J -The action of tl < the 



Mine a* that of an india-rubber valve, bat a thin sheet of 



.iue) ukrs the place of the indU rubber. 

 ^ now largely used in the pumps of marine 

 fngiiK^ a.ul ii fthnwn in fig. 96 M applied to an air-pump 

 bucket. Three val ves like the one shown are arranged n.und 

 tli.- 



now 60: Kiiqkor*'* Mrtallie Ka/w.-Fig. 66 shows an 



n sod plan of one form -f this valve. In the plan one half 



uard and metal sheet are supposed to be removed, so M to 



how the pr case U part of an air pumj. books*. 



Draw the views shown, and also a vertical section of the guard 



tfnr""^ the centres of the bolts. All the parts are of brass except 



the valve proper. of phosphor bronie. Scale 6 inches to a 



b .. 



Conical />i> To/Mi. A very common form of valve is 



that shown in tip*. r>7 and 68. This f live consists of 



a disc, the edge of illl the face) is conical The 



conical edge of this disc fiU accurately on a corresponding 



seat The angle which the valve face makes with its axis is 



generally 45. If the disc is raised, either by the action of 



the fluid as in the imliu rul>)-r vulvr. <>r by other means, an 



opening is formed aroutxl the <lis<- tl.r-.u-li whi.-h th> fluid 



can pass. The valve is guided in rising and falling either by 



three feathers underneath it, as in fig. 67, or by a central 



ss hi. i. moves freely through a hole in the centre of a 



bridge which stretches across the seat, as in fig. 68. The 



the vah<> is limited by a stop above it, which forms part of the 



casing containing the valve. The lift should in no case exceed 



one-fourth ..f the diameter of the valve, and it is generally 



less than this. The guiding feathers (fig. 67) are notched 



imme<i < ler the disc for the purpose of making available 



i-rential opening of the valve for the passage 



of the fluid These notches also prevent the feathers from 



ruing or scrap MOB. 



Conical disc valves and their seats are nearly always 

 of brass. 



