Machine element or mechanism – Rotary member or shaft indexing – e.g. – tool or work turret – Locking means
Patent
1996-02-06
1998-04-07
Bonck, Rodney H.
Machine element or mechanism
Rotary member or shaft indexing, e.g., tool or work turret
Locking means
74813L, B23Q 1608
Patent
active
057351805
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
The present invention relates to an indexing mechanism for angularly orienting one body relative to another in a number of discretely spaced and highly repeatable indexed locations. Such indexing mechanisms are typically used in articulating probe heads or rotary tables, which may be employed on coordinate positioning machines such as coordinate measuring machines or machine tools.
One known form of indexing mechanism includes a circular array of balls, provided on one of the two bodies, and three rollers, provided on the other of the two bodies, equispaced and extending radially with respect to the axis of rotation of the two bodies. In a given indexed orientation, each of the rollers seats in the convergent surfaces defined by an adjacent pair of balls in the circular array; the number of possible indexed orientations is defined by the number of pairs of convergent surfaces provided by the circular array of balls over a single 360.degree. rotation of one body relative to the other. In an alternative and entirely equivalent form of this indexing mechanism, a circular array of radially extending and equispaced rollers is provided on one of the bodies, and three balls, positioned at the vertices of an equilateral triangle are provided on the other of the two bodies; each of the balls sits in the convergent surfaces defined by an adjacent pair of rollers. A further known form of indexing mechanism is provided by two identical and mutually engageable rings of gear teeth, this form of indexing mechanism being known as a Hirth coupling.
SUMMARY OF THE INVENTION
The present invention seeks to provide an alternative indexing mechanism for first and second relatively rotatable bodies, comprising: a circular array of first elongate members provided on said first body, each first member having a pair of circumferentially spaced first surfaces, with confronting first surfaces from adjacent first members being mutually convergent; at least three second members provided on said second body, each second member having a pair of circumferentially spaced second surfaces, and being adapted to seat in a cleft defined by a pair of said mutually convergent first surfaces; wherein at least one of the first members and second members are symmetrical, and wherein a region of each of the surfaces of said at least one of the first members and the second members are curved, and have a radius of curvature greater than half the distance between centers of adjacent first members.
In one preferred embodiment, the curvature of said region of each of the curved surfaces will take place at least in a plane orthogonal to said axis. In a second preferred embodiment, the curvature of said region of each of the curved surfaces will take place in two mutually orthogonal planes, each of which lie parallel with said axis. In a further preferred embodiment, the curvature of said region of each of the curved surfaces will occur in three mutually orthogonal planes; one lying orthogonal to said axis, and the other two lying parallel with said axis.
In one embodiment of the present invention, the first and second bodies are identical, with each first member seating in a pair of convergent second surfaces defined by an adjacent pair of second members, and each second member seating in a pair of convergent first surfaces defined by an adjacent pair of first members. Many further embodiments exist. For example the first members may have requisitely curved regions, while only three second members are provided, which may for example be cylindrical rollers, balls or plane-faced gear teeth. Alternatively, the first members are plane-faced, and three or more second members are provided, having requisitely curved regions.
Various alternative embodiments of the present invention will now be described in detail, by way of example, and with reference to the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation of an indexing mechanism according to the present invention;
FIG. 2 is a section on II--II in FIG.
REFERENCES:
patent: 3088340 (1963-05-01), Shotey
patent: 3090633 (1963-05-01), Farnsworth
patent: 3177740 (1965-04-01), Firestone et al.
patent: 3252358 (1966-05-01), Moncrieff
patent: 3846912 (1974-11-01), Newbould
patent: 3908484 (1975-09-01), Degen et al.
patent: 4060007 (1977-11-01), Levesque
patent: 4153998 (1979-05-01), McMurtry
patent: 4644825 (1987-02-01), Yamazaki
Gleason Machine Division Brochure, "Curvic Couplings", New York, USA, 7 pages.
Bonck Rodney H.
Renishaw plc
Rodriguez Saul J.
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