It is, perhaps, deserving of notice, that the self-acting property of these presses adapts them for situations where advantage could be taken of the ebbing and flowing of the tide; the rising of the water would thus fill the buckets, and, upon its falling, leave them suspended with their loads to do the work of the press; the return of the tide would take off the pressure for the renewal of it upon its descent; and thus, every twelve hours, the presses might be worked with almost unlimited power and without any attendance to the moving force.
The most powerful and the most convenient machine for expressing oils, is, unquestionably, the hydrostatic pressinvented by the late Mr. Bramah. A press of this kind was sent out to Ceylon, by government, in the year 1814, which was made by Mr. Bramah expressly for the purpose of expressing oil from the cocoa-nut kernel; a very full description of all the important details of which is given in the thirty-fourth volume of the Transactions of the Society of Arts. But although the hydrostatic press is the most economical machine that the capitalist can employ, its expense is unsuited to the means of the small, or middle, manufacturers, to whom a press of some kind is indispensable; accordingly, the following one has been designed to meet their wants.
The annexed figure gives a front view of the machine, excepting that the front plate which encloses the lower part of the machine, and the bearings of the axes of the cams are removed to show better the construction, aaa is a strong frame of cast-iron (it maybe of wood strongly bolted together); the size may be as circumstances may require; but a convenient size would be 3 feet high, two feet wide, and 1 foot from front to back, b is the pressing-head, of solid wood, formed into three wedge-shaped teeth, and made so as to fit into a bed e e e, of a corresponding figure; d d are two cams, firmly attached to two expanding levers e e, which are loading at their extremities by suspending thereto any required number of flat circular weights: to each of the cams a strong hook, bent to the figure of the former, is fixed; and these hooks passing through eyes, or staples, in the head of the press, lift it up when the pressure is taken off, allow it to descend without obstruction, and keep them always connected.
At g is an aperture for conveying, by means of a pipe, hot air, or steam, into the chambers ooo, which have lateral openings one into theother; the angular roof of this chamber adapts it for collecting the heat, air, or vapour, whence it passes through the interposing iron plates into the bags under pressure. The bags being placed between the wedges as shown, the pressure is given by loading the levers (which may be drawn out to any length required), which gradually causes them both to descend to the position shown by the dotted lines e' e andf'f'; at which time the cams have turned a quarter round, so as to attain a vertical position when their utmost effect is produced. The bags between the wedges are thus compressed by a great force, and their contents reduced to hard dry cakes, while the expressed oil runs off in the angular gutters at the bottom, and is conducted out of the machine, by a pipe, into a proper recipient.
The operation being completed, the pressure is taken off by removing the weights (already close to the ground), and throwing up the levers which lift the head of the press, the chief labour of which may be obviated by a counterbalance weight. The oil cakes being taken out of the press, other bags, previously prepared, are put in their place, and the operation renewed simply by loading the levers, leaving them to do their work unassisted, and accumulate in power as they move through their assigned space. It should here be observed, that owing to an oversight in the drawing, the levers are not shown as fixed in the best position for commencing the operation. They should be placed slightly inclined from the vertical position; the power would then be considerably lessened at the beginning, and vastly increased towards the end. The extremities of the cams are furnished with strong anti-friction rollers, which come into action at the end of the process.
The action and power of this press may be described and estimated thus: the levers e e being fixed to the cams act with them as entire pieces, hence must be regarded as two bent levers, in which the points of pressure are constantly changing their position. Now supposing 5 cwt. appended to each lever, and each lever when drawn out to be ten feet long, and the pressure to be given at one inch from the fulcrum, this would give a power of 120 to 1, or 60 tons upon the head of the press. The head of the press, it will be observed, moves through a space, the treble of that which is between the opposite planes of the wedge-formed teeth, consequently, the power is here increased threefold, or raised to 180 tons; then, by applying similar levers and weights to the opposite ends of the axes of the cams, we have the force of 360 tons upon the goods in this little self-acting lever press. The friction in such a machine is undoubtedly considerable, but as any additional force within the limits of the strength of the structure may obviously be added, and the point of pressure be brought nearer to the fulcrum than the distance mentioned, at the close of the operation, any required power may be obtained at the period when it is wanted, to squeeze the cakes thoroughly dry.
The oil-maker will do well to consider, that the force transmitted to the screw presses as well as by the hydrostatic is inter missive, and not a constant self-accumulating force, as exerted by the lever presses we have just described.