WO1984001409A1 - Amplificateur pneumatique - Google Patents

Amplificateur pneumatique Download PDF

Info

Publication number
WO1984001409A1
WO1984001409A1 PCT/GB1983/000239 GB8300239W WO8401409A1 WO 1984001409 A1 WO1984001409 A1 WO 1984001409A1 GB 8300239 W GB8300239 W GB 8300239W WO 8401409 A1 WO8401409 A1 WO 8401409A1
Authority
WO
WIPO (PCT)
Prior art keywords
piston
spindle
chamber
gas
valve
Prior art date
Application number
PCT/GB1983/000239
Other languages
English (en)
Inventor
Timothy John Jones
Original Assignee
Original Android Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Original Android Co Ltd filed Critical Original Android Co Ltd
Priority to AU20705/83A priority Critical patent/AU2070583A/en
Publication of WO1984001409A1 publication Critical patent/WO1984001409A1/fr

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B9/00—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member
    • F15B9/02—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type
    • F15B9/08—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor
    • F15B9/09—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor with electrical control means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B9/00—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member
    • F15B9/02—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type
    • F15B9/08—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor
    • F15B9/12—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor in which both the controlling element and the servomotor control the same member influencing a fluid passage and are connected to that member by means of a differential gearing

Definitions

  • This invention relates to a fluid actuator, and more particularly concerns a pneumatic actuator which is capable of providing precise control over position, speed and acceleration.
  • Pneumatically driven actuators are well known and have the advantages of being able to generate large forces and being comparatively inexpensive.
  • motors and especially electric stepper motors enegrised by voltage pulses, which enable precise speed and position control.
  • Such motors are particularly suitable for low power applications, but where power demands are higher the cost and weight of the motors and their associated circuitry constitute severe drawbacks and often makes them impractical to use.
  • the aim of the present invention is to overcome the disadvantages of the devices mentioned above by providing a pneumatically driven actuator which is adapted to permit precision control.
  • a pneumatic actuator comprising a cylinder, a piston slidable in the cylinder and confining a chamber therewith, a piston rod attached to the piston and projecting through a n end of the cylinder, and valve means operable to admit pressurised gas into and release gas from the chamber, characterised in that a screw threaded spindle is rotat- able in the cyliner and is coupled to the piston and the valve means whereby rotation of the spindle in one direction causes gas to be admitted into the chamber to displace the piston in one direction along the cylinder, and rotation of the spindle in the opposite direction causes gas to be released from the chamber for the piston to be displaced in the other direction relative to the cylinder, the distance through which the piston is displaced being determined by the angle through which the spindle is rotated, and a rotary motor is connected to the spindle for rotating the spindle relative to the piston.
  • the motor is required only to rotate the spindle for operating the valve means and it can be of comparatively low power compared with the output power of the actuator.
  • a relatively small motor can be employed.
  • an electric stepper motor is used to enable accurate control over the rotation of the spindle.
  • the output force of the actuator is produced by the gas pressure, but as the piston displacement, and hence its position, are determined by rotation of the spindle the actuator is readily capable of accurate control.
  • actuator embodying the invention the piston separates two chambers in the cylinder and the valve means is operable to admit gas to and release gas from both chambers with gas being released from each chamber as gas is admitted into the other chamber.
  • the piston is driven pneumatically in both directions for providing power strokes whether the actuator is being extended or retracted.
  • Figure 1 is an axial section through a pneumatic amplifier embodying the invention:
  • Figure 2 shows the device of Figure 1 during extension thereof;
  • Figure 3 shows the device of Figure 1 during retract ⁇ ion thereof;
  • Figure 4 is an axial section through an actuator similar to that of Figure 1 but modified to provide power strokes in both directions;
  • Figure 5 is a schematic representation in axial section of an alternative linear pneumatic actuator constructed in accordance with the invention.
  • Figure 6 is a similar axial view of a modified form of the actuator shown in Figure 5 ,' and
  • Figure 7 is an exploded perspective view of one end cover of the cylinder of the actuator shown in Figure 6.
  • a piston 4 is slidable in the cylinder and carries a tubular piston rod 5 which extends freely through a central opening in the front end cover 2.
  • a return spring 6 is interposed between the piston and the front end cover and acts on the piston 4 to urge it rearwardly.
  • the piston and cylinder confine a pressure chamber 7 having an outlet or exhaust port defined by a central orifice in the piston which opens into the bore of the piston rod 5 «
  • On the side of the piston facing the chamber 7 is a conical valve seat surrounding the outlet port.
  • a poppet valve member 8 cooperates with this seat assembly to close the outlet port, the valve member being slidable axially relative to the piston for opening and closing the port
  • valve member 8 but being held against rotation relative to the piston by a radial pin or screw 9 which enters a longitudinal groove or slot in the valve member 8.
  • the valve member is internally screw-threaded and is carried by an externally screw threaded spindle 10 which extends axially through the cylinder.
  • the rear end cover 3 s provided with a front plate 11 and defines therewith a motor compartment in which an electric stepper motor 12 is accommodated.
  • the stator of the motor is fixed to the cover 3 and the rotor is rotationally fast with the spindle 10.
  • the end cover 3 includes also an inlet port for pressurised gas which opens axially into the motor compartment and communicates with the pressure chamber 7 through this compartment.
  • the inlet port is surrounded by a conical valve seat with which a poppet valve member 13 cooperates, the member 13 being urged towards the seat by a coil spring 14 acting between the valve member and the inner end of a gas connector 15 screwed into the cover 3.
  • the spindle 10 includes a projection 16 at its rear end which enters a blind hole in the inlet valve member 13 for opening the valve in a manner which will become clear from the following explanation of the actuator operation.
  • the parts will occupy the positions as illustrated in Figure 1 with the gas inlet and outlet valves being closed against the respective seats and the force on the piston 4 due to the gas pressure in chamber 7 being balanced by the spring 6 and the external load on the piston rod 5-
  • the actuator is to be extended, e.g. from the retracted condition illustrated in Figure 2, the appropriate voltage pulses are fed to the stator of the motor to cause the rotor to turn in a given direction, indicated by the arrow in the drawing, thereby causing
  • stepper motor 12 is energised to rotate the spindle 10 in the opposite direction to that in which it is turned to extend the actuator. Due to abutment of a shoulder on the spindle with the plate 11 the spindle 12 is unable to move forwardly and instead the valve member 8 is driven back off its seat to open the outlet port.
  • the pneumatic actuator provided in accordance with the invention can be accurately controlled electronically as regards position speed and acceleration.
  • the stepper motor need be of low power only since it is only required to operate the valves, and the actuator as a whole may have a high power to weight ratio, making it particularly suitable for robotic systems.
  • FIG 4 there is illustrated a modified actuator of basically similar construction to that of Figure 1, and only the main differences will be described in detail.
  • the actuator of Figure 4 is adapted to pro- vide power strokes in both directions and not just during extension as in the actuator of Figure 1.
  • the piston rod 5 is sealed to the forward end of the cylinder so that the piston 4 separates two chambers 7 and 20.
  • the stepper motor 12 is mounted externally of the cylinder, which has the advantage that the compressed gas does not flow through the motor and possibly contaminate it with any material entrained with the gas.
  • the motor rotor is coupled to the spindle 10 through a sliding coupling 21 which holds the spindle rotationally fast with the rotor but allows it to move rearwardly for opening the inlet valve 13 which is carried on the spindle.
  • a gas inlet duct 22 has one branch leading to the cavity inlet accomodating valve 13 for supplying gas to the chamber 7 , and a second branch leading to chamber 20 via a spool valve 23 and a passageway 24-
  • the spool valve also controls communication of the passage 24, and hence chamber 20, with an outlet port 25, the spool being biased in one direction by the pressure of gas in chamber 7 acting through a port 26, and in the opposite direction by the force of a spring 27.
  • the operation of the actuator is essentially the same as that described above for Figure 1. It differs in that when the motor 12 is operated to open the inlet valve 13 for extending the actuator, the pressure of the gas in chamber 7 pushes the spool of valve 23 against the force of spring 27 to allow gas from chamber 20 to escape through passage 24 and port 25, so that the piston 4 moves forward.
  • the motor is driven in the opposite direction to open the outlet valve 8 (as depicted in t e drawing) for retracting the actuator, the force of spring 27 over ⁇ comes the pressure of gas in chamber 7 so that the spool of valve 23 is adjusted to connect the passage 24 to the gas inlet duct 22.
  • the gas under pressure thereby enters the chamber 20 and acts on the piston 4 to push it back to re-seat the valve 8.
  • the piston is driven pneumatically in both directions. It will be realised that in this embodiment the return spring 6 of Figure 1 is not required.
  • FIG. 5 Another form of double acting or bi-directional amplifier is shown in Figure 5 «
  • the s_pindle 10 has a screw threaded connection with the piston 4 and in place of the inlet and outlet valves 8,13,23 a spool valve 30 is provided.
  • the valve housing includes an inlet port 31 and two exhaust ports 32, 33 -
  • the valve spool is fixed to the spindle 10 and includes a port 34 which is connected to an axial passage 35 through the spindle 10, this passage being in constant communication with the chamber 20 via a hole 36 in the spindle, the interior of piston rod 5 and a hole 37 in the piston rod.
  • the end of the spindle 10 is sealed to the rod 5 by a seal 38.
  • an external connection could be provided between the spool valve and the chamber 20, as indicated in broken line in the drawing.
  • a duct 39 connects the chamber 7 with the spool valve.
  • the actuator of Figures 6 and 7 is very similar to that of Figure $ , except the stepper motor 12 is mounted externally of the cylinder and is coupled to the spindle through the valve spool and by means of a coupling 21 which allows axial movement of the spool and spindle.
  • the cylinder is of simple construction with the end covers being held together on the cylinder body 1 wall by bolts 40.
  • the end cover 3 is integrally moulded with the valve housing which, as may be seen in Figure 7 consists of a single injection moulding 41 to which a cover plate 42 is fixed, e.g. by welding.
  • the pressures in the two chambers 7 and 20 are dependent upon the axial force exerted on the piston rod 5 «
  • the valves in these embodiments regulate the pressure and maintain a stable position of the piston rod and piston irrespective of the load fluctuations.
  • the pneumatic amplifier compensates atuomatically for load changes without loss of positional reference.
  • the speed of actuation is determined by the operating speed of the stopper motor and the pitch of the screw thread on the spindle, so that the speed and acceleration can be precisely controlled by the pulses fed to the stepper motor.
  • the embodiments of the invention have been described as having electric stepper motors it will be appreciated that other types of motor, e.g. a servo motor, could be used provided it allows the spindle to be rotated in a closely controlled manner. Other modifications are also possible and will occur to skilled readers.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Actuator (AREA)

Abstract

Un dispositif d'actionnement pneumatique permet d'obtenir une commande précise d'une position, d'une vitesse et d'une accélération. Le piston (4) et le cylindre (1) définissent une chambre (7) et des soupapes d'admission et d'échappement (13 et 18) commandent l'écoulement du gaz à l'intérieur et à l'extérieur de la chambre sous la commande d'un moteur pas à pas (12) qui fait tourner un axe fileté (10) dans un sens pour étendre le dispositif d'actionnement et dans le sens opposé pour rétracter le dispositif d'actionnement. Tout déplacement du piston dû à une variation de la charge sur la bielle ouvre soit la soupape d'admission (13) soit la soupape d'échappement (8) de manière à faire revenir automatiquement le piston dans sa position correcte. Une chambre de pression peut être prévue de chaque côté du piston pour obtenir une course à actionnement pneumatique dans les deux sens.
PCT/GB1983/000239 1982-09-27 1983-09-27 Amplificateur pneumatique WO1984001409A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU20705/83A AU2070583A (en) 1982-09-27 1983-09-27 Pneumatic amplifier

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8227503 1982-09-27

Publications (1)

Publication Number Publication Date
WO1984001409A1 true WO1984001409A1 (fr) 1984-04-12

Family

ID=10533185

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1983/000239 WO1984001409A1 (fr) 1982-09-27 1983-09-27 Amplificateur pneumatique

Country Status (2)

Country Link
EP (1) EP0120057A1 (fr)
WO (1) WO1984001409A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4845632A (en) * 1985-10-16 1989-07-04 Pitney Bowes Inc. Electonic postage meter system having arrangement for rapid storage of critical postage accounting data in plural nonvolatile memories

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1411023A (fr) * 1963-04-05 1965-09-17 Dispositif multiplicateur de force, applicable à la commande d'appareils et équipements
FR2118125A1 (fr) * 1970-12-17 1972-07-28 Hartmann Et Lammle Ohg
FR2131884A1 (fr) * 1971-04-01 1972-11-17 Maac Ets
FR2175062A1 (fr) * 1972-03-06 1973-10-19 Sig Schweiz Industrieges
DE2333098A1 (de) * 1973-06-29 1975-01-16 Manfred Dipl Ing Kraemer Servozylinder

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1411023A (fr) * 1963-04-05 1965-09-17 Dispositif multiplicateur de force, applicable à la commande d'appareils et équipements
FR2118125A1 (fr) * 1970-12-17 1972-07-28 Hartmann Et Lammle Ohg
FR2131884A1 (fr) * 1971-04-01 1972-11-17 Maac Ets
FR2175062A1 (fr) * 1972-03-06 1973-10-19 Sig Schweiz Industrieges
DE2333098A1 (de) * 1973-06-29 1975-01-16 Manfred Dipl Ing Kraemer Servozylinder

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4845632A (en) * 1985-10-16 1989-07-04 Pitney Bowes Inc. Electonic postage meter system having arrangement for rapid storage of critical postage accounting data in plural nonvolatile memories

Also Published As

Publication number Publication date
EP0120057A1 (fr) 1984-10-03

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