PRESS (PRÆSUM), in the mechanic arts, a machine made of iron or wood, serving to squeeze or compress any body very close.
The ordinary presses consist of six members, or pieces; viz. two flat smooth planks; between which the things to be pressed are laid; two screws, or worms, fastened to the lower plank, and passing through two holes in the upper; and two nuts, in form of an S, serving to drive the upper plank, which is moveable, against the lower, which is stable, and without motion.
PRESSES used for expressing Liquors, are of various kinds; some, in most respects, the same with the common presses, excepting that the under plank is perforated with a great number of holes, to let the juice expressed run through into a tub, or receiver, underneath.
A very useful machine for a press, in the process of cyder-making, has been constructed by Mr Antice, who, with his well-known zeal for the improvement of mechanics, permits us to lay before our readers the following description of it.
AA fig. 1. two pieces of timber, 21 feet long, 12 by 6 inches, laid side by side at the distance of 12 inches, and secured in that situation by blocks placed between and bolts passing through them; this frame forms the bed of the machine. BB, two uprights, 12 feet long, 6 by 8 inches, morticed upon them, and secured in their position by pins and iron squares. CC, two uprights, five feet long, six by ten inches, morticed near the end of the under frame, and secured as before. D, a lever, 17 feet long, 12 by 13 inches, turning on a large bolt which passes through the short uprights, also through iron straps, which secure them to the bed inside, and a stirrup of iron which passes over the end of the lever, and which makes the turning point in the line of its lower side, and not through its middle. E, a lever 20 feet long, six by eight inches at its largest part and tapering towards the other end: this lever turns on a bolt in the uprights BB. F, 1, 2, 3, 4. four pieces of oak (which he calls needles, 10 feet long), four by two and an half inches, morticed loosely into the upper lever, and hung thereto by bolts, so as to swing perpendicularly, and play in a long mortice or channel cut through the large lever to receive them. These needles have inch-holes pretty closely bored through them (in a direction crossing the machine), from the lower ends as far upwards as the great lever will reach, when it is as high as it can go. G, a bed to receive what is to be pressed. H, a frame to support a winch worked by a handle at I. At the end of the small lever two blocks or pulleys are fixed, one above, and the other below it; a rope of about half an inch diameter is then fastened to the ceiling (or continuation of the uprights of the winch frame if necessary) at K; then passed through the upper block on the lever, from thence passed through a block at L, and then goes with four turns round the winch, from whence it is carried through the block under the lever, and fastens to the machine at M; by this means, if the winch be turned one way, it raises the end of the small lever if the other depresses it.
To work the machine. If we suppose the great lever bearing on the matter to be pressed, an iron pin must be put into one of the holes in the needles above the great lever; and when the small lever is worked as
far as it will go, either up or down, another bolt is to be put into the hole, which comes nearest above the great lever on the other side of the uprights BB, and the winch then turned the contrary way, by which means the pressing goes on whether the small lever rises or falls. Before the resistance is very great, the needles farthest from the fulcrum of the small lever are used; after that the nearest are employed, which doubles the power of the machine. In raising the great lever, or lowering it to its bearing, the needles most distant from the fulcrum of the small lever, are used under instead of over it. As the rope is liable to stretch and get slack, he passes it, after taking two turns on the winch, through a pulley, to which is suspended a weight of half a hundred, and then takes two turns more before it is carried through the other block, by which means the slack is constantly gathered in, and the weight holds on without increasing the friction, as by hanging under the winch it counteracts the pressure upwards on its axis.
The power of this machine is very great, being as one to 1136 nearly, and capable by a trifling addition of any other proportion. It is applicable to many purposes beside cyder pressing, and is more simple, and less liable to injury, than any other which has fallen under our observation. Perhaps, however, it would be an improvement to use, instead of the ropes and pulleys, by which the lever E is moved, a small wheel or pinion of 10 or 12 teeth, on the axis of the winch W (fig. 2), and a stiff beam en down from the lever, having on its lower end an iron rack, of which the teeth take into those of the pinion. The action of these teeth would, in our opinion, be less diminished by friction and obliquity, than the pulleys are by friction and the stiffness of the rope; and the machine would retain all its other advantages.
PRESS used by Joiners, to keep close the pieces they have glued, especially panels, &c. of wainscot, is very simple, consisting of four members; viz. two screws, and two pieces of wood, four or five inches square, and two or three feet long; whereof the holes at the two ends serve for nuts to the screws.
PRESS used by Inlayers, resembles the joiner's press, except that the pieces of wood are thicker, and that only one of them is moveable; the other, which is in form of a tressel, being sustained by two legs or pillars, jointed into it at each end. This press serves them for sawing and cleaving the pieces of wood required in marquetry or inlaid work.
Founder's PRESS, is a strong square frame, consisting of four pieces of wood, firmly joined together with tenons, &c. This press is of various sizes, according to the sizes of the moulds; two of them are required to each mould, at the two extremities of which they are placed; so as that, by driving wooden wedges between the mould and the sides of the presses, the two parts of the mould wherein the metal is to be run may be pressed close together.
Printing-PRESS. See PRINTING-PRESS.