These are expression machines similar to those described in the chapter on brick-making but have a horizontal die. A single machine may even be used for both positions; the Joly machine (Figs, l01, 575), for instance, is turned round on an axis by means of the screw L and the nut M, so that the die can be made either vertical (Fig. 101) or horizontal (Fig. 575).

All that need be done, then, to adapt this machine for pipe-making is to place it over a pit which will admit the balanced receiving plate, and to provide it with a suitable die like the one shown in the figure.

In order to avoid having a pit, vertical machines with propelling cylinders are constructed, which rest upon cast-iron supports; between these is the receiving plate, balanced by counterpoises inside the supports. The machines are rilled with clay from the pug-mill by means of a floor built at the level of the cylinders. This machine can make pipes 4 feet long.

Fig. 575. Vertical Expression Machine (Joly).

The Chainbrette-Belon machine (Fig. 578) resembles the preceding one, but has only one support; pipes 4 feet in length can be made by it.

Some machines (Fig. 576) are placed upon one floor, while the lower storey contains the receiving plate, and the counterpoises are in a pit. All the preceding machines are provided with a special arrangement for throwing out of gear, usually a check pulley with belt and coupler, which allows of instant stoppage and starting. Piston machines may also be worked by steam. Fig. 579 shows an arrangement of this kind.

To make sure of a continuous service, the machine is provided with two cylinders turning round one of the uprights of the machine. One is being filled while the other is empty.

The direct action of steam has been used to produce pipes of large diameter. The piston-rod of a steam cylinder (Fig. 580) works another piston, which compresses the already blended clay; this is placed in a cylinder below the first one, and fitted at the bottom with a special die for large production. The table which receives the pipe is balanced.

Fig. 579. Piston Machine, worked by .Steam (Chambrette-Belon).

When pipes reach a large size, their weight is considerable, and the handling of them becomes difficult; in this case the plates which are to receive them are placed on a truck running on a railway.