Even before this patent was applied for, another patent was pending for the purpose of modifying the pitch of the lead screw without the use of change gears in spite of the wide acceptance of such gear mechanisms for over a hundred years.
Figure 21.—A hob-grinding machine of 1933, showing use of the master screw with a modifier but without change gears. Carl G. Olson’s U.S. patent 1901926.
Figure 22.—A sine-bar device to modify the effective lead of a master lead screw without introducing a complex mechanism which would be both difficult to make and to operate within the required close limits. Carl G. Olson’s (1933) U.S. patent 1901926.
[Figure 21] shows a plan view [7] of the machine, and [figure 22] a detailed view of the sine-bar mechanism actuated by the master screw, 6, to modify the effective pitch of the lead screw in accordance with the realities of practice as stated in the preamble of the patent:
This invention relates to material working machines, and particularly to machines such as hob grinders and the like, wherein the work is reciprocated through the agency of a lead screw.