The Technical Field of the invention is multiplying and reducing mechanisms for physical movement

Background Art

Linear actuators are widely used in industry for moving parts within machines and factories. They are powered by electric, pneumatic or hydraulic motors, but the linear output generally only matches or reduces the length of the input. For example ball screws form the largest segment of the market, but are reducers, that is, they reduce a rotary input length to a shorter output length, and are heavy, noisy and slow. Electric linear actuators require supports, such as expensive "v" slides to steady the effector platform and cannot extend into spaces where they are not supported by slides.

This invention is superficially similar to the scissors mechanism, which is also a multiplying or stroke amplifying mechanism.. However it is distinct from scissors mechanisms in that a scissors is essentially a two dimensional actuator and lacks stiffness, whereas the present invention is three dimensional and has the capability to be very stiff. Further, in a scissors mechanism, the entire force path passes successively through the joint between each pair of members along the entire length of the actuator. This results in high friction and instability. In the present invention the force supplied to expand the gap between the units is provided by relative rotation of the shaft and the slides and is therefore supplied separately to each gap and not delivered through the previous gap.

Disclosure of the invention

The stroke amplifier of the present invention comprises a plurality of slide-able units, such as discs arranged along a centre line. Alternate units are keyed to a central rotate-able shaft on the centreline or to slides co-axial with the shaft. These alternate units form two sets of units. All the units of a first set can be simultaneously rotated with respect to the second set by rotary movement of the shaft to which they are keyed. All the units of the second set can be rotated with respect to the first set by rotation of the outer slides. All units of each set are provided with linkages, balls, rollers, magnetic or physical means to move towards or away from its immediate neighbours of the other set when the sets are rotated, with respect to each other. In operation, a partial rotation or movement of either set causes the units to move apart or closer together

It is a purpose of this invention to provide a light, quiet and cheap stroke amplifier, that can be powered by any physical input, can multiply and thus greatly step up an input distance into a longer output distance and can extend beyond its initial length without requiring advanced supports. It is a further purpose of the invention that when operated in reverse and force is applied to the end of the extended stroke, thereby to reduce the extension, that the device produces a reduced output movement from the movement that is input..

Brief Description of Drawings

In a first embodiment (fig 1) of the invention an inner axial shaft (1) and outer (2) co-axial members act as slides which between them support radial units (3) which are able to slide axially. Units (3) slide on the inner shaft (1) and outer members (2) but alternate units are keyed against rotation either by splines to the shaft (1) or by rollers or runners on the outer slides (2). This provides two sets of alternating units that can slide axially but are constrained from rotating with respect to all the other members of their set and which will rotate in unison with their set. In unextended mode each radial unit is spaced slightly apart from and hinged to its immediate neighbours of the other set by substantially rigid linkage members(4). The outer co-axial members are steadied at the effector end by a stator (6). In operation a small rotation of either the shaft (1) or the slides (2) with respect to the other causes the linkages members(4) to push on their neighbouring units. As these cannot rotate away from the applied rotational force, the connecting members are constrained to move towards an axial orientation. This forces the units apart. All units move apart simultaneously in response to the input rotation. A stator unit (5) is provide at one end of the plurality of units. Thus all the units slide away from the both the stator and from each other. The acceleration of successive units is added to that of the preceding units, resulting in very high total acceleration as well as considerable multiplication of distance travelled over the original input distance.. Because a first end of each linkage describes an arc with respect to the second end, the axial speed of the first end slows as the linkage reaches a position that is parallel with the central shaft. As all the linkages move synchronously to reach end extended positions parallel with the central shaft, they move into toggle, providing high axial force at the end of travel . At the toggle position the rigidity of the structure is further increased.

In most embodiments using linkages, the central shaft will have straight spline(s). But is some applications it may be advantageous to curve the splines at the extension end to decrease speed more gradually than is provided by the linkages moving in an arc and coming into toggle down the length of the units. Curving is also applicable to embodiments using balls, which may have curved shafts to provide more gradual decelleration. Magnetic embodiments may have a curved central magnetic path to achieve the same end.

One drawback to present linear actuators is that the supporting structure is of fixed length and it would be desirable to enable the sliding supports to expand at the same rate as the units. Then the device could reach into areas where it is not supported, or, when acting as a screw jack for lifting, be unencumbered by fixed supports above the base platform, without having the supports rise from below the base. This is optimally achieved by telescopic or similar means. In this invention this may be achieved by attaching one end of each nested telescopic sections to each alternate unit. Thus, a telescopic support on the outside consists of sequentially smaller open slide sections sliding inside larger members, with the top of each section attached to alternate axial units of the same set . This would usually be the static member. Using slides, instead of tubular telescopic sections will give the ability to use friction reducing balls between each section and improve resistance to torsion.

Similarly, the central slides are provided by several telescopic slide members attached alternately to the other set of units (the rotating set) and mounted on a radial member keyed to the input. The means of extending the slides may also be semi-telescopic where alternate slides or tubes are fixed at one end and the other end slides through the next unit in its set.

In another embodiment of a device, the leading part of the device is an effector support fixedly attached to the leading end of the sets of slides and is also attached by a deep groove bearing to the leading end of the central shaft. Thus, actuating the device causes the units to move apart and the leading unit/effector to draw both the slides and shaft forward with it . The trailing end of the units is fixed to a stator, which is provided with holes through which the slides may move and optionally with a further stator on the other side from the units to support the elongated slides.

The device may be braked or locked by providing a disc, fixed against rotation relative to the stator, between the stator mount and a flat facing plane of the first unit. In operation, actuation means on the stator mount force the disc against the unit to provide high friction and prevent relative movement between the unit and the stator.

The central shaft may be hollow and of large diameter, or the central shaft comprises a plurality of small shafts of appropriate shapes to reduce weight and resist torsion and the device is then useful in robots to create an extendible limb with a hollow centre for other services to pass down.

It is envisaged that this mechanism could replace ball screw type actuators with the benefit of higher speed. In such an application, absolute precision in docking against a stator at full extension can be achieved by mounting short screw type actuators on the stator or effector end to provide fine adjustment of the terminal stop after a high speed movement of the stroke amplifier. Precision can also be obtained in a fixed length distance by providing the effector end with one or more pyramidal protrusions that co-operate with a triangular or square hole(s) at an end of travel stator to align and stop the platform in z y and z axes. Such a pyramid may have a base on the effector and three or more forward sides and be adjustable with reference to the docking hole or the docking hole may be adjustable with reference to the pyramid.

In a second embodiment (fig 2) of the invention, the slide-able units are not linked to the neighbouring units, but are separated from their neighbours by balls or rollers, which may be spaced relative to each other by a cage, as is usual in a conventional radial ball or roller bearing. In this second embodiment there is provided a sp lined shaft (1) supporting slides (2), a stator (3) wavy units (4), ball bearings (5) flat units (6) and moving end (7). The wavy units are slide-ably keyed to the shaft by spline(s) and the alternating flat units slide on round supports. As with the previous embodiment (fig 1), partially rotating the slide-able shaft with respect to the outer slides causes alternate sets of units to rotate with respect to the other, resulting in the balls, which, in operation, started at the bottom of a the wavy slopes, rising to the top of the waves and so move the stages apart.

To enable the device to handle high forces, the wavy and flat units may be supplied with grooves on either side so that balls or shaped rollers nay run round the units with larger contact patches with the units, thereby to reduce stress concentration at the contact patches.

The lack of a connection means that this embodiment requires a force to keep the units and balls in contact with each other and to provide a force for a return to start. As this embodiment is capable of being continuously rotated, this force can be provided by mirror image sets of units so that rotation of the shaft causes reciprocation of the units. Such force may also be applied overall by a spring. Preferentially it is applied by a plurality of springs joining the ball cages. If the stator member is mounted with an input rotor keyed to the shaft, input rotation can be applied thereby by belt, gear or similar, driving each of the two mirror sections to alternately move away from or towards the centre. If the relative positions of the wave peaks of the sets of units on one side of the central member are adjusted radially, this will adjust the phasing with respect to the set on the other side. Mechanical multiplying devices such as this invention can be reversed to be a reducing mechanism. Thus if the effector end of a ball bearing embodiment is attached to the piston in a cylinder, downward movement of the piston will press down the stack of units and in so doing will rotate the shaft and so provide rotary output. This embodiment can replace crank shafts and con rods for piston and cylinder internal combustion engines, expanders and pumps.. The device allows straight line reciprocation, without piston slap, enables well balanced opposed linear piston arrangements by supplying two mirror stacks of units, each linked to an outer piston and each stack supplying rotary force to the shaft in the same direction. A single piston and stack of units allows multi cylinder pumps and motors to be driven by, or drive, a single large gear via a gear on each shaft of the piston/stack assemblies. This is a packaging and efficiency improvement over swash plates currently employed in multi piston devices. Furthermore by changing the profile of the waves on the units, the dwell at top dead centre (tdc) and bottom dead centre (bdc) of piston movement in the cylinder can be designed to maximise engine efficiency. In the literature it is suggested that a long dwell at bdc to allow exit of exhaust gas and a short dwell at tdc to minimize heat loss is optimal. In addition, the compression ratio can be changed during operation by moving the stator, shaft, units and piston assembly towards or away from the cylinder, thus leaving a bigger or smaller volume at tdc.

Reciprocation by mirrored devices was described in the second embodiment (fig 2). This allows a small up and down leverage input to the shaft to drive a very fast movement of a magnet back and forth through a coil to make an improved linear generator. This is useful for wave energy generation. In these applications the first embodiment (fig 1) is preferable because of the greater amplification gives higher magnet speed through generating coils. The invention may also be realized with magnetic embodiments. The units are mounted with permanent magnets with North and South on opposite sides of each unit. The units are arranged on the shaft with the same polarity magnets facing each other. The magnets are evenly spaced on each unit so that relative rotation between the shaft and the slides causes the evenly spaced North magnets on one side of a unit to move further into the magnetic field of the North magnets on the neighbouring unit with consequent mutual repulsion and similarly the South to South magnets on the other sides repel each other. The units may physically slide in contact with both the shaft and slide or may be supported entirely magnetically so that there is no friction in the device when the shaft is rotated when the units move. Friction free movement provided by magnets is beneficial in vibration energy harvesting.

Industrial Applicability

Industrial applications of the invention comprise firstly devices using linkages. These are primarily linear actuators that are required in many industrial machines,in automobiles, for operating doors and windows, and for robot limbs. Secondly industrial applications for devices using balls include crank substitutes and linear generators. Thirdly magnetic embodiments include vibration energy harvesting.

Obviously a multiplying device according to this invention can be operated in reverse as a reducer and that there are various ways of ordering the assembly of the essential components without departing from the spirit of the invention.