Electromechanical centrifugal actuator

Abstract

An electromechanical actuator comprising: a motor (3); a shaft driven by the motor; a piston (5) movable along an axial direction between a lower position and a higher position; an upper tulip (8) mounted to slide on the shaft below the piston; a lower tulip (7) fixed on the shaft; arms (9) extending radially, fixed on the shaft (4) between the tulips (7) and (8); weights (10) elongated in shape along the axial direction, mounted to slide on said arms; lower ramps (11) and upper ramps (12) in contact with the axial ends of the weights, each ramp starting from one of the tulips (7) and (8) and moving away from the shaft towards the other tulip, the weights thus being interposed between two ramps in order to keep the tulips apart from each other; An electromagnet (14) for holding the piston in the raised position. Figure for the abbreviation: Fig. 2

Description

Title of the invention: Electromechanical centrifugal actuator technical field

[0001] The present application relates to a centrifugal electromechanical actuator, in particular an actuator for a safety brake for a lifting device. State of the art

[0002] A lifting device such as a crane, overhead crane, etc., usually comprises a line equipped with a drum around which suspension cables are wound, to which the load to be lifted is attached. Such a lifting device can be used to lift extremely heavy loads, for example, weighing from 50 to 500 tons.

[0003] The lifting equipment needs to be equipped with brakes for several functions, including: slowing down and then stopping the load when approaching a stopping position (service brake); locking the lifting equipment when it is in its stopping position, i.e. when the load is at the desired height (parking brake); stopping and locking the lifting equipment in the event of an electrical failure or, more generally, in the event of any kind of emergency (safety brake, also called emergency brake or "failsafe brake" in English).

[0004] A safety brake is specifically configured to activate when it is no longer supplied with electricity (in the event of a power failure): this is called a fail-safe brake or negative brake. Disc brakes have become the standard since the 1960s for this purpose, in particular because their overheating poses few or no problems.

[0005] A disc safety brake generally comprises:

[0006] - a disc attached to the line to be braked,

[0007] - a clamp, comprising two jaws or plates adapted to pinch and clamp the disc, whose jaws are generally equipped with friction pads,

[0008] - for each jaw or for one of the two jaws only, a reserve energy in the form of a spring, for example a washer spring or a helical spring, configured to impose a pressing force on said jaw in the direction of brake closure, that is to say, so as to push and maintain under pressure the jaws against the disc and thus tighten the caliper,

[0009] - an electrically controlled actuator comprising a piston which, when it When deployed, it pushes a plate against which the end of the spring rests. The extending piston then compresses the spring in the direction of the brake opening. Thus, when the actuator is under tension, it can be activated to move the plate to a high position where the spring is compressed, opening the clamp and releasing the rotating disc (and therefore the line). Alternatively, the piston is configured to act, not on the spring, but on the jaws (directly or via a mechanism) in the direction of the brake opening.

[0010] Some older installations still have drum safety brakes. These installations include a pulley attached to the line to be braked, a clamp having two curved shoes lined with a friction material, suitable for clamping and tightening the pulley, as well as an energy reserve and an actuator such as previously described for disc brakes.

[0011] Regardless of the type of safety brake considered (disc or drum), in the event of an electrical failure, the actuator suddenly becomes inoperative, releasing the spring or the shoes (or curved shoes), which causes the brake to close and the load to stop.

[0012] The constraints that determine the technical specifications of the safety brake actuators for lifting equipment include: the working environment of the brake in terms of temperature, humidity, access, available space, etc.; the brake stroke; the braking force imposed by the spring, which the actuator must counteract to open the brake, the spring itself being sized according to the loads to be lifted; the opening time; the brake response time (in the closing direction) in the event of a power outage affecting the actuator; the possibility of closing the brake progressively to slow the descent of a load.

[0013] The actuator used for opening a brake can be electro-hydraulic, electromagnetic or electromechanical.

[0014] Electrohydraulic actuators are susceptible to fluid leakage. In the event of a leak, the actuator may become inoperative, leading to a production stoppage for repair and / or replacement. To ensure the oil circuit is closed and the oil (fluid) contained, electrohydraulic actuators are equipped with a number of hermetic seals, which are wear parts requiring regular replacement, resulting in undesirable production downtime and significant maintenance costs.

[0015] Furthermore, when the brake is intended for use in a very hot environment, for example in a steel plant, the electrohydraulic actuator fluid must be a high-temperature stable oil. Above a certain temperature, all known actuator oils present a risk of flammability; the consequences of an oil leak can then be dramatic. Conversely, in very cold environments, it may be necessary to equip the actuator with a fluid heating system, which increases the weight and cost of the actuator and raises the risk of failure. Moreover, oils are generally environmental contaminants. While there are low-flammability and / or biodegradable oils available, they are generally more expensive and less effective.

[0016] Lacking an oil circuit, electromagnetic or electromechanical actuators (ball or screw type, for example) do not present the aforementioned disadvantages. However, they generally suffer from a longer, or even excessively long, response time (to close, in the event of an electrical failure).

[0017] The electromechanical centrifugal actuator disclosed by GB687222 is also known. This actuator comprises: - an actuating rod mounted to slide along an axial direction; sliding the actuating rod outwards from the actuator closes the brake, while sliding it inwards opens the brake. - a helical spring which, under compression, tends to move the actuating rod towards the inside of the actuator (brake closure), - an electric motor, - a square-section shaft driven in rotation by the electric motor - two lower arms whose proximal ends are rigidly fixed to the shaft at a low attachment point thereon, - a tulip-shaped piece mounted to slide on the shaft between a low rest position located above the attachment point of the lower arms and a high position which depends on the rotational speed of the shaft, which tulip tends to compress the spring and move the actuating rod outwards when it moves away from its low position under the effect of the rotation of the shaft, - two upper radial connecting rods articulated to the tulip joint at their proximal end, - two mass linkage elements connecting, on each side of the shaft, the distal ends of one of the lower arms and one of the upper connecting rods.

[0018] When the engine is stopped, the tulip joint is in the lowered position and the upper connecting rods are folded against the shaft. Rotation of the shaft causes the upper connecting rods to extend, driven by mass-connecting elements propelled radially outwards by centrifugal force. This causes the tulip joint to move upwards, compressing the spring and subsequently opening the brake. The final compression of the spring depends on the tulip joint's stroke and therefore, among other things, on the engine's rotational speed.

[0019] This brake has the advantage of not requiring an oil circuit, but, given its design, it has a short stroke which limits its applications. Description of the invention

[0020] The invention aims to overcome at least one of the aforementioned drawbacks by proposing a centrifugal electromechanical actuator having a stroke greater than that of other actuators. electromechanical components known for their suitability for use in a safety brake of a lifting device capable of lifting very heavy loads, for example, from 50 to 500 tons. The invention also aims to provide an actuator with a significantly reduced response time.

[0021] In particular, an objective of the invention is to provide an electromechanical actuator having a stroke of up to 60mm and a response time of less than 300ms in the event of an electrical failure.

[0022] To achieve this, the invention proposes an electromechanical actuator comprising: - an engine, - a shaft driven in rotation by the motor, - a piston, which can be moved along an axial direction between a low position and a high position, - an upper tulip, which is mounted sliding on the shaft and comes to rest on the piston when the shaft is driven in rotation.

[0023] The electromechanical actuator according to the invention is characterized in that it comprises: - a lower tulip fixed to the tree, - one or more (preferably at least two) radially extending arms, fixed to the shaft between the lower and upper tulips, - for each of said arms, a weight having an elongated shape along the axial direction, said weight being mounted to slide on said arm, - for each of said weights, a lower ramp and an upper ramp in contact with the axial ends of the weight, which lower and upper ramps follow curves starting respectively from the lower and upper tulips and moving away from the tree towards the other tulip, each of the weights being thus interposed between two ramps in order to keep the tulips separated from each other, - an electromagnet to hold the piston in the raised position.

[0024] According to particular embodiments of the invention, the electromechanical actuator further meets the following characteristics, implemented individually or according to any technically possible and operational combination.

[0025] In some embodiments, the electromagnet includes a housing containing a coil, incorporated in the actuator housing, for example on an upper wall of said housing, and the piston includes an armature configured to be attracted by said coil.

[0026] In certain embodiments, each weight has a roller at each of its axial ends, configured to cooperate with a rail formed in the corresponding ramp.

[0027] In certain embodiments, each of the upper and lower ramps has a stop at its free end, preventing the axial end of the associated weight from detaching from said ramp.

[0028] In certain embodiments, there are three arms, arranged at 120° intervals around the shaft, as are the weights, the lower ramps (from the lower flange), and the upper ramps (from the upper flange). The forces exerted on the shaft via the ramps and flanges due to the radial movement of the weights are thus perfectly balanced, allowing the upper flange to slide along the shaft with limited friction and without risk of jamming, and further preventing any deflection of the shaft in the long term.

[0029] The invention extends to a negative brake equipped with an actuator according to the invention. More particularly, the invention extends to a negative brake, comprising: - a disc, - a clamp with two jaws framing the disc, - a spring configured to apply a pressing force to at least one of said jaws in the direction of the clamp closing, - an actuator configured to counteract the action of the spring and allow the clamp to open, characterized in that the actuator is an actuator according to the invention, that is to say as described above.

[0030] In some embodiments, the spring and the actuator are separated and arranged in parallel with each other, the piston of the actuator not acting directly on the spring.

[0031] In certain embodiments: - The axial direction of the actuator and the axis of the spring are vertical, while the direction of movement of the brake shoes is horizontal. - the brake comprises an upper rocker arm mounted pivoting around a horizontal axis, and connected to the jaws by a mechanism configured to transform an upward pivoting movement of the rocker arm, respectively downwards, into a horizontal force on the jaws in the direction of opening, respectively closing, said jaws, - the spring has an upper end connected to the balance wheel in such a way as to pull the latter downwards (i.e. in the direction of closing the brake), - the actuator piston includes an actuating rod extending outward from an actuator housing, which actuating rod is connected to the rocker arm (104) so ​​as to push the rocker arm upwards (in the direction of brake opening) when the piston - and therefore the actuating rod - is moved upwards Brief description of the drawings

[0032] The invention, according to an exemplary embodiment, will be better understood and its advantages will become more apparent upon reading the following detailed description, given by way of example and in no way limiting, with reference to the accompanying drawings in which:

[0033] [Fig-1] [Fig.1] represents an example of an embodiment of an actuator according to the invention, seen in perspective with part of its casing torn off, the piston and the upper tulip of the actuator being in the lower position;

[0034] [Fig.2] [Fig.2] shows the actuator of [Fig.1], still in perspective but with the piston and the upper tulip in an intermediate position;

[0035] [Fig.3] [Fig.3] shows the actuator of figures 1 and 2, still in perspective but with the piston and the upper tulip in the high position;

[0036] [Fig.4] [Fig.4] shows the actuator of figures 1 to 3, in perspective and with the piston held in the high position while the upper tulip has moved back down into the low position;

[0037] [Fig.5] [Fig.5] is a perspective view of a disc brake incorporating an actuator according to the invention, which may be that of figures 1 to 4.

[0038] [Fig.6] [Fig.6] represents the disc brake of [Fig.5], seen in perspective from another point of view,

[0039] [Fig.7] [Fig.7] is a perspective view of a drum brake incorporating an actuator according to the invention, which may be that of figures 1 to 4.

[0040] Identical elements represented in the aforementioned figures are identified by identical numerical references. Detailed description

[0041] Figures 1 to 4 represent an actuator 1 according to the invention. This actuator comprises:

[0042] - a casing 2, shown partly transparent and of which a part is torn off on the figures to show the different parts that make up the actuator;

[0043] - an electric motor 3 arranged in the lower part of the actuator; for example, the Motor 3 can be a standard three-phase asynchronous motor, powered by 400V.

[0044] - a shaft 4, which extends along an axial direction Ai of the actuator and is driven rotated by motor 3; in use, particularly when associated with a safety brake of a lifting device, actuator 1 is arranged so that its axial direction Ai is vertical,

[0045] - a piston 5 mounted to slide on the shaft 4, provided with an armature configured to be attracted by the electromagnet 14 described below, and provided with an actuating rod 6 which protrudes from an upper wall 20 of the housing 2;

[0046] - a lower tulip 7, fixed on the tree 5 at a low point thereof, i.e. at proximity of engine 3;

[0047] - an upper tulip 8 mounted sliding on the tree 5 above the tulip in lesser 7;

[0048] - three arms 9 which extend radially, which arms are arranged at 120° to each other others and fixed on tree 4 between the lower and upper tulips;

[0049] - three weights 10, each weight being mounted to slide on one of the arms 9; to To this end, each weight has a central hole through which it is threaded onto the arm 9;

[0050] - an electromagnet 14, represented here in a very schematic way, reference numeral 14 pointing to a frame incorporating a coil (not shown).

[0051] The weights have a dimension along the axial direction that corresponds substantially to the desired stroke for the actuator. This dimension is advantageously on the order of 60 mm.

[0052] For each arm 9, the actuator 1 comprises a lower ramp 11 formed as an extension of the lower tulip 7. When the motor is stopped ([Fig. 1]), the lower ramp 11 extends from the lower tulip 7 to the distal end 90 of the arm. The lower ramp 11 follows a curve inscribed in a longitudinal (vertical) plane comprising the axis of the shaft 4 and the axis of said arm 9; this curve starts from the lower tulip 7 and radiates away from the shaft 4 towards the upper tulip 8 (i.e., upwards in the accompanying figures).

[0053] Similarly, for each arm 9, the actuator 1 comprises an upper ramp 12 formed as an extension of the upper tulip 8. When the motor is stopped ([Fig. 1]), the upper ramp 12 extends from the upper tulip 8 to the distal end 90 of the arm. The upper ramp 12 thus follows a curve inscribed in the longitudinal plane comprising the axis of the shaft 4 and the axis of said arm 9; this curve starts from the upper tulip 8 and radiates away from the shaft 4 towards the lower tulip 7 (downwards in the figures).

[0054] Each weight 10 is also essentially situated in the longitudinal plane comprising the axis of the shaft 4 and the axis of the arm 9 on which the weight is slidably mounted. The weight 10 is embedded between the lower ramps 11 and upper ramps 12 associated with said arm. It has an elongated shape along the axial direction. The length (dimension along the axial direction) of the weight 10 defines the distance between the upper and lower flanges when the actuator is at rest (engine stopped, [Fig. 1]). As will be understood later, the length of the weight also defines the maximum possible stroke of the actuator. The length of the weight also, and above all, allows for an increase in the mass of the weight and thus the force exerted by the actuator. In operation, the actual stroke of the actuating rod 6 depends on the radial distance traveled by the weights 10 on the arms 9.

[0055] At each of its axial ends, the weight 10 comprises a bearing 13 engaged in a rail (not visible) made in the ramp 11 or 12 against which said axial end of the weight rests.

[0056] When the engine is at rest, the weights 10 are pressed against the shaft 4. When the engine is running and the shaft 4 is rotating, the weights 10 are propelled radially outwards by centrifugal force. They then push on the upper ramps 12 and lower ramps 11 to which they are respectively associated, separating the upper tulip 8 (sliding) from the lower tulip 7 (fixed), which causes the piston 5 to move upwards as can be seen in [Fig. 2] and [Fig. 3].

[0057] Figure 3 illustrates the extreme position of the weights 10, when the radial ends of the weights reach the ends of the ramps 11 and 12. The piston 5 is then in a high position, in which its armature is pressed against the upper wall 20 of the housing 2, or rather against the casing of the electromagnet 14, and the actuating rod 6 is in its maximum extended position. The opening of the brake, that is, the movement of the piston from its low position (Fig. 1) to its high position (Fig. 3), takes approximately 200 ms.

[0058] In the event of a power failure while the actuator is in the configuration shown in [Fig. 3], the motor 3 and the shaft 4 stop and the electromagnet 14 is deactivated. No longer subjected to centrifugal force, the weights 10 return to their initial position against the shaft 4 under the effect of their own weight and that of the upper tulip 8. The upper tulip 8 and the piston 5 return to the lowered position, with the actuating rod then in its retracted position, as illustrated in [Fig. 1]. The descent of the piston and the upper tulip 8, slightly slowed by the weights 10, can take up to 300 ms.

[0059] If the motor 3 is stopped while the piston 5 is in the upper position and the electromagnet 14 is active, again, no longer being subjected to centrifugal force, the weights 10 return to their initial position against the shaft 4, under the effect of their weight and that of the upper tulip 8. The actuator may also include a small spring above the upper tulip 8 (this spring can be seen in [Fig.4]) allowing the upper tulip 8 and the weights 10 to descend a little faster. This spring makes it possible to overcome the inertia of the mechanism at the beginning of the downward movement of the tulip and the weights.

[0060] Thus, if the motor is stopped and the electromagnet 14 is activated, the upper tulip 8 returns to the lowered position while the piston 5, held by the electromagnet 14, remains in the upper position as illustrated in [Fig. 4]. The electromagnet therefore makes it possible to stop the motor while maintaining the actuator's force, which prevents the motor from overheating and failing. The electromagnet thus improves the reliability and robustness of the actuator and extends its service life.

[0061] In the event of a power failure while the actuator is in the configuration shown in [Fig. 4], the electromagnet 14 is instantly deactivated and the piston 5 falls under its own weight. Since it is not slowed by the upper tulip 8 and the weights 10, the piston 5 returns to its lower position in a time (called the response time) of approximately 100 ms. If the actuator is connected to a safety brake on a lifting device, the fall of the load carried by the lifting device is thus instantly stopped. The electromagnet 14 therefore also makes it possible to considerably reduce the response time of the actuator and the associated brake.

[0062] If the brake closure is desired during normal operation, i.e., in the absence of an electrical failure, a less abrupt (or even gradual) brake closure can be achieved by deactivating the electromagnet 14 while initially holding the piston 5 in the raised position using the motor 3, and then stopping the motor. A deceleration of the motor (before it stops completely) can even be used to manage the descent of the load.

[0063] Figures 5 and 6 show the actuator of Figures 1 to 4 integrated into a disc brake 100. This brake comprises:

[0064] - a disc 101, intended to be mounted on a braking line (not shown),

[0065] - on either side of the disc 101, jaws 102 parallel to the front faces of the disc 101 and forming a clamp that tightens disc 101,

[0066] - a spring 103, for example a helical spring as illustrated in [Fig.6], configured to push one or both jaws in the direction of brake closure (i.e., one towards the other),

[0067] - actuator 1.

[0068] In the illustrated example, the spring 103 is substantially parallel to the axial direction Aid the actuator, the latter being orthogonal to the working direction A2 of the jaws (i.e., to the axis of the disc 101). It will be readily understood that this design makes it possible to obtain a particularly compact brake, of limited size in the vertical direction.

[0069] Therefore, the brake further comprises a rocker arm 104 and a mechanism capable of transforming an upward and downward pivoting movement of this rocker arm into a movement of the jaws 102 in the direction of opening and closing the brake, respectively. This mechanism is not shown in detail, as those skilled in the art are able to design it using their general knowledge.

[0070] The lower end of the actuator housing 2 is fixed to a brake base 105. Similarly, the lower end of the spring 103 is fixed to said base 105.

[0071] The actuator rod 6 is connected to the rocker arm 104 such that the extension of this rod causes the rocker arm to pivot upwards, i.e., imposes a force on the jaws 102 tending to open the brake. Conversely, the end upper part of the spring is connected to the balance wheel 104 so that the spring (which, in the illustrated example, works in tension) causes the balance wheel to pivot downwards, that is to say, imposes on the jaws 102 a force tending to close the brake.

[0072] The stroke of the actuator 1 makes it possible to counter the action of the spring 103 and to separate the jaws 102 from the disc 101 to open the brake.

[0073] It should be noted that the spring compression depends on the displacement of the actuator rod 6, and therefore on the actuator force, which depends not only on the rotational speed of the motor 3 but also on the stroke of the tulip itself (the closer the tulip gets to the upper position, the greater the centrifugal force will be, and therefore the greater the actuator force will be). Thus, even if the motor is at a steady speed, the force continues to increase with the tulip stroke. Now, in an actuator according to the invention, the tulip can have a greater stroke than in a prior art actuator such as that of GB687222. With the same motor, the actuator according to the invention can therefore develop a greater force than prior art actuators.

[0074] Figure 7 shows a drum brake 200. This brake typically comprises two shoes 202 (which can be likened to the claimed brake shoes) forming a clamp that grips a drum (not shown), and it is notable in that it includes an actuator 1 according to the invention. It will not be described in further detail here, as those skilled in the art can design the mechanism 203 for converting the vertical movements of the actuator rod 6 into forces exerted by the shoes 202 against the drum.

[0075] Since the actuator 1 has no oil circuit, it can be used in very hot environments without risk of fire and in very cold environments without risk of oil solidification.

[0076] Furthermore, its relatively long stroke allows it to generate significant force, enabling its use in a safety brake for lifting equipment designed to lift loads of up to 500 tonnes or more. The use of the actuator's electromagnet 14 allows the brake to remain open without using the motor 3 and to achieve instantaneous closure (in less than 100 ms) of the brake in the event of a power failure.

Claims

Demands

1. Electromechanical actuator (1) comprising: - a motor (3), - a shaft (4) driven in rotation by the motor, - a piston (5), which can be moved along an axial direction (Ai) between a lower position and a high position, - an upper tulip (8), which is mounted to slide on the shaft (4) and bears against the piston (5) when the shaft is driven in rotation, characterized in that it comprises: - a lower tulip (7) fixed on the shaft, - one or more arms (9) extending radially, fixed on the shaft (4) between the lower (7) and upper (8) tulips, - for each of said arms (9), a weight (10) having an elongated shape along the axial direction, said weight being mounted to slide on said arm, - for each of said weights (10), a lower ramp (11) and an upper ramp (12) in contact with the axial ends of the weight,which lower and upper ramps follow curves starting respectively from the lower tulip (7) and upper (8) tulip and moving away from the shaft towards the other tulip, each of the weights being thus interposed between two ramps in order to keep the tulips apart from each other, - an electromagnet (14) for holding the piston (5) in the upper position.

2. Electromechanical actuator (1) according to claim 1, wherein the electromagnet (14) comprises a carcass containing a coil, incorporated in a housing (2) of the actuator, and the piston (5) comprises an armature configured to be attracted by said coil.

3. Electromechanical actuator (1) according to any one of claims 1 or 2, wherein each weight (10) has a bearing (13) at each of its axial ends, configured to cooperate with a rail formed in the corresponding upper or lower ramp (11, 12).

4. Electromechanical actuator (1) according to any one of claims 1 to 3, wherein each of the upper and lower ramps (11, 12) has a stop at its free end, preventing the axial end of the associated weight (10) from disengaging from said ramp.

5. Electromechanical actuator (1) according to any one of claims 1 to 4, wherein the arms (9) are three in number, arranged at 120° to each other

6.

7.

8. of the others around the tree (4), as well as the weights (10), the lower ramps (11) and the upper ramps (12). Negative brake (100; 200), comprising: - a disc (101) or a drum, - a clamp comprising two jaws (102; 202) framing the disc or drum, - a spring (103) configured to impose a pressure force on at least one of said jaws (102; 202) in the direction of closing the clamp, - an actuator (1) configured to counteract the action of the spring and allow the clamp to open, characterized in that the actuator (1) conforms to one of the preceding claims. Negative brake according to claim 6, wherein the spring (103) and the actuator (1) are dissociated and arranged in parallel with each other, the piston (5) of the actuator not acting directly on the spring. Negative brake according to claim 6 or 7, wherein: - the axial direction (Ai) of the actuator (1) and the axis of the spring (103) are vertical, while the direction (A2) of movement of the jaws (102) is horizontal, - the brake comprises an upper rocker arm (104) mounted to pivot about a horizontal axis, and connected to the jaws (102) by a mechanism configured to transform an upward pivoting movement of the rocker arm, respectively downward, into a horizontal force on the jaws in the direction of opening, respectively closing, said jaws, - the spring (103) has an upper end connected to the balance wheel (104) so ​​as to pull the latter downwards, - the piston (5) of the actuator includes an actuating rod (6) extending outward from a housing (2) of the actuator, which actuating rod (6) is connected to the rocker arm (104) so ​​as to push the latter upwards when the piston is moved upwards.

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