GB2169031A

GB2169031A - Double-acting hydraulic actuator units

Info

Publication number: GB2169031A
Application number: GB08429394A
Authority: GB
Inventors: Michael Pilbeam
Original assignee: Fairey Engineering Ltd
Current assignee: KNDS Defence UK Ltd
Priority date: 1984-11-21
Filing date: 1984-11-21
Publication date: 1986-07-02
Also published as: GB8429394D0; GB2169031B

Abstract

A double-acting hydraulic actuator unit comprises a cylinder 1 accommodating a piston 3, a hydraulic fluid pump 10 and a motor 11 connected thereto and a hydraulic fluid reservoir 12. The inlet of the pump is connected to the reservoir and the outlet of the pump is selectively directable to one side of the piston whilst permitting fluid to return from the other side of the piston, or, to the said other side of the piston whilst permitting fluid to return from said one side of the piston to the reservoir, whereby relative movement of the piston cylinder in both directions may be effected. The unit also includes a mechanical linkage constructed to convert linear motion into rotary motion, the linear portion 9 being pivotally connected at one end of the unit to the piston 3 and the rotary portion of the lineage including a mechanical coupling. The unit also includes a complementary mechanical coupling at the other end of the unit connected to the cylinder 2, whereby two or more such units may be connected end to end. <IMAGE>

Description

SPECIFICATION Double-acting hydraulic actuator units The present invention relates to Double-Acting Hydraulic Actuator units and is concerned with such units which are suitable for use, in particular, as a modular unit of a robot or manipulator.

Hydraulic Actuator units are known in which the linear movement of the piston is converted into rotary motion but such a unit can only effect movement or rotation in a single plane. If, as is frequently the case, movement in three planes is required it is necessary to connect three such units together with their respective axes of rotation inclined to one another. Conventionally, such actuator units are powered by an external source of pressurised hydraulic fluid and thus if three such units were connected together the resulting assembly would have a substantial number of trailing hydraulic lines which are not only inconvienient but are easily subject to damage.

It is an object of the present invention to provide a hydraulic actuator unit which may be readily connected to one or more similar units but which is so constructed that the resulting assembly does not have any trailing hydraulic lines and which preferably also has no trailing electrical lines.

According to the present invention a Double-Acting Hydraulic Actuator unit comprises a cylinder accommodating a piston, a hydraulic fluid pump and a motor connected thereto and a hydraulic fluid reservoir, the inlet of the pump is connected to the reservoir and the outlet of the pump being selectively directable to one side of the piston whilst permitting fluid to return from the other side of the piston to the reservoir or to the said other side of the piston whilst permitting fluid to return from one side of the piston to the reservoir whereby relative movement of the piston and cylinder in both directions may be effected.

The unit preferably also includes a mechanical linkage constructed to convert linear motion into rotary motion, the linear portion of the said linkage being connected at one end of the unit to one of the piston and cylinder and the rotary portion of the said linkage including a mechanical coupling, and preferably also includes a complementary mechanical coupling at the other end of the unit connected to the other of the piston and cylinder, whereby two or more such units may be connected end to end.

Thus in the unit in accordance with the present invention the cylinder accommodates not only the piston but also the hydraulic fluid pump and motor and the reservoir and thus there is no need to provide any trailing hydraulic lines. The provision of complementary couplings at the two ends of the unit permits two or more such units to be connected together end to end to constitute a limb which may articulate in one or more planes.

It is preferred that the unit includes a control valve connected to the outlet of the pump, the control valve being selectively operable to direct pressurised hydraulic fluid to one or the other side of the piston whilst permitting fluid to return from the other or the one side of the piston to the reservoir.

The couplings may be of any convenient construction but if they are of the type which can only be coupled to a corresponding coupling when the two couplings are in a predetermined angular orientation it is preferred that the unit includes means which permit the alteration of the relative angular orientation of at least one of the couplings with respect to the unit. Thus an assembly of two or more such units may be so arranged that the two units produce rotary motion about parallel axes but in general it is likely that the two axes will be inclined to one another. If three units are connected together it is likely that the axes will be inclined to one another at 90 . The couplings at the two ends of the assembly may be used for connecting it to,for instance, a tool holder and a support structure respectively.

It is preferred that an assembly of two or more such units also has no trailing electrical connections it is therefore preferred that the unit has a connector, e.g. a plug connector, at each end for connecting together the electrical cables of adjacent connected units for the purpose of transmitting electrical power and/or control signals and/or information.

Further features and details of the present invention will be apparent from the following description of one specific enbodiment which is given by way of example with reference to the accompanying drawings in which: Fig. 1 is a side sectional elevation of a hydraulic actuator unit in accordance with the present invention; Fig. 2 is an underplan view of the unit; Fig. 3 is a sectional view on the line X-X in Fig. 1; Fig. 4 is a sectional view on the line Y-Y in Fig. 1.

The actuator unit comprises an outer cylinder which accommodates an annular sleeve 2 at each end which together with the cylinder 1 defines two annular hydraulic working spaces 30. Within the cylinder 2 is a piston 3 with an annular land at each end accommodated in a respective one of the hydraulic spaces and seated with respect thereto by sliding pressure seals 4. The piston 3 accommodates an electric geared motor 11 and a hydraulic pump 10 connected thereto which, in this case, includes self regulating means which ensures that the delivery pressure of hydraulic fluid from the pump is maintained substantially constant irrespective of the rate of delivery of the hydraulic fluid.The pump communicates on its inlet side via a fluid filter 15 with a hydraulic fluid reservoir 12 from which air is excluded and which is maintained at a superatmospheric pressure, in this case by a spring-loaded piston 13. The hydraulic working spaces 30 communicate with the outlet side of the pump and with the reservoir via a plurality of fluid passages 32 (not all of which are shown for the sake of simplicity) and via an electro-hydraulic servo valve 14 which is controlled by remotely generated control signals. The piston and cylinder constitute a double acting hydraulic actuator and when the piston moves the motor, pump, reservoir and servo valve move with it.

The piston 3 thus moves linearly within the cylinder and at one end (the left hand end as seen in fig. 1 and 2) is connected to a linear to rotary motion converter, which in this case comprises a linkage which is described and claimed per se in European patent application No. 82304345, the disclosure of which is incorporated herein by reference. This linkage comprises two arms 9 which are pivotally connected to the piston 3 by a pin 34 and to an arm 8 by a pin 36. The arm 8 is pivotally connected by a pin 38 to one end of each of two arms 6 whose other ends are pivotally connected by a pin 40 to two lugs orbrackets 5 which are fixed in position and form an extension of the cylinder assembly 1,2.

The end of the linkage remote from the piston 3 constitutes a coupling by means of which the actuator unit may be connected to a tool holder or a similar actuator unit having a corresponding coupling. Such a corresponding coupling is shown secured by means of screws 41 to the other end of the unit, i.e.

the right hand end of the figures 1 and 2 and comprises four spaced longitudinally extending planar fingers through the upper portions of which a coaxial hole 42 extends. These fingers comprise two outer fingers 44 and two inner fingers 46, through the lower portions of which a coaxial hole 48 extends. Figures 1 and 2 show the actuator unit connected at its left hand end to a tool holder 7 having such a corresponding coupling. The connection is effected by means of a pivot pin 50 which passes through a coaxial hole in the brackets 5 and the hole 42 in the fingers 44 and 46 and by means of a further pivot pin 52 which passes through a hole in the arm 8 and through the holes 48 in the fingers 46. A pivot pin 50 is shown in position in the holes 42 on the right hand side of figures 1 and 2.

Thus movement of the piston relative to the cylinder will cause linear movement of the arm 8 relative to the brackets 5 and thus rotary movement of the tool holder 7 about the pivot pin 50.

Any desired number of transducers may be provided for generating electrical signals indicative of position, velocity or other Pam- meters. A transducer 17 is illustrated for transmitting a signal indicative of the position of the tool holder 7 relative to the unit. Electrical cables 18 and 19 are also provided for the transmission of electric power, command signals and information to and from the various components of the unit. The cables are connected to a plug connector 54 at each end of the unit for connection to a similar unit or a base. Atr release or bleed valves or screws 16 are provided to permit the venting of air from the hydraulic system.

In use, the servo valve is controlled to place the outlet of the hydraulic pump into communication with one of the working spaces 30 whilst simultaneously placing the other working space 30 into communication with the reservoir and the piston thus moves relative to the cylinder thereby pivoting the tool holder 7, or further actuator unit to which the actuator unit is connected.

In the illustrated embodiment the two end couplings are aligned in the same plane. However, by virtue of the fact that the right hand coupling is connected to the unit by four or more screws it may be angularly offset, e.g.

by 90 , from the left hand coupling. It will be appreciated that if the unit illustrated in the accompanying drawings is coupled by a further unit whose couplings are offset by 90 and which in turn is connected to a further unit whose coupling are offset by 90 and which in turn is connected to a further unit whose couplings are offset by 90 and which carries a tool holder, movement of the tool holder may be effected in all three planes.

It will be appreciated that numerous modifications may be effected to the construction described above. Thus the linear to rotary movement converter may be modified as described in the European patent application referred to above or may take a simpler form, e.g. a rack and pinion. A conventional single walled cylinder and piston may be used mounted within a separate outer casing replacing the outer cylinder 1. The pump 11 may be a servo controlled electric motor thereby permitting the elimination of the servo valve 14.

Furthermore, the coupling at the ends of the unit may be of any appropriate construction.

Claims

1. A double-acting hydraulic actuator unit comprising a cylinder accommodating a piston, a hydraulic fluid pump and a motor connected thereto and a hydraulic fluid reservoir, the inlet ofthe pump being connected to the reservoir and the outlet of the pump being selectively directable to one side of the piston whilst permitting fluid to return from the other side of the piston to the reservoir or to the said other side of the piston whilst permitting fluid to return from the said one side of the piston to the reservoir whereby relative movement of the piston and cylinder in both directions may be effected. the unit also including a comple mentary mechanical

2.A unit as claimed in claim 1 further including a mechanical linkage constructed to convert linear motion into rotary motion, the linear portion of the said linkage being connected at one end of the unit to one of the piston and cylinder and the rotary portion of the said linkage including a mechanical coupling.

3. A unit as claimed in claim 2 including a complementary mechanical coupling at the other end of the unit connected to the other of the piston and cylinder, whereby two or more such units may be connected end to end.

4. A unit as claimed in any one of the preceding claims further including a control valve connected to the outlet of the pump, the control valve being selectively operable to direct pressurised hydraulic fluid to one or the other side of the piston thus permitting fluid to return from the other or the one side of the piston to the reservoir.

5. A unit as claimed in any one of the preceding claims in which the pump, motor and reservoir are carried by the piston and adapted to move therewith.

6. A unit as claimed in claim 2 or claim 3 including means which permit the alteration of the relative angular orientation of one of the couplings with respect to the unit.

7. A unit as claimed in any one of the preceding claims which has a connector at each end for connecting together the electrical cables of adjacent connected units for the purpose of transmitting electrical power and/or control signals and/or information.

8. A double-acting hydraulic actuator unit substantially specifically herein described with reference to the accompanying drawings.