Adzer machine having failsafe head assembly

1. A head assembly for an adzer machine, comprising:

a lift frame;

a cutting head rotationally connected to the lift frame;

a skid;

a single-acting hydraulic cylinder connecting the skid to the lift frame;

a spring connecting the skid to the lift frame; and

a shim pack located between the skid and the lift frame;

wherein:

the skid includes a stem portion, a generally T-shaped end connected to the stem portion, and a base plate connected to the stem portion opposite the generally T-shaped end;

the lift frame includes a bracket that encircles a portion of the stem portion; and

the shim pack is located around the stem portion, between the bracket and the generally T-shaped end.

2. The head assembly of claim 1 , wherein the single-acting hydraulic cylinder is connected at a head-end to the lift frame and at a rod-end to the skid.

3. The head assembly of claim 2 , wherein the single-acting hydraulic cylinder is configured to extend and push the skid away from the lift frame when selectively activated.

4. The head assembly of claim 3 , wherein the spring is configured to bias the skid back toward the lift frame.

5. The head assembly of claim 4 , wherein the spring is configured to cause retraction of the single-acting hydraulic cylinder when the single-acting hydraulic cylinder is deactivated.

6. The head assembly of claim 1 , wherein the spring extends between the bracket and the base plate.

7. The head assembly of claim 1 , wherein the spring is a tensile spring.

8. The head assembly of claim 1 , further including a pair of lift arms pivotally connected at one end to a general center of the lift frame and pivotally connected at an opposing end to a machine frame of the adzer machine.

9. The head assembly of claim 8 , further including a double-acting lift cylinder disposed between the machine frame of the adzer machine and the lift arms, the double-acting lift cylinder being configured to selectively raise and lower the cutting head, the lift frame, and the skid.

10. The head assembly of claim 8 , further including a turnbuckle disposed between the lift arms and the lift frame, the turnbuckle configured to selectively affect an angle of the cutting head.

11. The head assembly of claim 1 , wherein:

the skid is a first skid;

the single-acting hydraulic cylinder is a first single-acting hydraulic cylinder;

the spring is a first spring; and

the head assembly further includes:

a second skid;

a second single-acting hydraulic cylinder connecting the second skid to the lift frame; and

a second spring connecting the second skid to the lift frame.

12. The head assembly of claim 11 , wherein the first skid, cutting head, and second skid are in fore/aft alignment with each other.

13. The head assembly of claim 1 , wherein:

the single-acting hydraulic cylinder is located outside of the lift frame; and

the spring is located inside the lift frame at a side of the skid opposite the single-acting hydraulic cylinder.

14. An adzer machine, comprising:

a machine frame;

wheels configured to support the machine frame and ride along a rail located at first ends of a plurality of cross ties;

track-type crawlers located opposite the wheels, configured to support the machine frame, and ride along second ends of the plurality of cross ties;

a rotatable cutting head configured to resurface the second ends of the plurality of cross ties and being located between the track-type crawlers;

skids configured to slide along the second ends of the plurality of cross ties and being located between the rotatable cutting head and the track-type crawlers;

a lift frame configured to mount the rotatable cutting head;

parallel lift arms pivotally connecting the lift frame to the machine frame;

a double-acting lift cylinder disposed between the parallel lift arms and configured to raise and lower the parallel lift arms;

a plurality of single-acting hydraulic cylinders, each connecting the lift frame to a corresponding one of the skids and to the lift frame, the plurality of single-acting hydraulic cylinders being configured to only extend the skids relative to the lift frame;

a plurality of springs each connecting a corresponding one of the skids to the lift frame and configured to bias each of the skids back toward the lift frame; and

a shim pack located between the skid and the lift frame;

wherein:

the skid includes a stem portion, a generally T-shaped end connected to the stem portion, and a base plate connected to the stem portion opposite the generally T-shaped end;

the lift frame includes a bracket that encircles a portion of the stem portion; and

the shim pack is located around the stem portion, between the bracket and the generally T-shaped end.