This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
To Joseph Bramah, an English inventor, belongs the palm of having constructed the first complete continuous apparatus. He took as his starting-point a machine which had been patented a few years previously by a person named Hamilton, and which embodied several substantial improvements in soda-water-making machinery as theretofore constructed. He afterwards devised an ingenious and efficient apparatus, in which were comprised all the principal features of the ordinary continuous process soda-water machines of the present day: that is to say, it contained the generator for producing the carbonic acid gas; the gasometer for accumulating it; the condenser for combining it with the water; and the force-pump. This machine was unquestionably a great step in advance, and it still remains, in all essential features, the same as left by Bramah, the only improvements since made therein being in constructive details of comparatively minor importance. Other soda-water machines have been devised from time to time, and brought into use more or less extensively, but few of these showing any practical advantages, they were sooner or later discarded.
There can be no doubt that Bramah perceived the defects of the machinery in use at that time, and made an improvement by an arrangement that would permit the carbonating and bottling to go on continuously and simultaneously. He found that the conditions under which this continuity of action could be realized were - that the pump should be capable of producing any amount of pressure, that the gas and the water should be pumped together, that there should be regulating cocks for supplying gas and water as fast as both were drawn off, that the receiver or condenser should be sufficiently strong to bear the required pressure, and lastly, that the liquid in the condenser should be continuously agitated to promote the solution of the gas. All these conditions are carried out in Bramah's continuous process machine, which is represented by the engraving on succeeding page.
One important feature of this machine is the peculiar construction of the pump. The piston is solid, and works upwards, so that its upstroke corresponds to the downstroke of the piston of an ordinary force pump.
It is provided with a flexible collar, which is affected by the pressure in such a way that the piston becomes tighter as the pressure within the pump increases. The valves are in a suitable valve-piece, situated at the top of the pump, and are easily got at by simply removing a screw plug. It will be evident from this description that when the pump has drawn in its charge of gas and water by a downstroke, the water being the heavier will naturally be at the bottom, surrounding the collar, and thus preventing the escape of gas. Even should the collar become leaky, nothing would escape but a few drops of water, which would be of no consequence. Then, by the upstroke of the piston, the gas is driven on first, and the water last, so that the most important material in the manufacture of carbonated waters is effectively utilized without waste. In the old machine, the pump was open at the top, the piston being formed of leather, fitting the bore of the barrel, and the valves were situated at the bottom. The gas was drawn in at the upstroke, and forced out at the downstroke, the prevention of escape depending on the fit of the piston in the barrel. Then again, the old pump, unless surrounded by water, became heated by the condensation of the gas. Attempts have been made to pump gas and water together with the former kind of pump, and there are some of them at work now, but they are always getting out of order. The objection to this kind of pump may be very shortly stated. The water being heaviest, will fall to the bottom, and consequently be driven out first, and the gas last, on the descent of the piston; or, if any escape takes place, the gas will pass by the piston, and the most essential material will be lost, The superior system of Bramah's pump is in principle the same as now adopted in all "continuous process" machines.
Fig. 54. - Bramah's First Continuous Machine.
The chief differences between these old Bramah machines and those now manufactured are in the design of the frame, and in the proportions of the condenser, which is now made much larger than was formerly the case.
The Bramah system is the "continuous system, English plan" of to-day, and if the cylinders are large enough they can also be worked semi-continuously when preferable.