US3319950A - Primary stage for hydraulic distributor - Google Patents

Description

May 16, 1967 R. LUCIEN 3,319,950

PRIMARY STAGE FOR HYDRAULIC DISTRIBUTOR Filed Feb. 18, 1965 3 Sheets-Sheet 1 i Y I W I 6 4 7 5 l i I l May 16, 1967 R. LUCIEN PRIMARY STAGE FOR HYDRAULIC DISTRIBUTOR 3 Sheets-Sheet 2 Filed Feb. 18, 1965 J\ \\N| m kw R k m. fi M wm N W .7 MN w .wv u m mv ax w m EN mm b mm Wm QQ N m GE y 6, 1967 R. LuclEN 3,319,950

PRIMARY STAGE FOR HYDRAULIC DISTRIBUTOR Filed Feb. 18, 1965 3 Sheets-Sheet 5 United States Patent 3,319,950 PRIMARY STAGE FOR HYDRAULIC DHSTRIBUTGR Rene Lucien, 56 Blvd. Maillot, Neuilly-sur-Seine, France Filed Feb. 18, 1965, Ser. No. 433,758 Claims priority, application France, July 17, 1961, 868,053, Patent 1,302,520 7 Claims. (Cl. 267-1) This application is a continuation-in-part application of my earlier application, 'Ser. No. 164,094 filed an. 3, 1962, now abandoned.

This application relates to improvements in hydraulic distributors.

More particularly, the present invention relates to hydraulic distributors with two stages, of the type in which the primary stage comprises a torque motor, the rotor of which is connected by a rigid shaft operable in rotation, to a blade controlling the flow-rate of two or four jets, the said rigid shaft being in turn mounted in the interior of a torsion tube insuring the threefold function of a support, of applying a torsion restoring force, and of sealing the chamber of the jets and the torque motor.

In these devices, especially when they have two jets, it is necessary, for the regularity of operation, to eliminate or neutralize the shear stresses due to the jets, since these stresses are liable to cause a stray bending of the torsion tube.

A similar problem arises also in connection with the elimination of the effect of parasitic vibrations to which the blades may be exposed.

Various structures have been proposed, which may be capable of meeting the general problem explained above. But when these structures, in accordance with present requirements of the art, are to have substantially reduced dimensions, they are no longer able to solve the problem in question, for two reasons each of which has an adverse influence on the other. On the one hand, the shear stresses must be suppressed in a particular manner, owing to the very reduction of the dimensions of the structural members while on the other hand, certain known constructions, which already extend the field of use toward small dimensions by locally reducing the end sections of said rigid shaft, suddenly and abruptly cease to be physically realizable, as will be shown below.

More precisely, the invention provides a field of use extending more miniaturization to micro-miniaturization. For example, the torque motor is electrically controlled and is actuated by a current of the order of milliamperes, while the displacement of the blade with respect to one of the jets is of the order of hundredths of a millimeter. The diameter of the rigid shaft is of the order of fivetenths of a millimeter. It goes without saying that structural configurations of the above size exclude from the outset the well known use of ball bearings (also excluded due to friction) for supporting the rigid shaft, and yet, said shaft must be mounted, at each of its ends, both rigidly with respect to fiexure and as flexibly as possible in rotation (for very small angles).

In order to meet these two essential requirements, it is known in US. Patent 2,835,265 to locally reduce, by machining, the section of the rigid shaft adjacent its end. It will be noted that, in the field of use provided by the invention, the diameter of the rigid shaft is of the order of five-tenths of a millimeter and that a machining for reducing the diameter appreciably and locally over about two millimeters of length is impossible in ractice. For example, it is impossible to avoid the notch effect and the concomitant risk of rupture due to stress concentration. It is also known in US. Patent 2,905,871 to locally form a shape of cruciform section in the rigid shaft adjacent its end. Such a cruciform section, when employed in the field of use provided by the invention, would require that the thickness of the arms of the cross be less than one-tenth of a millimeter, which is impossible to realize locally over about two millimeters of length of a shaft of about five-tenths of a millimeter in diameter. In particular, the relative value of the minimum tolerances necessary for such machining become unattainable. On the other hand, it will be noted that the above two patents necessarily employ the same material for the rigid shaft and for its reduced or cruciform section. The shaft must have a relatively high modulus of elasticity and this is inconsistent with the high torsional flexibility required at the reduced and cruciform sections.

In view of the foregoing, it is an object of the invention to provide a structural configuration of the primary stage of a torque motor, which permits elimination of the shear stresses and insures insensibility to vibrations by means which are compatible with the reduction of the dimensions in the field defined by the above-mentioned approximate values.

In accordance with the invention each end of the rigid shaft is secured by a rod of relatively small dimension in relation to those of the rigid shaft, said rods being embedded in the ends of the rigid shaft and in fixed structure, said rods being constituted of a material having a comparatively low modulus of elasticity.

It will be noted that in accordance with the invention the rigid shaft is constituted of a material having a high modulus of elasticity while the rods are of low modulus of elasticity which enables obtaining torsional flexibility at the ends of the shaft which is otherwise rigid whereby there is avoided the above-mentioned inconsistency in the known devices.

Further advantages of the invention will become more clearly apparent from the description which follows with reference to the accompanying drawing given by way of non-restrictive example, wherein:

FIGURE 1 is a diagrammatic axial section on a very much enlarged scale of the rotor of the primary stage of a distributor according to the invention;

FIGURES 2 and 3 are axial sections taken along lines IIII and III-III, on an enlarged scale, of a distributor according to the invention in which the secondary stage is diagrammatically outlined but not shown in detail; and

FGURES 4 and 5 are cross-sections taken along lines IVIV and VV at the level of the electromagnetic blade and at the level of the hydraulic blade respectively.

FIG. 1, which relates to a primary stage with two jets, shows a magnetic blade 1 adapted for oscillating about the axis XX in the air-gaps of a magnetic circuit under the elfect of the control currents passing through two windings (not shown). Said magnetic blade is coupled by a rigid shaft 2 to the hydraulic blade 3, the extremities of which are located in front of the two jets 4 and 5 respectively, at which terminate the piping systems serving the secondary stage (not shown). The torsion tube 6 surrounds the rigid shaft 1 and is secured, at one of its extremities, in the flange or fixed structure 7, or alternately it forms an integral portion of said structure. A screw 8 joins together the magnetic blade 1, the rigid shaft 2, and the torsion tube 6.

This type of primary stage operates as follows:

When a variation in current is produced in one of the windings, an electromagnetic couple force is applied to the blade 1, which causes the same to rotate against the action of the elastic restoring force of the torsion tube 6. The rotation of blade 1 causes rotation of tube 6 at the end thereof opposite fixed structure 7, which thereby also causes rotation of shaft 2 by virtue of the connection provided by screw 8. The rigid shaft 2 rotates the blade 3 which causes this blade to thus approach one of the jets while moving away from the other. In consequence, the pressure losses in the pipings terminating at these jets become unbalanced, and this results in a differential control pressure at the secondary stage. It is essential according to the invention that the angular rotation which the blade 3 undergoes must be in precise relationship wtih the magnetic blade 1. Hence, the requirement for substantial rigidity of the shaft 3. However, at the same time it is essential that the shaft 2 have as high a torsional flexibility as possible.

According to the invention, two rods 9 and 10 are each fixed, on the one hand, in the extremities of the rigid shaft 2 and, on the other hand, in the fixed portions 11 and 12 of the stationary structure. The rods may also be fixed by brazing. They are of small diameter so as to offer only a small stiffness in torsion, while they are of small length in order to have a great rigidity in bending.

Moreover, since it is necessary, in order to obtain maximal dynamic performance, that the stiffness in torsion of each rod 9 and 10 be as small as possible, it is expedient that the material of said rods have a very low modulus of elasticity whereby the rods constitute torsion axles. On the other hand, the rigid shaft 2 which firmly connects the magnetic blade 1 and the hydraulic blade 3 has a relatively small diameter, since said diameter is dictated by the size of tube 6 within which it is accommodated, said torsion tube 6 being in turn, of a small diameter in order to provide great flexibility in torsion. But in spite of said small diameter, the rigid shaft 2 must be rigid in torsion, in order to prevent an angular displacement of one blade in relation to the other, which would bring about a loss of efficiency in the control and might introduce objectionable parasitic natural frequency. It is therefore necessary that the rigid shaft 2 be constituted of a material having as high a modulus of elasticity as possible. As already stated above, the structural arrangements in US. Patents 2,835,265 and 2,905,871 are not applicable to the present device because these patents employ the same material for the rigid shaft and for its reduced or cruciform sections. In contrast thereto, the device of the invention is constructed and arranged to employ different materials for the rigid shaft 2 and for the rods 9 and 10 to enable the shaft and the rods to satisfy mutually distinguishing requirements. By way of example, the rigid shaft 2 may be constituted of tungsten carbide steel having a modulus of elasticity, E=60,000, whereas the rods 9 and 10, are beryllium bronze whose modulus of elasticity, E=l3,000. Thus, it becomes possible to make the shaft of material which is more than four times as rigid as the torsion axles, whereby said axles may be relatively torsionaliy flexible while the shaft is torsionally rigid.

It will further be noted that the invention offers with respect to external forces the same rigidity in bending in all directions and that, moreover, the system is very resistant to all stray shear stresses.

In FIGS. 2-5 there is shown a distributor whose primary stage is constructed in accordance with the invention as above described. The same members are designated with the same reference numerals as already described in connection with FIG. 1. The distributor comprises a secondary stage 21, which does not form part of the invention and which will therefore not be described in detail. Said secondary stage 21, which is only diagrammatically outlined in FIGS. 2 and 3, may be of any known type which is capable of being controlled by the difference of the hydrodynamic pressure drops at the jets 4 and 5 as controlled by the hydraulic blade 3. Above the secondary stage 21 the distributor 20 comprises a plate 22, a plate 23 which is recessed in its center, and an upper platen 23, all of which are assembled by centering pins 25 and screws 26 (FIGS. 4 and S). The inner space defined by the members 22, 23, and 24, is made fluid-tight by the seals 27, to form a hydraulic chamber 28, which accommodates the jets 4 and 5 and the hydraulic blade 3. Openings 29 and 30 (FIG. 4) supply the jets 4 and 5 respectively, and an opening 31 evacuates the hydraulic chamber 28 (FIG. 5). On the upper platen 24, two screws 33 hold the stator 34 of the torque motor (FIG. 3). Said stator is formed, in conventional manner, by two permanent magnets 35 and two coils 36 defining two airgaps 37 controlling the magnetic blade 1 (FIG. 4). Rigidly fixed in the upper portion of the stator 34 is the member 11 which holds the rod 10 of the rigid shaft 2. As already stated, slightly below the upper rod 16, a screw 8 joins together the rigid shaft 2, the torsion tube 6, and a tubular extension 39 of the magnetic blade 1. The lower end of the torsion tube is held rigidly by a flange 7 fixed in the upper platen 24. At the lower portion of the rigid shaft 2, the rod 9 is held by a member 12 fixed in a gap 41 below the upper platen 24 by two screws 42 (FIG. 3).

It must be emphasized that the device for suppressing or minimizing shear stresses according to the invention offers an advantage of a constructive nature in addition to its fundamental functional advantages already indicated. It will be seen that the torsion tube 6 extends wholly to one side only of its flange or base 7. For the same overall size of the apparatus and for the same thickness of the tube wall, this enables the tube to be made longer and therefore more flexible in torsion, which is favorable to the dynamic behavior of the apparatus.

As compared with known primary stages of similar type, the device according to the invention possesses the superiority of permitting the torsion tube to operate exclusively in pure torsion and of making it possible to obtain results which are more uniform and more comparable with each other than when the effect of torsion is combined with shear stresses, the characteristics of the stage being very greatly improved for that reason.

Finally, as compared with certain of these known primary stages, the device according to the invention also offers the advantage that it does not introduce either friction or hysteresis phenomena by virtue of the fact that the roclls 9 and 10 operate in torsion and constitute torsion ax es.

Numerous modifications and variations of the illustrated embodiment will become readily apparent to those skilled in the art without departing from the scope and spirit of the invention as defined in the attached claims.

What is claimed is:

1. In a hydraulic distributor having two stages, one of which is constituted by a torque motor; a rigid shaft having opposite ends, said torque motor being rigidly connected to said shaft, a blade rigidly connected to said shaft at a location spaced from said torque motor and controlling the other of the stages of the distributor, a torque tube encircling said shaft and having one end terminating at a location between the torque motor and the blade, said torque tube being fixedly supported at said one end externally of said shaft, said torque tube having an end remote from said one end, means fixedly connecting said torque tube at said remote end to the shaft, and a pair of separate rods each of circular section of substantially smaller diameter and length than the shaft, said rods each having one end fixedly secured externally of said shaft and an opposite end coaxially and fixedly secured to a respective end of the shaft to constitute torsion axles for said shaft and permit solely torsional deflection of said shaft.

2. A distributor as claimed in claim 1, wherein said shaft is constituted of material having relatively large torsional stiffness, said rods being constituted of material having substantially little torsional stiffness.

3. In a distributor as claimed in claim 1 wherein said torque tube and motor are secured to the shaft at one of the ends thereof, the said blade being secured to said shaft at the other of the ends thereof.

4. In a distributor as claimed in claim 2 wherein the stiffness of the material of the shaft is at least four times as great as that of the rods.

5. In a distributor as claimed in claim 1 wherein said rods are embedded at the said opposite ends thereof in the ends of the rigid shaft.

6. In a distributor as claimed in claim 2 wherein the shaft is constituted of tungsten carbide steel and the rods are beryllium bronze.

7. In a distributor as claimed in claim 1 wherein said shaft has a diameter of about 0.5 mm. and said rods have a diameter of 0.1 mm.

References Cited by the Examiner 5 UNITED STATES PATENTS 2,835,265 5/1958 Brandstadter l3782 2,905,871 9/1959 Martin 3l7l71 X ARTHUR L. LA POINT, Primary Examiner. 10 R. M. WOHLFARTH, Assistant Examiner.

Claims (1)

1. IN A HYDRAULIC DISTRIBUTOR HAVING TWO STAGES, ONE OF WHICH IS CONSTITUTED BY A TORQUE MOTOR; A RIGID SHAFT HAVING OPPOSITE ENDS, SAID TORQUE MOTOR BEING RIGIDLY CONNECTED TO SAID SHAFT, A BLADE RIGIDLY CONNECTED TO SAID SHAFT AT A LOCATION SPACED FROM SAID TORQUE MOTOR AND CONTROLLING THE OTHER OF THE STAGES OF THE DISTRIBUTOR, A TORQUE TUBE ENCIRCLING SAID SHAFT AND HAVING ONE END TERMINATING AT A LOCATION BETWEEN THE TORQUE MOTOR AND THE BLADE, SAID TORQUE TUBE BEING FIXEDLY SUPPORTED AT SAID ONE END EXTERNALLY OF SAID SHAFT, SAID TORQUE TUBE HAVING AN END REMOTE FROM SAID ONE END, MEANS FIXEDLY CONNECTING SAID TORQUE TUBE AT SAID REMOTE END TO THE SHAFT, AND A PAIR OF SEPARATE RODS EACH OF CIRCULAR SECTION OF SUBSTANTIALLY SMALLER DIAMETER AND LENGTH THAN THE SHAFT, SAID RODS EACH HAVING ONE END FIXEDLY SECURED EXTERNALLY OF SAID SHAFT AND AN OPPOSITE END COAXIALLY AND FIXEDLY SECURED TO A RESPECTIVE END OF THE SHAFT TO CONSTITUTE TORSION AXLES FOR SAID SHAFT AND PERMIT SOLELY TORSIONAL DEFLECTION OF SAID SHAFT.

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