Homework 3 - ewolz
Conclusion of Obviousness
In reading patent 2493811, it is apparent that ample evidence exists to show that the changes made by Graham and proposed in 2627798 were obvious to a mechanic acquainted with the business and of ordinary ingenuity and skill. Both patents claim a "plow having a frame and a ground working device provided with a shank". The shanks for each plow are designed to make the ground working tool pump in order to work fine soil to the bottom to act as a seed bed and the course materials to the top for better mulch and moisture collection.
However, there are two main differences between the two patents which are the point of contention. In patent '811, Graham claims "a rod having pivotal connection with the fulcrum member and extending through an elongated opening in said shank and through a registering opening of the bracket to anchor the shank to said bracket" which "provides sufficient longitudinal relative movement between shank and fulcrum member to accommodate oscillation of the shank". In this case, the shank is on top of the shank attaching member. In the '798 patent, besides reversing the position of the shank and shank attaching member, Graham claims a "shank attaching member having depending means embracing the shank at the rear end" (stirrup) and "a bolt connecting the forward end of the plate portion".
Regardless of location, in both cases, the hinge plate attached to the shank provides a means to reduce damage when the plow comes across fields of rocks and other obstructions as it allows the shank to pass freely over the obstruction by rotating up. Graham states in '798 that with these changes, he has provided a "plow structure wherein the shanks of the ground working tools are attached to the plow frame in a manner to permit the desired rocking action of the plow shanks...without producing destructive strains on the plow frame". Preventing these damages from occurring involved moving the position of the shank away from the top of the hinge plate and attaching it to the problem.
To any skillful mechanic, this is an obvious and easy change. The damage caused to '811 models was due to the shank applying pressure upon the upper plate when the hinge plate was rotated down, thereby sandwiching the shank in between the upper and lower plate. To prevent this damage, there was only one logical way to prevent the shank from being sandwiched-it could either go on top of the upper plate or below the lower hinge plate. Because the upper plate is fixed, if the shank were to be attached atop it, it would lose its rotating motion and thus encounter the same problem the patent was originally trying to avoid (damage due to rocky fields). Thus, in order to prevent damage due to rocky fields and other obstructions, the shank would still have to rotate and would have to remain attached to the lower plate. The only other possible location is to attach it underneath the lower hinge plate. This shows that reversing the shank and the lower hinge plate is obvious to any mechanic skilled in the arts.
The last point of contention was the introduction of the stirrup and bolt which attached the shank to the lower hinge plate in '798.