FIG. 62.—Dies for Gleason gear-hardening machine.
FIG. 63.—Gleason tempering machine.
Hardening Operation.—Hardening a gear is accomplished as follows: The gear is taken from the furnace by the furnaceman and placed in the lower die, surrounding the centering jaws, as shown at H in Fig. 62 and C in Fig. 63. Air is then turned into the cylinder D, and the piston rod E, the die carrier B, the top die F and the expander G descend. The pilot H enters a hole in the center of the lower die, and the expander G enters the centering jaws I, causing them to expand and center the gear C in the lower die. On further advance of the piston rod E, the expander G is forced upward against the pressure of the springs J and the upper die F comes in contact with the upper surface of the gear. Further downward movement of the dies, which now clamp the work securely, overcomes the resistance of the pressure weight K (which normally keeps up the plunger A), and the gear is submerged in the oil. The quenching oil is circulated through a cooling system outside the building and enters the tempering machine through the inlet pipe L. When the machine is in the position shown, the oil passes out through the ports M in the lower plunger to the outer reservoir N, passing to the cooling system by way of the overflow O. When the lower plunger A is forced downward, the ports M are automatically closed and the cool quenching oil from the inlet pipe L, having no other means of escape, passes through the holes in the lower die and the grooves in the upper, circulating in contact with the surfaces of the gear and passes to the overflow. When the air pressure is released, the counterweights return the parts to the positions shown in Fig. 63, and the operator removes the gear.
The gear comes out uniformly hard all over and of the same degree of hardness as when tempered in an open tank. The output of the machine depends on the amount of metal to be cooled, but will average from 8 to 16 per hour. Each machine is served by one man, two furnaces being required to heat the work. A slight excess of oil is used in the firing of the furnaces to give a reducing atmosphere and to avoid scale.
FIG. 64.—Hardening and shrinking sleeves.
Carburizing Low-carbon Sleeves.—Low-carbon sleeves are carburized and pushed on malleable-iron differential-case hubs. Formerly, these sleeves were given two treatments after carburization in order to refine the case and the core, and then sent to the grinding department, where they were ground to a push fit for the hubs. After this they were pushed on the hubs. By the method now employed, the first treatment refines the core, and on the second treatment, the sleeves are pushed on the hub and at the same time hardened. This method cuts out the internal grinding time, pressing on hubs, and haulage from one department to another. Also, less work is lost through splitting of the sleeves.
The machine for pushing the sleeves on is shown in Fig. 64. At A is the stem on which the hot sleeve B is to be pushed. The carburized sleeves are heated in an automatic furnace, which takes them cold at the back and feeds them through to the front, by which time they are at the correct temperature. The loose mandrel C is provided with a spigot on the lower end, which fits the hole in the differential-case hub. The upper end is tapered as shown and acts as a pilot for the ram D. The action of pushing on and quenching is similar to the action of the Gleason tempering machine, with the exception that water instead of oil is used as a quenching medium. The speed of operation depends on a number of variables, but from 350 to 500 can be heated and pressed on in 11 hr.