GB2361755A

GB2361755A - Means for converting reciprocating motion into rotation

Info

Publication number: GB2361755A
Application number: GB0010383A
Authority: GB
Inventors: Brown Matthew Thornton; Brown Ruth Thornton
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-04-28
Filing date: 2000-04-28
Publication date: 2001-10-31
Also published as: GB0010383D0; WO2001083288A1; AU2001250525A1

Abstract

Means for converting a reciprocating force into rotary motion about a rotary bearing 2 is provided, e.g. from a bicycle pedal (7, fig 5) to a chain wheel (9, fig 6). The rotatable member has force-imparting means located at a distance from the rotary bearing 2, by which the reciprocating force is applied to the rotatable member. The distance between the rotary bearing 2 and the force-imparting means is variable, preferably by means of a slot 3, so that the moment of the reciprocating force may be varied during rotation of the rotatable member. Many other crank shapes are disclosed, some having damping means and/or cams.

Description

2361755 MEANS FOR CONVERTING RECIPROCATING MOTION INTO ROTATION This

invention relates to means for converting reciprocating motion into rotation. More particularly, it refers to such means, e.g. a crank by means of which a greater force may be exerted during one portion of its rotation than during another.

There are a number of items of machinery in which a crank is used. Common examples are the pedals of bicycles, winches, and reciprocating steam or internal combustion engines. During the use of a crank, there will be one portion of its rotation where the force acting upon the crank is a push, often assisted by the force of gravity, while during another portion of the rotation, force acting on the crank will be pulling it, often against the force of gravity. This is particularly the case with pedal cycles and winches. There is, therefore, a need to provide a crank by means of which a greater force may be exerted during one portion of its rotation than during another. 15 The effect of this becomes particularly apparent when the action involved in riding a bicycle is considered. A major portion of the impulse to drive the bicycle comes from a downwardly exerted force, exerted by the leading leg of the cyclist when pedalling, so that the right and left legs of the cyclist 20 alternately produce a downthrust while the leg not producing the downthrust is largely occupied in controlling the respective pedal while it completes its rotation to reach the position in which it, in its turn, can exert a propulsive downthrust. In principle, the total propulsive force could be increased by increasing the length of the crank bearing the pedal, but this has 25 disadvantages with bicycles, in that the chain wheel would have to be raised higher to provide adequate ground clearance, while the cyclist must have additional leg movement, with each of the cyclist's feet performing a motion in a circle of greater radius than would be the case with cranks of conventional length. 30 The present invention provides means for the conversion of a reciprocating force into rotary motion of a rotatable member about a rotary bearing, wherein said rotatable member has force-imparting means, located at a distance from said rotary bearing, by which the reciprocating force is applied to said rotatable member, the distance between said rotary bearing and said forceimparting means being variable within the course of one rotation, whereby the moment of said reciprocating force may be varied while said rotatable member is rotating.

According to one embodiment, the rotatable member comprises a slot directed away from said bearing, and force-imparting means, is adapted to slide freely within said slot.

Another embodiment provides a crank comprising an elongated member with a rotary bearing at a first end, and with said slot extending longitudinally of said member towards a second end.

According to one embodiment, the elongated member and slot are essentially linear, whereby the slot effectively extends radially from the rotary bearing.

In an alternative embodiment, the elongated member and its slot may be curved over at least the outer section remote from the rotary bearing. In another embodiment, the above-mentioned curve may be a simple curve, or a more complex curve, such as one having an ogival form.

In another embodiment, a radially-symmetrical member, such as a disc, is provided with a slot having a first end and a second end, said first end being nearer said rotary bearing than said second end. The sloi"may be linear or curved, as in the above-described crank.

According to further embodiments of the invention, the force-imparting member may be fixed, and the rotary bearing may be movable within a slot.

2 Alternatively, both the force-imparting means and the rotary bearing may be movable within respective slots.

In further embodiments, the crank may be a telescoping member, with elastic means forcing the ends together.

A further embodiment comprises means comprising a drive wheel for driving a chain or belt drive, and having rotary bearing at its centre, a cam surrounding said rotary bearing and fixed with respect to the support of the rotary bearing, and a crank rod extending radially of said drive wheel and having a longitudinal slit at its end remote from said rotary bearing, said cam and crank rod being rotatable with said drive, a movable transverse member for applying said reciprocating force, movable lengthways of said slit, and a push rod extending longitudinally of said crank, and bearing at one end on said cam, and on the other end on the transverse member.

Another embodiment comprises means comprising a drive wheel for driving a chain or belt drive, and having a rotary bearing at its centre, a cam surrounding the rotary bearing and fixed with respect to the support of the rotary bearing, a crank rod extending radially of said drive wheel, and bearing on said cam, a sleeve surrounding the inward portion of the crank rod and having a first stop member at its outer end and a second stop member closer to said rotary bearing than the first, and spring means between said first and second stop members, said cam, crank rod and sleeve being rotatable with said drive wheel.

To propel a bicycle, the main chain wheel may be provided with a pair of cranks according to the invention, or with a pair of radially symmetrical members. In each instance, pedals will be freely movable in the slots, the slots in the respective cranks or radially-sym metrical members being diametrically opposed to one another.

3 The present invention will be further described with reference to the accompanying Drawings in which:

Fig 1 shows a side elevation of one form of crank, Fig 2 shows a side elevation of an alternative form of crank, Fig 3 shows a side elevation of another alternative form of crank.

Fig 4 shows a plan view of a crank, Fig 5 represents a plan view of a crank with a pedal attached to it, Fig 7 shows a view of a crank attached a chain wheel of a bicycle, Fig 7 shows the track of one foot of a cyclist while completing a rotation of the pedal and crank, Fig 8 shows a side elevation of another form of crank wherein the rotary bearing is movable within a slot, Fig 9 shows a side elevation of yet another form of crank wherein both the force-imparting means and the rotary bearing are movable within respective slots, Fig 10 shows a view of a crank of the embodiment of Fig 9, Fig 11 shows a further embodiment of the invention, Fig 12 shows a further embodiment of the invention, 4 Fig 13 shows another embodiment of the invention with a disc-shaped rotatable member, Fig 14 shows another embodiment of the invention with a disc-shaped rotatable member and both the rotary baring and the force-imparting means being movable within slots, and Figs 15 and 16 show further embodiments where the distance apart of the rotary bearing and force-imparting means are controlled by means of a cam, located around the rotary bearing.

Referring now to the Drawings, Fig 1 shows one embodiment of a crank according to the invention. This crank [11 is provided with a rotary bearing [21 at one end and has a slot [31 extending towards the further end. A stop member [4] is provided at the end of the slot furthest from the rotary member [2]. The stop member is preferably provided with an impact absorbing means, comprising, for example, a spring, an elastic polymer such as rubber, or a hydraulic device.

Fig 2 shows an alternative embodiment of the crank according to the invention, in which the elongated member [1 a] and the slot [31 are curved over at least the outer portion of the crank.

Fig 3 shows another alternative embodiment of the crank, in which both the crank [1b] and the slot are in the form of a complex curve.

Fig 4 shows a plan view of the crank [11 with the slot [31 and stop member [41, and a bore [51 adapted to fit the rotary member [2].

Fig 5 shows a crank in partial plan view with a pedal attached. From this, it will be seen that a transverse member [61 bearing a portion [71 such as a pedal adapted to provide driving force when the cycle is used, extends orthogonally of the crank and is retained within the limits [3a, 3b] of the slot by means of appropriate retaining members [8]. This transverse member [61 may, for example, be provided with an appropriate ball bearing or roller bearing in order to provide a smoother and easier movement along the extent of the slot from limit [3a] to limit [3b]. By means of this, when the pedal and its transverse member are in the forward position, extending to the limit [3b] of the slot, a greater force tangential to the crank, thereby producing a rotation about the bearing, will be exerted than would be if the pedal and its transverse member were at the rear end [3a] of the slot.

Fig 6 shows a schematic view of a crank attached to a chain wheel [91 of a bicycle. This wheel is shown only schematically since the teeth of the wheel, and the chain, will be of conventional type.

Fig 7 shows a plot of the orbit of a pedal sliding within the slot relative to the rotary bearing [2]. The orbit of a pedal of conventional fixed type [101 will be seen to be substantially a circle. The orbit [111 followed by a crank according to the invention, however, is very different since it deviates from the circle during the portion corresponding to an upward movement of the pedal, which and thereby follows a shorter distance. Correspondingly, the cyclist will have to exert considerably less leg movement during each pedal stroke.

In its simplest form, e.g. when used in connection with a bicycle, it may be possible to have the transverse member and driving force e.g. bicycle pedals, movable with respect to the slot without specific means for moving the pedals other than the feet of a cyclist.

Fig 8 shows a straight crank [121 with a rotary bearing [141 provided with an adaptor [151 movable longitudinally of the slot [131. An elastic means [161, comprising a spring, or pneumatic or hydraulic means is provided to control 6 the sliding of the bearing within the slot. A fixed bore [ 171 is provided to take a pedal.

Fig 9 shows a variation of this embodiment in which the crank [ 1 2a] is curved and both the rotary bearing [141 and the pedal are movable within respective slots [13, 31.

Fig 10 shows the orbit [181 for the embodiment of Fig 9.

It may be desirable to provide some alternative means of providing relative movement between the driving force and the crank. Such alternative means may include mechanical, electrical, magnetic, hydraulic or pneumatic mechanisms, as such or in combination.

Alternative embodiments of the invention are shown in Figs 11 and 12. In both, the cranks [ 191 are made of two sub-cranks telescoping one within the other. In the embodiment of Fig 11, the telescoping is controlled by the central arms [201 journalled to the ends of the crank and to one another, with spring means [211, or an equivalent thereof, forcing the link between the control arms away from the crank.

Alternatively as shown in Fig 12, the telescoping crank may be provided with an internal piston [221, with a spring [211 urging the ends of the crank together.

Figs 13 and 14 show alternative embodiments of the invention wherein the rotatable member is a disc [23, 241 in which the slot [3a] is curved. It may, however, be a straight slot, radially directed from the bearing [21, as in the case of the above-described crank. In Fig 13, this is a fixed rotary bearing [2].

In Fig 14, the bearing [141 is movable within slot 1131, as described above with reference to Fig 9.

7 Figs 15 and 16 show constructions in which a drive wheel [28], for instance one adapted for a belt or chain drive, or which may be provided with teeth as members of a gear train, surround the rotary bearing. A cam [271 is also provided surrounding the bearing. In the construction of Fig 15, a crank having a slot at its outer end, extends radially from the wheel. The slot has a bearing [251 movable longitudinally within it for transmission of the reciprocating force to the crank. The bearing [251 can, for instance, form part of a pedal assembly, as shown in Fig 5. A push rod [261 extends longitudinally of the crank, which may for instance be in the form of a sleeve surrounding the push rod. One end of the push rod bears on the bearing [271, and the other end bears on the cam [271. The cam is fixed with respect to the supports of the bearing, for instance, the frame in the case of a bicycle pedal assembly. Consequently as the wheel [281, the crank and the push rod rotate with respect to the bearing support, the rod [271 and bearing [251 are able to follow the contour of the cam, the bearing [251 moving along the slot.

In the embodiment of Fig 16, the crank [291 is provided with a bore for a transverse member, for instance a pedal assembly. The inner end of the crank has a wheel [321 contacting the cam [281. A sleeve surrounds the crank [291 and is provided with two retaining members, each provided with an appropriately shaped bore permitting axial movement of the crank. The sleeve is attached to and rotates with the drive wheel [281. The crank [291 also rotates with the drive wheel [281. A spring [301, bearing on a collar [311 and the outer of the stop members, ensures that the wheel [32] remains in contact with the outer surface of the cam [271, as the drive wheel rotates with respect to the support of the rotary bearing. This permits the moment exerted by the reciprocating force to vary during the course of revolution of the drive wheel.

When the invention is used in connection with a bicycle, some re-design of the bicycle frame may be required so that the pedals and saddle may occupy a slightly different position from the conventional.

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Claims

1 Means for the conversion of a reciprocating force into rotary motion of a rotatable member about a rotary bearing, wherein said rotatable member has force-imparting means, located at a distance from said rotary bearing, by which the reciprocating force is applied to said rotatable member, the distance between said rotary bearing and said f orce-imparting means being variable within the course of one rotation, whereby the moment of said reciprocating force may be varied while said rotatable member is rotating.

2. Means according to Claim 1 wherein said rotatable member comprises a slot directed away from said rotary bearing, and said force-imparting means is adapted to slide freely within said slot.

3. Means according to Claim 1 or 2 having the form of a crank comprising an elongated member with a rotary bearing at a first end, with said slot extending longitudinally of said crank towards a second end.

4. A crank as claimed in Claim 3 wherein said elongated member and said slot are linear whereby said slot extends radially of said rotary bearing -

5. A crank as claimed in Claim 3 wherein said elongated member and said slot are curved over at least the outer section remote from the rotary bearing.

6. A crank as claimed in any one of Claims 3 to 5 wherein the forceimparting means comprises a movable transverse member extending orthogonally of the crank and movable longitudinally with respect to said slot.

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7. A crank as claimed in Claim 6 wherein said movable transverse member imparts the force to said crank by means of a ball bearing or roller bearing movable in said slot.

8. Means according to Claim 1 wherein said rotary baring is located within a slot and is adapted to move lengthways of said slot during rotation of said rotary member.

9. Means according to Claim 8 which comprises first and second slots, one accommodating said rotary bearing and the other accommodating said force-imparting member.

10. Means according to Claim 8 or 9 comprising elastic means resisting movement of said rotary bearing within said slot.

11. Means according to Claim 2 in the form of a radially-symmetrical member with a slot having a first end and a second end, said first end being nearer said rotary bearing than said second end.

12. A radially-sym metrical member as claimed in Claim 11 in the form of a disc.

13. A radially-sym metrical member as claimed in Claim 11 or 12 when said slot is linear and extends radially of said rotary bearing.

14. A radial ly-sym metrical member as claimed in any of Claims 11 or 14 wherein said slot is curved over at least the section nearer its second end.

15. A radially-sym metrical member as claimed in any of Claims 11 to 14 wherein the force-imparting member comprises a movable transverse member extending orthogonally of the radially-symmetrical member.

16. Means according to Claim 11 wherein said rotary baring is located within a slot and is adapted to move lengthways of said slot during rotation of said rotary member.

17. Means according to Claim 11 which comprises first and second slots, one accommodating said rotary bearing and the other accommodating said force-imparting member.

18. Means according to Claim 16 or 17 comprising elastic means resisting movement of said rotary bearing within said slot.

19. Means according to Claim 1 which comprises a crank having the rotary bearing at one end and the force-imparting means at the other end wherein the crank comprisesfirst and second sub-members, telescoping one within the other, a pair of control arms, each having a first end journalled to a respective sub-member, and a second end, said second ends being journalled together, and elastic means urging said second ends away from said crank.

20. Means according to Claim 1 which comprises a crank having the rotary bearing at one end and the force-imparting means at the other end wherein the crank comprises first and second sub-members, telescoping one within the other, one of said sub-members being provided with elastic means urging said force-imparting means towards said rotary bearing.

21. Means according to Claim 1 which comprises a drive wheel for driving a chain or belt drive, and having rotary bearing at its centre, a cam surrounding said rotary bearing and fixed with respect to the support of the rotary bearing, and a crank rod extending radially of said drive wheel and having a longitudinal slit at its end remote from said rotary bearing, said cam and crank rod being rotatable with said drive, a 11 movable transverse member for applying said reciprocating force, movable lengthways of said slit, and a push rod extending longitudinally of said crank, and bearing at one end on said cam, and on the other end on the transverse member.

22. Means according to Claim 1 which comprises a drive wheel for driving a chain or belt drive, and having a rotary bearing at its centre, a cam surrounding the rotary bearing and fixed with respect to the support of the rotary bearing, a crank rod extending radially of said drive wheel, and bearing on said cam, a sleeve surrounding the inward portion of the crank rod and having a first stop member at its outer end and a second stop member closer to said rotary bearing than the first, and spring means between said first and second stop members, said cam, crank rod and sleeve being rotatable with said drive wheel.

23. Means according to Claim 1 and substantially as hereinbef ore described.

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