The present invention relates to a linear actuator which can transmit tractive forces and also thrust forces, in that case behaving as a unitary rigid bar
Thrust chains suitable for performing this function have already been proposed. Thrust chains of this type have already been described, for example, in the documents FR-1 297 285 and FR-2 061 884.
These chains are conventionally constituted by a series of links articulated to one another by means of pins that are arranged transversely.
Each link comprises two substantially parallel flanges which are pierced, respectively, by two holes for receiving the articulation pins and each of which is equipped with an extension defining a front transverse active face and a rear transverse active face which are caused to bear against the rear and front transverse active faces, respectively, of the flanges of the adjacent links when the portion of chain of which the links in question form part extends along a straight line.
Thrust chains of this type are driven, in the region of a curved end, by a device comprising a casing, a rotary pinion which has its axis parallel to the articulation pins of the links and is mounted in the casing and on which the chain is wound, as well as idle rollers for guiding the links of the chain around the rotary pinion.
Thrust chains of this type can transmit tractive and thrust forces in a satisfactory manner in any direction, including upwards, but have a fundamentally sophisticated configuration.
Moreover, these thrust chains are suitable purely for actuating “heavy” mechanical parts and, up to now, a similar device which is designed to enable changes in direction to be performed in small automatic mechanisms has never been proposed.
The object of the present invention is to fill this gap by proposing a linear actuator of the above-mentioned type which is characterized in that it comprises two identical actuating bolts which are toothed on each of their faces and are provided, on a first of their faces, with uniformly-spaced studs which mesh by means of drive members in a manner such that the two actuating belts are independent upstream of the drive members whereas, downstream of those members, they are assembled integrally so as to define a portion which extends along a straight line and in which the linear actuator behaves as a unitary rigid bar.
These actuating belts are preferably made of a flexible, reinforced plastics material and thus correspond to simple and inexpensive elements also having the advantage that they can be manufactured by moulding in a single piece.
According to a preferred characteristic of the invention, the drive members are constituted by a casing enclosing two rotary pinions, that is, a drive pinion and a driven pinion, which engage one another and drive two endless caterpillar-type bands mounted on one side and on the other side of the actuating belts, respectively, and equipped on their outer faces with teeth which cooperate with the teeth situated on the second faces of those belts and are fitted between those teeth so as to translate the belts whilst squeezing them against one another so that their facing studs engage one another.
According to the invention, the casing of the drive members also contains guide surfaces for the actuating belts, which guide surfaces are designed to enable the belts to bend in the region of the endless caterpillar-type bands in order to cause them to face one another so that their respective studs can engage one another.
According to another characteristic of the invention, the studs of the actuating belts comprise two side faces as well as a front transverse active face and a rear transverse active face each having a double curvature.
The front and rear transverse active faces of a stud of one of the actuating belts are caused to bear against the respective rear and front transverse active faces, respectively, of two associated adjacent studs of the other actuating belt when the two actuating belts are assembled integrally.
It is essential, in order for the linear actuator according to the invention to be able to perform its function, that the linear portion defined by the two actuating belts when they are assembled integrally should not include “voids” and, therefore, that the geometry of the actuating belts should be such that the shape and dimensions of the spaces between the studs should be identical to those of the studs.
According to another characteristic of the invention, the front and rear transverse active faces of the studs comprise a double shoulder forming an abutment.
These shoulders prevent any transverse sliding of the adjacent studs relative to one another when the two actuating belts are assembled integrally.
According to another characteristic of the invention, the front and rear transverse active faces of the studs are separated by a substantially rectilinear, toothed longitudinal face.
The teeth of the longitudinal face of a stud of one of the belts are caused to cooperate with corresponding teeth of the section of the first face of the other belt situated between the two studs associated with that stud, whilst being fitted between those teeth, when the two actuating belts are assembled integrally.
As a result, in this position, the faring first faces of the two actuating belts are intimately engaged over their entire length.
According to another characteristic of the invention, the two rotary pinions are extended coaxially by respective toothed extensions of smaller diameter cooperating with respective idle auxiliary gears of the same diameter so as to drive the endless caterpillar-type bands.
According to the invention, the casing of the drive members may also advantageously contain at least a pair of positioning rollers having axes substantially perpendicular to the axes of the rotary pinions and engaging on one side and on the other side of a linear portion of the actuator defined by the two integrally assembled actuating belts, against the side faces of the studs of those belts.
The characteristics of the linear actuator of the invention will be described in greater detail with reference to the appended drawings, in which:
In the lower portion of
A first face 10, 10′ of the actuating belts 1 is also equipped with uniformly-spaced studs 2, 2′ which are separated by toothed sections 5, 5′.
Each stud 2, 2′ comprises two side faces 6, 6′ as well as a front transverse active face 7, 7′ and a rear transverse active face 8, 8′ having a double curvature.
The front and rear transverse active faces 7, 7′, 8, 8′ of the studs 2, 2′ are separated by a substantially rectilinear toothed longitudinal face 20, 20′.
As can be seen in particular in
The rotary pinions 13, 13′ equipped with the toothed extensions 15, 15′ and the auxiliary gears 17, 17′ also rotate two endless caterpillar-type bands 18, 18′ the inner faces of which art equipped, for this purpose, with teeth corresponding to the teeth of the extensions 15, 15′ and of the auxiliary gears 17, 17′.
These two endless bands 18, 18′ are caused to sandwich the two actuating bolts 1, 1′ between them in order to guide the belts and translate them in one direction or in the other, according to the direction of rotation of the drive pinion 13.
For this purpose, the outer faces of the two caterpillar-type endless bands 18, 18′ also have teeth 21, 21′ which can engage the teeth 4, 4′ situated on the second faces 11, 11′ of the two actuating belts 1, 1′ in order to translate the belts in accordance with the arrows A, B and B′.
In the region of these bands, the actuating belts 1, 1′ are squeezed against one another so that the studs 2, 2′ mesh with one another and the two belts 1, 1′ are assembled integrally in a portion extending along a straight line.
For this purpose, the front and rear transverse active faces 7, 7′, 8, 8′ of the studs 2, 2′ of one of the actuating belts 1, 1′ bear, respectively, against the rear and front transverse active faces 8′, 8, 7′, 7 of the two associated adjacent studs 2′, 2 of the other actuating belt 1′, 1′ and the teeth 4, 4′ of the longitudinal faces 20, 20′ of the studs 2, 2′ of one of the actuating belts 1, 1′ engage, respectively, in the corresponding teeth of the respective section 5′ 5 of the other actuating belt 1′, 1 separating the two associated adjacent studs 2′, 2, so that the two actuating belts are fitted together perfectly to define a unitary rigid bar.
In this position, the double abutment shoulders 9 provided on the transverse active faces 7, 7′; 8, 8′ prevent any transverse sliding of the adjacent studs 2, 2′ relative to one another.
Naturally, when the drive pinion 13 turns anticlockwise, the displacement of the studs 2, 2′ of the two actuating belts 1, 1′ takes place in the opposite direction, that is, the studs enter the casing 12 fitted together and are separated at the level of the two caterpillar-type endless bands 18, 18′.
Moreover, and according to
Each of these pairs is constituted by a combination of two positioning rollers 22 1, 22 2 of axis Y-Y′ perpendicular to the axes X-X′ of the rotary pinions 13, 13′.
These positioning rollers 22 1, 22 2 engage against the side faces 6, 6′ of the studs 2, 2′ in order to ensure the correct positioning of the actuating belts 1, 1′ when they are fitted together.