The invention relates to a telescopic actuator with a main rod and an auxiliary rod. More precisely, the invention relates to controlling the extension and the program of the auxiliary rod from the cylinder of the actuator.
A telescopic actuator is known that comprises a main rod and an auxiliary rod, the actuator essentially comprising a cylinder, slide means between the cylinder and the main rod, and slide means between the main rod and the auxiliary rod, thereby enabling the rods to slide between retracted and extended positions.
The actuator also includes retaining means enabling the auxiliary rod to be blocked or released in the main rod, and brake means for braking said auxiliary rod while it is being extended. An example of this type of embodiment is described in particular in document FR 2 895 483 A1.
This type of actuator is particularly advantageous since, in the event of the main rod becoming blocked, it makes it possible to continue lengthening the actuator by causing the auxiliary rod to be released by the retaining means, thereby unblocking the movement of the mechanical system in which it is included.
With reference to
The main rod 2 is hollow and defines a cavity in which an auxiliary rod 20 is mounted to slide inside the main rod 2 along the axis X and to project through an open end thereof that forms a bearing.
The actuator further includes controlled retaining means for retaining the auxiliary rod 20 in its retracted position inside the main rod 2. These retaining means comprise:
The actuator further includes brake means for braking sliding of the auxiliary rod 20 in the main rod 2 in the direction for extending the auxiliary rod 20.
These brake means, which also form a bearing 21 for guiding the auxiliary rod 20 in the main rod 2, comprise:
An object of the invention is to propose a telescopic type actuator having main and secondary rods in which the control and the braking of the auxiliary rod are both simplified and improved.
To this end, the present invention relates to a telescopic actuator comprising a cylinder receiving a main rod to slide along a sliding axis between a retracted position and an extended position, the actuator further including an auxiliary rod slidable in the main rod between a retracted position and an extended position, and a rotary bearing carried by the main rod or the auxiliary rod and co-operating respectively with the auxiliary rod or the main rod via a reversible helical connection such that sliding of the auxiliary rod causes the rotary bearing to rotate.
According to the invention, the actuator includes retaining means for retaining the sliding of the auxiliary rod and comprising a blocking member arranged to act directly on the rotary bearing so as to cause rotation of the rotary bearing to be blocked or to be released, blocking rotation of the rotary bearing preventing the auxiliary rod from moving in the main rod.
Thus, the actuator is considerably simplified compared with the state of the art. This characteristic makes it possible to reduce the weight of the actuator and to reduce its cost price since, in particular, the blocking and the release of the auxiliary rod by the blocking member do not require the use of a special motor.
According to an advantageous characteristic of the invention, the retaining means also include passive type brake means adapted to brake rotation of the rotary bearing when the auxiliary rod is sliding, the retaining means thus serving to perform functions both of controlling and of braking the extension of the auxiliary rod.
Other characteristics of the invention appear clearly on reading the following description of an embodiment given by way of non-limiting example.
Reference is made to the accompanying figures in which, in addition to above-described
To facilitate reading and understanding
A first difference between the actuator of the invention and the prior art actuator lies in how the auxiliary rod 20 is controlled and braked, with the retaining means in the invention serving to block the auxiliary rod 20 in the retracted position by preventing the rotary bearing from rotating.
In the invention, the auxiliary rod 20 includes a thread 101 on its outside surface. The main rod 20 receives a bearing 102 that is mounted to rotate on the main rod 2 by rolling means 103 and 104. The rotary bearing 102 is connected to the auxiliary rod 20 via a reversible helical connection by means of threaded satellite rollers 105 extending between the auxiliary rod 20 and the rotary bearing 102 so that extending the auxiliary rod 20 causes the rotary bearing 102 to rotate. Sliding retaining means 112 act on the rotary bearing 102 either to block the auxiliary rod 20 via a blocking member 116, or to brake it via brake means 117.
Advantageously, the blocking member 116 is constituted by a brake. By an electromagnetic brake with a moving armature 113 mechanically connected to the nut body 114 and a stationary yoke 115 carrying a coil, the yoke 115 being connected to the cylinder 1 and prevented from moving axially or in rotation relative to the auxiliary rod 20. In the embodiment of
Conversely, when the brake 116 is deactivated, the nut body 114 is free to turn and enables the bearing 102 to rotate, thereby releasing the auxiliary rod 20. The blocking member 116 thus acts directly on the element (the rotary bearing) that is in helical connection with the auxiliary rod 20.
Various technologies can be used for making the brake member 116, in particular it may comprise an electromagnetic brake 116 that brakes when drawing electricity or indeed when not drawing electricity, and/or a single- or multi-disk brake, or indeed a positive blocking member such as a jaw clutch or a gear clutch.
The brake means 117 and the auxiliary rod 20 are advantageously of the passive type, and they act on the rotary bearing 102 to brake rotation thereof. More precisely, the brake means 117 comprise:
The rotor 106 and the stator 110 interact magnetically such that when the rotary bearing 102 and thus the rotor 106 rotate, an opposing electromagnetic torque is established that tends to brake the rotation of the rotary bearing 102, and thus to brake the extension of the auxiliary rod 20. These magnetic brake means are purely passive and they exert a braking force on the auxiliary rod 20 that is proportional to the speed of rotation of the rotary bearing 102, and thus to the speed at which the auxiliary rod 20 is being extended.
The brake means 117 thus act directly on the element (the rotary bearing) that is in helical connection with the auxiliary rod 20.
Naturally, other embodiments within the competence of the person skilled in the art could equally well be envisaged without thereby going beyond the ambit of the invention as defined by the following claims. For example, in one possible embodiment, the blocking member 116 could serve simultaneously to perform a blocking function and a braking function on the auxiliary rod 20. For this purpose, a blocking member could be provided that includes a disk brake suitable for providing proportional braking of the rotary bearing 102.
Furthermore, although the rotary bearing described is the end bearing of the main rod, which bearing is prevented from rotating in order to keep the auxiliary rod stationary in the main rod, it would naturally be possible, and in accordance with the invention, to use the same strategy to brake the rotary bearing 22 of the embodiment shown in
Number | Date | Country | Kind |
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FR 08 05272 | Sep 2008 | FR | national |