Cushions from Frothed Latex
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Mixed with a Coagulant, Poured into Moulds of Any Shape and Cured, Nothing Else but a Baseboard and Cover is Required
ONE of the secrets of the new series of cushions which has been produced by the Dunlop Rubber Cu., Ltd., at Fort Dunlop, Birmingham, is the employment of specially prepared rubber latex. Until comparatively recently, many manufacturers were busily engaged in producing goods from solid, dried rubber, but the use of concentrated latex has revolutionized many processes.
Ordinary latex, as it comes from the Plantations, contains less than one-third of rubber, the remainder being water. The Dunlop Co., however, brings the rubber content up to approximately 60 per cent., by using Alfa-Laval centrifu gal separators, a half of the watery fluid with its impurities being removed.
This creamed latex presents many advantages over dried rubber, as it does not require mechanical kneading or mastication between powerful rollers, which, whilst being essential, considerably reduces the strength and elasticity.
In making the new cushions, the latex is further concentrated at the works until it is some 80 per cent. rubber. It is then frothed in machines, which are replicas of those used by confectioners, and mixed with a coagulant which causes it to solidify in approximately 10 minutes. While liquid, it is poured into moulds and cured.
It should be noted that this latex sponge froth does not resemble in any way the sponge rubber which is produced by the employment of special gas-producing chemicals, and there is no crust, only a superficial skin, which possesses the important advantage of being very porous, the whole of the cushion being perfectly ventilated. This is shown by the fact that smoke blown into the cushion at one side will dis
perse through it and emerge all over the surface. Furthermore, this rubber is absolutely vermin-proof. This is a very big consideration in bus work, for one of the troubles experienced when ordinary flock is employed for stuffing seats is that insect eggs, which are sometimes present in the original flock, may be incubated by the warmth of the passengers.
An Excellent Shock Absorber.
suitably moulded, the rubber forms an excellent shock absorber, and, unlike metal springs, the periodicity is so low that there is no bouncing. No stuffing at all is required, the rubber cushion being merely covered with the seat material.
Many cushions are ruined by acid from wireless accumulators, 'which attacks flock and wool, but the latex-froth cushions are unaffected by it. The seats are merely mounted on plywood boards, which are drilled to permit breathing of the cells.
It is claimed that with these seats a saving in weight of 3 ewt, can be
effected in a double-saloon bus; for instance, the double seat for a London bus weighs approximately 6 lb. 3 oz. without the leather or moquette cover. No great depth of cushion is required. For the utmost comfort a maximum of 5 ins, is desirable at the front and 4 ins. at the back, but many seats are giving complete satisfaction with depths of 31 ins, at the front and 21 ins, at the back.
The London General Omnibus Co., Ltd., is utilizing these seats on 250 of Its buses, whilst 50 "Midland Reds" are likewise equipped.
Any additional cost of Aireellite, as it is called, against that of springs is offset by the saving in material and labour charges. One of its good points is that unequal distribution of the load does not affect good riding. The life is claimed to be fully equal to that of the vehicle as a whole, thus the maintenance charges are bound to be reduced.
An advantage in the course of maimfacturels that the moulds can be very light, as they are utilized only for the setting of a mobile froth.