The reciprocating plunger with which the die-chamber is provided, and by which the clay delivered from the tempering-hopper is pressed through the opening in the die, consists essentially of a pair of heads 20 21, connected by a yoke 22, and a top plate 23. The heads 20 21 fill the entire area of the chamber, substantially like pistons, and the head 20 is provided with an ordinary flap or other valve 24, so arranged that, as the plunger moves backward, air will be allowed to enter the die-chamber and prevent the formation of a vacuum in front of the plunger. The plate 23, which connects the front and rear heads of the plunger, extends the entire width of the die-chamber, or is at least of sufficient width to cover the opening 7, and prevent the clay from falling in the rear of the head 20 when the plunger is at the forward end of its travel. This plate is also made slightly adjustable by means of set-screws 25, so that it can be moved outward to compensate for wear.

The bottom of the die-chamber is provided with an opening 26, located as shown in Figs. 161 and 164, through which the interior of the chamber can be reached for the adjustment of the parts.

The plunger just described is operated to press the clay through the opening in the die by means of hydraulic or other analogous pressure applied from the cylinder 28 upon the rear end of the die-chamber through the piston 29 and piston-rod 30, the latter of which passes through the head 21, and is secured to the yoke 22, as clearly shown in Figs. 161 and 164.

The fluid (preferably oil or some other substance which

is nearly or quite non-compressible), which drives the piston 29, is forced into the cylinder 28 through a main pipe, as 31, connected with any appropriate form of pumping apparatus operated either from some moving part of the machine or independently thereof, as may be desired. In the present case this pumping apparatus is shown as consisting of a double force-pump 32, the pistons 33 whereof are connected with and driven by excentrics 34 upon the driving-shaft of the machine. These pumps are provided with valves, so arranged in the ordinary manner that the motion of their pistons draws the oil or other fluid from the tank 35, through pipe 36 and chamber 37, into the pumps, and ejects the same through chamber 38 and pipe 27 into the pipe 31. One end of the main pipe 31 enters and terminates near the top of the tank 35, as shown in Fig. 161, at which point it is provided with a safety-valve 39, controlled by a spring or other device which can be adjusted, so that in case the plunger meets with any undue resistance, as would happen if a stone or other solid substance should pass into the diechamber, a relief may be afforded to the pressure of the fluid in the cylinder 28, and all danger of breaking the machine be avoided. This pipe also communicates with an air-chamber 40, in which the elasticity of the confined air serves to make the movements of the piston regular and uniform. The opposite end of the pipe 31 enters the valve-chamber 41, which contains an oscillating valve 42, which operates to direct the oil or other fluid alternately through the pipes 43 44 and into the cylinder 28 upon the opposite sides of the piston 29.

Referring particularly to Figs. 167 and 168, it will be seen that the valve-chamber 41 consists of a cylindrical casing provided with ports 45 46 47, communicating respectively with pipes 31 43 44, and with a port 48, communicating with the exhaust-pipe 49, through which the motor-fluid is returned to the tank 35. The valve 42 consists of a slightly tapering cylindrical plug provided with parallel passages 50 51, which may be made to communicate with ports 46 47 and branch passages 52 53, which open into ports 45 48. To give greater strength to the plug the passages 50 51 52 53 are provided with a partition-wall 68, as shown in Fig. 167. This plug is provided with a stem 54, extending through the wall of the valve-chamber, and with adjusting-screws 55 56, located as shown, by which it can be maintained in such position as to preserve a perfectly tight joint between it and the casing.

The stem 54 is provided with an arm 57 (see Fig. 165), which is connected by a link 58, with a pivoted lever 59, the end of which is loosely connected to a collar 60, which slides freely upon the valve-rod 61, which is connected to the head 21 of the plunger, The rod 61 is provided with two adjustable collars 62 63, which, by means of set-screws, can be secured to the rod in any desired position, and is also provided between said collars with springs 64 65, the purpose of which will hereinafter appear. The end of the lever 59 extends below the collar 60, and engages with the face of a double-inclined block 66, which slides in suitable ways secured to the side of the cylinder 28, and is pressed upward against the end of said lever by a spring 67, as shown in Figs. 165 and 166.

When the plunger has thus

The operation of the mechanism just described is as follows: The clay, being introduced through the opening 1 into the tempering-hopper, will pass gradually downward in the hopper, being tempered during its passage by the blades 3. As it arrives at the bottom of the hopper the tempered clay passes through the opening 7 into the die-chamber in front of the plunger. When a sufficient quantity of the clay has thus passed into the die-chamber, the pumps will be started, and the fluid, forced into the cylinder 28, behind the piston 29, will cause the plunger to advance, thereby forcing the clay through the die-opening and forming the tile as shown in Fig. 165. advanced a proper distance the spring 65 will come into contact with the collar 60, and said spring will be compressed until it has acquired sufficient tension to move the lever 59 against the resistance of the inclined block 66. As soon as the lever 59 is started the expansion of the spring 65 will throw its end quickly over the apex of the block 66, when the expansion of the spring 67 will at once raise the block to its normal position. This movement of the lever 59 will, through link 58 and arm 57, turn the valve 42, so as to permit the fluid forced into the pipe 31 to pass through port 45, passages 52 50, port 46, and pipe 43 into the cylin der in front of the piston 29, to retract the plunger. At the same time that a passage is thus opened for the admission of the fluid to the cylinder in front of the piston a pas sage will be opened through pipe 44, port 48, passages 53 51, port 47, and pipe 49, which will permit the fluid in the rear of the piston to pass back to the tank 35. When the

piston has gained the rear end of its stroke, the spring 64 will come into contact with the collar 60, and the valve will in like manner be moved in the opposite direction, so as to admit the fluid through port 45, passages 52 50, port 47, and pipe 44 to the cylinder behind the piston, thereby causing the plunger to again advance, while at the same time the fluid in front of the piston will be allowed to escape through pipe 43, port 46, passages 51 53, and port 48.

By reason of the cylindrical sleeve 69, which surrounds the piston-rod in front of the piston, the front area of the piston is reduced to one-third or less than one-third of its rear area, from which it results that the piston and plunger are retracted very much more rapidly than they are advanced, thus effecting a great increase in the rapidity of the operation of the machine.

It is to be observed that the partition 70, which separates the passages 50 51 in the valve, is slightly less in thickness than the diameter of the ports 46 47, from which it results that in reversing the piston there is never a time when the passage of the fluid through the valve is entirely arrested, it being allowed to enter the passage 50 before it is entirely shut off from the passage 51, and vice versa. This feature relieves the strain to which the valve would be subjected by totally arresting the flow of the fluid.

It will readily be seen that by varying the positions of the collars 62 63, the length of the stroke of the piston and plunger, and the amount of clay delivered through the die can be regulated at pleasure.

As before stated, the pump 32 may be of any approved