Patent GB-326488-A (GB)
Title: Means for projecting coloured light
IPC: F21V9/40
Filed: 1928-12-10
Abstract: 326,488. Jones, G. Thornton- Dec. 10, 1928. Optical-projection apparatus. - Apparatus for projecting coloured light comprises means for producing a plurality of light beams, colouring media and continuously-operating shutters being disposed in the paths of the projected beams. The shutters consist of discs or plates provided with light passages, means being provided for effecting a limited relative movement of the discs or plates whereby the light passage area through the shutters and thereby the intensity of each projected beam may be varied. In the example described, four sets of apparatus, each comprising a pair of shutter-members 4, Fig. 1, a light projector 5 and a colouring screen 16 are mounted on a common framework. The shutters rotate on spindles 3 passing through uprights 1. The pro-. jectors 5 are pivoted in forked brackets 6 each attached by means of an arm 7 having a universal joint at each end to an adjustable collar mounted on an upright 1. A motor 9 drives a pulley 10 on a spindle 11, two smaller pulleys 12, one fixed to the pulley 10 and the other running freelv on the spindle 11, being provided. An endless band passes over the smaller pulleys 12 and over pulleys 14, Fig. 3. fixed to sleeves 13 surrounding the-shutter spindles 3. The shutters are formed by pairs of discs 4a, 4b which normally rotate together, each disc having one or more spindles. The amount of light projected is varied by causing the relative rotation of the discs. One disc 4<a> is attached to a sleeve 21 secured to the driving sleeve 13, the other disc 4b being attached to a freely-mounted inner sleeve 22. These sleeves have oppositely-directed spiral slots 20, an operative connection between the sleeves being formed by pins 19 projecting from a member 18 rotatably mounted on the spindle 3. The spindle is moved axially by means of a nut 17 engaging its screwed outer end, the nut itself being held from axial movement. The member 18 is also prevented from moving axially along the spindle 3, and an axial movement of the spindle thus causes a relative rotational movement of the shutters 4<a>, 4b. A pointer 27 secured to the nut 17 and moving over a scale is used to denote various shutter settings. The position of the light beams may be varied by rotary discs 25, Fig. 1, having eccentric openings 26, the discs being situated in front of the projectors. The various beams may be focussed on the same area of a receiving screen. Iris diaphragms may be provided in connection with each lamp. The colouring screens 16 may be rotated by hand or by power, and they may be replaced by any other colouring-means such as containers filled with coloured liquids. The apparatus may be arranged to produce " colour music " effects. Four projectors PR, PO. PG, PB, Fig. 5, each comprising a lamp, a dual shutter unit and a colouring screen, and arranged to project red, orange, green, and blue light respectively are controlled from a keyboard 28 containing keys arranged in five groups a - e. Each group contains four keys R, 0. G, B, which control the red, orange, green, and blue light projectors respectively. The shutters are operated by solenoids 29, the operation of which opens the shutters to their full extent. Auxiliary solenoids 29a, 29b restrict the shutter openings to one-third and to two-thirds of the full amount respectively. In addition to the coloured light projectors, a white light projector PW is provided. The operation of the red light controlling key R in group c operates the solenoid 29 of the red light projector PR and fully opens the shutter. Operation of the corresponding R key in group d energizes both the main solenoid 29 and the auxiliary solenoid 29a of the red light projector PR. This restricts the shutter opening to one-third of the full amount. Similarly operation of the R key of group e energizes the main solenoid 29 and the auxiliary solenoid 29b, the opening being restricted to two-thirds of the full amount. Operation of the R key in group a energizes, in addition to the solenoid 29 of the redlight projector PR, a solenoid 31 opening a sliding shutter on the white-light projector PW and a solenoid 32 which opens to its full extent an iris diaphragm on this white-light projector. Operation of the R key of group b causes a similar operation of the solenoids 29, 31, but a solenoid 32<a> causes only the partial opening of the iris diaphragm. The other keys in the various groups control correspondingly their respective projectors. Additional means 34, such as foot or hand operated sliding shutters, may be provided to vary further the dimensions of the coloured light beams.