The plow in patent number 2,627,798 (‘798) by Graham is so similar to his previous patent number 2,493,811 (‘811) that I would consider the ‘798 patent as obvious. They have such a similar set up, that it is difficult to tell them apart based on the drawings. The only main difference found in the patents is in the naming and numbering of the parts. In the ‘811 patent, the fulcrum plate lies on the bottom with the shank on top of it, which is underneath the area where the spring is mounted on the rod. In the ‘798 patent, the shank (called the boss end) is beneath the fulcrum plate (called the movable part of the mounting), which is underneath the spring seat. The spring seat is where the spring is mounted on the rod. The only difference between these two devices is the position of the shank. For both inventions, the shank and fulcrum plates are enclosed by flanges. The shank is connected to the chisel part of the plow for both inventions, so when the chisel encounters an obstruction in the dirt, the shank rotates downward and pulls down the rod, which compresses the spring. For the ‘811 patent, the shank presses on the upper half of the fulcrum plate, which pulls down the rod. For the ‘798 patent, the shank presses the lower half of the fulcrum plate while pulling down the rod. When the obstruction is removed from the chisel’s path, the compressed spring returns the plow chisels to their original position for both inventions. Since the two devices perform the same function using the same parts in only slightly different configurations, I think the ‘798 patent is obvious. It would not take much skill to switch the position of the shank and the fulcrum plate.