Horizontally supported planar surfaces – Tiltable surfaces – Pivotally adjustable about horizontal axis
Patent
1995-01-12
1997-02-25
Brown, Peter R.
Horizontally supported planar surfaces
Tiltable surfaces
Pivotally adjustable about horizontal axis
108 2, 108 8, A47F 512
Patent
active
056051018
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a tiltable mounting for supporting a payload and is particularly although not exclusivcely applicable to tiltable mountings for supporting articles such as television, cinematograph or video cameras to enable the camera to be tilted about a horizontal axis in a required position of adjustment and automatically to remain balanced in any position to which it is moved.
GB-A-2231548 discloses a mechanism for balancing the weight of an object to be swivelled about an axis and especially for balancing the weight of a film or television camera mounted on a tripod head. The pitching torque produced during swivelling of the object is compensated by a restoring torque which acts with the aid of a spring arrangement on the pitch axis via a lever arm. Provision is made for increasing the pitching range and achieving a compensating torque for all pitch angles. In order to cater for cameras of different weights, an appropriate choice of spring strength has to be made and bolts have to be adjusted to provide the requisite degree of precompression in the springs.
GB-A-2049601 discloses a torque counterbalancing mechanism for use on tiltable tables, the mechanism comprising a cam operated on by a spring loaded cam follower so their interaction produces a force equal opposite to the torque generated as the tiltable table with load rotates to either side of the vertical. At the null position, i.e. no torque, the spring is at rest with no prestressing and means are provided for changing the effective weight of the spring to adjust the mechanism to accommodate different heights of the centre of gravity of the load or changes in load. Further more complex arrangements for achieving similar effects are shown in GB-A-2080406, GB-A-2190703 and DE-A-2711772.
It is an object of the present invention to provide a counterbalancing arrangement for a tiltable mounting supporting a payload which is readily and simply adjustable to cater for different payload weights and which at the same time provides perfect compensation for the tiltable mounting throughout its range of movement.
This invention provides a tiltable mounting for a payload comprising a base, a support member for supporting the payload thereon, the support member being tiltable about a horiztonal axis on the base for tilting about each side of a top dead centre position about said horizontal axis, and torque generating means mounted on the base and acting on the tiltable support to generate a torque in response to tilting of the support equal and opposite to the out of balance moment of the support with its payload to hold the support balanced in any position of movement about said axis, wherein a plurality of torque generating means are provided each generating a torque which varies sinusoidaly with displacement, means being provided for adjusting the phase angle between the torque generating means to vary the collective amplitude of the torque generating means to suit the weight of the payload on the support member.
Preferably means are also provided for adjusting the torque generating means in the same direction with respect to the mounting to compensate for off-centre location of the load when the support member is in the top dead centre position.
The following is a description of a specific embodiment of the invention, reference being made to the accompanying drawings in which;
FIG. 1 is a partly cut-away elevation view of a tiltable camera mounting embodying an automatic counter-balancing mechanism;
FIG. 2 is a section on the line 2--2 on FIG. 1 with the counter-balancing mechanism in one mode of operation; and
FIG. 3 is a similar view to FIG. 2 with the counter-balancing mechanism in another mode of operation.
FIG. 4 represents a diagram depicting the combined mass of the camera and mounting rotating about an angle from the vertical.
FIGS. 5A and 5B represent diagrams depicting two torque balancing units.
The drawings show a tiltable mounting for a T.V., video or cinematagraph camera comprising a base 10 in the form of an upstanding enclosur
REFERENCES:
patent: 2845263 (1958-07-01), Gund
Barfield Anthony D.
Brown Peter R.
Vitec Group PLC
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