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. The pantographic tilt control mechanism 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 pantcgraphic-type linkage in which the angular position of a first element relative to a second element is controlled by the meshing of at least two rotational members, such as toothed gears, and means are provided for constraining an intermediate point of the linkage to move along a horizontal path.

In particular, the first element may be a toothed gear, whilst the meshing members may be supported by a central element of the linkage. This central element may embody the point constrained to move in a horizontal path.

The second element may be a rigid arm attached to a gear wheel, which may constitute one of said meshing members. The above-described arrangement effectively provides a pantographic linkage, with unlimited freedom for folding in either sense without risk of instability. If a mounting head is fixedly carried by the second element, its freedom for tilt is substantially unlimited. At the same time, by constraining an intermediate point of the linkage to move in a horizontal path or locus, the centre of gravity of a camera or other item of equipment on the mounting head can be constrained to move, during tilting, in a horizontal path, so that the weight of the item is not a factor which enters into the tilting action. Reference may be made to the above-mentioned patent specification for a fundamental understanding of this action.

Description of embodiment

The invention is now exemplified in the following

description, making reference to the accompanying drawing, in which:-

the single figure shows a pantographic-type linkage in diagrammatic manner.

Referring to the drawing, the illustrated pantographic- type linkage comprises a first gear wheel 10 fixedly carrying an arm 12 having its remote end pivotally mounted at 14 to a fixed structure 16.

Gear wheels 18 and 20 form a gear chain with the first gear wheel 10, the axes of all three gears being inter¬ connected on a straight line by a rigid arm 22, which effectively constitutes a central element of the linkage.

The gear wheel 20 fixedly carries an arm 24 supporting a mounting plate 26 for a camera or other item of equipment which is to be controlled in tilt, without influenςe of its weight on the tilting action. In order to achieve this, a point 28 of the interconnecting arm 22 is constrained to move in a horizontal path or locus 30 defined by the fixed structure 16, as by means of a pin and slot connection.

Considering appropriate radii embodied in the outer gear wheels 10 and 20 of the gear chain, i.e. pairs of parallel radii defined by the direction of the respective arms 12 and 24 fixedly carried by these gear wheels, the above- described linkage can be understood effectively to comprise two pantographs coupled in movement by the central gear wheel 18. Moreover, the additional constraint on the point 28 of the interconnecting arm 22 which supports the gear chain makes it possible to limit

movement of the centre of gravity of a camera or the like on the mounting head to a horizontal locus when the camera is tilted by application of manual effort thereto. Thus, the weight of the camera does not affect the tilting action. However, unlike the known arrangement previously referred to, the angle of tilt within which this advantageous effect is achieved is not limited, and a tilting range up to 180 degrees, and theoretically up to 360 degrees, can readily be achieved.

Adjustment to compensate for variation .due to differing positions of the centre of gravity of different payloads, is affected by altering the position of the roller 28 along the length of the intermediate strut 22.