Patent GB-564799-A (GB)
Title: Improvements in or relating to colour comparators
IPC: G01N21/29
Filed: 1942-09-29
Abstract: 564,799. Colour comparators. WALLACE & TIERNAN PRODUCTS, Inc. Sept. 29, 1942, No. 13677. Convention date, Sept. 30, 1941. [Class 97 (i)] A colour comparator of the kind described in U.S.A. Specification 1.976,672, wherein a pair of transparent vessels containing liquid samples to be compared are placed in juxtaposition in a pair of open-ended chambers between a window and means for viewing the samples simultaneously while a variable colour standard in the light path through one of the samples is adjusted until colour matcliing is observed, is combined with an illuminating device comprising a casing which encloses the window and contains an electric lamp which illuminates both samples, means for energizing the lamp and means for controlling the energization, and with shutters for rendering the sample chambers light-proof. In the form shown in horizontal section in Fig. 4, the front part of the apparatus is of the kind described in U.S.A. Specification 1,976,672, and comprises a casing 12 having front and rear walls 10, 11 and partitioned into vertical compartments 13, 14 housing the sample containers 31, 32, and 15 housing a bottle of reagent. or indicator, of which a portion is added to one sample for the purpose of colour comparison ; a window 33 of diffusing material in the rear wall 11 ; apertures 20, 24 in the front wall 10 opposite the samples ; a rotatable disc 16 between the front wall and the compartments, having a central glass plate 19 of clear glass or standard colour opposite the compartment 14 surrounded by a ring of glass plates 22 of graded colour, any one of which may be brought opposite the compartment 13 by turning the disc ; and a viewing device 27 provided with an eyepiece 28 and a pair of prisms 29, 30 for permitting observation of the samples in close juxtaposition. Indicia against each plate on the disc 16, observable through a window in the front wall 10, give readings of chemical composition corresponding to the various plates. The rear part of the apparatus comprises, according to the invention, a lamp housing 40 closed by a detachable rear cover-plate 42 on which are mounted a compartment having an open front registering with the window 33 and enclosing an electric lamp 55 which may be of the " daylight " kind ; and above and below the lamp compartment housings for electric dry cells, each of which is carried in a clip comprising a base 60, Fig. 6, having at one end an upturned convex spring ring 62 for engaging the base of the cell, and at the other end an upturned arm 63 provided with an insulated concave contact disc 65 for engaging the positive pole of the cell. Between the cell clips, and to one side of the lamp compartment, is a coiled wire holder 79 for a spare lamp. The lamp 55 and cells are wired in series through a switch comprising a spring contact arm 73 adapted to be displaced by pressure on a button 76 recessed into the cover-plate 42 into contact with an arm 71 fixed to the socket of the lamp. The front and rear plates 10, 42 are held by interchangeable turnscrews 45, 46 to permit easy access to the disc 16 and lamp assembly. The compartments 13, 14, 15 are open both above and below, the various containers being held therein by springs 91, 92 ; and they are adapted to be closed by light-excluding plates mounted one on the top and the other on the bottom of the casing 40 so as to turn through a limited angle about a pivot at the corner of the plate, the pivot including spring provision for pressing the plate against the top (or bottom) of the casing throughout the movement. The casings 12, 40 may be made of hard rubber or synthetic resin, of dark colour except inside the lamp compartment, which may be whitened. The use of the apparatus for making pH readings and for estimating the residual chlorine content of water after purification with chlorine, is referred to.