WO2009124957A1

WO2009124957A1 - Hydraulic actuator and structure for actuating a manipulator arm employing at least one such actuator

Info

Publication number: WO2009124957A1
Application number: PCT/EP2009/054190
Authority: WO
Inventors: Tanguy Jouan De Kervenoal; Olivier David
Original assignee: Commissariat A L'energie Atomique
Priority date: 2008-04-10
Filing date: 2009-04-08
Publication date: 2009-10-15
Also published as: FR2930004A1; FR2930004B1

Abstract

The invention relates to a hydraulic actuator comprising: an externally tubular first part (40) provided with an internal annular cavity (42) surrounding a central tubular part traversed by a longitudinal duct (44) and by an internal tubular cavity, and opening into at least one orifice (47) and into a centred circular opening (48); an externally tubular second part (50) provided with a tubular central cavity (51) opening into a centred orifice (53) and into an opening (55) so as to be able to slide in a sealed manner on the central part, comprising a fluid communication means (56), and terminating in a cylindrical end part (57) so as to allow this second part to slide in a sealed manner in the first part, this second part additionally comprising a longitudinal duct designed for the return of fluid. The invention also relates to a structure for actuating a manipulator arm.

Description

HYDRAULIC CYLINDER AND STRUCTURE FOR ACTUATING A MANIPULATOR ARM USING AT LEAST ONE SUCH

DESCRIPTION TECHNICAL FIELD

The invention relates to a hydraulic cylinder and a structure for actuating a manipulator arm implementing at least one such cylinder.

The field of the invention is that of the hydraulic power supply for manipulators comprising rotating joints, and in particular manipulators having a telescopic translation used for example in environments in which the user does not have access, for example for applications nuclear power plants and public works.

STATE OF THE PRIOR ART

In the nuclear field, to maintain and / or control installations to which a human being does not have access, without having first knowledge of the operations to be performed, haptic feedback robots are used. These robots are equipped with hydraulic cylinders fed by hydraulic hoses, which allow wiring between pumps, valves and cylinders and can compensate the stroke of telescopic movements. The hoses have several major disadvantages, mainly for manipulator arms:

- Their minimum bending radii are important and increase the size of the arms. - These flexible, unprotected, run the risk of being torn off, which can not be tolerated for security reasons.

- These hoses are very stiff, especially at pressures of 200bars, to bend them is problematic.

- Their variation of volume (swelling) under the effect of pressure calls during an actuation disrupts the servocontrol of the cylinders. The document referenced [1] at the end of the description describes a hydraulic telescopic system comprising two cylinders, wherein the first jack is fed by its hollow rod. A stitching in the chamber of this jack allows to feed, at the same pressure, the next cylinder. This gives a telescopic cylinder whose elements are not concentric. This system uses both single and double acting cylinders as actuators and as fluid supply devices. Such a solution, which eliminates hoses, is limited to feeding a telescopic system. If the telescopic system is not in action, the fluid can not be routed to an upstream cylinder independently of the operation of the telescopic system. An improvement of the document referenced [1], described in the document referenced [2], consists in fixing, parallel to a telescopic power system, a second telescopic system whose useful section S2 'of the jack, as illustrated in FIG. is small compared to that of the power cylinder. The thrust F is then: F = P x S2 ', where

P = the pressure of thrust, S2 '= useful section of the jack, VA: downstream jack,

CH: hydraulic power station.

This thrust F can add up or oppose the thrust of the power cylinder.

It is also possible, as illustrated in FIG. 2, to simultaneously feed the two chambers 10 and 11 of the telescopic supply system in order to limit the parasitic thrust:

F = P x (S2 '-Sl') where (S2'-S1 ') = surface of the cross section of the rod.

In the two devices described above, the internal volumes are not preserved. These devices require the use of accumulators or relief valves in the supply circuit. In all cases, the power cylinder must overcome the parasitic force of the supply cylinder of the upstream devices.

It is also possible, as illustrated in FIG. 3, to eliminate the parasitic thrust by using a cylinder with two rods 20 and 21 with a translation T. In this solution, the section is the same in the two chambers 22 and 23, and the piston is in equilibrium. But this solution is, at equal stroke, twice as bulky as a single-rod cylinder. Finally, it is possible, as illustrated in FIG. 4, to use two identical single-acting jacks 30 and 31, mounted head-to-tail, as described in document referenced [3]. The thrust is balanced. This device is twice as bulky as a single rod cylinder with equal stroke. The length of the device is twice the useful stroke, which is penalizing in the case of a telescopic system whose quality is to have a length folded lower than the race.

The subject of the invention is a hydraulic cylinder which makes it possible to overcome the drawbacks of the cylinders of the prior art and a structure for actuating a manipulator arm implementing such cylinders.

STATEMENT OF THE INVENTION

The invention relates to a hydraulic cylinder comprising: - a first tubular outer portion provided, at a first end, with an inner annular cavity surrounding a central tubular portion traversed end to end of a longitudinal channel and, at a second end, of an inner tubular cavity, this first portion opening, at its first end, on at least one orifice, and at its second end, on a centered circular opening,

a second externally tubular portion of outside diameter slightly smaller than the diameter of the centered circular opening provided with a tubular central cavity opening, at a first end, on a centered orifice and, at a second end, on an opening of internal diameter slightly greater than the outer diameter of the central part so as to be able to slide in a sealed manner thereon, second portion comprising fluid communication means between the tubular central cavity and an annular cavity formed between the first portion and the second portion, which second portion terminates at its second end with a cylindrical outer diameter end portion slightly less than the inner diameter of the annular cavity so as to allow this second part to be leaktight in the first part, characterized in that the second part further comprises a longitudinal channel adapted for the return of fluid.

According to a variant of the invention, the fluid communication means is a longitudinal channel formed in the thickness of the transverse wall of the second part, this channel having a first opening opening in the central tubular cavity and a second opening opening in the annular cavity. According to a variant of the invention, the cross-sectional area of the central portion is equal to the cross-sectional area of the cylindrical end portion so as to balance the thrust forces and maintain the total volume of fluid in the central portion. the channeling when extending or retracting the second part.

According to another variant, the central tubular part comprises two concentric cylinders forming between them a free space functioning as fluid communication means.

These two cylinders can be welded to a ferrule at each end.

According to another variant of the jack according to the invention, the fluid communication means comprises an outer tube adapted to communicate the tubular central cavity with an annular cavity formed between the first part and the second part. According to an improvement of the invention the second part is provided with a longitudinal low-pressure return channel passing right through it and such that PIxS1-P2xS2 + TxS3 = 0, with:

- Sl, Pl: surface of the cross section of the central part and pressure applied to this surface,

S2, P2: surface of the internal cross section of the cylindrical end portion and pressure applied to this surface; S3: surface of the external cross-section of the cylindrical end portion.

The invention also relates to a structure for actuating a manipulator arm, for example a hydraulic telescopic system, comprising at least one passive cylinder according to the invention. This structure may comprise three rotary cylinders arranged in series, each connected to a servovalve, at least one passive cylinder according to the invention being interposed between two servovalves. The rotary cylinders are mounted in series if we consider the geometry of the manipulator arm. On the other hand from a hydraulic point of view their feeding is done in parallel through the servovalves. The servovalves are therefore mounted in parallel on the hydraulic circuit. In contrast, the passive cylinders according to the invention are mounted in series on the hydraulic circuit and, as such, servovalves can be found downstream or upstream of these passive cylinders.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, objects and advantages of the present invention will be apparent from the description which follows, which is purely illustrative and not limiting and should be read in conjunction with the appended figures which illustrate embodiments of the method according to the invention.

Figures 1 to 4 illustrate power cylinders of the prior art.

Figures 5 to 8 illustrate different features of the hydraulic cylinder of the invention.

Figure 9 illustrates the hydraulic cylinder of the invention.

Figure 10 illustrates a servo valve powered by the cylinder of the invention. Figures 11 and 12 respectively illustrate an actuating structure of an arm manipulator of the prior art, and such a structure comprising a jack according to the invention as illustrated in FIG. 9.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

The hydraulic cylinder illustrated in FIG. 5 comprises:

a first externally tubular portion 40 provided, at a first end 41, with an internal annular cavity 42 surrounding a central tubular portion 43 traversed end-to-end by a longitudinal channel 44 and, at a second end 45, with a internal tubular cavity 46, this first part opening, at its first end, on at least one orifice 47, and at its second end, on a centered circular opening 48,

a second externally tubular portion 50 of outside diameter slightly smaller than the diameter of the centered circular opening, provided with a central tubular cavity 51 opening, at a first end 52, on a centered orifice 53 and, at a second end 54, on an opening 55 of inner diameter slightly greater than the outer diameter of the central portion 43 so as to be able to slide sealingly thereon, this second portion comprising a means of fluid communication between the tubular central cavity and an annular cavity 46 formed between the first portion 40 and the second portion 50, formed here of an eccentric longitudinal channel 56 in the wall thereof, the second portion ending, at its second end 54, by a cylindrical end portion 57 of outer diameter slightly smaller than the inner diameter of the annular cavity 42 so as to allow this second part to be leaktight in the first part.

This jack, which comprises a single rod while balancing the thrust forces, is less cumbersome than that shown in Figures 3 and 4. The stroke of this cylinder is equal to its empty length. This jack is designed so that the surfaces of the useful sections S1 and S2 (S1 surface of the cross section of the central tubular portion 43, S2 inner surface (as opposed to the outer section S3 illustrated in FIG. cross-section of the cylindrical end portion 57) are equal so that:

Fl = P X Sl = P X S2 where

Fl = the thrust P = the supply pressure

This cylinder can be modified to include several concentric stages, to increase its stroke while maintaining a small footprint in the folded position. In an advantageous embodiment, the seals between the different parts are made with joints 60 and 61 called "composite", as shown in Figure 6. The tubes and rods are rectified steel. The tubes and rods can be made of any material having a good roughness, for example a chromed steel. Holes long can be made using drills called "Η" whose geometry allows abundant lubrication and ease of evacuation chips during machining. Figure 7 illustrates a variant of the cylinder of Figure 5, wherein the cylinder is devoid of long eccentric holes. The second portion 50 then comprises two concentric cylinders 65 welded together. The internal tubular cavity 46 illustrated in FIG. 5 is no longer supplied with fluid by an eccentric longitudinal channel 56, but by a free space formed between the walls of the concentric tubes 65. The two tubes 65 are welded on a ferrule 66 at each end. FIG. 8 illustrates another variant of the jack of FIG. 5. This jack comprises elements similar to those of the jack of the invention as shown in FIG. 5, which here have the same references, that is to say in particular a second portion 50 sealingly slidable in a first portion 40. In this variant, the cylindrical chamber internal to the second portion is connected to the annular chamber 68 formed between the first and the second portion with the aid of an outer tube 67 reported and fixed, by welding or using fittings, to the first part, on one side at a location near its second end 45 to be in communication with the annular chamber 68 and on the other hand in a near place its first end 41 to be in communication with the longitudinal channel 44. Figure 9 illustrates the cylinder of the invention. This embodiment differs from the jack of FIG. 5 in that the second tubular portion further comprises a channel 80 adapted for the return of fluid T (RT). The cylindrical end portion 57 of the second portion 50 is provided with an outer section S3.

In this embodiment, it is not possible to satisfy both the conservation of the volume between the two high pressure chambers (which implies Sl = S2) and the equilibrium in force between the three chambers of the jack. And the user has to make a choice.

In the particular case where it is desired to obtain a balance of effort, the variation of fluid volume is therefore limited "at best" and the error compensated by the leakage flow of the actuators located downstream of the jack.

To have the equilibrium of effort, it is necessary that Fl - F2 + F3 = 0, Fl, F2 and F3 being the forces applied respectively on sections S1, S2 and S3, ie:

Pl x S1 - P2 x S2 + T x S3 = 0

If Pl = P2 = P

PxS1 -P x S2 + T x S3 = 0

PxπRl ² -P x π (R 3 ² -R ² ² ) + T x π (R 3 ² -R ¹ ² ) = 0 We have the dimensions R 1, R 2, R 3 and e as illustrated in FIG. 9.

We fix Rl and e, and we deduce R3

In one exemplary embodiment, it is thus possible to have: R 1 = 9 mm e = 8 mm R2 = R1 + e = 17 mm

P = 210 bar

T = 20 bar

R3 = 20.01 mm With this embodiment, a servovalve and its actuator can be fed parallel to a telescopic system. The pressure return circuit T is also provided. The high pressure circuit P remains at constant volume (i.e. the volumes V1 and V2 associated with the sections S1 and S2).

Servo valve powered by the cylinder of the invention

FIG. 10 illustrates a servovalve powered by a jack of the invention, illustrated here with the embodiment of FIG. 9, comprising first and second nozzles 70 and 71, a pallet 72 provided with a first face and a second face, a torque motor 73. The servovalve is connected to a chamber housing the jack according to the invention. The pallet 72 is provided with an extension 74 in the form of a spring. Nozzles 70 and 71 are connected to feeds S ^* for example at a pressure P = 210 bar. The leak rate is about 1 liter / minute at a pressure of about 20 bar, in one embodiment. The servo valve also includes outlets S1 ^* and S2 ^* connected to the cylinder chambers at pressures A and B, respectively, and a return T having a pressure of about 20 bar. Chokes 75 and 76 are located between the cylinder chamber and the power supplies. The restrictions 75 and 76 have the function of allowing the pressure to vary without this is instantly compensated by the flow from the S ^* feeds. These leaks or return flows 77 are collected by a specific circuit. These leaks are losses of charges necessary for the operation of the servovalve. A slide 78 distributes the oil to the inlet and outlet of the robot cylinder.

The function of the servovalve flow or pressure according to Figure 10 is to slave the cylinders of a hydraulic manipulator arm. Unlike "all or nothing" distributors, the operation of this servovalve requires a permanent leakage flow (77) which makes it possible to regulate continuously the flow and / or the pressure in the cylinders. A jet is sent from the nozzles 70 and 71 on both sides of the pallet 72. When the pallet 72 is in the median plane of the nozzles, the pressure upstream of the two nozzles is the same. This pressure is a function of the existing leak between the nozzle and the pallet. When the pallet 72 is deflected by the torque motor 73, the fluid passage section between the nozzle and pallet is decreased by a first side and increased by a second side. The pressure upstream of the nozzles 70 and 71 therefore drops on one side and increases on the other. In an operating mode, the spool 78 moves proportionally from left to right, opening the fluid passage from P to the pressure A. The pressure B is simultaneously connected to the return duct T. The recall of the spool 78 is ensured by the spring 74. The fluid exiting the return T returns to the tank of the hydraulic unit at atmospheric pressure P = P. The pressure of about 20 bar is due to pressure drops between the servovalve and the tank of the plant. Ideally, this pressure T is equal to the atmospheric pressure, but the large leakage flow rate and the section of the return ducts cause pressure losses which maintain a pressure in the return circuit T.

As illustrated in Figure 10, the output of the longitudinal channel 44 of the actuator of the invention illustrated in Figure 9 may be connected to power supplies S ^*, and the return conduit T to be connected to the orifice 47 of the first portion 40 .

In an exemplary embodiment, the servovalve has two different upstream circuits necessary for its installation: - a pressure supply circuit

P = 210 bar,

- a return circuit T - 20 bars. Sl ^* and S2 ^* are connected to the two chambers of the cylinder driven by this servovalve. The objective is always to supply the servovalve which is located downstream of the telescopic cylinder, without using hoses. This requires two independent circuits, a first high pressure P = 210 bars in this embodiment, a second low pressure T = about 20 bars in this embodiment.

To supply the servovalve, two separate devices can be used, selected from those described above, a first device for high pressure, and a second device for low pressure. In this example, for the high pressure P, a balanced cylinder is used, for example a double-rod cylinder (see Figure 3), a head-to-tail cylinder

(see Figure 4), or a cylinder balanced to a rod or cylinder without long holes (Figure 5, Figure 7). For low pressure, one can use a balanced cylinder as for high pressure.

However, this is not necessarily necessary, the pressure being relatively low compared to the pressure P, one can as well use a less complex and less expensive unbalanced jack known to those skilled in the art. The parasitic force is low and is compensated by the telescopic power jack. Volume variations are less troublesome because it is the return to the tank (the atmospheric pressure). Excess volumes are pumped back into the tank.

Operating structure of a manipulator arm

In the actuating structure of a manipulator arm of the known art illustrated in FIG. 11, the pressure supply of each actuator is done in parallel manner in order to be able to ensure their driving independence. The mounting of the cylinders 90, 91 and 92 relative to each other is carried out in series so that the movement of a jack moves in space all three cylinders located downstream of its position, three servovalves 93, 94 and 95 being respectively connected to each of these cylinders.

This type of supply can be achieved with rotary jacks, since the distances L1 and L2 separating the jacks remain constant. On the face

11 are illustrated the inlet pressures of the cylinders pi, p2, p3, p4, p5 and p6 and the outlet pressures P1, P2, P3, P4, P5 and P6 of these cylinders. P * and T * correspond to the pressure of the supply circuit, and to the pressure of the return circuit. This is no longer the case when one wants to be able to vary the distances L1 and L2 between the jacks. In this case, the change in length requires the use of a device to accommodate this change without changing the volume of the supply chain.

The fact of inserting a passive jack of the invention 100, as illustrated in FIG. 9, in this chain as illustrated in FIG. 12, then makes it possible to solve the problem explained in the preceding paragraph. The parallel fluid supply guaranteeing the independence of movement of each cylinder 90, 91 or 92 is retained and the mechanical assembly in series with variable length (L1, L2) of these cylinders is feasible.

REFERENCES

[1] US 5, 638, 616

5 [2] EP 0 924 158

[3] US 3, 858, 396

Claims

1. Hydraulic cylinder that includes:

a first tubular outer portion (40) provided, at a first end (41), with an inner annular cavity (42) surrounding a central tubular portion traversed end to end of a longitudinal channel (44) and, in one second end (45) of an internal tubular cavity, this first part opening, at its first end, on at least one orifice (47), and at its second end, on a centered circular opening (48),

- a second portion (50) externally tubular outer diameter slightly smaller than the diameter of the centered circular opening, provided with a central tubular cavity (51) opening, at a first end (52), on a centered orifice (53) and, at a second end (54), on an opening (55) of inner diameter slightly greater than the outer diameter of the central portion (43) so as to be able to slide tightly thereon, this second portion comprising a means (56) for fluid communication between the tubular central cavity (51) and an annular cavity (46) formed between the first portion (40) and the second portion (50), the second portion terminating at its second end (54). ), by a cylindrical end portion (57) of diameter slightly smaller than the inner diameter of the annular cavity (42) so as to allow this second part to be leaktight in the first part, characterized in that the second portion (50) further comprises a longitudinal channel (80) adapted for fluid return.

A cylinder according to claim 1, wherein the fluid communication means is a longitudinal channel (56) formed in the thickness of the transverse wall of the second portion (50), the channel having a first opening opening into the the tubular central cavity (51) and a second opening opening into the annular cavity (46).

3. A cylinder according to claim 1, wherein the cross sectional area of the central portion is equal to the cross sectional area of the cylindrical portion so as to balance the thrust forces and maintain the total volume of fluid in the channeling during extension or retraction of the second portion (50).

4. Cylinder according to claim 1, wherein the central tubular portion comprises two concentric cylinders (65) forming between them a free space functioning as a fluid communication means.

5. A cylinder according to claim 1, wherein the fluid communication means comprises an outer tube (67), adapted to communicate the central tubular cavity (51) and the annular cavity. (46) formed between the first portion (40) and the second portion (50).

6. A cylinder according to claim 1, wherein the second portion is provided with a longitudinal channel (80) of low pressure return T through it from one side and such that: PIxSl - P2xS2 + TxS3 = 0, with: - Sl , Pl: cross-sectional area of the central tubular portion (43) and pressure applied thereto,

S2, P2: surface of the internal cross-section of the cylindrical end portion (57) and pressure applied to this surface,

S3: surface of the external cross section of the cylindrical end portion (57).

7. Operating structure of a manipulator arm comprising at least one passive cylinder according to any one of the preceding claims.

8. Structure according to claim 7, comprising three rotary cylinders (90, 91, 92) arranged in series, each connected to a servovalve (93, 94, 95), at least one passive cylinder (100, 101) being interposed between two servovalves (94, 95).

9. Structure according to claim 7, which constitutes a hydraulic telescopic system.