GB2377969A

GB2377969A - Actuator mechanism with magnetically coupled uni-flexible member

Info

Publication number: GB2377969A
Application number: GB0115900A
Authority: GB
Inventors: Joseph Peter William Baker
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-06-29
Filing date: 2001-06-29
Publication date: 2003-01-29
Also published as: GB0115900D0

Abstract

An actuator mechanism (20) has a rotary input member (64,65) and an elongate output member (35) for extension and retraction in a generally tangential direction with respect to an arcuate surface of the rotary input member (64,65). The elongate output (35) member is a "uni-flexible" member and coupled magnetically to the rotary input member (64,65). The elongate output member (64,65) is "uni-flexible" in the sense that it is substantially more resistant to flexure in one lateral direction than in an opposite lateral direction. It may also be resistant to flexure in two opposite directions each normal to said one lateral direction. Preferably the uni-flexible member (35) has a plurality of vertically parallel elongate elements (34) of generally rectangular cross-section touching, or disposed in close proximity to, one another along the member (35) and of a material susceptible to magnetisation. The actuator member may also be used to operate a closure member (10) for an opening (11).

Description

ACTUATOR MECHANISMS DESCRIPTION Technical Field This invention relates to actuator mechanisms and in particular to such mechanisms as provide a linear output from a rotary input.

Background Such actuator mechanisms are known for use in opening/closing fan light windows, doors, gates and other closure members (both pivoting and linear). A well-known format for such mechanisms is a worm gear device to impart a linear drive to a sheathed cable. These known actuator mechanisms involve gearing devices and are therefore expensive to produce and prone to jam or seize up. It is therefore considered desirable to devise an actuator mechanism capable of minimising or avoiding such difficulties and/or disadvantages.

Summary of the Invention According to a first aspect of this invention there is provided an actuator mechanism comprising a rotary input member and an elongate output member for extension and retraction in a generally tangential direction with respect to an arcuate surface of the rotary input member, characterised in that the elongate output member is a"uniflexible"member and is coupled magnetically to the rotary input member at least when retracted. The adjectival term"uni-flexible"in relation to a member is used to describe the member as being substantially more resistant to flexure in one lateral direction than in an opposite lateral direction.

Advantageously the uni-flexible member is substantially resistant to flexure in two opposite directions each normal to said one lateral direction.

Preferably the uni-flexible member comprises a plurality of vertically parallel elongate elements of generally rectangular cross-section touching, or disposed in close proximity to, one another along the member, and of a material susceptible to magnetisation. The term"close proximity"refers to a spacing between neighbouring elements less than approximately lmm. Advantageously, hinge means are provided between neighbouring elements to one lateral side only of the member. The hinge means, in one example, may comprise individual hinge pins between the neighbouring elements. In another example the hinge means is provided by attaching to one lateral side of the member a flexible thin strip of material. The strip material may be a magnetically susceptible material (e. g. steel) or a plastics material that does not unduly affect the permeability of the magnetic coupling between the elements and the rotary input member.

It will be apparent that, in use, and with the uni-flexible member drivingly engaged with a member to be actuated, the latter imposes a reactive load to extension of the uniflexible member-in a first sense-away from the rotary input member and at least aids in maintaining the uni-flexible member substantially rigid during such extension, whereas the uni-flexible member is susceptible to collapse or deformation-when drawn up in a second, opposite sense-towards and around the rotary input member.

Brief Description of the Drawings By way of example one embodiment of this invention will now be described with reference to the accompanying drawings of which: Figure 1 is a schematic perspective view of apparatus comprising a closure member and an actuator member therefor according to the present invention, Figure 2 is a plan view of the apparatus shown in Fig 1 in closed condition, Figure 3 is a plan view of the apparatus shown in Fig 1 in opened condition,

Figure 4 is a radial cross-section through a rotary input drive member shown in Figs 1-3, Figure 5 is a schematic perspective view of parts of the apparatus shown in Figs 1-3 in a fully extended condition, and Figure 6 is a schematic plan view of parts of the apparatus shown in Figs 1-3 in a partially withdrawn condition.

Detailed Description of Example (s) of the Invention Figs 1 to 3 illustrate a closure member in the form of a gate 10 movable from a closed condition (Figs 1 and 2) to an open condition (Fig 3) in relation to an opening or throughway 11 between two posts 12,13. The gate 10 is mounted pivotally on post 12, the vertical pivot axis being referenced 22. An actuator mechanism 20 is provided for opening and closing the gate, this mechanism comprising a drive device 65 mounted on the post 12 (but spaced from the gate's vertical pivot axis 22) and a uni-flexible member 35 that is pivotally mounted by its other end to the gate 10, e. g. via a roller 33. The uni-flexible member 35 is of steel or other material susceptible to magnetisation, and is magnetically coupled to the drive device 65.

As best shown in Fig 4, the drive device 65 comprises an annular body 15 of magnetic material that is polarised axially with a North (seeking) pole N at one radial end and a South (seeking) Pole S at the opposite radial end. The body 15 has an axial bore 13 therethrough and a pair of pole plates 14,16 of generally disc-like form are mounted on an axial, stub adaptor 18. Bore 13 is of non-circular, preferably square, crosssection and the axial adaptor 18 is of a correspondingly-shaped cross-section and made of brass or other suitable high reluctance or non-magnetic material. The axial adaptor 18 is fastened to the drive shaft 17 of an electric motor (not shown) and provides rotational drive to the body 15.

Optionally and preferably the axial adaptor 18 is a loose fit in the bore 13. For example, bore 13 is marginally greater-e. g. 1rmn to 2mm (preferably 1. 4mm) greater-than the side dimension of the axial adaptor 18 that transmits drive thereto

and such as to permit the body to tilt or slew to a limited degree. For example, with the bore through body 15 and pole plates 14,16 of a square cross-section having a nominally 24mm side dimension the square-section axial adaptor 18 may have a side dimension of22. 6mm ( ? fa inch) so as to pass loosely or with clearance into the bore 13.

The clearance provided by this dimensional difference allows the end pole plates 14,16 in use to maintain physical contact with the uni-flexible member 35, notwithstanding surface imperfections or variations in stiction between co-operating parts, and this ability to cope with a slightly uneven running surface serves to maximise efficiency of the transmitted drive.

The two pole plates 14,16 are of substantially similar dimensions each having a periphery that, all round, is spaced outwardly away from the periphery of the magnetic

body 15, e. g. of the order of 1 or 2mm (with a maximum of about 5mm). In one preferred embodiment the plates 14, 16 are each 6mm thick and of 75mm nominal diameter.

The two pole plates 14,16 may be identical discs or as disclosed in UK Patent Application No. 0019719. 4, may provide for a degree of keyed or geared connection between one of the pole plates and the uni-flexible member 35, this keying being surmountable without giving rise to damage. To achieve his one of the pole plates may be provided with a plurality of peripherally spaced (preferably equi-spaced) pimplelike protrusions that engage in correspondingly spaced recesses or holes in the uniflexible member 35.

The uni-flexible member 35 of this exemplary embodiment comprises a plurality of vertically parallel elongate steel elements 34 of rectangular cross-section disposed next to one another in mutual abutment along the member. Neighbouring elements 34 are connected to one another-to one side only of the member 35-e. g. by hinge means, by individual hinge pins between them or by attaching said one side of the elements 34 to a flexible thin strip 36 of steel or of plastics material (that does not unduly affect the permeability of the magnetic coupling between the elements 34 and the pole pieces

14,16 of drive device 65). The arrangement is such that the member 35 can flex very easily in one direction shown by arrow A in Fig 5 but resists flexure in the opposite direction when the free and non-hinged edges of elements 34 come into abutment with one another, e. g. under a lateral force on the member 35 in a direction opposite to arrow A.

One end of the uni-flexible member 35 is connected to a point on the periphery of device 65 (i. e. either directly to pole pieces 14,16 or to an intermediate cylindrical wall (not shown) driven rotatably by the pole pieces 14,16). The other end of the uniflexible member 35 is connected to the gate 10 or some other structure that is to be moved back and forth in opposed directions.

If the rotary input drive device 65 is driven in the clockwise direction shown by arrow C in Fig 5, the uni-flexible member 35 retracts, i. e. moves linearly towards drive device 65 in the direction of arrow B and the segments 34 splay open or separate and bind themselves magnetically to the periphery of the drive device 65 (see Fig 6)-this being permitted by the action of the hinge means 38 between the individual neighbouring elements 34. When the latter is driven in the reverse direction opposite to arrow C, the uni-flexible member unwinds. Magnetic flux from the drive device 65 is conducted through each of the segments or elements 34 of the uni-flexible member 35 binding them one to the other to form a virtually rigid shaft. Conceivably, this rigid shaft may adopt a somewhat bowed shape (convex with respect to the concavity of the surface of rotary drive member 65) when it extends away from member 65 and reacts against the load of the gate 10 that it is pushing into closure of the opening or throughway 11 between posts 12 and 13. This can arise as the individual neighbouring elements 34 pivot with respect to one another about the hinge means 38 provided on said one side only.

In a specific form of the embodiment illustrated, fifty (50) of the elements 34 of mild steel, each 30mm wide by 10mm long by 10mm thick, joined to one another by hinges provided along the long edges on just one side of each element 34 and such that the

pivotally interconnected elements 34 form a continuous strip for the uni-flexible member 35. The assembly resembles a collapsible wand which is substantially less resistant to flexure in the lateral direction A of Fig 5 than in the opposite lateral direction. One end of the uni-flexible member 35 is fixed to an eccentric or spiral surface 64 of rotary input device 65, the surface 64 in this specific example being 30mm high (corresponding to the width of the uni-flexible member 35) and of nominally 75mm in diameter. With the rotary input device 65 is located adjacent the pivot axis of a pivoting gate, door or other closure member 10, and the distal end of the uni-flexible member 35 attached to the gate, door or other closure member about mid-way along it, then (a) as the rotary input device 65 is rotated in the direction of arrow C of Fig 5 by the electric motor that drives it, the uni-flexible member 35 winds itself onto that discoid surface and (b) when rotated in the reverse direction the closure member will move in reverse and effect closure of the gateway, doorway or throughway 11. During motion (b), the uni-flexible member 35 is unfurled in sympathy with the arc described by the fixing point 33 around the gate's pivot axis 22.

Until motion (b) is complete, magnetic attraction maintains contact between the uniflexible member 35 and the surface 64.

The segments are preferably shaped to nest in one another, and their inside surfaces are serrated or roughened to prevent unwanted slippage. When the member 35 is extended and the gate 10 is open, the elements 34 are maintained in their relationship by magnetic attraction conducted from member 65 as well as by the load urging the elements towards one another (due to the motor and/or the auto-closing tendency of the gate 10).

The arrangement is dimensioned and positioned such that, when the uni-flexible member 35 passes the end of its travel, its position passes'top-dead-centre'with regard to the fixing position for the motor to rotary input member 65, such that the gate is locked in the closed position

In one modified construction the strip 36 may have a concave cross-section in the vertical plane to provide a degree of resilient flexibility when it is wound up around the rotary input member provided by drive device 65 but remain rigid when extended generally tangentially therefrom (in a manner similar to the operation of a conventional metal tape measure). In such a case the elements 34 may have a concave recess in the said one side (i. e. the side provided with the hinge means) to accommodate the concave strip 36.

In another modification the pole pieces 14,16 may engage an intermediate band, e. g. the cylindrical wall of an inverted cup-shaped member, which is of steel or another material susceptible to magnetisation. The provision of such a cylindrical wall engaging pole pieces 14,16 is disclosed in UK Patent Publication No. 2338603-A.

In still another modification, the elements 34 are formed as magnets and the rotary input drive member is of a material susceptible to magnetisation.

In yet another modification, elements 34 of the extended uni-flexible member 35 are not in abutting contact with one another but are instead slightly spaced apart (to accommodate the hinge means 38), e. g. by a distance somewhat less than lmm, and such as to be in close proximity to one another. Although this can reduce the transfer of magnetic flux from one element 34 to the next, and thus reduce the overall rigidity of the uni-flexible element 35 in its extended state, it may yet achieve a workable result - especially if the elements 34 are connected to the optional backing strip 36 such as is mentioned above.

The aforesaid modifications as well as other modifications and embodiments of the invention, which will be readily apparent to those skilled in this art, are to be deemed within the ambit and scope of the invention, and the particular embodiment (s) hereinbefore described may be varied in construction and detail, e. g. interchanging (where appropriate or desired) different features of each, without departing from the scope of the patent monopoly hereby sought.

Claims

CLAIMS 1. An actuator mechanism comprising a rotary input member and an elongate output member for extension and retraction in a generally tangential direction with respect to an arcuate surface of the rotary input member, characterised in that the elongate output member is a member that is uni-flexible-as hereinbefore definedand is coupled magnetically to the rotary input member at least when retracted.
2. An actuator mechanism according to Claim 1, wherein the uni-flexible member is substantially resistant to flexure in two opposite directions each normal to said one lateral direction.
3. An actuator mechanism according to Claim 1 or Claim 2, wherein the uniflexible member comprises a plurality of vertically parallel elongate elements of generally rectangular cross-section touching, or disposed in close proximity to, one another along the member, and of a material susceptible to magnetisation.
4. An actuator mechanism according to Claim 3, wherein hinge means are provided between neighbouring elements to one lateral side only of the member.
5. An actuator mechanism according to Claim 4, wherein the hinge means comprises individual hinge pins between the neighbouring elements.
6. An actuator mechanism according to Claim 4, wherein the hinge means is provided by a flexible thin strip of material attached to one lateral side of the member.
7. An actuator mechanism according to Claim 6, wherein the strip material is a magnetically susceptible material (e. g. steel) or a plastics material that does not unduly affect the permeability of the magnetic coupling between the elements and the rotary input member.

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8. An actuator mechanism substantially as herein described with reference to and/or as illustrated in the accompanying drawings.
9. An actuator mechanism according to any one of the preceding Claims operatively connected to a closure member for an opening.
10. An actuator mechanism according to Claim 9, wherein the closure member is a pivoted gate for a throughway.
11. An actuator mechanism and closure member substantially as herein described with reference to and/or as illustrated in the accompanying drawings.