Claims
- 1. Means for effecting movement of an object in a closed loop planar path comprising a six-bar linkage mechanism the dimensions of the link members of which are derived from a four-bar linkage and a second linkage cognate with said four-bar linkage, said four-bar linkage being dimensioned to generate a path passing through at least selected precision points, on an idealized version of said closed loop path, said six-bar linkage mechanism including a link member which maintains a substantially fixed attitude relative to a given plane in space during execution of at least an appreciable portion of the path, said object forming at least part of or being mounted on said link member for movement therewith.
- 2. A method of designing a linkage mechanism for effecting movement of an object in a closed loop planar path while maintaining the major axis of the object in substantially fixed attitude in the execution of at least an appreciable portion of the path, comprising selecting a set of a finite number of discrete precision points, around an idealised version of the said closed loop path, establishing the dimensions of a four-bar linkage which will generate a synthesized path passing through the said selected precision points and deriving from said four-bar linkage the dimensions of a six-bar linkage which will cause the required fixed attitude motion in the synthesized path.
- 3. The method as claimed in claim 2, wherein the said selected precision points are chosen to yield a path of motion which deviates from said idealized path by only an acceptable amount.
- 4. The method as claimed in claim 3, wherein the choice of precision points is arrived at by a series of relocation of selected precision points and evaluating the resulting linkages.
- 5. The method as claimed in claim 2, wherein the minimum choice of precision points is five.
- 6. The method as claimed in claim 2, wherein said precision points are selected by an optimisation process to provide a successive reduction of structural error.
- 7. The method as claimed in claim 2, wherein the Roberts-Chebychev Theorem, as hereinbefore identified, is used to establish two cognate four-bar linkages from which the six-bar linkage is derived.
- 8. The method as claimed in claim 7, wherein a pair of cognate linkages is spaced and orientated relative to one another and linked to provided the six-bar linkage.
- 9. Means in accordance with claim 1, for effecting movement of an object in a closed loop planar path while maintaining the object in substantially fixed attitude during execution of at least an appreciable portion of the path, wherein at least one of the link bars in the derived six-bar linkage is constituted by at least one eccentric device.
- 10. Means in accordance with claim 9, wherein said eccentric device is constituted by a disc member with a circular hole off-centre of the disc and mating with a second link bar.
- 11. Means in accordance with claim 10, wherein said second link bar is also constituted by an eccentric device in the form of a second disc member having a circular hole off-centre of said second disc member and fixed to a drive shaft.
- 12. Means in accordance with claim 11, wherein said drive shaft is keyed into an off-centre hole in at least one further disc member which mates with a hole in yet another, pivoted, link bar.
- 13. Means for effecting movement of an object in a closed loop planar path while maintaining the major axis of the object in substantially fixed attitude in the execution of at least an appreciable portion of the path, comprising a six-bar linkage mechanism the dimensions of the members of which are derived from a four-bar linkage and cognate linkage to ensure said fixed attitude motion of said object during said portion at least of the said path, said four-bar linkage being dimensioned to generate a path passing through at least selected precision points, as hereinbefore defined, on an idealized version of said closed loop path, wherein the derived six-bar linkage comprises first and second planar members pivoted to each other, the said object being associated with said first planar member at a point spaced from the pivotal axis, said first planar member having a circular hole therein, the center of which is spaced from said pivotal axis by a distance equivalent to one of the link bars, a disc member rotatably mating with said first hole and having a circular hole therein with centre which is offset from the centre of said first disc member by a distance equivalent to a second link bar, a second disc member rotatably mating with said hole in the first disc member and having a hole with centre offset from the centre of said second disc member, a drive shaft for the six-bar linkage, said shaft being fitted concentrically within said hole in said second disc member and being fixed rigidly thereto, a third disc member having a hole therein with centre offset from its centre within which said shaft is concentrically fitted, said third disc member being rigidly fixed to said shaft, the magnitudes of said two offsets and the relative angular disposition of the directions of these offsets in said second and third members being equivalent to a third link bar, said third disc member rotatably mating with a circular hole in said second planar member and said second planar member being pivoted to a second pivotal point, the relative disposition of the centre of said hole in said second planar member and the two said pivotal points therein being equivalent to a fourth link bar, and a pivot providing said second pivotal point and being mounted on a fourth disc member, the axis of the said pivot being offset from the centre of said fourth disc member by a distance equivalent to a fifth link bar of the linkage, the axes of all said disc members and said pivotal axes being parallel to each other and to the axis of rotation of said shaft, said fourth disc member being rotatable about its central axis but having its axis restrained at a distance from said shaft axis equivalent to the sixth link bar of the linkage.
- 14. Means in accordance with claim 13, wherein said fourth disc member rotatably mates with a circular hole in an anchor member.
- 15. Means in accordance with claim 14, wherein mounting means is provided for said anchor member, said mounting means being adjustable whereby the said second pivotal axis and the axis of said shaft may be set in different relative dispositions.
Priority Claims (1)
Number |
Date |
Country |
Kind |
01106/75 |
Jan 1975 |
GBX |
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Parent Case Info
This is a continuation of application Ser. No. 647,982 filed Jan. 8, 1976, now abandoned.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
3964523 |
Benedict |
Jun 1976 |
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3964524 |
Benedict |
Jun 1976 |
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Foreign Referenced Citations (1)
Number |
Date |
Country |
15,622 |
Sep 1928 |
AUX |
Non-Patent Literature Citations (1)
Entry |
Hinkle-Kinematics of Machines-1953, 1960, pp. 256-265. |
Continuations (1)
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Number |
Date |
Country |
Parent |
647982 |
Jan 1976 |
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