A CAMERA SUPPORT DEVICE

Abstract: The invention relates to a camera support device of the type comprising a girder along which there are displaceable a camera chariot and a counterweight chariot in such a way that the girder is always statically in balance. The invention solves the problem to attain a noiseless movement of the counterweight unit by providing it with at least three pairs of wheels (5, 6), the wheels in each pair being by a spring (8) urged apart along a shaft (7) and kept in contact with the girder both at its envelope surfaces and at tapered corner portions.

Description: A camera support device The present invention relates to a camera support device comprising a track in the form of a box girder and a chariot movable along said girder and supporting the camera. The chariot is over an endless wire, running over pulleys at the girder ends, in sucn a way connected to a counterweight movable inside the girder that, upon change in either direction of the camera position rela¬ tively the longitudinal centre of the track, the counter¬ weight are displaced in the opposite direction. In that way the track along with the camera chariot and the counter¬ weight is maintained statically a balanced relatively the centre of the girder which is there mounted on a tripod- The box girder is generally manufactured by extrusion from an aluminum alloy which results in relatively large dimen- sion tolerances. A typical distance between each pair of mutually opposite girder walls is about 70 mm. However, that distance may deviate from nominal figure by a tole¬ rance of -0.5 mm. In order for an equipment of this type to be as versatile as possible it must allow the camera to be positioned in three dimensions. In other words, the box girder must be rotatable in a horizontal plane, tiltable around a central horizontal axis and finally rotatable about its longitudinal axis. In all positions of the girder offered by those possibilities the wheels of the counterweight unit must be in such a contact with the interior of the box girder that all of them do perma¬ nently contact the inner wall and roll in such contact. This is so because a clearance at any or some of the wheels would, when the unit is displaced, create scratch- ing sounds. This cannot be permitted because they would disturb the accompanying sound registration. On the other hand, if all clearance were avoided, due to the just mentioned tolerance interval of the girder, the wheels would during the movement momentarily be braked by a jamming action. This would result in a jerky movement of the camera chariot which cannot be permitted. Another problem stems from the fact that the wheels of the counterweight unit in order to offer a soft and noiseless movement must consist of a relatively soft plastic material. It should be inserted here that this unit, which obviously must have the same weight as that of the camera chariot including the weight of the camera, may weigh up to 18 kgs. When the device is not in use, it is stored in a horizontal position. This means that due to the high surface pressure the soft wheels may at their surfaces in contact with the inner wall of the box girder be deformed to non-circular form. Even if this deformation is theoretically elastic, the practical con¬ ditions are such that it takes an unacceptably long time, about 3-4 hours, before the wheels have resumed their circular shape. For that reason the girder is to be stored upside-down. The pressure force generated by the weight of the counterweight unit will then be absorbed by the wheels normally located at the upper part of the unit. Naturally those wheels are deformed instead but, since in the position of use they do not contact the ceiling of the girder but have a clearance there, this deformation will not be disturbing. All these problems have according to the main characteris¬ tic of the invention been solved in such a way that the counterweight has at least three pairs of wheels, the two wheels in each pair being located adjacent the ends of their common shaft and a spring urging them apart and that the wheels are arranged to perform a rolling movement in contact with the inner wall of the girder on the one hand with the envelope surfaces contacting the horizontal walls of the girder and, on the other, their obliquely, preferably at 45 , tapered corner portions, contacting the girder corner portions parallel therewith. One embodiment of the invention will be described below, reference being made to the accompanying drawing which shows a cross-section through the box girder and through the counterweight chariot. Reference numeral 1 is the box girder which in the pre¬ sent example is of substantially square profile and at each of its four corners has external profile rims 2 and 3. The upper rims 2 are intended to serve as mountings for the rails of the camera chariot whereas the lower rims 3 are arranged to receive one or more mounting plates which in turn are attached to tripods. The coun¬ terweight, not shown here, is inside a housing 4 at the same time serving as the chassis of the counterweight unit. It has upper and lower wheel pairs. The drawing shows one upper and one lower pair of wheels, the two wheels on the right hand side being shown in cross- section. The lower pair of wheels consists of two wheels 5 and 6 mounted on a common shaft 7. This has an axial bore re¬ ceiving a pressure spring 8 which over a ball 9 exerts a pressure against the lateral wall of the wheel 6. Con¬ sequently, the spring tends to keep wheels 5 and 6 apart from each other in the axial direction. It appears from the drawing that each wheel is shaped like a relatively wide, cylindrical roller, the external corner of which is tapered, in this example with a taper of about 45 . The tapered portion has been designated 10. The upper wheel pair is designed in much the same way, the only difference being that, as has already been mentioned. there is a clearance between the envelope surfaces of the upper wheels and the adjacent interior wall of the box girder. When the device is in use and the camera chariot dis- * placed, causing a displacement of the counterweight chariot in the opposite direction, the gravitational force thereof will substantially be absorbed by the lower wheels 5 and 6. It should however be mentioned here that each counterweight chariot does normally have two more pairs of lower wheels. As has been mentioned, spring 8 urges wheels 5 and 6 axially apart whereby they will on the one hand with their envelope surfaces contact the inner wall 11 of the lower part of the girder and, on the other, have their tapered corner portions in con¬ tact with a parallel girder wall surface 12. In this position the upper wheels are out of contact with the ceiling of the box girder. On the other hand, thanks to the spring force, their tapered corner portions will in the same way as at the lower wheel pair be kept in con¬ tact with the parallel inner walls of the girder corner portions. The end result is that, disregarding the dimension deviations which, due to the manufacturing tolerances mentioned above, are present both in the horizontal and in the vertical direction as far as the girder is concerned, all wheels in each pair of wheels will always be in contact with the inner side of the girder when the chariot is displaced inside the girder. This contact in four different points, as counted in the cross-sectional plane, and in several points, as counted in the longitudinal direction of the girder, results in that the counterweight unit will displace in a noiseless way and exert the same resistance against the displacement movement along all of the track. In other words both disturbing sounds and a jerky movement are eliminated.

Claims: Claims 1. A camera support device comprising a track in the shape of a box girder (1) along which there is movable a chariot supporting the camera and over an endless wire, running around pulleys at the girder ends, in such a way connected to a counterweight chariot (4) movable inside the girder (1) that, upon a change in either direction of the camera position relatively the centre of the track as counted in the longitudinal direction thereof, the counterweight chariot (4) is displaced in the opposite direction whereby the track with the two chariots is kept in static balance rela¬ tively said centre, where the track is supported by a tripod or the like, c h a r a c t e r i z e d in that the counterweight chariot has at least three pairs of wheels (5, 6) , the two wheels in each pair being locatec adjacent the ends of their common shaft (7) , a spring (8) urging them apart, the wheels (5, 6) performing a rolling movement in contact with the inner wall of the girder (1), on the one hand with the envelope surfaces of the wheels contacting the horizontal vails (11) of the girder and, on the other, their obliquely, prefe¬ rably at 45°, tapered corner portions (12) , contacting the girder corner portions parallel therewith. 2. A device as claimed in Claim 1, c h a r a c t e¬ r i z e d in that the spring of each pair of wheels (5, 6) is constituted by a pressure sprirg (8) which is located inside a central bore in the shaft (7) and does at its outer end, preferably via a ball (9) , contact the inner side of the lateral wall of one of the wheels.

Inventors: RIDDERSTOLPE JOHAN, RIDDERSTOLPE, JOHAN
Applicants: MULTIGLIDER AB
Application year: 1990
Main classification: F16M11
IPC codes: B66F11, F16M11