GB2202590A

GB2202590A - Hydraulic actuator and driving mirror assembly incorporating it

Info

Publication number: GB2202590A
Application number: GB08804264A
Authority: GB
Inventors: David Scarrow
Original assignee: DRG UK Ltd
Current assignee: DRG UK Ltd
Priority date: 1987-02-24
Filing date: 1988-02-24
Publication date: 1988-09-28
Also published as: GB8704308D0; GB8804264D0

Abstract

An actuator has (preferably several) closed systems each having a compressible chamber 18 connected to an expandable chamber 14 via a conduit 12. Expansion of the expandable chamber is arranged to urge a desired displacement, e.g. pivoting of a driving mirror 16. There may be an array of closed systems, arranged to pivot the mirror 16 in different directions. The compressible chamber(s) 18 may be formed from sheets of plastics material (preferable PVC modified with nitrile rubber to give flexibility at low temperatures), welded together to define the chamber(s) 18 and to seal about the conduit(s) 12. The chambers 18 may have filling tubes 27 sealed off after filling. There may be injection sites for subsequent alteration of the fluid content. As shown in Fig 5, the chambers 18 may be located in a tube 32 and acted upon by a joystick control 34. <IMAGE>

Description

HYDRAULIC ACTUATOR AND DRIVING MIRROR ASSEMBLY INCORPORATING IT The present invention relates to a hydraulic actuator for producing remote displacement; and to a device, particularly a driving mirror assembly, incorporating such an actuator.

The actuator comprises one or more sealed hydraulic lines having at one end a chamber whose volume is reducible and at the other end an expandable chamber having a protrudable portion; the protrudable portion being arranged in use to urge a desired displacement. The reducible chamber may be formed of sheet material portions welded to form said chamber and to seal about a conduit leading to the expandable chamber. There may be a plurality of lines with respective pairs of chambers, the expandable chambers being arranged in use to urge different displacements, e.g.

to pivot a mirror in different directions.

An embodiment of the invention will now be described with reference to the accompanying drawings in which: Fig. 1 is a schematic view of a driving mirror assembly embodying the invention; Fig. 2 is a plan view of the displacement means thereof; Figs. 3 and 4 are schematic sectional views of a detail of the displacement means; and Fig. 5 is a view of one form of control means.

Fig. 1 shows a control means 10 connected by tubes 12 to displacement means 14 associated with a pivotably mounted mirror 16. The control means 10 has, in this example, three control elements 18, each having the form of a compressible chamber. In order that the chambers 18 should remain flexible at low temperatures (e.g. down to -30 C) they may be made of PVC modified with nitrile rubber.

A suitable "alloy" is available from Norsk Hydro Polymers Ltd. The control means 10 is formed from two portions of sheet material (e.g. 0.04mm thick) secured to one another and sealed about the ends of the tubes 12, suitably by RF welding. The tubes may be of PVC, optionally modified with nitrile rubber. They may be held neatly together, e.g. by a heat-shrunk sleeve.

The displacement means 14 comprises a base member 22 and a plurality of protrudable portions 24. Both, or at least the latter, may be made of PVC modified with nitrile rubber. The base member 22 may be an injection moulding, of general thickness lmm. It has a disc portion 26 with a plurality of socket portions 28 each communicating with a conduit portion 30 within which an end portion of a respective tube 12 is sealed, suitably by R.F. or solvent welding.

The protrudable portions 24 are flexible, evertable cups, suitably of 0.4mm thick material like the control means 10. They can be thermoformed or injection moulded.

Each is sealed around a peripheral flange 25 to a respective socket portion 28, suitably by RF welding. They may be separate from one another as shown, or provided by portions of a sheet.

A cup portion has a preferred orientation, so that it has a tendency to adopt either the configuration shown in Fig. 3, or that shown in Fig. 4. (For an injection moulded cup this will generally be the configuration with the injection gate on the exterior.) For the displacement means it is generally preferred that the cups should be urged to the configuration of Fig. 3, i.e. with the chamber volumes reduced so that fluid is urged to the control means.

A similar cup construction may be used for the control means, in which case the opposite configuration (Fig. 4) may be preferred. Thus fluid is urged into the control means, ready for actuation.

Each tube 12 is thus sealed at one end to a compressible chamber 18 of the control means 10; and at the other end, to an expandable chamber formed of a socket 28 and an evertable cup 24. The enclosed volume contains a fluid, preferably one with a low freezing point. A glycol-type liquid such as ethylene glycol or propylene glycol is suitable. An aqueous fluid is generally not preferred as we have found that, over an extended period, water is lost. This may have been filled in through a tube portion 27 initially communicating with a respective chamber 18 and subsequently welded closed. Compression of a chamber 18 urges the associated cup 24 to dome outwardly (Fig. 4). In use the displacement means is mounted adjacent a pivotable mirror 16, generally sandwiched by a rigid backing plate 31. Thus the actuation of a cup 24 urges the mirror 16 to pivot in one direction.

Fig. 5 shows a convenient arrangement for operating the control means 10 by a joystick. An array of control elements 18, suitably as described above, is formed into a tube and inserted into a tubular support 32. A joystick rod 34 extends along the axis. It is pivoted at one end and has a grip portion 36 at the other. It is thus pivotable so that abutment surface portions compress respective elements 18. It can be arranged so that the displacement of the grip portion 36 corresponds to the displacement of the mirror 16 urged thereby.

In an alternative construction, a control means 10 can be disposed on a flat frame with means (e.g. piano keys) for compressing individual chambers 18.

Although the invention has been described primarily with reference to means for displacing a driving mirror, it is also applicable to permitting remote displacements in other contexts, e.g. for operating from a safe location a switch located in a hostile environment.

The manufacture of the actuator can employ welding and sealing technology as applied in the medical equipment field, e.g. in the manufacture of "giving bags" for medical fluids. For example, filling can use such known apparatus.

Desirably, this has tubular filling heads that are inserted into outer regions of the filling tubes 27. Preferably the filling apparatus first applies a vacuum to evacuate the tubes and chambers, and then injects a predetermined volume of filling liquid. In a subsequent sealing operation, sealing jaws clamp the tubes 27 and a seal is produced by RF welding. Since this weld is performed through liquid, a higher than normal RF frequency may be required, e.g. 40.68 MHz or even higher. (RF welding of the displacement means can use a conventional frequency such as 27.12 MHz.) There may be means for changing the fluid contents of the system. Thus there may be injection sites on the tubes 12. A site may be provided by a branch containing a rubber septum through which a syringe needle can be passed.

Claims

CLAIMS:

1. A hydraulic actuator for producing remote displacement which comprises one or more sealed hydraulic lines having at a first end a first chamber whose volume is reducible and at the other end an expandable second chamber having a protrudable portion; the protrudable portion being arranged in use to urge a desired displacement.

2. An actuator according to claim 1 wherein the reducible first chamber is formed of sheet material portions welded to form said chamber and to seal about a conduit leading to the expandable chamber.

3. An actuator according to claim 1 or 2 having a plurality of lines with respective pairs of first and second chambers, the expandable second chambers being arranged in use to urge different displacements.

4. An actuator according to claim 3 wherein the reducible first chambers are arranged about a joystick control rod which is selectively urgeable against them to urge reductions in volume.

5. An actuator according to any preceding claim wherein at least some of the chambers have flexible portions to permit variation in volume, and at least the flexible portions comprise PVC modified with nitrile rubber to enhance flexibility at low temperatures.

6. An actuator according to any preceding claim provided with an injection site for injecting hydraulic fluid into a sealed line.

7. An actuator according to any preceding claim wherein at least one said chamber comprises a pair of cup-shaped portions whereof one is evertable between concave and convex configurations to vary the volume of the chamber; the evertable portion being biased to one configuration so as to urge reduction or expansion of the chamber.

8. An actuator according to claim 7 having an expandable second chamber which comprises said cup-shaped portions and whose protrudable portion is provided by a said evertable portion which is biased to the volume-reducing, nonprotruding configuration.

9. An actuator according to claim 7 or claim 8 having a reducible first chamber which comprises said cup-shaped portions whereof said evertable portion is biased to the expansion configuration.

10. An actuator according to any preceding claim wherein each said hydraulic line is filled with a substantially non-aqueous glycol.

11. A hydraulic actuator substantially as any herein described with reference to and as illustrated in the accompanying drawings.

12. A driving mirror assembly comprising a pivotably mounted driving mirror and a hydraulic actuator according to any preceding claim coupled to the mirror for urging pivoting thereof.

13. A method for producing a hydraulic actuator according to any of claims 1 to 12 comprising producing an assembly which comprises a hydraulic line sealingly connected at its ends to a reducible chamber and an expandable chamber, the assembly having a filling tube; inserting a filling head into the filling tube and injecting a predetermining volume of liquid into the assembly; and sealing the filling tube.

14. A method according to claim 13 in which the assembly is evacuated through the filling head prior to the injection of liquid.

15. A method according to claim 13 or 14 wherein the filling tube is sealed by RF welding.

16. A method for producing a hydraulic actuator substantially as any herein described with reference to and as illustrated in the accompanying drawings.

17. A method for producing a driving mirror assembly comprising producing a hydraulic actuator by a method according to any of claims 13 to 16; providing a pivotally mounted driving mirror; and coupling the actuator to the mirror for urging pivoting thereof.