SLIDE FLOW DISTRIBUTOR

Abstract

Slide flow distributor (100) comprising a motor (1) moving directly a spool (2) by means of a rod (8) of the motor, a charge chamber (3) of the working fluid, in central position, in fluid communication with two discharge branches (4, 5) and two delivery branches (6, 7) and characterized in that from the portion of the spool (2) proximal to the motor (I) it is provided a pneumatic servo-actuator (9) generating a force in the same direction and development of the axial force of the motor (I), with the result that the spool (2) is accelerated in a predetermined direction, said pneumatic servo-actuator comprising a profiled body (52), a plurality of balls (50) and corresponding elastic means (5 1) which press said plurality of balls (50) on the side surface of the profiled body (52).

Claims

1. A slide flow distributor (100) comprising a motor (1) moving directly a spool (2) by means of a rod (8) of the motor, a charge chamber (3) of the working fluid, in central position, in fluid communication with two discharge branches (4, 5) and two delivery branches (6, 7) and characterized in that from the portion of the spool (2) proximal to the motor (1) it is provided a pneumatic servo-actuator (9) generating a force in the same direction and development of the axial force of the motor (1), with the result that the spool (2) is accelerated in a predetermined direction, said pneumatic servo-actuator comprising a profiled body (52), a plurality of balls (50) and corresponding elastic means (51) which press said plurality of balls (50) on the side surface of the profiled body (52).

2. The distributor (100) according to claim 1, wherein said balls (50) are provided exactly in a number of five and the elastic means (51), whose elastic characteristics are adjustable, are provided exactly in a number of five.

3. The distributor (100) according to claim 1, wherein said profiled body (52) at a first end is coupled to a central rod (53) of the spool (2), and at the opposite end, is coupled to the rod (8) of the motor.

4. The distributor (100) according to claim 1, wherein said servo-actuator (9) comprises also two main chambers, an inlet chamber (54) and a storage chamber (55) of air, separated by a seal (56) positioned at the right end of the central rod (53), and said inlet chamber (54) of air contains the central rod (53) of the spool (2).

5. The distributor (100) according to claim 1, further comprising a sized discharge channel (57), which allows the air provided in the storage chamber to be vented to the environment.

6. The distributor (100) according to claim 3, wherein said central rod (53) of the spool (2), profiled body (52) and rod (8) of the motor are coupled to the movement of the spool (2) when the axial force of the motor (1) does not exceed a predetermined threshold (F.sub.thr).

7. The distributor (100) according to any one of claims 3, wherein said spool (2) is decoupled said central rod (53) of the spool (2), profiled body (52) and rod (8) of the motor when the axial force of the motor (1) exceeds said predetermined threshold (F.sub.thr).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] These and other advantages of the invention will be described in the following in more detail with reference to the appended drawings, in which:

[0016] FIG. 1 shows a preferred embodiment of the slide flow distributor;

[0017] FIG. 2 shows a scheme of the forces and the electric power used by a flow distributor with servo-actuator;

[0018] FIG. 3 shows a preferred embodiment of the servo-actuator;

[0019] FIG. 4 shows a preferred embodiment of the system made up of central rod of the spool, profiled body and motor rod of the servo-actuator;

[0020] FIG. 5 shows a preferred embodiment of the system made up of the spool and the various components of the servo-actuator integral thereto;

[0021] FIG. 6 shows a detail of the Dx end of the spool in opening step of the pneumatic servo-actuator;

[0022] FIG. 7 shows a detail of the Sx end of the spool in closing step of the pneumatic servo-actuator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] As it is shown in the appended figures, object of the present invention is a slide flow distributor

[0024] 100 comprising a motor 1 moving directly a spool 2, this latter having a plurality of holes 2′, a central charge chamber 3, two downwards discharge branches 4, 5 and two upwards delivery branches 6,

[0025] 7 and a pneumatic servo-actuator 9 positioned in the portion of the spool 2 nearer to the motor 1.

[0026] With reference to FIGS. 3-7, according to a preferred embodiment, the servo-actuator 9 represented in FIG. 3 comprises various components, arranged between the spool 2 and the motor 1. In particular, there are provided five balls 50 pressed on the side surface of a profiled body 52 by means of five pre-loaded and adjustable elastic means 51. The profiled body 52 makes integral the central rod 53 of the spool 2 with the rod 8 of the motor 1, and thanks to the elastic means 51, makes the whole system integral to the spool 2 by means of said balls 50.

[0027] In addition, the servo-actuator 9 comprises two main chambers, an inlet chamber 54 and a storage chamber 55 of air, separated by a seal 56 positioned on the right of the central rod 53. Said inlet chamber 54 of air contains the central rod 53.

[0028] Moreover, it is provided a sized discharge channel 57, which allows the air provided in the storage chamber 55 to be vented to the environment.

[0029] As it is shown in FIG. 4, the central rod 53, the profiled body 52 and the rod 8 of the motor 1, can be considered a first system, while the spool 2 and the various components integral thereto and shown in FIG. 5 can be considered a second system.

[0030] In particular, in order to describe the functioning of the servo-actuator 9 two configurations are described separately: the one in which the servo-actuator system is not actuated and so the first system is integral to the second system, and the one in which it is actuated and there is a relative displacement between first and second system.

[0031] The FIG. 2 shows a diagram having the control electric current I on the x axis and the force F acting on the spool on the y axis. The first section of curve 200 represents the distributor characteristic when only the linear electric motor (VCM) acts. The second section of curve 210 represents the characteristic of the distributor in presence of the activation of the pneumatic servo-actuator. As it is clear from said graph, the system is able to move the spool without the help of the servo-actuator, however the presence of this latter improves its performances definitely.

[0032] The configuration in which the servo-actuator is not actuated is shown in FIG. 3, in which it is represented the right end of the spool 2. The configuration in which the servo-actuator is actuated is shown in FIGS. 6 and 7, wherein in FIG. 6 it is represented the opening configuration of the pneumatic servo-actuator 9 at the right end of the spool 2 and wherein in FIG. 7 it is represented the closing configuration of the pneumatic servo-actuator at the left end of the spool 2.

[0033] In the configuration in which the servo-actuator system 9 is not actuated, the force exchanged by the first system results lower than a certain threshold value F.sub.thr and therefore the forces exerted by the elastic means 51 cause the balls 50 not to go out from their grooves. In this way, the first system remains rigid and integral to the second system.

[0034] Naturally, the threshold value F.sub.thr depends on the preload of the elastic means 51, on their characteristic of stiffness and on the shape of the section of the profiled body 52. The regulation of such parameters allows to modulate the threshold value F.sub.thr according to the needs, and so, as a consequence, to actuate the servo-actuator 9 or not.

[0035] Vice versa, in the configuration in which the servo-actuator system is actuated, the forces increase exceeding the threshold value F.sub.thr and a relative little movement between the first and the second system is obtained.

[0036] The functioning of the system implies that the motor 1 generates an axial force able to thrust leftwards the first system. So, such force tends to press the left seal 66 of the central rod 53 and to release the right one 56, which does not guarantee the sealing any more (FIG. 6). In this way, there is opened a passage for the air towards the right head of the spool (indicated by the arrows in FIG. 6).

[0037] Besides being allowed by the no more sealing right seal 56, the communication between the storage chamber 55 (under pressure) and the inlet chamber 54 of the right head of the spool 2 is allowed also by other holes provided in the remaining components of the second system (indicated by the arrows in FIG. 6).

[0038] During such a step, the storage chamber 55 is always supplied and the sized channel 57 is not able to dispose of the exceeding air flow rate thus causing an increase in inner pressure of the same storage chamber 55. In such a condition, the air pressure on the surface of the right head of the spool 2 generates a force in the same direction and development of the initial axial force of the motor 1 (white arrows in FIG. 6) with the result that the spool 2 is accelerated in the desired direction (leftwards in this case). Once the resisting force is won, the balls 50 acting on the slanted plane of the profiled body 52 bring the second system (so the spool) to be integral to the first system (so to the motor) again. The seal 56 will be sealing again, the storage chamber 55 will not be supplied any more and the stored air under pressure will be discharged gradually to the environment through the sized channel 57, so that the axial components of the forces acting on the spool will be brought in balance again.

[0039] In the opposite moving direction of the spool 2 (so rightwards), at the left end of the spool 2, it happens that the seal 66 of the central rod 53 of the spool 2 is no more sealing, thus putting in communication the inlet chamber 54 with the storage chamber 67 (FIG. 7). Naturally, also the storage chamber 67 of the spool 2 is in communication with the environment through a sized channel (of known kind and therefore not shown in FIG. 7).

[0040] Another embodiment of the pneumatic servo-actuator allows the charging and discharging step in each one of the ends of the spool to be managed separately. In particular, during the opening step of the servo-actuator mechanism, the relative movement of the first system with respect to the second system always allows the chamber of the right head of the spool to be supplied, but it closes the discharge channel towards the environment, characterized in this case by an enlarged section. During such step the chamber of the left head is not supplied but the relative discharge channel is opened, thus favouring the air previously stored to be discharged. The same goes obviously for the opposite movement direction of the spool.

[0041] Therefore the most mechanic complication leads to a yet higher dynamics of the forces on the spool since the system provides for the rapid reduction of the pressure at the end on the spool opposite to the one under pressure. Moreover, the end under pressure results faster in going under pressure since, during the charging step of the respective chamber, the sized channel does not dispose of the air flow rate to the environment.

[0042] In addition to the embodiments of the invention, as just described, it is clear that many other variants are possible. It is also to be intended that said embodiments are only example and do not limit the object of the invention, its applications or possible configurations. On the contrary, while the above description allows the experts in the field to carry out the present invention at least according to a configuration example thereof, it is to be intended that many variations of the described components are possible, without departing from the scope of the invention, as defined in the appended claims, literally interpreted and/or according to their legal equivalents.