AU2022273820A1

AU2022273820A1 - Actuator mechanism

Info

Publication number: AU2022273820A1
Application number: AU2022273820A
Authority: AU
Inventors: Jennifer Lynn Fraser; Marc Randall FRASER
Original assignee: Ideation Training Pty Ltd
Current assignee: Ideation Training Pty Ltd
Priority date: 2021-05-11
Filing date: 2022-05-05
Publication date: 2023-12-21
Also published as: WO2022236360A1

Abstract

A low friction actuator mechanism including a lever mechanism including a lever arm extending from a pivotal mounting to allow the lever arm to at least partially rotate about a pivot axis and a drive member operatively coupled to the lever arm, the drive member including a helically shaped drive surface extending circumferentially part of the way around the pivot axis and axially along the pivot axis such that a force applied to the drive surface causes rotation of the lever about the pivot axis, and a driver including a rotatable member that engages the drive surface to thereby actuate the lever.

Description

- 1 -

ACTUATOR MECHANISM

Background of the Invention

[0001] The present invention relates to an actuator mechanism, and in one example to an actuator mechanism incorporating a lever mechanism, as well as to the lever mechanism itself.

Description of the Prior Art

[0002] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgement or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

[0003] A lever typically consists of a beam or rigid rod pivoted at a fixed hinge, or fulcrum. The locations of the fulcrum, and the applied load and effort, can be used to alter the result of an applied input force and movement, for example to amplify an input force to provide a greater output force, which is said to provide leverage, or to amplify an input movement, to provide a greater output movement. As such, the lever is a mechanical advantage device, trading off force against movement with the ratio of the output force to the input force being the mechanical advantage of the lever.

[0004] It is known to provide rotary actuators to convert a linear actuating force into a rotary force. An example of such an arrangement is described in US-7,185,852, which relates to an actuator assembly for actuating a door or aerodynamic surface of an aircraft. The actuator includes a housing having first and second ends and a longitudinal axis. The housing center portion further includes first and second helical slots extending along the longitudinal axis. A cam follower, having first and second ends, is movably mounted in the center portion, the cam follower movable along the longitudinal axis of the housing. An actuator is provided for actuating the cam follower in first and second directions along the longitudinal axis. A bolt assembly, having first and second ends, is mounted through the cam follower with the first and second ends thereof extending into the first and second helical slots. First and second bearings are mounted to the first and second ends of bolt assembly such that the first and second bearings - 2 are movably mounted in the first and second helical slots. An actuation rod has its first end in the form of a clevis with first and second lugs movably connected to the first and second ends of the bolt assembly.

[0005] GB 1389601 describes a mechanism for converting axial reciprocating deflecting movements of a pressure or temperature responsive diaphragm into rotary movement of an indicator pointer of a pressure or temperature measuring gauge comprises a plastics (P.T.F.E.) lever pivoted on the gauge base and having a projection engaging the diaphragm, the outer end of the lever having a projection engaging a helical groove of a plastics (P.T.F.E.) spindle rotatably mounted at in the gauge base and carrying at its upper end the pointers. In operation, deflections of the diaphragm rock the lever which via the projection and helical cam slot rotate the spindle to move the pointer across a calibrated scale dial, a hairspring serving to return the pointer against a stop at the lowest measured values.

[0006] DE 8909527 relates to a data transmission device, preferably for rotary satellite reception systems for positioning a parabolic mirror. The system contains a linear guide consisting of a guide plate, a guide piece, a pin and a threaded spindle. The guide piece moves linearly in the guide plate and is connected via the pin to a helix which is located in a drive shaft. The helix converts the linear movement of the guide piece into a rotary movement of the drive shaft.

[0007] US 9027423 describes a linear-to-rotary actuator that includes an elongated drive member constrained to linear movement, and a rotary member constrained to rotary movement. The elongated drive member has a coupling end and an engaging member that projects from the coupling end. The rotary member has a track defining an Archimedean spiral. The track is adapted to receive the engaging member. The engaging member is constrained to slide in the track such that linear movement of the elongated member effects rotation of the rotary member. The track may be a slot, a groove, or other guide. Alternatively, instead of a track defined directly in the rotary member, the actuator may include a linking member (such as a disk or rectangular bracket) attached to the rotary member, the linking member having a track defining an Archimedean spiral defined therein, the engaging member being slidable in the track to convert linear motion into rotary motion. - 3 -

[0008] US 2014/0034858 describes a valve actuator for a rotary valve includes a piston and housing assembly, wherein axial movement of the piston along a bore of the housing causes an actuator rod to twist or rotate about an axis of the bore. The rotary motion of the actuator rod is caused in some arrangements by axial rotation of the piston along a helical housing wall and/or by axial rotation of a generally helical shape of the actuator rod engaged with a central opening through the piston.

[0009] US 4586259 describes a rocking rotational angle altering system equipped with an improved output rotational angle indicating device. The device includes a movable block and a cam rod brought into engagement with each other in rolling contact. The movable block has rolling elements mounted to act as a unit therewith and the cam rod is formed with a flat cam surface engageable with the rolling elements of the movable block.

[0010] GB2417837A describes a drive mechanism including a rail with mounting brackets disposed at the ends of the rail. Each bracket can accommodate a rotary element. A helical ribbon screw is disposed between said mounting brackets and is coupled to shafts via coupling elements. A slider comprises a pair of jaws and a lever. The lever protrudes through a slot in the rail and is capable of sliding along the rail. The jaws of the slider are engaged with the helical screw. Uimit blocks are positioned to limit the rectilinear movement of the slider. The rectilinear motion of the slider engaged with the helical screw causes simultaneous rotation of the rotary elements. Preferably these rotary elements could be potentiometers, switches, encoders, tuners, electric motors and valves or combinations there of.

[0011] However, such arrangements are generally intended for use in scenarios where a high force is required, making these unsuitable for low force applications.

Summary of the Present Invention

[0012] In one broad form, an aspect of the present invention seeks to provide a low friction actuator mechanism including: a lever mechanism including: a lever arm extending from a pivotal mounting to allow the lever arm to at least partially rotate about a pivot axis; and, a drive member operatively coupled to the lever arm, the drive member including a helically shaped drive surface extending circumferentially part of the way around the pivot axis and axially along the pivot axis such that a force applied to the drive surface causes rotation of the - 4 - lever about the pivot axis; and, a driver including a rotatable member that engages the drive surface to thereby actuate the lever.

[0013] In one embodiment the rotatable member includes at least one of a roller, cog, gear or roller ball, that engages the drive surface.

[0014] In one embodiment the actuator mechanism has a coefficient of friction of at least one of: less than 0.1; less than 0.05; and, less than 0.01.

[0015] In one embodiment the driver includes an actuator.

[0016] In one broad form, an aspect of the present invention seeks to provide a low friction actuator mechanism including: a lever mechanism including: a lever arm extending from a pivotal mounting to allow the lever arm to at least partially rotate about a pivot axis; and, a drive member operatively coupled to the lever arm, the drive member including a helically shaped drive surface extending circumferentially part of the way around the pivot axis and axially along the pivot axis such that a force applied to the drive surface causes rotation of the lever about the pivot axis; and, a contactless driver that applies a force to the drive surface to thereby actuate the lever.

[0017] In one embodiment the contactless driver includes at least one of: a moving fluid; airflow; liquid flow; electromagnetic forces; light pressure; and magnetic forces.

[0018] In one embodiment one of: the drive member and driver move relative to each other; the driver is static and the lever mechanism moves relative to the driver; and, the lever mechanism is static and the driver moves relative to the lever mechanism.

[0019] In one embodiment the lever arm is attached to a pivotal shaft supported by at least one of: bearings; magnetic bearings; concave seats that receive opposing pointed ends of the shaft; and, concave seats that magnetically support ends of the shaft.

[0020] In one embodiment the lever arm is attached to a hub rotatably mounted on an axle.

[0021] In one embodiment the drive member is at least one of: attached to the lever arm; attached to a pivotal shaft; attached to a pivotal shaft via one or more support arms; attached to a hub; and, attached to a hub via one or more support arms. - 5 -

[0022] In one embodiment a degree of mechanical advantage provided by the lever is dependent on at least one of: a radius of the drive surface; a pitch of the drive surface; and, a length of the lever arm.

[0023] In one embodiment the driver applies a force to the drive member in a direction that is at least partially parallel to, or along, the pivot axis, and wherein the pitch of the drive surface varies so that at least one of: a degree of mechanical advantage changes through a stroke of the lever; and, the lever provides a non-linear response.

[0024] In one embodiment the drive surface is at least one of: aligned with the lever arm; rotationally offset from the lever arm; and, in opposition to the lever arm.

[0025] In one embodiment the drive surface extends at least one of: less than 270° around the pivot axis; less than 180° around the pivot axis; less than 135° around the pivot axis; less than 90° around the pivot axis; less than 60° around the pivot axis; less than 45° around the pivot axis; and, less than 30° around the pivot axis.

[0026] In one embodiment the drive surface is at least one of: flat; concave; convex; curved; rough; serrated; keyed; toothed; and, smooth.

[0027] In one embodiment at least one of: a shape of the drive surface is configured depending on a direction of the applied force; an orientation of the drive surface is configured depending on a direction of the applied force; and, an axis of the helical drive surface is orientated so it is at least approximately parallel to a direction of the applied force.

[0028] In one embodiment the lever includes first and second drive surfaces configured to cause rotation of the lever arm in opposing directions.

[0029] In one embodiment at least one of: the drive member includes the first and second drive surfaces; and, the lever includes first and second drive members, each having a respective one of the first and second drive surfaces.

[0030] In one embodiment: a force applied to the first drive surface in a first drive direction causes rotation of the lever arm in a first rotational direction; and, a force applied to the second 6 drive surface in a second drive direction causes rotation of the lever arm in a second rotational direction opposite to the first rotational direction.

[0031] In one embodiment the first and second drive surfaces have the same pitch directions so that the first drive direction is opposite to the second drive direction.

[0032] In one embodiment the first and second drive surfaces have opposing pitch directions so that the first drive direction is the same as the second drive direction.

[0033] In one embodiment the first and second drive surfaces are axially and rotationally offset so that a driver moving in a drive direction causes successive rotations in first and second opposing directions.

[0034] In one embodiment the first and second drive surfaces have at least one of: different pitches from each other; and, different radii from each other.

[0035] In one embodiment the actuator mechanism provides substantially no mechanical advantage and operates to redirect the applied force.

[0036] In one embodiment the lever arm is at least one of: adjustable; retractable; extendible; telescopic; slidable; jointed; and, concertinaed.

[0037] In one embodiment an effective length of the lever arm alters as the lever arm pivots about the pivot axis.

[0038] In one embodiment the actuator mechanism is used as an indicator to provide an indication of at least one of: a magnitude of an applied force; and, a distance of an applied movement.

[0039] In one embodiment a scale is used to provide an indication through at least one of: movement of a lever arm positioned proximate the scale; and, movement of an electromagnetic radiation source to illuminate the scale.

[0040] In one broad form, an aspect of the present invention seeks to provide a lever mechanism including: a lever arm extending from a pivotal mounting to allow the lever arm to at least partially rotate about a pivot axis; and, a drive member operatively coupled to the lever arm, - 7 - the drive member including a helically shaped drive surface extending circumferentially part of the way around the pivot axis and axially along the pivot axis such that a force applied to the drive surface causes rotation of the lever about the pivot axis.

[0041] It will be appreciated that the broad forms of the invention and their respective features can be used in conjunction and/or independently, and reference to separate broad forms is not intended to be limiting. Furthermore, it will be appreciated that features of the method can be performed using the system or apparatus and that features of the system or apparatus can be implemented using the method.

Brief Description of the Drawings

[0042] Various examples and embodiments of the present invention will now be described with reference to the accompanying drawings, in which: -

[0043] Figure 1A is a schematic perspective view of an example of a lever mechanism;

[0044] Figure IB is a schematic end view of the lever mechanism of Figure 1A;

[0045] Figure 1C is a schematic side view of the lever mechanism of Figure 1A;

[0046] Figure ID is a schematic plan view of the lever mechanism of Figure 1 A;

[0047] Figure 2A is a schematic perspective view of a first alternative example of a lever mechanism;

[0048] Figure 2B is a schematic perspective view of a second alternative example of a lever mechanism;

[0049] Figure 3A is a schematic perspective view of a further example of a lever mechanism; [0050] Figure 3B is a schematic end view of the lever mechanism of Figure 3A;

[0051] Figure 3C is a schematic side view of the lever mechanism of Figure 3A;

[0052] Figure 3D is a schematic plan view of the lever mechanism of Figure 3A;

[0053] Figure 4A is a schematic perspective view of a further example of a lever mechanism; 8

[0054] Figure 4B is a schematic end view of the lever mechanism of Figure 4A;

[0055] Figure 4C is a schematic side view of the lever mechanism of Figure 4A;

[0056] Figure 4D is a schematic plan view of the lever mechanism of Figure 4A;

[0057] Figure 5A is a schematic perspective view of a further example of a lever mechanism;

[0058] Figure 5B is a schematic end view of the lever mechanism of Figure 5A;

[0059] Figure 5C is a schematic side view of the lever mechanism of Figure 5 A;

[0060] Figure 5D is a schematic plan view of the lever mechanism of Figure 5A;

[0061] Figures 6A to 6C are schematic side views of the lever mechanism of Figure 4A undergoing actuation;

[0062] Figure 7A is a schematic end view of the lever mechanism of Figure 1A with a telescopic lever arm; and,

[0063] Figure 7B is a schematic end view of the lever mechanism of Figure 7A showing retraction of the telescopic lever arm.

Detailed Description of the Preferred Embodiments

[0064] An example of a lever mechanism, which in one example can be used as part of an actuator mechanism, will now be described with reference to Figures 1A to ID.

[0065] In this example, the lever mechanism 100 includes a lever arm 110 extending from a pivotal mounting 120 to allow the lever arm 110 to at least partially rotate about a pivot axis. In this example, the pivotal mounting includes a hub 122 rotatably mounted on an axle 121, although it will be appreciated that this is not essential and any form of pivotal mounting could be used. Additionally, in this example, the lever arm 110 includes a load 111, such as a mass, on a distal end, which undergoes movement as the lever arms moves. However, this is shown for the purpose of illustration only, and in practice the lever arm may be used in any appropriate manner, and could for example be attached to an object to cause movement of the object. Similarly, the load could comprise the mass of the lever arm itself. - 9 -

[0066] The lever mechanism 100 further includes a drive member 130 operatively coupled to the lever arm 110. In this example, this is achieved by having the drive member 130 attached to the hub 120 via support arms 133, but this is not essential and other arrangements could be used, such as attaching the drive member 130 directly to the lever arm 110, or directly to the hub 120. The drive member includes a helically shaped drive surface extending circumferentially part of the way around the pivot axis, and axially along the pivot axis. This configuration is such that when a force is applied to the drive surface this causes rotation of the lever about the pivot axis.

[0067] Specifically, in this example, the drive member 130 includes drive surfaces 131, 132 provided on opposing surfaces of the drive member, so that a force Fi, F2 can be applied to a respective one of the surfaces 131, 132 in opposite directions, as shown by the respective arrows. This in turn allows the lever arm 110 to be rotated in either an anti-clockwise direction Ri or clockwise direction, R_. depending on the direction of the applied force. This allows a force to be used to rotate the lever arm in one direction, with a second opposing force being used to return the lever arm to a starting position. It will be appreciated that the particular directionality of this example is for the purpose of illustration only, and the orientation of the drive surfaces could be mirrored, for example so that forces Fi, F2 cause rotations R2- Ri.

[0068] In the above example, the forces Fi, F2 are applied at least partially in a direction parallel to the pivot axis, so that at least a component of the applied forces are parallel to the pivot axis. However, it will be appreciated that this is illustrative only, and that in practice forces can be applied in any direction, which could include applying forces whose orientation changes, for example following an arcuate path or similar. It will be appreciated that the orientation and/or shape of the drive surface may need to be altered depending on the direction of the applied force, so that if the force is applied in a direction that is angled relative to the axis, the helical drive surface may also be orientated at an angle relative to the axis. For example, an axis of the helical drive surface can be orientated so it is roughly parallel to the direction of the applied force, and that this drive surface axis might be angled relative to the pivot axis. Additionally, the geometry of the drive surface may be otherwise configured to optimise force transfer to the drive surface, for example by warping the shape of the drive surface depending on the direction of the applied force. 10

[0069] It will also be appreciated that in the above examples, the use of two drive surfaces is not essential and only a single drive surface might be provided, so that the lever arm is only rotated in one direction using a force applied to a drive surface. In this instance, if needed, the lever arm can optionally be returned to a starting position using another mechanism, such as a gravitational force, or biasing mechanism, such as a spring, or the like.

[0070] In any event, the above described arrangement provides a lever arrangement that can provide a number of benefits.

[0071] Firstly, the degree of mechanical advantage provided by the lever arrangement depends on a radius of the drive surface, a pitch of the drive surface and a length of the lever arm. This provides a greater degree of control over the mechanical advantage than can be achieved using traditional levers. For example, if it is desired to increase the mechanical advantage provided by the lever, this can achieved either by increasing the radius of the drive surface and/or increasing the pitch of the drive surface. Conversely, if the mechanical advantage is to be lowered, for example to provide greater output movement, this can be achieved by decreasing the radius of the drive surface and/or decreasing the pitch of the drive surface. It will be appreciated that this therefore provides greater flexibility for the lever mechanism to achieve a desired output force or movement. Furthermore, and related to this, the pitch of the drive surface can vary along the length of the drive surface, so that the lever arrangement can provide a varying degree of mechanical advantage throughout a stroke. This can be useful for example to provide a varying force profde, which could be used for example to overcome initial inertia of the lever and an associated load, with more of the input force being converted to movement of the load once the inertia has been overcome.

[0072] It will also be further appreciated from the above that the arrangement could be configured to provide no mechanical advantage, in which case the mechanism effectively redirects the force applied to the drive surface, for example converting a linear or arcuate force, which may be applied in a direction along the axis, into a rotational movement (and hence a rotational force) about the pivot axis.

[0073] Secondly, the lever arrangement can be used to provide a low force actuator. In this regard, the force can be applied to the drive surface using a driver, which can be configured to minimise friction, thereby providing a low friction actuator mechanism. 11

[0074] The nature of the driver will vary depending on the preferred implementation, but in general the drivers fall into one of two categories. The first of these employ drivers with a rotating member, such as a roller, cog, gear, roller ball mechanism, or similar, that engages the drive surface, and which can rotate as the drive surface moves relative to the driver. The second of these involve the use of "contactless" engagement to apply a force to the drive member, for example using a moving fluid, such as airflow or water flow, or other contactless mechanisms, such as using electromagnetic radiation, and in particular magnetic engagement and/or light pressure, for example caused by photon impact on the drive member. It will be appreciated that in contrast to sliding engagement, or other similar approaches, these arrangements result in minimal frictional losses, so that effectively the entire applied force is used to actuate the lever, thereby maximising the output force that is achieved for a given input force. Again, suitable configuration of the pitch and/or radius of the drive surface can be used to ensure the force profile is appropriate for the application.

[0075] It will also be appreciated that depending on the configuration of the driver and drive member, the driver could move relative to a stationary lever mechanism, or the lever mechanism could move relative to a stationary driver. For example, in a signalling application on a model railway, the driver could be mounted on a train, which then engages a lever mechanism mounted statically beside the track, to thereby actuator the lever mechanism and move a signal as the train passes. Conversely, the lever mechanism could be mounted on the train and activated when the train passes a static driver mounted beside the track, to thereby actuate a mechanism onboard the train.

[0076] In any event, it will be appreciated that such low friction actuator arrangements make the lever useful for situations in which a low actuation force might be required. For example, this could be used in applications where an input force is generated by movement of fluids, particularly gases or vapours, such as wind or steam, by gravitational forces, electromagnetic forces, sound waves, or the like. For example, this could be used in creating a particle detector, in which incident particles, such as photons, alpha radiation, or similar, are used to provide the input force and thereby move the lever.

[0077] In another example, the lever apparatus could be used as an indicator, for example to indicate a magnitude of an applied force or a distance of an applied movement, such as a 12 distance of movement of a driver. In this instance a scale could be positioned proximate and/or adjacent to the lever arm, so that movement of the lever arm represents a degree of force / distance of movement on the scale. A biasing mechanism, such as a spring or gravity, could be used to return the indicator to a zero reading when no force is applied, and/or to provide a counter force, which can be used to counteract the applied force, thereby allowing a force measurement to be performed. It will be appreciated that sensitivity could be adjusted by altering a length of the lever arm and/or pitch of the drive surface. Altering the pitch of the drive surface could also be used to allow a non-linear response to be provided, which if used with a corresponding non-linear scale, could be used to measure forces logarithmically.

[0078] A further variation is for the lever arm to be a virtual arm, for example using an electromagnetic radiation source, such as a laser or light emitting diode, to illuminate a scale and provide an optical output. In this instance, the light source can be attached to or effectively replace the lever arm. It will be appreciated however that the apparatus still effectively functions as a lever by virtue of the drive surface converting an input force / movement into a corresponding movement of the light source, and hence the direction in which the optical radiation is emitted. Again shaping of the drive surface can be used to induce a non-linear response, which in turn can allow a non-linear input to be converted into a linear output. For example a fluid level in a non-uniform shaped vessel will vary non-uniformly for a constant outflow rate. In this instance, a float could be used as a driver to move a non-linearly pitched drive surface, and thereby generate a linear optical output representing a volume of fluid remaining. The non-linear response could result in the degree of motion varying during a cycle and/or could involve the rate of movement varying, for example so that the speed of movement of the load and/or lever could vary, for example speeding up and/or slowing down.

[0079] Thirdly, the lever arrangement allows the lever to be actuated using a force applied in a lateral direction that may be parallel to, or along, or with a component of force parallel to, or along, the pivot axis, which can be particularly useful in constrained spaces. This is especially the case where the radius of the drive surface is minimised, for example if the drive surface is located proximate the pivot axis, in which case an actuator, such as a linear or non-linear actuator, can be positioned adjacent to the pivot axis and/or hub. Nevertheless, in this arrangement, significant mechanical advantage can still be achieved through suitable configuration of the pitch of the drive surface. - 13 -

[0080] It will be appreciated that the combination of low friction and hence low force actuation and small footprint, and potential large mechanical advantage, is particularly useful in microelectronics and other similar situations, for example to provide an actuator in a MEMS (micro-electromechanical system) application, for use in activating a micro-switch, or the like, as well as for use inside automata, kinetic art, horological mechanisms, such as watches and time pieces, miniature orreries, or the like.

[0081] A number of further features will now be described.

[0082] As mentioned above the actuator mechanism is a low friction actuator, and typically has a coefficient of friction of less than 0.1, less than 0.05 or more preferably less than 0.01.

[0083] In the above example, the lever arm 110 and drive member 130 are attached to a hub that is supported by an axle 121, which allows rotation of the lever arm 110 and drive member 130 about a pivot axis. However, it will be appreciated that other arrangements that allow such rotational movement could be used. For example, the lever arm 110 and drive member 130 could be attached to a shaft, which is rotationally supported, for example using bearings, such as ball bearings, washers, or other suitable friction reducing arrangements. In one particular example, the shaft includes pointed ends that are received in concave, or otherwise indented, seats positioned at either end of the shaft, so that the shaft is rotatably supported. In this arrangement, the pointed ends of the shaft result in minimal contact with the seats, thereby minimising friction, whilst reducing the complexity of the pivotal arrangement, and avoiding the need for complex bearings or similar. Other arrangements that can be used include the use of magnetic bearings, to suspend the shaft so that there is no physical point of contact with the shaft. Such bearings can be passive, for example including magnetic material in the seats, which then repel magnetic material in the ends of the shaft, and/or could include active bearings, for example using electromagnets that are actively controlled to thereby suspend the shaft. Such arrangements are well known from other applications, such as magnetically suspended impellers in rotary heart pumps.

[0084] In the above example, the drive surface 131 is in opposition to the lever arm 110, so that the drive surface 131 is located 180° around the pivot axis from the lever arm 110. However, this is not essential and alternatively, the drive surface could be aligned with the lever arm, and examples of this are shown in Figures 2A and 2B. For the purpose of ease of - 14 - illustration, similar features to those of Figures 1A to ID are denoted by similar reference numbers increased by 100.

[0085] Thus, in these examples, the lever arrangement 200 includes a lever arm 210 having a load 211, which extends from a pivotal mounting 220 that includes a hub 222 rotatably mounted on an axle 221. The drive member 230 having a drive surface 231 (with an optional opposing drive surface not shown) is operatively coupled to the lever arm 210 by having the drive member 230 attached to the hub 220 via support arms 233. In these arrangements, the drive member 230 is generally aligned with the lever arm 210, meaning the lever arm 210 and drive member 230 are both on the same side of the pivot axis, which can be beneficial in some applications.

[0086] It will also be appreciated that the arrangements of Figures 1A to ID are 2A and 2B represent extreme arrangements in which the lever arm and drive surface are aligned or are in opposition, but that intervening arrangements could be provided in which the drive surface is rotationally offset from the lever arm by an amount anywhere between 0° and ±180°.

[0087] In the example of Figure 2A, the supporting arms 233 are longer than the lever arm 210, so that the drive surface(s) 231 are provided outwardly of the load 211, whereas in the example of Figure 2B, the supporting arms 233 are shorter than the lever arm 210, so that the drive surface(s) 231 are provided inwardly of the load 211. It will be appreciated that these two arrangements would therefore provide different mechanical advantage, assuming the drive surface pitches are equal. Again, it will be appreciated that a variety of different arrangements and in particular relative length of lever arm and supporting arms (and hence drive surface radius) could be used. In these examples, opposing drive surfaces are not shown, but could be implemented if required, for example by axially increasing a distance between the lever arm and the drive surface in an axial direction (along the pivot axis), to allow sufficient space for a driver, such as a small roller, to pass between them as the mechanism rotates, or by using a lever arm deformed to allow passage of the driver. Alternatively, this could be achieved by providing a further drive member on a different side of the lever arm.

[0088] In the above examples, the drive surface extends approximately 90° around the pivot axis. However, greater or shorter lengths of drive surface could be used, with this in turn influencing the stroke length of the lever arm. Whilst the drive surface could extend more than - 15 -

360° around the pivot axis (in effect being similar to a screw thread), this would lead to overlapping threads, and a stroke length of over 360°, which generally complicates the actuation arrangements. Typically the drive surface is therefore configured to extend around less than 270° around the pivot axis, less than 180° around the pivot axis, less than 135° around the pivot axis, less than 90° around the pivot axis, less than 60° around the pivot axis, less than 45° around the pivot axis or less than 30° around the pivot axis. However, it will be appreciated that the exact dimensions will depend on the intended application, and the desired stroke length for the lever arm.

[0089] In one example, the drive surface can be configured to optimise force transfer to the lever mechanism. The manner in which this is achieved will vary depending on the nature of the force, and how this is applied. For example, the drive surface could be flat, allowing a roller, cog, gear, roller ball, or other similar driver to engage the surface and ensure all forces are evenly transferred to the driver member. The drive surface could be concave, and may include baffles or other fluid guides, to ensure fluidic driving forces are captured, whereas a convex and/or smooth surface could be used to reduce friction between a roller, cog, gear, roller ball, or sliding driver and the drive surface. The drive surface could be textured, roughened, keyed, serrated or toothed, to facilitate engagement with a driver, which may include a complementary surface structure. For example, the driver could include a toothed gear and the drive surface may include corresponding teeth that engage the toothed gear and prevent unwanted slippage.

[0090] As mentioned, in the above examples, the lever can include first and second drive surfaces configured to cause rotation of the lever arm in opposing directions, for example allowing the lever to act as a switch capable of moving between two or more positions, depending on the preferred implementation. It will also be appreciated that through progressive application of the force, this allows the lever to act as an analogue control, allowing a position of the lever to be moved through a variety of positions as needed. Such a switch could be held in a set position through appropriate positioning of a driver, for example using a driver to bias the lever into a set position, and then holding the driver against the drive surface to retain the lever in position. Additionally and/or alternatively, a catch and release mechanism, or the like, could be used to retain the lever in a desired position. - 16 -

[0091] In the above examples, the lever mechanism includes a single drive member that includes first and second drive surfaces on opposing sides of the drive member, so that forces are applied in opposing directions to cause opposing rotations of the lever arm.

[0092] In another example, a drive member can be provided with two drive surfaces on a single side, and an example of this will now be described with reference to Figures 3A to 3D. For the purpose of ease of illustration, similar features to those of Figures 1A to ID are denoted by similar reference numbers increased by 200.

[0093] Thus, in these examples, the lever arrangement 300 includes a lever arm 310 having a load 311, which extends from a pivotal mounting 320 that includes a hub 322 rotatably mounted on an axle 321. The drive member 330 is operatively coupled to the lever arm 310 by having the drive member 330 attached to the hub 322 via support arms 333. In this example, the drive member includes first and second drive surfaces 331, 332, having opposing pitches, but provided on the same side of the drive member 330. As a result, in this arrangement, a force Fi, F2 applied to a respective one of the surfaces 331, 332 causes the lever arm 310 to rotate in either an anti -clockwise direction Ri or clockwise direction, R_. with the forces I' . F2 being applied in the same direction.

[0094] In a further example, the lever includes first and second drive members, each having a respective one of the first and second drive surfaces, and a first example of this will now be described with reference to Figures 4A to 4D. For the purpose of ease of illustration, similar features to those of Figures 1A to ID are denoted by similar reference numbers increased by 300.

[0095] In this example, the lever arrangement 400 includes a lever arm 410 having a load 411, which extends from a pivotal mounting 420 that includes a hub 422 rotatably mounted on an axle 421. First and second drive members 430.1, 430.2 are provided, with each being operatively coupled to the lever arm 410 by having the drive member 430.1, 430.2 attached to the hub 422 via support arms 433. In this example, each drive member 430.1, 430.2 includes a respective drive surface 431, 432, having opposing pitches. As a result, in this arrangement, a force Fi, F2 applied to a respective one of the surfaces 431, 432 causes the lever arm 410 to rotate in either an anti -clockwise direction Ri or clockwise direction, /A. with the forces I' . F2 being applied in the same or similar directions. It will be appreciated however, that in this - 17 - arrangement, the drive surfaces 431, 432 could have the same pitches and could be provided on different sides of the drive members 430.1, 430.2, so that forces I' . F2 are applied in opposing directions to rotate the lever arm 410 in either an anti -clockwise direction Ri or clockwise direction, R2.

[0096] In the above examples, the drive surfaces typically have the same pitch angles, even if the pitch directions are the same or opposing, which leads to the lever having the same mechanical advantage irrespective of the rotation direction. However, this is not essential, and an example arrangement in which different drive surfaces have different pitches from each other will now be described with reference to Figures 5A to 5D. For the purpose of ease of illustration, similar features to those of Figures 1A to ID are denoted by similar reference numbers increased by 400.

[0097] In this example, the lever arrangement 500 includes a lever arm 510 having a load 511, which extends from a pivotal mounting 520 that includes a hub 522 rotatably mounted on an axle 521. First and second drive members 530.1, 530.2 are provided, with each being operatively coupled to the lever arm 510 by having the drive member 530.1, 530.2 attached to the hub 522 via support arms 533. In this example, each drive member 530.1, 530.2 includes a respective drive surface 531, 532, with the drive surfaces having opposing pitch directions so that forces Fi, F2 applied to a respective one of the surfaces 531, 532 cause the lever arm 510 to rotate in either an anti -clockwise direction Ri or clockwise direction, /A. with the forces Fi, F2 being applied in the same direction. In this example, however, the drive surface 531 has a much larger pitch than the drive surface 532, meaning there is a greater mechanical advantage when the lever 510 is moved in the anti-clockwise direction Ri than in the clockwise direction R2.

[0098] It will be appreciated from this that a variety of different drive surfaces could be provided, with different drive surfaces optionally including different pitches, allowing a range of different lever actions to be achieved. This might be required, for example, as different forces might be required to move the lever mechanism in different directions. For example, depending on the orientation of the lever mechanism, the gravitational force applied to the load might be greater when moving in one direction to lift the load, as opposed to moving in a counter direction to lower the load. In this case, different pitched surfaces might be used so - 18 - that the magnitude of the applied force required to move the lever is equal in both directions. Similar arrangements might be required to counteract differences in frictional forces that might arise when moving loads in different directions.

[0099] Similarly, the drive surfaces could be provided in different locations, and could be rotationally and/or axially offset. For example, first and second drive surfaces could be axially and rotationally offset so that a driver moving in a drive direction causes a first rotation in first direction when impinging upon the first drive surface, and with continuing axial movement of the driver, then causes a second opposing rotation when impinging upon the second drive surface. It will also be appreciated that lever mechanisms with a single drive surface could be used, with return of the lever mechanism to a starting point being achieved using another biasing mechanism, such as a spring, gravitational force, or the like.

[0100] As mentioned above, the lever arrangement can be used in any appropriate manner, in one example, this is used in conjunction with a driver that engages the drive member, so that the lever mechanism acts as an actuator mechanism, and an example of this will now be described with reference to Figures 6A to 6C.

[0101] For the purpose of illustration, this example uses the lever mechanism of Figure 4A to 4D, and hence similar reference numbers are used to identify similar features, which will not therefore be described in any detail. Nevertheless, it will be appreciated that the techniques are equally applicable to the other lever mechanisms described and/or illustrated within the current application.

[0102] In this example, the actuation mechanism includes the lever mechanism 400 and a driver 640 that engages the drive surface 431 to thereby actuate the lever. Specifically, in this example, the driver 640 is moved relative to the lever mechanism 400 in the direction of arrow D, either by moving the driver 640 in the direction of arrow D and/or by moving the lever mechanism in a counter direction. This results in the driver 640 imparting a biasing force I_' . on the driver surface 431, thereby causing rotation Ri of the lever mechanism, as described above.

[0103] In the current example, the driver 640 includes a rotatable member in the form of a roller 641, mounted on an axle 642, so that the roller can engage the drive surface 431, and - 19 - rotate relative to the drive surface 431 as the drive surface 431 and lever arm 410 rotates about the pivotal mounting 420. This minimises friction between the driver 640 and driver surface, minimising losses in the applied force, and hence maximising the resulting output force generated by the lever. This is particularly important in low force applications, where even minor amounts of friction can hamper effectiveness of the lever and/or actuator.

[0104] In one example, the driver 640 is driven by a linear or other suitable actuator, which could include a mechanical actuator, hydraulic actuator, pneumatic actuator, piezoelectric actuator, ultrasonic motor, electro-mechanical actuator, linear motor, telescoping linear actuator, non-linear actuator, such as an actuator that traverses a circular or arcuate path, or the like. However, this is not essential, and other actuation mechanisms could be used.

[0105] For example, the driver could include a moving fluid and/or particles that impinge on the drive surface. From this it will be appreciated that the term "engage" will be understood to encompass any form of interaction between the driver and drive surface.

[0106] For example, the driver could be static, and the lever mechanism provided on a moving object, such as a vehicle, or vice versa. This can be used so that the lever mechanism is actuated as the object moves past the lever mechanism or driver, for example by having the lever mechanism actuated as it is moved past and engages with a stationary driver, or by having a stationary lever mechanism actuated as a driver moves past and engages the lever mechanism. An example of this could include altering signals or points in a railway, such as a model railway. In this example, a driver can be mounted on a locomotive or carriage, with the lever mechanism mounted adjacent to the track so that the driver engages the drive surface of a lever mechanism as the locomotive or carriage passes the lever mechanism. By having the lever mechanism operatively connected to a signal, such as a semaphore signal, this could be used to trigger the signal, for example by raising or lowering the semaphore signal arm as the train passes. In this instance, the triggering could be achieved using a low force, thereby minimising the impact on the train, whilst still allowing sufficient output force to be generated by the lever mechanism to allow the orientation of the semaphore signal arm to be altered.

[0107] In the above examples, the lever arm is fixed so that the load traverses an arcuate path about the pivot axis as the lever arm rotates. However, this is not essential and alternatively a configuration of the lever arm can alter as the lever arm pivots about the pivot axis, allowing a 20 path followed by the load to vary, for example to allow a load to follow a straight travel path. In one example, this can be achieved by varying an effective length of the lever arm, for example altering the effective length of the lever arm as the lever arms moves, which in turn can provide an increasing and/or decreasing degree of mechanical advantage as the lever arm moves.

[0108] An example of this will now be described with reference to Figures 7A and 7B.

[0109] For the purpose of illustration, this example uses the lever mechanism of Figures 1 A to ID, and hence similar reference numbers are used to identify similar features, which will not therefore be described in any detail. Nevertheless, it will be appreciated that the techniques are equally applicable to the other lever mechanisms described and/or illustrated within the current application.

[0110] In this example, the lever arm 710 is telescopic, allowing it to move between retracted and extended positions. A guide surface 750 is provided adjacent to the lever mechanism, with the lever arm 710 being arranged so that the load 111 engages the guide surface. As the lever mechanism rotates as shown in Figure 7B, the load engages and moves along the guide surface 750 and the lever arm 710 retracts, so that the load traverses a straight path. A guide could also be used in a similar manner to extend the lever arm 710, so that the load could effectively run in a channel to follow a straight path. Additionally and/or alternatively, the lever arm 710 could include a biasing mechanism, such as a spring, to thereby extend and/or retract the lever arm as needed. It will also be appreciated that the guide surface 750 could be profiled to guide movement of the load 111, for example including dimples or recesses to stop or retain the load at particular locations.

[0111] It will further be appreciated that adjustment of the lever arm could be achieved in a wide variety of manners depending on the preferred implementation. For example, the lever arm could be extendible and/or retractable, telescopic, slidable for example sliding within a slotted guide, deformable, sprung, concertinaed, biased, hinged, bendable, or the like. In another example, the lever arm could be jointed, for example using an elbow joint, or other similar hinging mechanism, allowing the effective length of the lever arm to be altered as desired. Adjustment could be bi- or uni- directional, and may additionally, and/or alternatively, be controlled using an actuator, such as an electronic or pneumatic actuator, memory metal, or - 21 similar or could be achieved using a guide to guide adjustment of the lever arm and/or the travel path of the load. It will also be appreciated from this that whilst a straight travel path is shown in the above example, the travel path of the load could be varied as desired, and is not limited to straight and/or arcuate paths.

[0112] Accordingly, it will be appreciated that the above described arrangements provide a lever mechanism, and an actuator mechanism, that can be operated using an extremely low input force. Despite this the arrangement is highly configurable and can provide a range of different mechanical advantage, depending on configuration of the drive surface, meaning even low driving forces can be used to achieve significant output forces, which can be useful in many applications.

[0113] Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers. As used herein and unless otherwise stated, the term "approximately" means ±20%.

[0114] Persons skilled in the art will appreciate that numerous variations and modifications will become apparent. All such variations and modifications which become apparent to persons skilled in the art, should be considered to fall within the spirit and scope that the invention broadly appearing before described.

Claims

22

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1) A low friction actuator mechanism including: a) a lever mechanism including: i) a lever arm extending from a pivotal mounting to allow the lever arm to at least partially rotate about a pivot axis; and, ii) a drive member operatively coupled to the lever arm, the drive member including a helically shaped drive surface extending circumferentially part of the way around the pivot axis and axially along the pivot axis such that a force applied to the drive surface causes rotation of the lever about the pivot axis; and, b) a driver including a rotatable member that engages the drive surface to thereby actuate the lever.

2) An actuator mechanism according to claim 1, wherein the rotatable member includes at least one of a roller, cog, gear, and roller ball that engages the drive surface.

3) An actuator mechanism according to claim 1 or claim 2, wherein the actuator mechanism has a coefficient of friction of at least one of: a) less than 0.1; b) less than 0.05; and, c) less than 0.01.

4) An actuator mechanism according to any one of the claims 1 to 3, wherein the driver includes an actuator.

5) A low friction actuator mechanism including: a) a lever mechanism including: i) a lever arm extending from a pivotal mounting to allow the lever arm to at least partially rotate about a pivot axis; and, ii) a drive member operatively coupled to the lever arm, the drive member including a helically shaped drive surface extending circumferentially part of the way around the pivot axis and axially along the pivot axis such that a force applied to the drive surface causes rotation of the lever about the pivot axis; and, b) a contactless driver that applies a force to the drive surface to thereby actuate the lever.

6) An actuator mechanism according to claim 5, wherein the contactless driver includes at least one of: a) a moving fluid; - 23 - b) airflow; c) liquid flow; d) electromagnetic forces; e) light pressure; and f) magnetic forces. ) An actuator mechanism according to any one of the claims 1 to 6, wherein one of: a) the drive member and driver move relative to each other; b) the driver is static and the lever mechanism moves relative to the driver; and, c) the lever mechanism is static and the driver moves relative to the lever mechanism.) An actuator mechanism according to any one of the claims 1 to 7, wherein the lever arm is attached to a pivotal shaft supported by at least one of: a) bearings; b) magnetic bearings; c) concave seats that receive opposing pointed ends of the shaft; and, d) concave seats that magnetically support ends of the shaft. ) An actuator mechanism according to any one of the claims 1 to 7, wherein the lever arm is attached to a hub rotatably mounted on an axle. 0) An actuator mechanism according to any one of the claims 1 to 9, wherein the drive member is at least one of: a) attached to the lever arm; b) attached to a pivotal shaft; c) attached to a pivotal shaft via one or more support arms; d) attached to a hub; and, e) attached to a hub via one or more support arms. 1) An actuator mechanism according to any one of the claims 1 to 10, wherein a degree of mechanical advantage provided by the lever is dependent on at least one of: a) a radius of the drive surface; b) a pitch of the drive surface; and, c) a length of the lever arm. 2) An actuator mechanism according to any one of the claims 1 to 11, wherein the driver applies a force to the drive member in a direction that is at least partially parallel to, or - 24 - along, the pivot axis, and wherein the pitch of the drive surface varies so that at least one of: a) a degree of mechanical advantage changes through a stroke of the lever; and, b) the lever provides a non-linear response. )An actuator mechanism according to any one of the claims 1 to 12, wherein the drive surface is at least one of: a) aligned with the lever arm; b) rotationally offset from the lever arm; and, c) in opposition to the lever arm. )An actuator mechanism according to any one of the claims 1 to 13, wherein the drive surface extends at least one of: a) less than 270° around the pivot axis; b) less than 180° around the pivot axis; c) less than 135° around the pivot axis; d) less than 90° around the pivot axis; e) less than 60° around the pivot axis; f) less than 45° around the pivot axis; and, g) less than 30° around the pivot axis. )An actuator mechanism according to any one of the claims 1 to 14, wherein the drive surface is at least one of: a) flat; b) concave; c) convex; d) curved; e) rough; f) serrated; g) keyed; h) toothed; and, i) smooth. ) An actuator mechanism according to any one of the claims 1 to 15, wherein at least one of: a) a shape of the drive surface is configured depending on a direction of the applied force; - 25 - b) an orientation of the drive surface is configured depending on a direction of the applied force; and, c) an axis of the helical drive surface is orientated so it is at least approximately parallel to a direction of the applied force. ) An actuator mechanism according to any one of the claims 1 to 16, wherein the lever includes first and second drive surfaces configured to cause rotation of the lever arm in opposing directions. ) An actuator mechanism according to claim 17, wherein at least one of: a) the drive member includes the first and second drive surfaces; and, b) the lever includes first and second drive members, each having a respective one of the first and second drive surfaces. ) An actuator mechanism according to claim 17 or claim 18, wherein: a) a force applied to the first drive surface in a first drive direction causes rotation of the lever arm in a first rotational direction; and, b) a force applied to the second drive surface in a second drive direction causes rotation of the lever arm in a second rotational direction opposite to the first rotational direction.) An actuator mechanism according to any one of the claims 17 to 19, wherein the first and second drive surfaces have the same pitch directions so that the first drive direction is opposite to the second drive direction. ) An actuator mechanism according to any one of the claims 17 to 20, wherein the first and second drive surfaces have opposing pitch directions so that the first drive direction is the same as the second drive direction. ) An actuator mechanism according to any one of the claims 17 to 21, wherein the first and second drive surfaces are axially and rotationally offset so that a driver moving in a drive direction causes successive rotations in first and second opposing directions. ) An actuator mechanism according to any one of the claims 17 to 22, wherein the first and second drive surfaces have at least one of: a) different pitches from each other; and, b) different radii from each other. ) An actuator mechanism according to any one of the claims 1 to 23, wherein the actuator mechanism provides substantially no mechanical advantage and operates to redirect the applied force. - 26 - ) An actuator mechanism according to any one of the claims 1 to 24, wherein the lever arm is at least one of: a) adjustable; b) retractable; c) extendible; d) telescopic; e) slidable; f) jointed; and, g) concertinaed. ) An actuator mechanism according to any one of the claims 1 to 25, wherein an effective length of the lever arm alters as the lever arm pivots about the pivot axis. ) An actuator mechanism according to any one of the claims 1 to 26, wherein the actuator mechanism is used as an indicator to provide an indication of at least one of: a) a magnitude of an applied force; and, b) a distance of an applied movement. ) An actuator mechanism according to claim 27, wherein a scale is used to provide an indication through at least one of: a) movement of a lever arm positioned proximate the scale; and, b) movement of an electromagnetic radiation source to illuminate the scale. ) A lever mechanism including: a) a lever arm extending from a pivotal mounting to allow the lever arm to at least partially rotate about a pivot axis; and, b) a drive member operatively coupled to the lever arm, the drive member including a helically shaped drive surface extending circumferentially part of the way around the pivot axis and axially along the pivot axis such that a force applied to the drive surface causes rotation of the lever about the pivot axis.