Kesey represents the power dynamics of post-war, post-industrial American society through the allegory of "the Combine." A combine can refer to an organization of people or corporations working together to advance their aligning interests. It can also refer to a piece of farming equipment that was pivotal to the Industrial Revolution.
Prior to the invention of the combine harvester, there were many more steps to harvesting grain. Reaping, or removing crops from the field, was the first step. The crops then required threshing, which loosened the seeds from the non-edible parts of the plants. Winnowing further isolated the grain inside the seed from the lightweight chaff, or husk, surrounding it. Finally, the winnowed grain needed to be gathered so it could be further processed into food. A combine harvester is a complex machine that can perform all four of these steps at once. It revolutionized agriculture by making it far more efficient; with the advent of the combine, agricultural operations were able to grow larger and larger over the 20th century, until some began to operate on a massive, nationwide scale.
Bromden presents an allegory in which society is a huge combine whose goal is to grow ever-larger and keep producing more and more. There can never be enough grain, money, or products in the capitalism-obsessed society that dammed the Columbia River for profit. The Combine wants every person to be a functioning gear that makes the overall system more efficient, just as combine harvesters made farming more efficient. In Part One, Bromden describes how the ward helps the Combine run:
The ward is a factory for the Combine. It’s for fixing up mistakes made in the neighborhoods and in the schools and in the churches, the hospital is. When a completed product goes back out into society, all fixed up good as new, better than new sometimes, it brings joy to the Big Nurse’s heart; something that came in all twisted different is now a functioning, adjusted component, a credit to the whole outfit and a marvel to behold.
In the allegory, Bromden and the other patients are misshapen pieces of the combine. They are the "mistakes made in the neighborhoods and in the schools and in the churches." Nurse Ratched's role in the combine is as the foreman presiding over the "factory" (the psychiatric ward) meant to reshape the patients into gears that will help the combine run more efficiently instead of gumming it up.
For Bromden, the combine is almost more of a paranoid delusion than an allegory. At times, he thinks society really is a giant machine. His conspiratorial thinking allows Kesey to hint at the way we all conspire by consenting to help capitalism run more efficiently. Kesey's novel protests the conditions patients endure in psychiatric hospitals, but it also suggests that there is something powerful in Bromden's decade-long refusal to be "fixed" and returned to work for the combine. By the end of the novel, there is hope that Bromden can escape the ward and continue to live more freely outside the role prescribed for him by the combine.