble of claim 1.

[0012] The positive actuator consists of a first piston mounted to slide within a housing and a first chamber that can receive pressurized fluid. An increase in fluid pressure in this first chamber causes the piston to move in the direction of brake application. The return of this first piston (for releasing the brake when the brake pedal is released) is ensured by a spring-loaded seal housed in a groove between the outer peripheral face of the piston and the housing, as explained in US patent 3,377,076, incorporated by reference in US patent 3,647,030.

[0013] The negative actuator consists of a second piston and a second chamber that can hold pressurized fluid. An increase in fluid pressure in the second chamber causes the brake to open. The second piston has a flange against which a stack of spring washers rests. When a fluid pressure failure occurs in the circuit, the pressure in the second chamber drops, and the stack of spring washers can relax and push the second piston, which in turn pulls the first piston with it, causing the brake to close. Maintaining high pressure in the second chamber allows the brake formed by the second piston to be neutralized.

[0014] Such a brake has the advantage of combining, in a single device, a positive actuator serving as a service brake and a negative actuator serving as an emergency brake. It can be described as a hybrid brake due to this combination. However, it has the following disadvantages.

[0015] Firstly, the travel (opening) of the US 3,647,030 brake is limited to a few millimeters. This brake therefore cannot be used with large discs, making it unsuitable for lifting equipment.

[0016] Indeed, lifting equipment requires large diameter brake discs (sometimes several meters in diameter), unlike motor vehicles whose discs have a diameter of around 250mm. Due to their large diameter, the discs of lifting equipment can have a runout of several millimeters, incompatible with the use of a brake with a similar travel (it is important that the brake linings do not rub against the disc when the brake is in the open position; furthermore, in the closed position, the braking force applied by the linings on the disc must be controllable and not depend on the angular position of the disc).

[0017] Furthermore, given the design of the US 3,647,030 brake, if its positive actuator fails, such as due to a brake fluid leak, the brake must be completely removed and disassembled for repair. For a motor vehicle brake, this isn't a problem in itself. However, for a lifting equipment brake, whose weight and size are vastly different from those of motor vehicle brakes, it would be advantageous to be able to repair the brake in situ without having to remove it.

[0018] FR2092932 discloses a hybrid brake for motor vehicles which has similar disadvantages to that of US 3,647,030, particularly in terms of travel, and is therefore unsuitable for lifting equipment.

[0019] The same applies to DE3509042, which discloses another hybrid brake. PRESENTATION DE L'INVENTION

[0020] Throughout the rest, the expression " engin de levage » encompasses both industrial lifting equipment such as cranes, lifting bridges, etc., and elevators, for industrial or domestic use.

[0021] The invention aims to overcome at least one of the aforementioned drawbacks by providing a brake suitable for lifting equipment, which can be used simultaneously as a parking brake and emergency brake, or even as a service brake if lifting standards evolve in this direction, without sacrificing safety, the compactness of the brake, or its simplicity of design, and without increasing its manufacturing and maintenance costs.

[0022] The invention aims in particular to provide a hybrid brake with a large travel so that it can be used with large diameter discs, for example discs from one to several meters in diameter.

[0023] Another objective of the invention, in a preferred version thereof, is to be able to easily and inexpensively transform an existing safety brake into a hybrid brake. Another objective of the invention, in a preferred version thereof, is to provide a hybrid brake for lifting equipment that is easier to maintain.

[0024] To achieve the aforementioned objectives, the invention proposes a hybrid brake for lifting equipment, designed to cooperate with a disc of the lifting equipment extending in a plane orthogonal to an axial direction, the hybrid brake comprising: two plates extending parallel to the disc on either side thereof, the two plates forming a clamp that can be actuated between an open brake position in which the plates are away from the disc and a closed brake position in which the plates clamp the disc, a rigid body comprising a tubular upper part, called the upper half-caliper, located on one side of the disc, one of the plates, called the upper plate, being carried by a shoe mounted to slide along the axial direction in a central recess through the upper half-caliper, a stack of spring washers arranged in the central recess of the upper half-caliper around a central axis parallel to the axial direction, the stack of spring washers being able to be compressed beyond a level, called emergency braking compression, in which said stack exerts a force on the shoe corresponding to a desired emergency clamping force on the disc,a negative actuator, comprising a negative piston driven by a first energy source, which negative piston has a face on which rests a lower end of the stack of spring washers, the negative piston being mounted to slide along the axial direction in the central recess of the upper half of the caliper between an upper open brake position in which the negative piston compresses the stack of spring washers beyond the emergency braking compression, and a lower closed brake position in which the brake is closed and in which the negative piston maintains the stack of spring washers at the emergency braking compression on one side and is in direct or indirect contact with the shoe on the other side,The negative piston being placed in its upper open brake position when the first energy source is activated and in its lower closed brake position when said first energy source is inactive (either because there is an electrical fault or because the first source is not activated or is intentionally deactivated), a positive actuator comprising a positive piston driven by a second energy source, the positive piston being mounted to slide along the axial direction between an upper open brake position (in which the brake is open) and a lower closed brake position (in which the brake is closed and more or less engaged), the positive piston being placed in its upper open brake position when the second energy source is inactive and being able to be placed in its lower closed brake position when the second energy source is activated.

[0025] The hybrid brake according to the invention is characterized in that it includes a positive piston return spring, configured to raise the positive piston to its high open brake position.

[0026] In case of emergency, the negative actuator is deactivated and the brake is closed with a desired emergency clamping force, which is fixed by the structure of the stack of spring washers.

[0027] The positive actuator can be used as a parking brake, and possibly also as a service brake, subject to evolving standards in this regard. As such, it must be sized to be rated for approximately one million cycles of use (preferably rated for several million, for example, at least 10 million cycles). The positive actuator can also be used for short-term static load holding (short-term parking brake, when the installation is energized, with the negative actuator remaining on standby to ensure load safety).

[0028] Given its design, the negative brake is automatically engaged in the event of a power failure (secondary power source unavailable and negative actuator inactive). The negative brake can also be used actively for any emergency dynamic braking (in case of any fault) and for long-term static load holding (long-term parking brake, for example, when the installation is taken out of service). The stack of spring washers, which constitutes the negative brake's energy reserve for emergency braking, must therefore be sized to be rated for 200,000 cycles. Since the negative brake is not used as a service brake, the stack of spring washers does not need to be sized for several million cycles, thus reducing its size and cost.

[0029] Thanks to the return spring, the positive piston can be moved over a much greater stroke than, for example, the positive piston of US 3,647,030. In other words, the brake can have a much larger opening, making it compatible with a large-diameter disc in a lifting device. In a preferred version: The negative piston includes a cylindrical upper cavity receiving a lower portion of the spring washer stack, the negative piston further including a lower end configured to bear directly or indirectly on the shoe when the negative piston is in the lower position, so that the pressure exerted by the spring washer stack on the bottom of the piston cavity is transmitted to the shoe (when the negative piston is in the lower position), the positive piston includes a shaft extending along the central axis through the spring washer stack, which shaft has a lower end configured to couple to the shoe and an upper end that protrudes out of the upper caliper half regardless of the position of the positive piston.

[0030] We therefore have a configuration that is, in a way, "reversed" compared to that proposed by US 3,647,030 (where the central shaft corresponds to the negative piston and not the positive piston). This configuration has two main advantages.

[0031] Firstly, such a brake can be obtained from an existing safety brake, which consists solely of a negative actuator formed by a negative piston bearing directly or indirectly on a shoe, and a stack of spring washers resting on one face of said negative piston. A positive actuator can easily be formed from a shaft-shaped piston (having a lower end adapted to couple with the shoe) and a cover attached above the caliper half. A central hole is provided in the bottom of the negative piston if necessary, and the shaft can easily be inserted into the central hole of the spring washers and said negative piston. The cover is also designed to receive the means for actuating the shaft (positive piston) around the central axis.

[0032] Secondly, this brake is advantageous because its positive actuator, which, as the service brake, is the most frequently used actuator and therefore the most prone to failure, is directly accessible from the upper outer face of the caliper half, without needing to dismantle another major brake component, such as the negative actuator, and without removing the hybrid brake assembly. This simplifies maintenance and any necessary repairs to the positive actuator. They can be carried out in situ, without removing the brake, which is particularly valuable when the brake is large and / or heavy. Furthermore, the power source and activation means for the positive piston can be located at the top of the caliper half or above it (for example, in a cover that fits over the half), making them easily accessible as well.Maintenance and repair operations are made easier, and maintenance costs are reduced.

[0033] According to one possible feature of the invention, the first energy source (energy source of the negative actuator) is hydraulic, the negative piston having an external shoulder oriented towards the disc and defining, in the central recess of the caliper half, a chamber called the negative hydraulic chamber. The filling of said negative hydraulic chamber by the fluid from the first energy source thus exerts pressure on said shoulder in the opposite direction to the disc, which causes the negative piston to move in the opposite direction to the disc.

[0034] Alternatively, the first energy source can be electromagnetic or electromechanical.

[0035] According to one possible feature of the invention, the second energy source (energy source of the positive actuator) is hydraulic or electromechanical or electromagnetic.

[0036] Typically, each disc is fitted with one or more friction pads. According to a possible feature of the invention, the brake includes a wear compensation device between the stack of spring washers and the shoe to compensate for wear on the friction pads.

[0037] Advantageously, and according to the invention, this wear compensation device comprises: a thread called a compensating thread, provided on the shaft of the positive actuator between the lower end of the stack of spring washers and the lower end of the shaft, shells called compensating shells, arranged around the compensating thread, each compensating shell having a threaded face complementary to the compensating thread, for each compensating shell, a housing provided in the negative piston and in which said shell is housed, the housing having an axial dimension greater than an axial clearance of the compensating shell increased by at least one compensating thread pitch so that the compensating shell can move axially in this housing over an axial distance of at least one thread pitch,The housing also having sufficient radial depth to allow the shell to move radially over a distance at least equal to the depth of the compensating thread pitch, so that the shell's tapping can disengage from the compensating thread. An elastic ring surrounds the shells, exerting a centripetal radial pressure on them, tending to keep the compensating shells pressed against the compensating thread. For example, the elastic ring bears against a peripheral outer face of the shells opposite their tapped face.

[0038] According to one possible feature of the invention, there are three catching shells, uniformly distributed around the catching thread, i.e. arranged on radii forming angles of 120° between them.

[0039] According to one possible feature, the wear compensation device further includes an actuator configured to drive the positive piston in rotation and means for controlling said actuator.

[0040] Wear compensation can therefore be done not only automatically by step skipping as explained later in the detailed description with reference to the attached figures, but also in a controlled manner by rotating the positive piston (and therefore the compensation thread) by the aforementioned dedicated actuator.

[0041] The hybrid brake according to the invention can be a sliding brake or a symmetrical brake.

[0042] If the hybrid brake according to the invention is a sliding brake: Besides the upper half-caliper, the rigid body of the brake includes a lower part, called the counter-caliper, located on the other side of the disc, the other plate, called the lower plate, being located on this counter-caliper and being fixed relative to it, the brake is without an actuator for braking on the side of the counter-caliper; it therefore preferably includes only the negative actuator and the positive actuator previously defined, which are arranged in the upper half-caliper, the brake includes a column on which the rigid body (half-caliper + counter-caliper) is mounted sliding along the axial direction.

[0043] If the hybrid brake according to the invention is a symmetrical brake: In addition to the upper caliper, the rigid body of the brake includes a lower caliper, located on the opposite side of the disc. Similar to the upper caliper, the lower caliper is supported by a lower shoe mounted to slide along the axial direction within a central recess in the lower caliper. The brake includes a second positive actuator and a second negative actuator arranged in the lower caliper and configured to move the lower shoe. The second negative and positive actuators can be identical, respectively, to the negative and positive actuators of the upper caliper, but arranged symmetrically (with respect to the braking plane represented by the disc) in the lower caliper. In short, the entire brake assembly can be symmetrical with respect to the disc.

[0044] The invention extends to a braking system comprising a hybrid brake as previously defined and a microprocessor controller(s) to which the positive and negative actuators of said hybrid brake are connected, the controller being configured to use the positive actuator for all dynamic service braking and for all static holding when the lifting equipment is in service, energized and in the absence of fault ("short-term" static holding), and to use the negative actuator for all dynamic emergency braking and for all static holding ("long-term") when the lifting equipment is taken out of service (i.e. is no longer energized), the negative actuator also being, by its design, automatically triggered without action from the controller for all dynamic emergency braking in the event of an electrical failure.

[0045] The invention extends to a lifting device characterized in that it is equipped with a hybrid brake as previously defined. In the preceding sentence, the expression "a hybrid brake" should not be understood as meaning "one and only one" hybrid brake but as meaning "at least one" hybrid brake, that is to say, one or more hybrid brakes. BREVE DESCRIPTION DES DESSINS

[0046] The invention, according to an exemplary embodiment, will be better understood and its advantages will become clearer upon reading the following detailed description, given by way of example and in no way limiting, with reference to the attached drawings in which: [ Fig. 1 ] there figure 1 is a cross-section by an axial plane of an embodiment of a hybrid brake according to the invention; [ Fig. 2 ] there figure 2 is a symbolic representation of the hybrid brake of the figure 1 ; Fig. 3 ] there figure 3 is a symbolic representation of a wear compensation device that can be fitted to a hybrid brake according to the invention, showing the brake in the case of new friction pads and with the positive piston in the open brake high position, the negative piston being in the high position; [ Fig. 4 ] there figure 4 is a symbolic representation of the wear compensation device of the fig. 3 in the case of new friction pads and with the positive piston in the lower position of the closed brake, the negative piston being in the upper position; Fig. 5 ] there figure 5 is a symbolic representation of the wear compensation mechanism of fig. 3 à 5 in the case of worn friction pads, simulating the closing of the positive brake, i.e. the descent of the positive piston towards the disc from its upper position, the negative piston being unused and therefore fixed in the upper position; Fig. 6 ] there figure 6 is a symbolic representation of the wear compensation device of the fig. 5 (with worn friction pads), simulating the opening of the positive brake, i.e., the upward movement of the positive piston in the opposite direction to the disc, after braking following the situation of the fig. 5 the negative piston being always fixed in the upper position. DESCRIPTION DETAILLEE

[0047] Identical elements represented in the aforementioned figures are identified by identical numerical references.

[0048] Throughout this description, the brake is defined and described in the position in which it appears in the accompanying figures. The terms "up," "down," "upper," "lower," "above," "below," "up," "down," etc., refer to this position and are unrelated to the direction of gravity, as the brake can operate in any position. Thus, for example, when the brake is described in a position where its actuators are located above the disc, the expression "the piston moves down" is used to mean more generally that the piston in question moves toward the disc (which does not necessarily mean that it follows the direction of gravity), while the expression "the piston moves up" means that the piston moves away from the disc.

[0049] There figure 1 represents a hybrid brake 100 according to the invention, seen in cross-section along an axial plane (plane containing the central axis of the brake body). More precisely, the axial plane in question is a plane of symmetry of the brake.

[0050] The hybrid brake 100 is associated with a disc 1 of a lifting device (not shown), which disc is attached to a rotating line of said lifting device. The hybrid brake 100 comprises an upper plate 2 fitted with friction pads 7 (also called wear linings) and a lower plate 3, similarly fitted with friction pads 7. The plates and the disc are parallel to each other and orthogonal to a central axis X 100 of the brake, the reference X 1 designating the axis of rotation of the disc 1, which is parallel to the central axis X 100. The term "axial direction" refers to the direction of the central axis X 100 of the brake.

[0051] The hybrid brake 100 further comprises a rigid body including an upper half-caliper 4, hereinafter simply called the "half-caliper," and a counter-caliper 5. The half-caliper 4 is tubular: it includes a central recess 40 extending through it along the axial direction. This central recess 40 is not necessarily cylindrical; it may comprise a series of sections of different diameters forming various internal shoulders. However, for reasons of economy, these different sections preferably all have a circular cross-section to allow for sealing and guidance using conventional gaskets. Other cross-sections (polygonal, for example, particularly square) are possible, provided that specific gaskets of complementary shape are used.

[0052] Plate 2 is carried by a shoe 6 mounted sliding inside the central recess 40 of the half-stirrup (plate 2 could, alternatively, correspond to the lower face of said shoe 6), while plate 3 is carried by the counter-stirrup 5 (it is for example fixed on the upper face of the latter).

[0053] The hybrid brake 100 also includes a stack of 10 spring washers. The spring washers are chosen for their dimensional characteristics, material, and properties (particularly stiffness), just as the brake pads are chosen for their coefficient of friction, based in particular on the maximum load the brake is designed to withstand. The spring washer stack is thus dimensioned to generate a clamping force, known as the emergency clamping force, which induces (via the brake pads and therefore according to their coefficient of friction) a braking force that must correspond to the braking force required to instantly stop the aforementioned maximum load.

[0054] The hybrid brake 100 further includes both a negative actuator 8 and a positive actuator 9, which together with the stack of spring washers 10 form a negative brake (or lack brake) and a positive brake.

[0055] The illustrated hybrid brake 100 is a sliding brake: both actuators are located on the same side of the disc 1; they both act on the upper plate 2, and the brake has no actuator on the other side of the disc. The upper plate 2 can be moved closer to or further from the disc by the actuators, while the lower plate 3 remains stationary. For the two plates to simultaneously apply a pinching force to the disc, the rigid body of the brake must be able to move axially. To this end, the brake includes a column 12 on which the rigid body of the brake (half-caliper 4 + counter-caliper 5) is mounted to slide along the axial direction, via a bracket 120 which, in this example, extends from the counter-caliper 5. The bracket 120 and the column 12 thus form a sliding joint. The column 12 is fixed to a base plate 15.The brake 100 also includes a screw 121 allowing the rigid body to be locked onto the column 12 if necessary, particularly during maintenance operations.

[0056] Alternatively, the hybrid brake could be a symmetrical brake. It would then include four actuators: a positive actuator and a negative actuator on each side of the disc. The sliding brake is preferred because it offers lower manufacturing and maintenance costs, as well as increased reliability (fewer actuators, therefore less risk of failure or breakage).

[0057] The negative actuator 8 includes a negative piston 80 mounted to slide in the central recess 40 of the half-caliper.

[0058] The illustrated example uses a hydraulic negative actuator 8. A chamber 81 (called the negative chamber) is therefore provided, which negative chamber 81 is delimited by the inner face of the recess 40 and the outer face of the negative piston. More precisely, the negative chamber 81 is delimited by an external shoulder 84 of the piston oriented downwards (i.e., towards the disc 1) and an internal shoulder 401 of the half-caliper oriented upwards (i.e., in the opposite direction to the disc 1). This negative chamber 81 is connected to a pressurized fluid supply device (not shown) which constitutes the hydraulic energy source (called the primary energy source) for the operation of the negative actuator 8.

[0059] Alternatively, the negative actuator could be electromechanical or electromagnetic, the person skilled in the art being able, without demonstrating inventive activity, to adapt the shape of the half-caliper and to integrate therein for example the electromagnets necessary for the movement of the negative piston towards its upper position when the electromagnets are energized for the realization of an electromagnetic negative brake.

[0060] The negative piston 80 has an upper cavity 82 in which is housed a lower part of the stack of spring washers 10. The lower end of the stack 10 thus rests on a bottom 83 of the upper cavity 82. The upper end of the stack of spring washers 10 also comes against a fixed element of the rigid body of the brake, in this case the lower face of a cover 11 fixed to the top of the half-caliper 4.

[0061] The presence of the cover facilitates maintenance by allowing access to the inside of the caliper half and, in particular, to the stack of spring washers 10. If, for example, a broken spring washer needs to be replaced, simply unscrew the screws that pass through the lower flange of the cover 11 and secure it to the caliper half 4, then remove the cover to access the stack of spring washers 10 housed in the upper cavity 82 of the negative piston. This cover also provides easy access to the positive piston 90, described in detail below.

[0062] The central recess 40 of the half-stirrup extends axially by a central recess 110 through the cover 11 in the axial direction.

[0063] With the stack of spring washers 10 wedged between the lower face of the cover 11 (which is fixed) and the bottom 83 of the upper cavity of the negative piston 80, the compressive force of the stack of spring washers 10 tends to move the negative piston 80 downwards, towards the shoe 6.

[0064] When the chamber 81 of the negative actuator is empty or when a low or zero pressure is imposed on the fluid contained in said chamber, the negative piston 80 descends under the effect of the push of the stack of spring washers 10; the lower end 85 of the negative piston 80 comes to press, directly or indirectly, on a stop or ball joint 97 carried by the lower end of the positive piston 90; the stop or ball joint 97 comes to couple with the shoe 6 and the negative piston pushes the shoe 6 in the direction of the disc 1 as the stack of spring washers 10 relaxes.

[0065] When the friction pads 7 of the plate 2 come into contact with the disc 1, the rigid brake body slides upwards as a single unit along the column 12, while the negative piston 80 continues to descend relative to the caliper half, until the negative piston 80 is in a fully closed brake position in which the friction pads of both plates are in contact with the disc and together exert a clamping force on the disc. The clamping force, known as the emergency clamping force, then applied to the disc depends on the residual compression of the stack of spring washers 10 in this lower position of the negative piston. This residual compression can be adjusted during the brake design by changing the number, stiffness, material, and / or dimensions of the washers used. A desired emergency clamping force can thus be achieved.

[0066] When the negative piston 80 is in the upper position as illustrated in the Fig. 1 that is, when chamber 81 is filled with a fluid pressure greater than or equal to a given threshold value, the stack of spring washers 10 is compressed beyond the emergency braking compression (which corresponds to the low position of piston 80).

[0067] In the event of a power failure or if the fluid supply to chamber 81 is intentionally stopped—that is, if the (primary) power source of actuator 8 is inactive (or deactivated)—the pressure in chamber 81 drops abruptly and the chamber empties; the negative piston 80 falls to its lowest position and the brake closes in a fraction of a second. Actuator 8 is therefore indeed a negative actuator.

[0068] The positive actuator 9, meanwhile, includes a positive piston 90 mounted to slide in the central recesses 40 and 110 of the half-caliper and the cover.

[0069] In the illustrated example, the positive actuator 9 is also hydraulic. It therefore includes a chamber 91 (called the positive chamber) located above one face of the positive piston 90 oriented upwards (opposite direction to the disc), which chamber is supplied with fluid via a supply conduit 92. This fluid constitutes a second source of energy, which enables the operation of the positive actuator 9.

[0070] The positive piston 90 comprises, from top to bottom, a first section 901 of smaller diameter and then a second section 902 of larger diameter, so that an external shoulder 903 oriented upwards (i.e. in the opposite direction to the disc 1) is formed between the first and second sections of the piston.

[0071] The positive chamber 91 of the positive actuator is delimited by the outer face of the positive piston 90 and by the inner face of the recess 110 in the cover 11 above this outer shoulder 903. In other words, the positive chamber is formed inside the cover 11, outside the half-stirrup 4. The entire positive actuator 9 (piston 90, chamber 91, fluid supply conduit and valve 92 for the chamber, return spring 98) is accessible simply by opening the cover 11. This facilitates maintenance operations (checking and repairing any leaks, for example) of the positive actuator, which is the most frequently used component and therefore the most susceptible to wear. Similarly, the stack of spring washers 10 (which are breakable parts) is accessible once the cover 11 and the piston 90 are removed.Thus, the main faults of the hybrid brake can be fixed on site, without the need to remove the brake.

[0072] The external diameter of the second section 902 of the positive piston is substantially equivalent (with minimal clearance) to the internal diameter of a corresponding section of the central recess 110 in the cover, to allow the piston 90 to slide about the central axis X 100 while preventing fluid leaks from the chamber 91 between the external face of the piston and the internal face of the recess 110 in the cover. A seal may be provided to limit these leaks, as well as a groove 94 and a conduit 95 for collecting any leaks downstream (i.e., below) the seal.

[0073] The positive piston 90 then includes a third section forming a shaft 904 which passes through the stack of spring washers 10 (the shaft 904 passes through the central hole of each of the spring washers); the shaft 904 also passes through the lower end 85 of the negative piston 80. As already mentioned above, the lower end of the shaft 904 of the positive piston is provided with a stop ( fig. 1 ) or a kneecap ( fig. 2 ), referenced 97 in both cases, which fits into a corresponding niche 60 of the shoe 6 when the positive piston 90 is moved downwards towards the disc 1. Note that the lower end 96 of the piston may be without a ball joint or stop and be configured to couple directly with the shoe 6.

[0074] A bellows 99, fixed on one side to the external face of the lower portion 85 of the negative piston and on the other side to the lower end 96 of the positive piston (for example to the stop or ball joint 97), is advantageously provided to prevent the entry of dust and lining particles which may disrupt the wear compensation system.

[0075] The hybrid brake 100 is also associated with a controller (not shown) which allows the positive actuators 9 and negative actuators 8 to be controlled by acting on the power supply to these actuators.

[0076] When dynamic service braking or static parking braking is required, the controller commands the injection of pressurized fluid into the positive chamber 91 (activation of the second energy source) of the positive actuator 9. This causes the positive piston 90 to move downwards until the stop or ball joint 97 at the lower end of the shaft 904 engages with the brake shoe 6 and then pushes the shoe towards the disc 1. When the friction pads 7 of the backing plate 2 come into contact with the disc 1, the rigid brake body slides upwards as a single unit along the column 12 while the positive piston 90 continues to descend relative to the caliper half, until the friction pads of both backing plates are in contact with the disc and together exert a clamping force on the disc. The clamping force then applied to the disc 1 is a function of the fluid pressure in the positive chamber 91.The positive brake can therefore be controlled to exert a variable, controlled clamping force.

[0077] Meanwhile, the negative brake 8 is held open as illustrated in the figure 1 that is to say, a fluid pressure at least equal to a predetermined threshold pressure (capable of compensating for the emergency braking compression of the stack 10) is maintained in the negative chamber 81 so that the negative piston 80 remains in the raised position as illustrated in the figure 1 .

[0078] According to the invention, the brake 100 includes a return spring 98 configured to raise the positive piston 90 to its upper open brake position. In the illustrated example, the return spring 98 is housed around the shaft 904 inside the stack of spring washers 10. The return spring 98 bears on one side against the bottom 83 of the upper cavity of the negative piston and on the other side against an external shoulder 905 of the positive piston, which shoulder 905 is located at the junction between the sections 902 and 904 of the piston (the shoulder 905 is therefore oriented downwards).

[0079] The return of the positive piston 90 by this spring 98 allows a significant travel of the positive piston, which makes the hybrid brake according to the invention suitable for lifting equipment fitted with a large diameter disc.

[0080] The illustrated hybrid brake 100 also includes a wear compensation device 13 arranged between the stack of spring washers 10 and the shoe 6, which will now be described with reference to the fig. 3 à 6 , on which only half of the positive and negative brake actuators are represented symbolically, the other half being obtained by symmetry with respect to the X 100 axis.

[0081] The wear compensation device 13 comprises: a thread 131, called a compensating thread, provided on a lower portion of the shaft 904 of the positive piston, a plurality of shells 130, for example three shells 130 arranged at 120° to each other around the thread 131, an elastic ring 133 surrounding the shells and exerting on them centripetal radial forces which keep the shells in contact with the compensating thread 131; each shell 130 has an inner face 132 (face oriented towards the axis X 100) which is tapped with a thread pitch complementary to the thread pitch of the compensating thread 131, so that the tapped inner face 132 of the shells fits into the compensating thread 131, under the pressure of the elastic ring 133.for each shell 130, a housing 134 receiving said shell (the housing being specific to said shell or common to several shells), which housing 134 is provided in the negative piston 80 and is open towards the central axis X 100, the housing 134 having an axial dimension greater than that of the shell so that the shell can move axially in the housing over a stroke at least equal to the pitch of the thread 131, the housing 134 also having a radial depth sufficient for the shell to move radially over a stroke allowing the tapping 132 to exit the thread 131.Note that the compensation device 13 may include a plurality of separate housings 134, in particular one housing per shell 130, or a single circular housing which goes around the shaft 904 (i.e. a circular groove made in the inner face of the negative piston 80) and which accommodates all the shells 130, or even a plurality of housings each accommodating several shells.

[0082] On the fig. 3 et 4 The brake has 7 unworn friction pads. On the figure 3 The negative piston 80 is in the open brake high position as illustrated on the fig. 1 (The negative chamber 81 contains a pressurized fluid exerting on the piston 80 a force greater than the emergency braking compression force). The positive piston 90 is also in the high position of the open brake (the positive chamber 91 is empty and the shoulder 903 (see fig. 1 ) of the piston 90 is in contact with or near the cover 11). In this position, each shell 130 is resting against the upper face 135 (or upper stop) of its housing 134.

[0083] When the positive actuator 9 is actuated, for example for a service operation, the positive piston 90 is pushed downwards by the pressurized fluid injected into the positive chamber 91, and the positive piston 90 moves from its upper position ( fig.3 ) to its low, closed brake position, illustrated on the fig. 4 Meanwhile, the negative piston 80 is held fixed in its high open brake position.

[0084] When the positive piston 90 is in the closed brake position, the friction pads 7 are in contact with the disc 1. As the piston, and therefore the thread 131, descends, the brake shoes follow until they come to rest against the lower face (or lower stop) 136 of the housing. The thread may possibly descend slightly further than the brake shoes (this is the case on the fig. 4 ), pushing these radially without however going so far as the tapping 132 of the shells disengages from the thread 131.

[0085] There figure 5 illustrates the positive piston 90 in its downward phase, but in the case where the friction pads 7 are worn. In this case, when the positive piston 90 reaches the height of the fig. 4 (which corresponds to the low position of the closed brake when the pads are new), the (worn) pads 7 are still some distance from the disc 1 since they have a reduced thickness due to their wear, and the piston can continue to descend, pushed by the pressurized fluid in the positive chamber 91. The shells 130 can no longer descend, held by the lower face 136 (or lower stop) of the housing. They are then forced to move radially, pushed by the thread 131, until their threaded section 132 disengages from the thread 131.

[0086] It should be noted that the threads of the compensating thread 131 and the tapped hole 132 of the compensating shells advantageously have a triangular cross-section with an upper face orthogonal to the central axis X 100 and an inclined lower face. Thus, when the positive piston 90 descends, the compensating thread exerts a force on the compensating shells 130 that comprises both an axial component, which drives the shells downwards, and a radial component, which tends to radially displace the shells outwards when they reach the abutment against the lower face 136 of the housing. Conversely, when the positive piston 90 ascends, the compensating thread 131 exerts a purely axial force on each shell 130, which ensures that the tapped hole 132 of the shells remains engaged in the compensating thread 131 of the shaft, even when the shells reach the abutment against the upper face 135 of the housing.

[0087] Having reached the situation of fig. 5 , piston 90 continues to descend and the shells skip one step of thread 131, or possibly several steps, to end up in the position illustrated in the fig. 6 When the positive brake energy source is subsequently deactivated or reduced, the piston 90 rises until the shells come to a stop against the upper face (or upper stop) 135 of the housing, thus stopping the piston 90 in a new high open brake position ( fig. 6 ). This new high position of open brake is offset by one or more thread pitches 131 compared to the previous high position, the offset corresponding to the thickness lost by wear of the friction pads 7. Thus, with the same stroke, the actuation of the positive piston 90 always allows the brake to be closed, whether the pads are worn or not.

[0088] The adjustment mechanism also serves the negative brake, since when the positive brake is not used and the negative piston 80 is in the open brake high position (see fig. 3 And fig. 5The shells are always in contact with the upper face 135 of the negative piston housing 134. However, in the example described, the negative piston 80 acts (i.e., indirectly bears against) the shoe 6 via the adjusting device 13, more precisely via the shells 130, the adjusting thread 131, and the lower end 96 of the shaft 904. Thus, when the negative piston 80 is in the open brake position, the lower end of the negative piston is already in indirect contact with the shoe via the shells 130 and the positive piston shaft 904. When the emergency brake is applied, the negative piston 80 therefore immediately pushes the shoe 6 towards the disc.The relative position of the shells 130 and the thread 131 taking into account the thickness of the friction pads 7 and their possible wear, the closing of the brake (with a predetermined emergency braking torque) is guaranteed with the same stroke of the negative piston 80, whether the pads are worn or not.

[0089] The presence of a positive brake in the hybrid brake does not interfere with the emergency braking function. The negative piston 80 can be actuated (moved down) regardless of the position of the positive piston 90. If the positive piston 90 is in the open brake position, as previously described, the negative piston 80 will drive the brake shoes 130 and the shoe 6 from the beginning of its stroke. If the positive brake is in use and the positive piston 90 is, for example, in the closed brake position, the negative piston 80 will only press on the brake shoes 130 and the shoe 6 at the end of its stroke, to ensure that the torque applied to the disc is at least equal to the emergency braking torque.If the positive brake is in use and the positive piston 90 is in an intermediate position (in the descent or ascent phase), the negative piston 80 will take over at an intermediate point in its own stroke when the upper face 135 of the housings 134 comes into contact with the shells 130. Note that, even if it is in the ascent phase, the positive piston 90 does not oppose the descent of the emergency negative piston since the ascent of the positive piston is carried out with negative energy (the chamber 91 empties) and the return spring 98 which pushes the positive piston upwards rests on the negative piston 80 (the spring 98 therefore exerts a downward force on the negative piston 80 which compensates for the upward force exerted on the negative piston 80 by the positive piston 90 via the shells of the compensation device).

[0090] The hybrid brake 100 preferably also includes a recentering device 14 which allows the brake body to be recentered relative to the disc in order to guarantee a symmetrical opening relative to the disc over the entire wear range of the friction pads 7 (the pads of plate 2 may be more or less worn than those of plate 3. This device will not be described in detail here.

Claims

1. A hybrid brake for lifting machinery, intended to cooperate with a disc of the lifting machinery extending in an orthogonal plane to an axial direction, the hybrid brake comprising: - two plates (2, 3) extending parallel to the disc on either side thereof, the two plates forming a clamp that can be actuated between an open brake position in which the plates are at a distance from the disc and a closed brake position in which the plates clamp the disc, - a rigid body (4, 5) comprising a tubular upper part (4), referred to as an upper half-bracket, located on one side of the disc, one of the plates (2), referred to as the upper plate, being supported by a shoe (6) mounted so as to slide in the axial direction in a central through-recess (40) in the upper half-bracket, - a spring washer stack (10) arranged in the central recess (40) of the upper half-bracket about a central axis (X100) parallel to the axial direction, the spring washer stack (10) being configured so that it can be compressed beyond a certain level, referred to as the emergency braking compression, at which point the stack exerts a force on the shoe (6) corresponding to a desired emergency clamping force on the disc, - a negative actuator (8), comprising a negative piston (80) moved by a first energy source, which negative piston has a face (83) on which a lower end of the spring washer stack (10) rests, the negative piston (80) being mounted so as to slide in the axial direction in the central recess (40) of the upper half-bracket between an upper open brake position, in which the negative piston (80) compresses the spring washer stack (10) beyond the emergency braking compression, and a lower closed brake position, in which the brake is closed and in which the negative piston (80) holds the washer spring stack (10) at the emergency braking compression on one side and is in direct or indirect contact with the shoe (6) on the other side, the negative piston being placed in its upper open brake position when the first energy source is activated and in its lower closed brake position when said first energy source is inactive, - a positive actuator (9) comprising a positive piston (90) moved by a second energy source, the positive piston being mounted so as to slide in the axial direction between an upper open brake position, in which the brake is open, and a lower closed brake position, in which the brake is closed, the positive piston being placed in its upper open brake position when the second energy source is inactive and being able to be placed in its lower closed brake position when the second energy source is activated, the hybrid brake being characterised in that it comprises a return spring (98) of the positive piston, configured to raise the positive piston (90) into its upper open brake position.

2. Hybrid brake according to claim 1, characterised in that: - the negative piston (80) comprises a cylindrical upper cavity (82) receiving a lower part of the spring washer stack (10), the negative piston further comprising a lower end (85) configured to bear directly or indirectly on the shoe (6) when the negative piston is in the lower closed brake position, - the positive piston (90) comprises a shaft (904) extending along the central axis (X100) through the spring washer stack (10), which shaft has a lower end configured to couple to the shoe (6) and an upper end that projects out of the upper half-bracket (4) regardless of the position of the positive piston.

3. Hybrid brake according to any one of claims 1 or 2, characterised in that the first energy source is hydraulic, the negative piston (80) having an external shoulder (84) which is oriented towards the disc (1) and which delimits, in the central recess (40) of the half-bracket, a hydraulic chamber (81) referred to as the negative chamber.

4. Hybrid brake according to either claim 1 or 2, characterised in that the first energy source is electromagnetic or electromechanical.

5. Hybrid brake according to any one of claims 1 to 4, characterised in that the second energy source is hydraulic or electromechanical or electromagnetic.

6. Hybrid brake according to any one of claims 1 to 5, characterised in that each plate (2, 3) is provided with one or more friction pads (7) and in that the brake comprises a wear take-up device (13) between the spring washer stack (10) and the shoe (6) in order to compensate for the wear of the friction pads.

7. Hybrid brake according to claim 6 and according to claim 2, characterised in that the wear take-up device (13) comprises: - a thread (131), referred to as the take-up thread, provided on the shaft (904) of the positive actuator between the lower end of the spring washer stack (10) and the lower end (96) of the shaft, - shells (130), referred to as the take-up shells, arranged around the take-up thread (131), each take-up shell (130) having an internally threaded face (132) complementary to the take-up thread (131), - for each take-up shell (130), a housing (134) which is provided in the negative piston (80) and in which said shell is housed, the housing (134) having an axial dimension greater than an axial footprint of the take-up shell increased by at least one take-up thread pitch so that the take-up shell (130) can move axially in this housing over an axial distance of at least one thread pitch, the housing also having radially a depth sufficient for the shell to be able to move radially over a radial distance corresponding to at least one depth of the take-up thread pitch, - a resilient ring (133) surrounding the shells, exerting a radial centripetal pressure on them tending to keep the take-up shells (130) pressed against the take-up thread (131).

8. Hybrid brake according to claim 7, characterised in that the wear take-up device further comprises an actuator configured to drive the positive piston (90) in rotation and means for controlling said actuator.

9. Hybrid brake according to any one of claims 1 to 8, characterised in that: - in addition to the upper half-bracket (4), the rigid body of the brake comprises a lower part (5), referred to as the counter-bracket, located on the other side of the disc (1), the other plate (3), referred to as the lower plate, being located on this counter-bracket (5) and being fixed with respect thereto, - the brake has no actuator for braking on the side of the counter-bracket (5); - the brake comprises a column (12) on which the rigid body (4, 5) is mounted so as to slide in the axial direction.

10. A braking system for lifting machinery, comprising a hybrid brake according to any one of claims 1 to 9 and a microprocessor controller to which the positive actuator (9) and the negative actuator (8) of said hybrid brake are connected, the controller being configured to use the positive actuator for any dynamic service braking and for any static holding when the lifting machinery is in service, powered on and in the absence of a failing, and to use the negative actuator for any dynamic emergency braking in the event of a failing and for any static holding when the lifting machinery is taken out of service.

11. Lifting machinery, characterised in that it is equipped with a hybrid brake according to any one of claims 1 to 9.