473 



ingenious. A long strip is cut from a thin sheet of dough, and this 

 is cut into lengths of a few inches, not by simple cross diversions 

 but by oblique cuts. These lozenge shaped strips are then wrapped 

 round a smooth circular rod and the sloping ends pressed together. 

 A band is thus formed round the rod and the line of junction of 

 the two original ends of the strip passes obliquely across the band. 

 The workman, or rather workwoman, then rolls up into a ring 

 with her fingers this flat band, still upon the rod, and by rolling it 

 backwards and forwards upon the rod makes a smooth ring of it. 

 The object of cutting the strip with oblique ends — or " on the 

 cross" — is now evident, because the line of original junction 

 which naturally would would be the weakest place in the ring, is 

 spread out over a considerable length of the ring and it is every- 

 where wrapped round and supported by whole and unjointed 

 avers of rubber, becoming thus nowhere more than a small portion 

 of any part of the cross section of the ring. Screw stoppers for 

 bottles are mechanically stamped out of a dough which contains 

 a high proportion of sulphur and which gives a hard product on 

 vulcanisation, the dough is stamped in two stages, first a simple 

 cylindrical rod is made and cut lengths of this are then fed into a 

 powerful press which produces the final shape. For large and 

 awkwardly shaped goods, such as the outer covers for pneumatic 

 tyres, specially devised iron moulds to completely encase the trye 

 and exert pressure upon it during vulcanisation are prepared. 

 These moulds are in several portions and have to be fitted round 

 each tyre separately and the portions keyed into contact. Flexible 

 rubber tubbing where the rubber is solid and not, as in hose piping 

 associated with canvas, is squirted out of a machine provided with 

 compound nozzles, the apertures in which are ring-shaped. The 

 rubber dough is ejected through this annular orifice as a hollow 

 tube which only requires heat vulcanisation for completion. 



A detailed account of the mechanical difficulties encountered 

 in this part of the work, and the way they are surmounted, would 

 be of little use and certainly tedious ; the principal underlying all 

 processes is the same— namely, moulding plastic dough and then 

 reproducing the elasticity and tenacity of the rubber goods by 

 heat and vulcanisation. 



20. Rubber goods that are " built up " fall naturally into two 

 classes, according to their being pure dough or compounded with 

 other materials, as in the case of outer covers for tyres, hose piping, 

 rubber belting, etc. The general mode of treatment is the same .m 

 all cases, and it is a mixture of joinery and tailoring. The dough 

 is soft and plastic and so can be rolled to any thickness cu : to an> 

 shape, and applied to the goods in any manner. The dough con- 

 tains raw rubber and therefore is adhesive, cut ^..^J^^ 

 pressed into contact and that with the greatest ease if the edges or 

 surfaces are previously moistened with any rubb ^ ^ 

 tools necessary for use in this work are .consequently of th simgest 

 -a keen knife or stamps for cutting shapes, a .squeeje for pressing 

 surfaces into contact, and a pot of benzine with a piece of cloth as 



