FR2731749A1 - Hydraulic servo motor for manipulator arms - Google Patents

Abstract

The servo-motor is of a type consisting of a transmitter assembly of pressure principally made up of a cylindrical body (1), a mobile end plate (3), a fixed end plate (2), and a rotary distributor. The rotary distributor contains a casing (5) carrying out the functions of a distributor body and the shaft for the servo-motor and a distribution rotor (4). The mobile end plate operates in an annular volume (21) formed between the distributor bodies (5) and the servo-motor body (1). Also the orifices or distribution grooves (15), provided in the rotor (4), present a square or rectangular section for joining up the volume chambers (21) with the channels (HP and BP) (22,23) of the casings aligned parallel to the shaft of the servo-motor.

Description

 The invention relates to a servomotor for a preferred but non-limiting application to the construction of manipulator arms with multiple axes of rotation.

 No current hydraulic servomotor is satisfactory in this preferred application, their drawbacks are in particular their weight, their bulk, the rapp distribution (> rtée at the base of the articulated chain, and the piping connecting the distribution to the servomotors, on the other hand the flexible pipes stiffen under the effect of pressure.

 Electric geared motors develop significantly lower torques and require brakes to avoid the collapse of the articulated pulpit.

 The invention aims to overcome these drawbacks.

For the above-mentioned preferential application, an object of the invention is to propose a servomotor meeting the following criteria:
- handling a 10 kg mass at the end of the articulated chain deployed with a radius of action of one meter,
- the mass of the arm without the hydraulic unit must not exceed 20 kgs,
- the servomotor must be a complete module integrating the power transmission system, the distribution, the sensors and the connections,
- the connection between the modules must be made quickly,
- for an intervention, accessibility to all components must be excellent.

- the actuator must guarantee that the position is maintained without the brake,
- in case of need: breakdown, release, security, a valve must allow the communication of the high and low pressure chambers.

 The composition of the servomotor must allow all possible associations: assembly in line, at any angle to obtain open or closed articulated chains.

Another object of the invention is to propose a versatile servomotor allowing numerous other applications, for this purpose:
- the actuator must also be used for other purposes, such as controlling valves, doors, replacing systems combining linear cylinders, racks and pinions, it must be able to be used in hostile and aggressive environments, or even deflagrants by means of a special protection of the electrical distributor control and information systems,
- the elements connecting the servomotors of the articulated chain together must be standard,
- to promote safety and aesthetics, no protuberance, pipe, cable, part or components must protrude from the cylindrical casing fixed according to the model,
- position and speed control must be simple,
- the design must be identical whatever the size of the actuator,
- for the proposed application, the torque developed by the servomotor is 150
Nm for a hydraulic fluid pressure of 70 bar. This pressure may be greater for other applications.

 Another object of the invention is to provide a particular construction making it possible to calculate the dimensions of the parts in a simple manner as a function of the desired power, as well as a new design of the distribution which should allow perfect control of the law of flow rate the speed of rotation of the servomotor.

 The inventive idea, in order to achieve this goal, consisted in going against the habits of those skilled in the art and in making rectangular or square distribution orifices.

 All these objectives are achieved thanks to the invention which consists of a booster of the type comprising a power transmitter assembly mainly comprising a cylindrical body, at least one movable flange, a fixed flange, a rotary distributor, characterized in that the rotary distributor comprises a part ensuring the functions of distributor body and axis of the servomotor and a distribution rotor, the movable flange (s) evolving in an annular volume formed between the body of the distributor and the body of the servomotor, and characterized in that the orifices or distribution grooves, provided in the rotor, have a square or rectangular section for placing the chambers of the annular volume in communication with the channels (HP and BP) of the body arranged parallel to the axis of the booster.

The invention will be better understood using the following description made with reference to the following appended figures:
FIG. 1: view in longitudinal section of a booster according to the invention, section made according to the arrows AA in FIG. 2,
- Figure 2: left view of the booster according to the invention without motor,
- Figure 3: right view of the same servomotor with the position sensor fixing bracket, Figure 4: sectional view along BB of Figure 1,
- Figure 5: overall perspective view of an intermediate flange used in the booster to increase the torque and angular deflections by mounting them in series, Figure 6: top view of the flange of Figure S,
- Figure 7: obte view of the flange of Figure S,
- Figure 8: detail of the flange of Figure 5 according to section MM,
- Figure 9: detail according to section NN showing the channels connecting the rooms of the different floors,
FIG. 10: detail of a variant of a dispenser which can replace that of FIG. 1,
-Figure 11: section KK of Figure 10,
- Figure 12: section LL of Figure 10,
- Figure 13: detail of the mounting of flanges on the fixed flange of the booster according to section CC of Figure 2,
- Figure 14: detail of the connection between coupler and rotary joint according to section HH of Figure 1.

- Figure 15: line joint design,
- Figure 16: elbow joint design,
- Figure 17: detail of the valve connecting the high and low pressure chambers,
FIG. 18: first execution of the communication system of the sectional valve according to EE of FIG. 17,
FIG. 19: second execution of the communication system of the sectional valve according to EE of FIG. 17,
- Figure 20: second execution of the axial stop flange of the valve,
- Figure 21: section according to GG in Figure 4 showing the section of the distributor square holes,
- Figure 22: section according to DD of Figure 4,
- Figure 23: section along FF of Figure 4,
- Figure 24: view in longitudinal section of a variant of distributor and rotary joint for high pressures,
- Figure 25: perspective view of a booster according to the invention used as a gripper,
- Figure 26: horizontal section view of the booster of Figure 25,
- Figure 27: detail according to JJ showing the fixing lug of an encoder.

A booster according to the invention consists of four main elements:
- a power transmitter assembly mainly comprising a cylindrical body (1), a movable flange (3) secured to movable shoes (12), a fixed flange (2) secured to fixed shoes ((11). All these parts can be produced in steel,
- A rotary distributor whose part (5) (for example steel) performs two functions of distributor body and axis of the servomotor, and whose rotor (4) performs the function of distributor. The movable flanges evolve in an annular volume (21) formed between the body of the distributor (5) and the body of the booster (1).

The movement of the distributor can be ensured by a stepping motor or a small actuator of the pallet type allowing use in explosion-proof environments,
- a rotary joint (6), for example in bronze, is also located in the axis of the actuator and in the extension of the distributor, its function consists in not subjecting the high pressure (HP) and low pressure (BP) pipes to bending due to the relative movements of one joint with respect to the other. This design has the advantages of not tiring the pipes and of not penalizing the engine torque by the rigidity of the high pressure (HP) pipe.

 Preferably quick couplings are provided to allow instant connection and facilitate assembly and maintenance.

 - a safety system (37) or bypass system (Figure 17) made in the fixed shoe (11) for example by a valve or by a needle or stud screw, allows to connect the high and low pressure chambers, in case necessary, for example to be able to fold the arm in the application of the manipulator arm. The power can be turned off using a valve at the central unit.

 The servomotor further comprises a protective sheath (7), for example made of aluminum, composite or plastic material, a coupler for example made of steel having the function of receiving the next segment of the structure such as a manipulator arm element, a flange circular (9) for example made of aluminum, a plurality of circular seals (lOa, lOb ...) providing static sealing, a bearing (13) with two rows of balls, a stop flange (14) of the body ( 5) of the distributor, assembly screws (20), a flange (29) for fixing a position sensor.

 A special feature of the booster according to the invention lies in the special shape of the dispensing orifices (15) whose square or rectangular section (see FIG. 21) allows precise speed control. Indeed when an orifice (15) (HP or BP) opens on a chamber of the volume (21), the variation of the fluid passage section is linear which is not the case with circular sections of prior art.

 Two alternative embodiments of the distribution rotor (4) are possible: with grooves (15) parallel to the axis (Figures 1 to 4) or grooves (15 ') perpendicular to the axis of the actuator (Figures 10 to 12 ).

 The operation of the servomotor is now described.

The servomotor is a complete power transmission element integrating the functions of distribution, rotary joint and information gathering. It can be mounted in series or in parallel to form arbitrary architectures with several degrees of liberty
The high and low pressure circuits (HP-BP) pass through the body (5) of the distributor in channels (22,23) parallel to the axis. The distributor also forms the axis of the servomotor around which one or more movable shoes (12) rotate to transmit power. In this body (5) are the distribution rotor (4) and the rotary joint (6). Depending on the environment and the application, the rotor will be operated by a stepping motor (16), a mechanical system or a small hydraulic actuator of the pallet type used in an explosion-proof environment.

 The rectangular shape of the dispensing orifices (15) allows excellent control of the speed and the proportionality thereof as a function of the opening of the orifices. The torque is regulated by the fluid pressure regulated at the hydraulic unit.

 A rotation of the distribution rotor (4) in the counterclockwise direction turns the actuator in the same direction (34), a reverse rotation of the rotor initiates a reverse movement (35).

 Two forms of distribution rotors are proposed according to the positioning of the grooves (15), the function provided is strictly the same, only the machining is different.

 The supply pipes (24,25) can, depending on the desired architecture, enter axially (not shown) or radially (see Figure 1) into the body of the distributor (5).

 The same remark is valid for the outgoing pipes (26,27) of the rotary joint (6).

 The distributor body (5) is stopped axially and in rotation by two flanges (14) fixed to the fixed flange (2) (see Figure 13). The rotary joint (6) is linked to the coupler (8) by two flats plus an axial stop (see Figure 14). The circuits (BP and HP) pass through this rotary joint (6) to supply the next servomotor. They are blocked with two screws on the extreme servomotor. A small hole (36) drilled in the channel (BP) of the rotary joint allows the return of leaks.

 The "Position and Speed" information is taken by means of a plastic pinion (28) mounted on the movable flange or the coupler (8). This pinion transmits the movement to sensors.

 Figures 15 and 16 show by way of nonlimiting examples an articulated chair comprising a servomotor (1) and a position encoder (32) coupled between an upstream segment (30) and a downstream segment (31) according to a design online and an elbow design.

 Depending on the location of the actuator in the articulated chain or on the receiver, the motor (16) actuating the distribution rotor and actuating the sensors can be placed on either side of the fixed and movable flanges (Figure 15) or on the periphery (figure 16). In the latter case, the transmissions are carried out by synchronous belts (33).

Power is transmitted by the coupler. The coupling is carried out:
- for medium torques, small servomotors, by centering, fixing screws and a stud against shearing,
- for large torques, large servomotors, by a vee system and fixing screws.

 The booster according to the invention can also be used for high pressures (see FIG. 24), going up to 350 bars thus making it possible to develop torques five times greater than with a pressure of 70 bars.

For this variant embodiment for high pressures, the following modifications are made:
- removal of the internal shoulder of the body of the distributor (5) and replacement with a single bore allowing very small dimensional tolerances of concentricity and coaxiality during manufacture,
- machining of the distribution rotor (4) and of the rotary joint (6) (this time in steel) and their rectification before separating them also promotes the low tolerances mentioned above,
- preloading of a ball stop (39) using the stop flange and stepper motor support (38) which maintains contact between the distribution rotor (4) and the rotary joint (6). eliminates the axial action of the fluid on the distribution rotor, generating passive torque due to friction,
- Limiting the angular travel to a value between 270 and 300th to ensure at these high pressures an excellent seal between the high and low pressure chambers of the booster.

 According to another alternative embodiment shown in Figures 25 and 26, the booster can be used as a gripper.

 For this use, the mobile end flange (8) is replaced by another mobile flange (8a) in which two or more cams are drawn in which the heads (44) of two (or more) gripping fingers (40) move. ) of known type. The fingers (40) are articulated by pins (42) on their respective supports (41) fixed on the circular flange (9).

 The shape and dimensions of the cams (43) are chosen according to the characteristics of the fingers used.

 Safety in the event of a breakdown for finger clearance is always ensured by the valve (37).

 The other parts are unchanged.

The advantages of the booster according to the invention are numerous and are in particular the following:
- Compact actuator integrating distribution and information gathering functions.

 - Transmission and maintenance of a large torque.

 - Safety guaranteed, thanks to the bypassing of the chambers making it possible to fold the articulated system.

 - Limited leaks at the distribution and the rotary joint. The "high pressure" circuits are in the center of the actuator, and the "low pressure" circuits at the ends, thus serving to return leaks. An additional seal can, for high pressures, be installed between the distributor body (5) and the movable end flange (8).

 - Thanks to the rectangular shape of the distribution orifices, the supply to the chambers and the flow rate vary linearly, which is not the case for the circular orifices. The control will be simplified for speed control.

 - The servomotor forms a complete module which can be used to make any articulated chains of drives or maneuvers combining, linear actuator, rack, pinion.

 - The angular movement and the torques can be increased by the interposition of intermediate flanges (17) provided with shoes (18). Oblique holes (19) on these flanges allow the various chambers to be supplied in high and low pressure series (see Figures 5 to 9).

 - In its standard execution, the servomotor has a fixed shoe and a mobile shoe, the transmitted torque can be multiplied by installing two or even three fixed and mobile shoes, the angular movement will be reduced by the same amount, or it will be necessary to interpose intermediate flanges to keep the same travel. With two or more fixed and movable shoes, the distribution axis will be balanced radially.

 - Accessibility to all parts for maintenance or replacement of elements.

 - Integration of connectors and sensors (of all types).

- For the use of the servomotor in an explosive environment, the distributor will be hydraulically actuated, the angular position sensor may also give analog, hydraulic or pneumatic information. The hydraulic hoses for the operation of the distributor rotor and those for the sensors are small in diameter, they carry little fluid, at low pressure. However, if the distribution control and information-taking equipment use electrical energy even low voltage (12 V) and intensity, they can be protected or overmolded to prevent them from generating deflagration,
- Thanks to the quick couplings and plug-in connection technology, any articulated chains can be made very quickly. Standard elements, for example tubes, can connect the servomotors. The replacement of a defective element is also done very quickly, thus limiting the intervention time.

 - A purge system can be installed on each servomotor, it is useful for filling and draining the fluid.

 - The design of the servomotor is identical whatever its size, the change of scale and therefore the desired power are done by homothety.

 - The parts making up the servomotor can be made of other materials making it possible to resist aggressive, corrosive or dangerous products.

 - On the end drive of the articulated chain, can be installed either a tool or a gripper with two or more rigid fingers or with a flexible structure of the honeycomb rubber type to form enveloping fingers for handling fragile parts and any shape . The power transmission can be separated or use the high and low pressure hydraulic fluid which flows through all the servomotors.

 The invention applies preferably but not limited to the construction of manipulator arms for the disabled, for nuclear power or other ...

The invention can also be used for other applications such as for example:
- Design of any articulated chains with open or closed loop and robots.

 - Servomotor for fluid, fuel or oxidant control valves.

 - Replacement of the "linear cylinder-rack-pinion" assembly, the servomotor performs the same function.

 - Alternative rotations for mixers.

 - Control of shutters in aeronautics.

 - Orientation of deflectors for air, for water (blowers, adjustment of convergent-divergent).

 - mobile gear wheel steerer (steering).

 - Orienter for machining and welding assembly.

 - Compact design of ball joint.

- Loading platform control
- Realization of strongholds and winches.

 This list is not exhaustive. The servomotor can be used in all cases where the transmitted or maintained torque is high and when the speed must be perfectly controlled.

 The actuator does not require any brake to maintain the position. Its movement, thanks to the bipass system, can be driven insane if necessary to fold the chain or release the action exerted.

Claims (14)

1. Booster of the type comprising a power transmitter assembly mainly comprising a cylindrical body (1), at least one movable flange (3), a fixed flange (2), a rotary distributor, characterized in that the rotary distributor comprises a part (5) ensuring the functions of the distributor body and of the servomotor axis and of a distribution rotor (4), the movable flange (s) evolving in an annular volume (21) formed between the distributor body (5) and the body of the servomotor (1), and characterized in that the distribution orifices or grooves (15), provided in the rotor (4), have a square or rectangular section for placing the chambers of the volume (21) in communication with the channels ( HP and BP) (22,23) of the body (5) arranged parallel to the axis of the servomotor. 2. Booster according to claim 1, characterized in that the orifices or grooves (15) of distribution are arranged parallel to the axis of the booster. 3. Booster according to claim 1, characterized in that the orifices or grooves (15) of distribution are arranged perpendicular to the axis of the booster.  4. Booster according to one of claims 1 to 3, characterized in that it further comprises at least one intermediate flange (17) provided with shoes (18).  5. Booster according to the preceding claim, characterized in that the shoes (18) have oblique holes (19) for fluid passage.  6. Booster according to one of claims 1 to 5, characterized in that it further comprises a rotary joint (6) located in the axis of the booster, in the extension of the distributor.  7. Booster according to the preceding claim, characterized in that the rotary joint (6) is traversed by LP and HP channels and has a hole (36) drilled in the BP channel for the return of leaks. 8. Booster according to one of the preceding claims, characterized in that it further comprises an information-taking element (position-speed). 9. Booster according to one of the preceding claims, characterized in that it further comprises a security system (37) in the fixed shoe (1 11). 10. Booster according to one of the preceding claims, characterized in that it comprises a single bore for the distribution rotor and the rotary joint and in that it comprises a micro thrust ball bearing (39) preloaded by the motor support (38). 11. Booster according to one of the preceding claims, characterized in that the mobile end flange (8a) comprises a plurality of guide cams for the heads (44) of gripping fingers (40). 12. Articulated chain formed by coupling a plurality of servomotors, characterized in that the servomotors which constitute it are servomotors according to at least one of claims 1 to 11. 13. Articulated clevis according to claim 12, characterized in that it comprises at least one servomotor (1), a motor (16) for actuating the rotor, a position encoder (32) coupled between an upstream segment (30) and a downstream segment (31) according to an in-line design. 14. Articulated clevis according to claim 12, characterized in that it comprises at least one servomotor (1) coupled between an upstream segment (30) and a downstream segment (31) according to an elbow design, and synchronous belts (33 ) transmitting the movement to the motor (16) and to the sensor (32) placed on the periphery.