30 



Equipment of the Class Rooms. 



N.I. r.oisa - 



be traced to the employment of material which is unusitable for the purpose. By using: o 11 r 

 system of darkening it is possible to exclude the light entirely 

 over surfaces to 5 met res width and 9 metres height. 



The darkening devices can also be supplied of simpler construction. In this case the blinds 

 consist of black, impregnated sail cloth and on three sides of the window the 

 framing is fitted with cornices. The price is reduced by about a q u a r t e r in this con- 

 struction. 



As the price of the device is calculated according to the space to be obscured and the length of the 

 transmission parts, it is necessary when sending inquiries to give an elevation and section of the 

 window wall and to state the height and width of the window bay, of the distance apart of the 

 bays, and their distance from the windows and the walls, so that we may be enabled to quote 

 the price correctly. If there aie iron girders over the windows, or pipe-lines, heating units, or 

 the like in the neighbourhood of the windows, these should be shown in the drawing. 



We shall be glad to submit drawings, prices and references as to work already carried out by 

 us in this connection. 



50.182. Window Darkener (W e i n h o 1 d's), for working by hand (W. D., Plates I and II - s. <i. 

 and Fig. 2 A, B, C), without rope pulley, wire rope or winder; according to the size of . 



the windows. Roller Blinds of felt with inlaid fabric , application 



In the hand-operated darkeners a rope-pulley with wire rope is fixed on the shaft of the blind, 

 the latter being rolled up and down by a winder. This winder has an automatic clutch and remains 

 in any desired position. The handle of the windlass is detachable. 



50.183. --The preceding, simpler, with blinds of impregnated sail cloth. Framing 

 on three sides of the window, w r ith cornice. The price is about a quarter lower than 

 in No. 50,182. 



50.184. Rope Pulley, 13 cm diameter 0. <. <> 



50.185. --The preceding, 20 cm diameter 0. 13. 6 



50.186. Winder, for 1 window, with automatic clutch and detachable handle 0. 13. 6 



50.187. --The preceding, larger, for a number of windows 0. 19. 



50.188. Wire Rope, 3 mm diameter Per metre | 0. 0. 5 



50.189. --The preceding, 5 mm diameter Per metre 0. 0. 9 



50.190. Skylight Darkener, for large rooms having Skylight Pricc " 



application 



The roller blind is fixed to massive wood shafts having wheels at both ends. The wheels run 

 on rails. 



50.191. Darkeners, motor-driven (Figure), these being operated rapidly and conveniently 

 by simply switching on a switch or pressing a button: the window or windows being 

 darkened in a few seconds and the motor automatically switched off. The above can 

 be supplied on application on giving details of the conditions prevailing, drawings, etc. 



In this arrangement the operation of darkening can be carried out from any desired position of 

 the room and all windows can be darkened simultaneously. If the windows lie on different sides of the 

 lecture room, the driving shafts are connected with each other by special coupling pieces. The blinds 

 are rolled up and down automatically in a few seconds by means of an electric motor fitted with worm 

 gearing Nos. 50,194 50,196. The operation can be quickly and conveniently effected in two ways - 

 either by means of a switch or press buttons. 



In the arrangement provided with switches, the 3-pole commutator with the requisite fuses are 

 mounted on a marble panel (No. 50 197), the latter being fixed in any convenient position in the 

 lecture room as a rule on the wall behind the lecturer. It is only necessary to throw the switch 

 up or down, and the blinds move "sympathetically" up and down with the hand lever, the corres- 

 ponding direction of rotation being imparted to the motor. By placing the switch lever in the central 

 position the blinds can be brought to a standstill at any desired height. On reaching their highest or 

 lowest position, the current is cut out by an "end" circuit breaker (No. 50,200). In 

 cases in which a motor of more than */ 4 HP. is used, a reversing starter (No. 50,198) is used instead of 

 the 3-pole switch. The blind roller is driven from the motor by means of a worm gearing and sprocket 

 f chain. 



When the blind or blinds are controlled by press buttons a small switch panel is also 

 necessary (see No. 50,199) with 3 differently coloured buttons. The contacts of the buttons are con- 

 nected to a device (Fig. 50,199 B) which can be placed in any desired part of the room, and these i 



