The principal parts of these machines are: a framework, rollers, wire-carrier, and a stop-pallet: we shall describe them in turn.
The Framework is composed of two cast-iron brackets joined by cross-pieces (Figs. 140, 141), or of a cast-iron frame resting on four legs (Figs. 101, 102, 103), or simpler still, of a frame resting on one support and one leg (Fig. 104). The four legs generally have adjustment screws (Figs. 101, 140, 142), so that the table can be raised at will and placed in a perfectly horizontal position.
The Rollers are of wood covered with chamois leather, or of plaster; this is because certain clays adhere to the plaster and slip on the leather. The rollers are movable about an iron axis whose ends rest on notches made in the sides of the framework. The rollers made of wood covered with chamois are supplied all ready mounted by the makers; when the leather is worn out it is renewed.
To make the plaster rollers, a bronze mould (Fig. 139) is used, divided into two parts, which are slightly conical in exterior shape, and are held together by two rings. The inside of the two parts is greased, they are fixed together by means of the rings, and the iron axis is placed through the middle, one end resting in a hollow in the lower part of the mould. The axis is held quite vertical, and plaster in a fairly liquid condition is poured round it. When it becomes solid it is taken out of the mould and dried. The plaster rollers get quickly worn out, but it is easy to remake them; the cost of plaster is small.
The Wire-carrier consists of a frame of variable shape, across which are stretched steel wires of excellent quality. One end of these wires is fixed to a socket movable on one of the sides of the frame; the other end is fixed to a screw and hook fitted with a. fluked nut. A special arrangement allows these hooks to slide along the rod which holds them. They are fixed by means of the nut. These wires can therefore be moved at will and placed at any desired distance from one another: care must of course be taken that they pass between the rollers. This wire-carrier swings on an axis fixed to the frame of the machine (Figs. 101, 140).
This is a movable piece placed at the end of the trolley; its object is to fix the thickness of the first brick, the thickness of the following ones being given by the distance between the wires. The work of this pallet is very important, for on it depends a good or a bad division. In certain cutting machines its motion is linked to that of the wire-carrier (Fig. 142); in others it is independent of it (Figs. 101, 102, 140).
We shall describe a small cutting machine (Fig. 102), which gives good results in cutting bricks, especially hollow bricks, in a flat position. It is composed of the same parts as the previous ones, but has no trolley.
The pallet is movable round a cylindrical rod; it is kept in position by two rings fixed by bolts to the rod itself. On the rod also slides the wire-carrier; this is fixed by bolts pressing on the rod as in the case of the movable rings. The distance between the pallet and the first wire is equal to that between the wires. In the ordinary position this pallet rests on the rollers (3, Fig. 140), and, by sliding the rod through two sockets fixed to the framework, it may be dropped on to a stop; it is then in the position of Fig. 102. To cut, the pallet is raised, the wire-carrier is pushed to the left, and the pallet is allowed to fall upon the rollers. When the prism of clay reaches it, the wire-carrier is quickly lowered, and to raise it again a slight pressure to the right is exerted in order to follow the motion of the clay, and bring the wires back through the same path. As soon as the wires are freed, the frame is pushed to the right; the pallet follows this motion, and falls on its stop. The cut bricks are taken away, the pallet is replaced on the rollers by pushing the wire frame, and the same process is repeated.
The cutter represented in Fig. 140 is similar in arrangement to the preceding one: it carries at the entrance a wire the use of which is to cut the prism horizontally in the case, in which it has the thickness of two bricks.
Trolley Cutting Machines consist of the same parts as the preceding ones, but a certain number of rollers are mounted on a trolley which runs by means of flanged wheels on rails forming the edges of the frame. Sometimes these flanged wheels are inside the frame and are consequently invisible, sometimes they are visible. In other cutting machines (Fig. I42)the trolley is double.
Fig. 139. Bronze Mould for making Plaster Rollers (Chavassieux).
According to the manner in which the wire attacks the prism of clay, we shall have -