IMPROVEMENTS IN OR RELATING TO TILTABLE PAYLOAD MOUNTING

Abstract: The disclosure relates to a tiltable mounting for a payload comprising a base (10), a support member (15) for supporting the payload thereon, the support member being tiltable about a horizontal axis (14) on the base for tilting about each side of a top dead centre position about said horizontal axis, and torque generating means (17) 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. A plurality of torque generating units (20, 21) are provided each generating a torque which varies sinusoidaly with displacement, and means (22, 23, 31, 32, 35, 36, 37) 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.

Description: IMPROVEMENTS IN OR RELATING TO TILTABLE PAYLOAD MOUNTING This invention relates to a tiltable mounting for supporting a payload and is particularly although not exclusively 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. 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; Figure 1 is a partly cut-away elevation view of a tiltable camera mounting embodying an automatic counter-balancing mechanism; Figure 2 is a section on the line 2-2 on Figure 1 with the counter-balancing mechanism in one mode of operation; and Figure 3 is a similar view to Figure 2 with the counter-balancing mechanism in another mode of operation. The drawings show a tiltable mounting for a T.V., video or cine atagraph camera comprising a base 10 in the form of an upstanding enclosure having spaced side walls 11. A pair of stub-shafts 12, 13 are rotatably mounted about a common axis 14 in the side walls. A platform 15 for receiving the camera is mounted on a pair of dependent legs 16 secured to the ends of the stub-shafts projecting from the side walls to support the platform for tilting movement about the axis 14. The camera/mounting assembly is thus tiltable from the top dead centre position in which the platform is horizontal about the horizontal axis 14 in either direction. A torque generating counter balancing mechanism indicated at 17 is provided in the housing of the base which acts in response to tilting of the assembly automatically to support the assembly in any position of adjustment to which it is moved about the horizontal axis. Before the specific mechanical arrangement of the torque balancing mechanism is described, the geometry on which the arrangement is based will be described. The followng diagram represents, in simplified form, the combined mass of the camera and mounting rotating about a radius R generating an angle θ from the vertical. The out-of-balance torque T = MR Sin θ Assume that two torque balancing units are provided as indicated by the diagrams below: Balance Unit 1 Balance Unit 2 The torque produced by the respective balance units will be given by the following equations: (1) T. = MR Sin (Θ + α) (where α is phase angle) 2 (2) T- = MR Sin (θ + 3) (where is phase angle) With the two balance units acting in parallel, the resulting total torque will be given by the following equation: Total torque == TT 1- ++τT2, MMRR I I sSiin (θ + α ) + ( θ + β ) 2-B j T = MRSin overall phase σveSfeTl amplitude Thus a pair of torque generating means operating in parallel and each of which varies sinusoidally with angular displacement can be used collectively to provide the total torque required. By adjusting the phase angle between the torque generating means, the collective amplitude and phase of the torque generating means can be varied according to the magnitude and location of the payload on the pivotal mounting. Referring again to Figures 1 to 3 of the drawings an example of a suitable form of torque generating means which may be employed in the invention is indicated at 17. The torque generating means comprises a pair of torque generating units 20, 21 each of which comprises a gear wheel 22, 23 having an internal sinusoidally shaped cam surface 24, 25. Each gear wheel encircles and is supported for rotation on a cylindrical housing 26, 27 mounted on the respective ends of stub-shafts 12, 13 within the enclosure 10. Each housing is of the hollow cylindrical open ended form and has rollers or balls 28 spring loaded by a spring 29 extending through the housing to project from either end and engage the encircling cam surface 24, 25 of the respective gear wheel. It will be appreciated from the shape of the cam surface 24, 25 that rotation of the housing 26, 27 with the respective stub-shaft 12, 13 will cause the rollers 28 to compress and release the springs 29 resulting in a torque which resists rotation of the housing and which varies sinusoidally with rotation of the housing. A drive mechanism for rotating the gear wheels 22, 23 in the same or opposite directions as required is indicated at 30 on Figures 2 and 3 to which reference will now be made. The drive mechanism comprises a main drive shaft 31 mounted for both and rotation and axial movement in the enclosure 10. The shaft has a pair of spaced pinions 32 fixed thereon which engage external gear teeth 22, 23 on the respective gear wheels to provide a driving connection with the gear wheels. One end of the shaft 31 projects from the housing and carries a knob 35 for effecting rotation/axial movement of the shaft by hand. A lay shaft 36 is mounted in the housing parallel to the drive shaft and carries a single pinion 37 engageable with the teeth of one of the gear wheels 23. The pinion 37 is relatively long and is partially off-set from the gear wheel 23 with which it engages so that one of the pinions 32 on drive shaft 31 is selectively engageable by axial adjustment of the drive shaft with gear 23 either direct or via pinion 37 on the lay shaft whilst the other pinion 32 is permanently engaged with its gear wheel 22. As shown in Figure 2, the drive shaft 31 rotates both gear wheels in the same direction and, as indicated above, this enables the torque generating means to be adjusted to compensate for an offset payload on the tiltable mounting when the latter is in its top dead centre position. With the drive shaft in the position shown in Figure 3, the cam gears are rotated in opposite directions to vary the amplitude of the collective torque provided by the two torque generating means to cater for different sizes of payloads on the mounting. Thus the arrangement according to the invention provides a convenient and relatively simple means for providing a fully automatic counter balancing mechanism for a camera or other payload mounted on a tiltable mounting.

Claims: CLAIMS 1. 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. 2. A tiltable mounting as claimed in Claim 1, wherein means are 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. 3. A tiltable mounting as claimed in Claim 2, wherein two torque generating means are provided each of which provides a sinusoidally varying output and drive means are provided for selectively adjusting the torque generating means in opposing directions to vary the total amplitude of the torque provided and in the same direction to vary the phase angle of total torque with respect to displacement of the torque generating means to compensate for off-centre location of the payload on the support member in the top-dead-centre position thereof. 4. A tiltable mounting as claimed in Claim 3, wherein each torque generating means comprises an annular reaction member having an annular cam surface and a rotary cam follower coupled to the tiltable support member and embodying means to generate a resistance to rotation which varies with movement of the follower over the cam surface, said drive means being arranged to rotate the annular reaction members in opposite directions to vary the total torque provided and in the same direction to vary the phase angle of the total torque provided. 5. A tiltable mounting as claimed in Claim 4, wherein the rotary cam follower comprises a rotary hub on which a follower element is spring mounted to engage with the cam surface so that, as the cam follower rotates with respect to the reaction member, the spring stress varies to provide a sinusoidally varying resistance to rotation of the follower determined by the shape of the cam surface. 6. A tiltable mounting as claimed in Claim 5, wherein the rotary hub of the cam follower comprises a hollow cylindrical housing having rolling elements spring loaded outwardly from either end to engage the encircling cam surface. 7. A tiltable mounting as claimed in Claim 6, wherein the rolling elements are supported and spring loaded outwardly by a coil spring extending through the housing. 8. A tiltable mounting as claimed in any of Claims 3 to 6, wherein the annular reaction members have gear teeth around their outer peripheries and the drive means for the members comprises a reversible gear drive mechanism.

Inventors: LINDSAY RICHARD ARTHUR, LINDSAY, RICHARD, ARTHUR
Applicants: LINDSAY RICHARD ARTHUR, VINTEN GROUP PLC
Application year: 1993
Main classification: F16M11
IPC codes: F16M11