Machine element or mechanism – Mechanical movements – Oscillating to oscillating
Patent
1991-08-09
1993-06-15
Herrmann, Allan D.
Machine element or mechanism
Mechanical movements
Oscillating to oscillating
74 98, 2482811, 354293, 414917, F16H 2144, F16M 1110
Patent
active
052188760
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a control device for a tiltable mounting head.
PRIOR ART
A pantographic control device for a tiltable mounting head, for example a mounting head for a camera or antenna, is known from U.K. Specification No. 1451088, to which reference may be made for a fundamental understanding of a pantographic tilt control mechanism. The control device described in this specification provides the substantial advantage that, during tilting, the centre of gravity of an item of equipment mounted on the mounting head, is constrained to move along a horizontal path, so that the weight of the item does not have a variable effect on the tilting action.
The known arrangement is effective for angles of tilt up to a limit of about 40 degrees. Beyond this angle of tilt the arrangement can become unstable.
It is an object of this invention to provide an improved pantographic control device which remains effective up to much larger angles of tilt for removing a variable weight factor from the tilting action.
THE INVENTION
According to the invention, there is provided a control device for a tiltable mounting head, comprising a three element pantographic linkage having two outer elements secured by a central element, wherein the relative angular position of the two outer elements is controlled by at least two intermediate links joined to the outer elements so that, irrespective of the relative angular position of said two outer elements, at least one of the intermediate links is always laterally spaced from the central element even if another intermediate link is aligned with the central element, and means constraining a point of the central element to move along a horizontal axis.
Thus, the major problem with the known control device described above is that the angle of tilt permissible can only be increased by allowing the pantograph linkage to pass through the position in which the links become aligned. However, this results in the problem that, in the in-line condition of the links, the device becomes unstable due to the fact that the weight of the camera or other item of equipment is completely counterbalanced through its centre of gravity, so that the pantograph may fold either way out of the in-line condition if tilting movement is continued.
In accordance with the invention, this problem is resolved by the use of two intermediate links, arranged so that stability is always maintained by at least one of them, even when the other passes through a condition which does give rise to instability.
In one embodiment, the intermediate links are rigid members each pivotally connecting between the two outer members, effectively to form two parallelogram linkages having the central element in common, with differing degrees of fold for any angle of tilt in the range. This range can be up to 360 degrees, but usually a range of 180 degrees is the maximum required.
The same result is achievable in another embodiment by intermediate links constituted by the opposed parallel runs of a chain or belt which passes around outer elements in the form of gear wheels or pulleys, a toothed arrangement being preferred. In this second embodiment, the central element is a rigid element interconnecting the axes of rotation of the two outer elements.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a first embodiment of the invention where the outer elements of the pantographic-type linkage are legs; and
FIG. 2 shows a second embodiment where the outer link of element is a chain .
DESCRIPTION OF EMBODIMENTS
The invention will be further explained in the following description of two embodiments, which are diagrammatically shown in FIGS. 1 and 2 of the accompanying drawings, respectively.
In both embodiments of the invention, the control device is a pantographic-type linkage system having a central element and two outer elements.
In the embodiment of FIG. 1, the outer elements each comprise a rigid arrangement of three legs in tripod-like formation, namely legs 10, 12 and 14 for one outer element and l
REFERENCES:
patent: 2326657 (1943-08-01), Johnston
patent: 2548476 (1951-05-01), Horstmann
patent: 3263516 (1966-08-01), Chisholm
patent: 3883105 (1975-05-01), Matsumoto
patent: 3995797 (1976-12-01), Knight
patent: 4067245 (1978-01-01), Santic' et al.
Herrmann Allan D.
Laub David W.
Vinten Group plc
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