The present invention relates to pressurized fluid distributors which are used to enable one or more downstream devices, operating with a pressurized fluid, to be controlled by means of a manually maneuvered member.
More particularly, the invention relates to hydraulic manipulators intended to provide control of different hydraulic functions of a public works vehicle, for example.
There is a known fluid distributor, disclosed in WO-96/30652 in particular, of the type comprising:
In these fluid distributors, a first drawback lies in the possibility of the undesired disengagement (also called “tear-out”) of the armature from the means forming the solenoid. This is because, when public works vehicles are traveling on site, a distributor mounted on such a vehicle is subjected to accelerations and decelerations which give rise to tear-out forces in the armature which exceed the attractive force exerted on the armature by the magnetic field. This is accentuated by the inertia of the control member.
A second drawback lies in the fact that the operator may not be required to perform an action with a predetermined force on the control member at the time of the tear-out. Therefore he will not know exactly when the armature has become disengaged from the solenoid.
These drawbacks are due to the fact that the armature is generally fixed rigidly to the push rod in such a way that it has no degree of freedom in rotation about horizontal axes. Consequently, in a tear-out, the armature is only in contact with the solenoid over a part of the bearing surface, so that the attractive force of the magnetic field on the armature decreases to an unknown value which is smaller than the predetermined force.
The object of the present invention is, in particular, to overcome these drawbacks by providing a fluid distributor in which the disengagement of the armature from the solenoid can only occur as a result of a force maintained at a predetermined level, this object being achieved by simple, efficient and inexpensive means.
For this purpose, according to the invention, a fluid distributor of the aforesaid type is essentially characterized in that it additionally comprises means for fastening the armature to the finger, these means delimiting a window in which the finger projects substantially transversely; in that the push rod is mounted so that it passes with a clearance into the armature and projects into the window; and in that the finger is interposed between the fastening means and the push rod.
By these arrangements, the armature is suspended under the finger of the control member, in such a way that the number of degrees of freedom of the armature is increased. Thus, when this armature is disengaged from the solenoid, it is free to shift with respect to the surrounding components, in such a way that the armature remains in contact with the whole surface of the means forming the solenoid. The magnetic attractive force exerted on the armature therefore remains at a constant predetermined level.
In a preferred embodiment, the fastening means and the armature jointly delimit the window.
Preferably, the fastening means comprise a stirrup which delimits the upper jamb and the side walls of the window, the lower jamb of the window being delimited by the armature.
It is also preferable for the finger to be in point contact with the upper jamb of the window.
In a variant, the finger has a spherical tip on which the upper jamb of the window bears.
Preferably, the armature comprises a washer made from ferrous material.
In a variant, the stirrup is overmolded on the washer.
In yet another variant, the stirrup and the armature are formed in one piece.
In yet another variant, the upper jamb and the side walls are joined to the washer by screwing.
In this case, the side walls are preferably made in the form of open channels in which screws are housed.
Other characteristics and advantages of the invention will be made clear by the following description of four embodiments thereof, provided by way of example and without restrictive intent, with reference to the attached drawings, in which:
A pressurized fluid distributor, and more particularly a hydraulic manipulator, is shown in
The pressurized fluid distributor comprises at least one pressure reducing valve 2. Preferably, as in the case of hydraulic manipulators currently used for public works vehicles, it is provided with four pressure reducing valves which are identical to each other. Only two of these pressure reducing valves are shown in
Each pressure reducing valve 2 comprises a plunger 3 which can move in a cavity 4 formed in the body 5 of the distributor.
As is well known in the field, the pressure reducing valve is calibrated by an operator who acts on a control member 6 (partially shown in
The cavity 4 has one end 9 opening on the face 8 of the body 5. The control member 6 also has a finger 10 extending from the joint 7 to project substantially perpendicularly to the plunger 3 mounted in the cavity 4.
The pressure reducing valve comprises, in a known way, a push rod 11 and a control spring 12, in such a way that, under the action of the control member 6, the push rod 11 has a reciprocating translational motion within the cavity 4 at the open end 9 of this cavity.
Therefore the control member 6 enables the position of the push rod 11 to be modified in order to calibrate the pressure reducing valve, and thus to control the pressure delivered by the distributor to the upstream device (not shown).
The operation of such a fluid distributor is well known to those skilled in the art, and is described, for example, in FR-2 376 978, FR-2 507 732 and FR-2 781 846.
Additionally, as is also well known to those skilled in the art, the pressurized fluid distributor has means forming a solenoid 15 interacting with an armature 16 to lock the push rod 3 in a predetermined position.
The means forming a solenoid 15 consist, for example, of a coil. This coil is mounted in the body 5 substantially coaxially with the push rod 11. One end of this coil opens on the face 8 of the body 5 to form a bearing surface 17 which is substantially coplanar with this face. This bearing surface 17 can also be set back slightly from the face 8, while being substantially parallel to this face. The coil 15 thus delivers a magnetic field in a direction substantially parallel to the direction of translation of the push rod 11.
The armature 16 can be moved in translation simultaneously with the push rod 11 and is made from a material, such as a ferrous material, which is sensitive to the magnetic field. This armature has a contact surface 18 which faces the bearing surface 17, so that it bears on this bearing surface 17 in a predetermined position of the push rod 11. In this position, the push rod is thus locked with a predetermined attractive force between the armature and the coil.
According to an essential characteristic of the present invention, the fluid distributor 1 also has means 20 for fastening the armature 16 to the finger 10 of the control member 6. These fastening means enable the armature 16 to be made to move together with the finger 10, in such a way that the armature 16 is mounted by a form of suspension under the finger 10. Consequently this armature has five degrees of freedom, to keep its contact surface 18 constantly parallel to the bearing surface 17 of the coil, regardless of a possible slight misalignment between the axis of the push rod 11 and the direction of the force exerted by the finger 10 on the fastening means 20 during the movement of the push rod.
For this purpose, the fastening means 20 are located on the opposite side of the armature 16 from the face 8 of the body 5. These fastening means 20 (
The finger 10 is placed in the window substantially transversely with respect to it, so that it is interposed between the fastening means 20 and the push rod 11. The push rod 11 is fixed with respect to the finger 10 with regard to translation, for example by means of a circlip 22 mounted to bear on the armature 16, inside the window 21.
As shown more particularly in
To enable the armature 16 and the stirrup 25 to swing around the finger 10, the stirrup 25 is in point contact with the finger 10 at the upper jamb 26 of the window 21. The finger 10 therefore has a spherical tip 30. More particularly, this tip is hemispherical for example, so that the upper jamb 26 bears virtually with a point contact on the spherical part of the tip 30. Similarly, the push rod 11 bears on the tip 30 with a point contact, opposite the contact between the tip 30 and the upper jamb 26.
The armature 16 takes the form of a washer, for example.
As shown more particularly in
In yet another variant, the stirrup 25 is fixed to the washer 16 by screwing, as shown in
In the variant shown in
In yet another variant shown in
Clearly, the invention is not limited to the examples described above, and various modifications can be made to it without departure from the scope of the present invention.
Number | Date | Country | Kind |
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02/13689 | Oct 2002 | FR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/FR03/03209 | 10/28/2003 | WO | 4/15/2005 |