Counterweighted mechanical boom

Claim 1

An articulated swivelling boom combination adapted to carry on one of its extremities a device and to enable said device to be moved about smoothly in any direction of 360° in a given plane within a predetermined area, said boom combination comprising: A. a base, said base including a supporting platform and first pivot bearing means projecting perpendicularly with reference to said platform, said bearing means being rotatable about a substantially vertical axis in a predetermined arc of rotation; B. an elongated rigid member, said member being mounted at a point intermediate its extremities on said pivot bearing means thereby to be pivotable in a plane normal to said axis, said member having in the vicinity of one of its two extremities a further second pivot bearing means and, in the vicinity of the other of its two extremities a third pivot bearing means, each of said second and third pivot bearing means being rotatable about an axis parallel to the axis of rotation of the first pivot bearing means; C. a first rigid elongated element, one end of said element being rotatably mounted on said member by the second pivot bearing means to be rotatable about the axis of said second bearing means, said first rigid element extending in a first direction from said second bearing means, and the other end of said element having means to carry said device; D. a second rigid elongated element, one end of said second element being rotatably mounted on said member by the third pivot bearing means to be rotatable about the axis of said third bearing means, said second rigid element extending from said third bearing means in a second direction, and the other end of said second element carrying counterweight means, the end of said member in the vicinity of which said second rigid element is mounted being counterweighted to equalize any static weight differential between that portion of said rigid member extending from the first pivot bearing means and rotatably carrying the first rigid element and said device, and the remaining portion of the rigid member extending oppositely from the first pivot bearing means and rotatably carrying the second rigid element, and said second rigid element being counterweighted at a point remote from the third pivot bearing means to equalize any change in weight distribution with reference to the second pivot bearing means which may be occasioned by rotation of the first rigid element carrying said device about said second pivot bearing means; E. two circular gear means, one of said circular gear means being secured to rotate with said first rigid element, the other of said circular gear means being secured to rotate with said second rigid element, each of said gear means being disposed coaxially with the axis of rotation of its respective rigid element about its respective pivot bearing means; and F. means connecting both of said gear means for co-ordinated rotation.